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D'Aoust, Jean-Yves. "Psychrotrophy and foodborne Salmonella." International Journal of Food Microbiology 13, no. 3 (July 1991): 207–15. http://dx.doi.org/10.1016/0168-1605(91)90004-9.
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GARCÍA-ARMESTO, M. ROSARIO, and ALASTAIR D. SUTHERLAND. "Temperature characterization of psychrotrophic and mesophilic Bacillus species from milk." Journal of Dairy Research 64, no. 2 (May 1997): 261–70. http://dx.doi.org/10.1017/s002202999600204x.
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A total of 50 isolates of Bacillus spp. and one reference strain were investigated for their growth at 6·5°C for 10 d, 30°C for 3 d and 40°C for 2 d. The results obtained differentiated three physiological groups: one clearly psychrotrophic (able to grow at 6·5°C in 10 d, but not at 40°C in 2 d), one intermediate in psychrotrophy (it grew at both 40 and 6·5°C) and one mesophilic (capable of growth at 30 and 40°C, but not at 6·5°C). The proportion of strains in the second group was higher among isolates of B. cereus than for other Bacillus spp. However, the proportion of real mesophilic strains was lower for B. cereus isolates. Psychrotrophic B. cereus grew better at both 6·5 and 30°C than other psychrotrophic Bacillus spp. Using eight strains, a correlation between differential growth at mesophilic temperatures (count at 30°C minus count at 40°C) and a standard psychrotrophic count at 6·5°C for 10 d (r=0·95) was obtained in mixed cultures when the psychrotrophic flora count was [les ]1 log (cfu/ml) lower than the mesophilic count.
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Malimon, Z., M. Kukhtyn, N. Grynevych, and N. Mekh. "Analysis of the insemination of the mesophilic and psychrotrophic microflora of frozen fish." Naukovij vìsnik veterinarnoï medicini, no. 1(149) (May 30, 2019): 22–29. http://dx.doi.org/10.33245/2310-4902-2019-149-1-22-29.
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The article presents the results of research on the dehiscence of frozen fish with mesophilic and psychrotrophic microflora. Physico-chemical and organoleptic changes which appear in fish during refrigeration are connected with the life of the psychotropic group of microflora, which is more active than mesophilic. Fish are a nutrient medium for the development of microorganisms of all groups, due to its high nutritional and biological value, so the fish are perishable food products, the conditions and terms of their storage require appropriate temperature regimes to stop the development of microorganisms. The aim of the work was carrying out a comparative analysis of insemination of frozen fish with mesophilic and psychrotrophic microflora to make an amend to standards according to microbiological criteria. The microbial number in frozen fish samples was estimated with the temperature of (30 ± 1) ºC incubation of crops for 72 hours (mesophilic microflora) and incubation for 10 days (psychrotrophic microflora) with the temperature (6.5 ± 0.5) ºC. It was identified that there were taken the samples from frozen fish with a quantity of mesophilic bacteria to 102 CFU/g, 1.4-1.8 times (p <0.05) more psychotropic microorganisms. The researched samples with the number of mesophilic microorganisms from 103 to 104 CFU/g were contaminated with psychotropic microflora, which in 1.7-6.8 times (p <0.05) exceeded the content of the mesophilic microflora. With such amount of mesophilic microorganisms, on average of up to 25% of samples, this had a content of psychotrophs of more than 105 CFU/g of fish. According to the content of mesophilic bacteria the samples of frozen fish, which were mathed to a certain norm of 5 × 104 CFU/g, basically in the number of psychrotrophic microflora did not correspond to this indicator, and exceeded it 2 times or more. In the cold period of the year, 63.6 ± 2.1% of frozen fish samples were mesophilic bacteria containing less than 101 CFU/g. At the same time, samples with such content mesophilic bacteria in the warm period of the year was 9.0%, or 7.0 times (p <0.05) less. In addition, in the cold period of the year, only 9.0% of samples were detected, which, according to the content of mesophilic bacteria exceeded the maximum allowable level. At the same time, during the warm period, the number of samples with an excess of mesophilic bacteria content was 27.3 ± 0.3%. Practically the same pattern was observed regarding the insemination of the psychrotrophic microflora in these periods of the year, which was characterized by the fact that in the warm period of the year, frozen fish contains a large number of psychrotrophic microorganisms. Consequently, the results of studies on the amount of microflora in the warm period of the year established 3,0 times (p <0,05) more samples of frozen fish, which, according to the content of mesophilic bacteria, exceeded the maximum permissible level compared with the cold period of the year. It was established that samples of frozen fish containing mesophilic microorganisms less than 101 CFU/g were most unevenly contaminated with psychrotrophic microflora. Among these samples, only 30.1 ± 1.4% were with the number of psychrotrophic microflora less than 101 CFU/g, at the same time, 60.0 ± 0.5% of the samples were contaminated with a psychrotrophic microflora of 101 to 105 CFU/g and 10, 0 ± 0.2% over 105 CFU/g. In the study of frozen fish samples with the number of mesophilic bacteria from 101 to 102 CFU/g revealed a coincidence in the content of psychrotrophs in only 16,7 ± 0,3% of samples, and 33,3 ± 0,3% of fish samples were with the content of psychrotrophic microflora from 102 to 103 CFU/g and 103 to 104 CFU/g and 16.7 ± 0.3% were contaminated with psychrotrophy more than 104 CFU/g. It was established that samples of frozen fish containing mesophilic microorganisms less than 101 CFU/g were most unevenly contaminated with psychrotrophic microflora. Among these samples, only 30.1 ± 1.4% were with the number of psychrotrophic microflora less than 101 CFU/g, at the same time, 60.0 ± 0.5% of the samples were contaminated with a psychrotrophic microflora of 101 to 105 CFU/g and 10, 0 ± 0.2% over 105 CFU/g. In the study of frozen fish samples with the number of mesophilic bacteria from 101 to 102 CFU/g revealed a coincidence in the content of psychrotrophs in only 16,7 ± 0,3% of samples, and 33,3 ± 0,3% of fish samples were with the content of psychrotrophic microflora from 102 to 103 CFU/g and 103 to 104 CFU/g and 16.7 ± 0.3% were contaminated with psychrotrophy more than 104 CFU/g. It was found that that the psychrotrophic microflora of frozen fish is quantitatively predominantly content of mesophilic bacteria several orders of magnitude. During the warm period of the year, more samples of frozen fish were detected in 3,0 times (p <0,05), which, according to the content of mesophilic bacteria, exceeded the maximum permissible level in comparison in the cold period of the year. It was found that 92,6 ± 2,5% of frozen fish samples were in compliance with the requirements of DSTU 4868: 2007. The fish is frozen. At the same time, during the fish evaluation, the contents of the psychrotrophic microflora showed that samples exceeding 5 × 104 CFU/g was in 2.6 times (p <0.05) more than the mesophilic bacteria content. In future the generic and species composition of the psychrotrophic microflora of frozen fish will be studied and the fish evaluating criteria according to the psychrotrophs in order to make corrections according to the microbiological criteria. Key words: frozen fish, psychrotrophic microflora, mesophilic bacteria, contamination, microbial number.
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CHAMPAGNE, C. P., F. GIRARD, and N. MORIN. "Inhibition of the Psychrotrophic Bacteria of Raw Milk by Addition of Lactic Acid Bacteria." Journal of Food Protection 53, no. 5 (May 1, 1990): 400–403. http://dx.doi.org/10.4315/0362-028x-53.5.400.
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Two commercial cultures of lactic acid bacteria (LAB) were added to raw milk in order to inhibit the development of psychrotrophic bacteria. The effects of inoculation level, pH development, media for culture preparation, and milk heat treatment on the inhibitory activity of LAB were studied. Inoculation levels of 2.5 × 106/mL and less of LAB did not significantly reduce psychrotrophic growth. Maximum inoculation level of LAB studied was 25 × 106/mL and this reduced psychrotrophic development by a factor of 10; however, milk pH was reduced to 6.54 over 48 h of incubation at 7°C with this inoculation level. This acidification was not responsible for the inhibitory activity of LAB on psychrotrophs. The LAB were more effective when psychrotroph populations had high multiplication rates. Initial populations of Pseudomonas putida in pasteurized milk did not influence the activity of the LAB. Pseudomonas putida grew faster in sterile milk than in pasteurized milk, but average inhibition rates of LAB were similar in both media.
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NORTJÉ, G. L., L. NEL, E. JORDAAN, K. BADENHORST, G. GOEDHART, W. H. HOLZAPFEL, and R. J. GRIMBEEK. "A Quantitative Survey of a Meat Production Chain to Determine the Microbial Profile of the Final Product." Journal of Food Protection 53, no. 5 (May 1, 1990): 411–17. http://dx.doi.org/10.4315/0362-028x-53.5.411.
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Samples from carcasses, personnel surfaces, equipment, and minced meat, packaged and displayed in cabinets were taken at a city abattoir, a wholesaler, and 10 different supermarkets. Bacteria enumerated were 1) psychrotrophs; 2) Enterobacteriaceae; 3) enterococci; 4) micrococci; 5) Pseudomonas spp; and 6) Brochothrix thermosphacta. The non integrated production system of abattoirs, wholesalers, and retailers yielded psychrotrophic and enterococci counts at retail which compared fairly well with those reported in literature, while the Enterobacteriaceae and micrococci counts were higher. Besides the psychrotrophs the pseudomonads were the most numerous group in the final product. Different surfaces were not sanitized with the same efficacy, while a general tendency towards lower counts at one supermarket group was monitored. The counts described 96% of the variation in the psychrotrophic count at the abattoir, while the success in using these counts in estimating the psychrotrophic count at the wholesaler and retailers was not as significant. At the abattoir the Enterobacteriaceae and psuedomonads were the biggest contributors to the psychrotrophic count, at the wholesaler the Enterobacteriaceae and micrococci counts, and at the retailers the micrococci and pseudomonads respectively. This indicates that Enterobacteriaceae might be common psychrotrophs in the meat production chain, maybe originating from the abattoir and wholesale environments.
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Vigentini, I., A. Praz, D. Domeneghetti, S. Zenato, C. Picozzi, A. Barmaz, and R. Foschino. "Characterization of malolactic bacteria isolated from Aosta Valley wines and evidence of psychrotrophy in some strains." Journal of Applied Microbiology 120, no. 4 (March 17, 2016): 934–45. http://dx.doi.org/10.1111/jam.13080.
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Munsch-Alatossava, Patricia, Jean-Pierre Gauchi, Bhawani Chamlagain, and Tapani Alatossava. "Trends of Antibiotic Resistance in Mesophilic and Psychrotrophic Bacterial Populations during Cold Storage of Raw Milk." ISRN Microbiology 2012 (March 12, 2012): 1–13. http://dx.doi.org/10.5402/2012/918208.
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Psychrotrophic bacteria in raw milk are most well known for their spoilage potential and cause significant economic losses in the dairy industry. Despite their ability to produce several exoenzyme types at low temperatures, psychrotrophs that dominate the microflora at the time of spoilage are generally considered benign bacteria. It was recently reported that raw milk-spoiling Gram-negative-psychrotrophs frequently carried antibiotic resistance (AR) features. The present study evaluated AR to four antibiotics (ABs) (gentamicin, ceftazidime, levofloxacin, and trimethoprim-sulfamethoxazole) in mesophilic and psychrotrophic bacterial populations recovered from 18 raw milk samples, after four days storage at C or C. Robust analysis of variance and non parametric statistics (e.g., REGW and NPS) revealed that AR prevalence among psychrotrophs, for milk samples stored at C, often equalled the initial levels and equalled or increased during the cold storage at C, depending on the AB. The study performed at C with an intermediate sampling point at day 2 suggested that (1) different psychrotrophic communities with varying AR levels dominate over time and (2) that AR (determined from relative amounts) was most prevalent, transiently, after 2-day storage in psychrotrophic or mesophilic populations, most importantly at a stage where total counts were below or around CFU/mL, at levels at which the milk is acceptable for industrial dairy industrial processes.
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Shtenikov, M. D., O. Y. Zinchenko, and V. V. Boldyreva. "ANTAGONISTIC ACTIVITY OF MARINE BACTERIA OF BACILLUS, PRIESTIA AND PAENIBACILLUS GENERA OF DIFFERENT THERMOTYPES." Microbiology&Biotechnology, no. 2(55) (September 20, 2022): 50–65. http://dx.doi.org/10.18524/2307-4663.2022.2(55).261778.
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SummaryAim. To study the antagonistic activity of bacteria of genera Bacillus, Priestia and Paenibacillus at different conditions of cultivation. Methods. Antagonistically active spore-forming bacteria isolated from deep-sea bottom sediments of the Black Sea were used for the study. Determination of thermotypes was performed using the results of analysis of fatty acid profile parameters. Antagonistic activity to test strains of bacterial opportunistic pathogens was detected by the method of agar blocks on Gauze № 1 and Nutrient Agar media at different cultivation temperatures. Results. Aerobic bacilli of genera Bacillus, Priestia and Paenibacillus of all three thermotypes – thermotolerants, mesophiles and psychrotrophes, in general show lower antagonistic activity when cultured at 37 °C on both media, except for a marked increase in psychrotrophe antagonistic activity at 37 °С on Gauze № 1. Conclusions. It was established that belonging to a certain thermotype affects the character of the antagonistic activity of sporeforming bacteria. The antagonistic activity of mesophilic and thermotolerant bacteria at a higher temperature of cultivation is lower, and that of psychrotrophic bacteria at a higher temperature and on Gauze № 1 medium is higher.
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Teider Junior, Pedro I., José C. Ribeiro Júnior, Eric H. Ossugui, Ronaldo Tamanini, Juliane Ribeiro, Gislaine A. Santos, Amauri A. Alfieri, and Vanerli Beloti. "Pseudomonas spp. and other psychrotrophic microorganisms in inspected and non-inspected Brazilian Minas Frescal cheese: proteolytic, lipolytic and AprX production potential." Pesquisa Veterinária Brasileira 39, no. 10 (October 2019): 807–15. http://dx.doi.org/10.1590/1678-5150-pvb-6037.
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ABSTRACT: The most consumed cheese in Brazil, Minas Frescal cheese (MFC) is highly susceptible to microbial contamination and clandestine production and commercialization can pose a risk to consumer health. The storage of this fresh product under refrigeration, although more appropriate, may favor the growth of spoilage psychrotrophic bacteria. The objective of this study was to quantify and compare Pseudomonas spp. and other psychrotrophic bacteria in inspected and non-inspected MFC samples, evaluate their lipolytic and proteolytic activities and their metalloprotease production potentials. Twenty MFC samples were evaluated: 10 inspected and 10 non-inspected. Counts of psychrotrophic bacteria and Pseudomonas spp., evaluation of the proteolytic and lipolytic potential of the isolates, and identification of potential producers of alkaline metalloprotease (AprX) were assessed. The mean total psychrotrophic counts were 1.07 (±2.18) × 109CFU/g in the inspected samples and 4.5 (±5.86) × 108CFU/g in the non-inspected, with no significant difference (p=0.37). The average score of Pseudomonas spp. was 6.86 (±18.6) × 105 and 2.08 (±3.65) × 106 CFU/g for the inspected and non-inspected MFC samples, respectively, with no significant difference (p=0.1). Pseudomonas spp. represented 0.06% and 0.004% of psychrotrophic bacteria found in inspected and non-inspected MFC samples, respectively. Collectively, 694 psychrotrophic strains and 47Pseudomonas spp. were isolated, of which 59.9% and 68.1% were simultaneously proteolytic and lipolytic, respectively. Of the 470 psychrotrophs isolated from inspected and 224 from non-inspected cheese samples, 5.74% and 2.23% contained aprX, respectively, while 100 and 86.96% of the Pseudomonas spp. isolates in inspected and non-inspected cheese samples contained the gene. The production potential of AprX did not, however, determine the proteolytic activity on plates of these isolates under the conditions evaluated in this study. Of total, 65.63% of the psychrotrophs that contained aprX gene were confirmed as Pseudomonas spp., using genus-specific PCR. Phylogenetic analysis of the 16S rRNA gene of the other psychrotrophs that were potential producers of AprX identified them as Serratia spp. (n=7), Raoultella ornithinolytica (n=1), and Acinetobacter schindleri (n=1) in the inspected samples and Psychrobacter sanguinis (n=1) and Leuconostoc mesenteroides (n=1) in the non-inspected samples. The production conditions of Brazilian MFC of these samples, while meeting the legal determinations, are not sufficient to control Pseudomonas and other spoilage-related psychrotrophs. Thus, stricter hygienic measures are required during the formal production of this type of cheese.
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Nurlinawati, Kristof Vanoirbeek, Abram Aertsen, and Chris W. Michiels. "Role of 1-acyl-sn-glycerol-3-phosphate acyltransferase in psychrotrophy and stress tolerance of Serratia plymuthica RVH1." Research in Microbiology 166, no. 1 (January 2015): 28–37. http://dx.doi.org/10.1016/j.resmic.2014.11.001.
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MEER, R. R., J. BAKER, F. W. BODYFELT, and M. W. GRIFFITHS. "Psychrotrophic Bacillus spp. in Fluid Milk Products: A Review." Journal of Food Protection 54, no. 12 (December 1, 1991): 969–79. http://dx.doi.org/10.4315/0362-028x-54.12.969.
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Psychrotrophic bacteria have been recognized as a recurring problem in the refrigerated storage and distribution of fluid milk and cream and other perishable dairy products for several decades. Much emphasis has been focused on postpasteurization contaminants that are psychrotrophic, (e.g., Pseudomonas, Flavobacterium, and Alcaligenes spp.). Common sources of these gram-negative, non-sporeforming organisms are equipment surfaces and water supplies. Although these organisms are generally heat sensitive, many of their associated proteinases and lipases can withstand moderate to severe heat treatments and cause product deterioration. With the advance of improved control of postpasteurization contamination by nonheat-resistant psychrotrophs, more recent attention has been directed at psychrotrophic sporeformers and their potential impact on milk quality and shelf life properties. Heat-resistant psychrotrophs include members from the genera Clostridium, Arthrobacter, Microbacterium, Streptococcus, Corynebacterium, and Bacillus. However, the predominant microorganisms which comprise this category are Bacillus species. These bacteria can be introduced into milk supplies from water, udder and teat surfaces, or from soil and milkstone deposits on farm bulk tanks, pumps, pipelines, gaskets, and processing equipment. There is speculation that they can also be postpasteurization contaminants. When in the spore state, these microorganisms easily survive the typical range of pasteurization conditions with subsequent germination and outgrowth of vegetative cells. These organisms produce degradative enzymes (e.g., proteinases, lipases, and phospholipases) similar to those of non-sporeforming psychrotrophs. Enzymatic activity results in the development of objectionable flavor and quality defects in dairy products. The unique combination of both heat-resistant and psychrotrophic properties with the same microorganism represents substantial potential for causing spoilage of perishable milk products. Recent trends of higher pasteurization temperatures and extended refrigerated storage time of both raw and pasteurized milk and cream products exacerbates the significance of this group of microorganisms for the dairy foods industry.
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Whyte, Lyle G., Charles W. Greer, and William E. Inniss. "Assessment of the biodegradation potential of psychrotrophic microorganisms." Canadian Journal of Microbiology 42, no. 2 (February 1, 1996): 99–106. http://dx.doi.org/10.1139/m96-016.
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Bioremediation of polluted temperate and cold temperature environments may require the activity of psychrotrophic bacteria, because their low temperature growth range parallels the ambient temperatures encountered in these environments. In the present study, 135 psychrotrophic microorganisms isolated from a variety of ecosystems in Canada were examined for their ability to mineralize14C-labelled toluene, naphthalene, dodecane, hexadecane, 2-chlorobiphenyl, and pentachlorophenol. A number of the psychrotrophic strains mineralized toluene, naphthalene, dodecane, and hexadecane. None of the psychrotrophs were capable of mineralizing 2-chlorobiphenyl or pentachlorophenol. Those strains demonstrating mineralization activity were subsequently screened by the polymerase chain reaction (PCR) and Southern hybridization of PCR products for the presence of catabolic genes (alkB, ndoB, todC1, and xylE) involved in known bacterial biodegradative pathways for these compounds. Some of the psychrotrophs able to mineralize toluene and naphthalene possessed catabolic genes that hybridized to xylE or todC1, and ndoB, respectively. The alkB PCR fragments obtained from the strains that mineralized dodecane and hexadecane did not hybridize to an alkB gene probe derived from Pseudomonas oleovorans. Psychrotrophic strain Q15, identified as a Rhodococcus sp., also mineralized the C28n-paraffin octacosane. A gene probe constructed from the "alkB" PCR fragment from strain Q15 did hybridize with the alkB PCR fragments from most of the psychrotrophic alkane biodegraders, indicating that the alkB primers may be amplifying another gene(s), perhaps with low homology to P. oleovorans alkB, which may be involved in the biodegradation of both short chain (dodecane) and longer chain alkanes (hexadecane, octacosane). All of the psychrotrophic biodegradative isolates examined were capable of mineralization activity at both 23 and 5 °C, indicating their potential for low temperature bioremediation of petroleum hydrocarbon contaminated sites.Key words: psychrotrophic microorganisms, biodegradation, catabolic gene probes, organic pollutants.
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Hantsis-Zacharov, Elionora, and Malka Halpern. "Culturable Psychrotrophic Bacterial Communities in Raw Milk and Their Proteolytic and Lipolytic Traits." Applied and Environmental Microbiology 73, no. 22 (September 21, 2007): 7162–68. http://dx.doi.org/10.1128/aem.00866-07.
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ABSTRACT During cold storage after milk collection, psychrotrophic bacterial populations dominate the microflora, and their extracellular enzymes, mainly proteases and lipases, contribute to the spoilage of dairy products. The diversity, dynamics, and enzymatic traits of culturable psychrotrophs in raw milk from four farms were investigated over a 10-month period. About 20% of the isolates were found to be novel species, indicating that there is still much to be learned about culturable psychrotrophs in raw milk. The psychrotrophic isolates were identified and classified in seven classes. Three classes were predominant, with high species richness (18 to 21 species per class) in different seasons of the year: Gammaproteobacteria in spring and winter, Bacilli in summer, and Actinobacteria in autumn. The four minor classes were Alphaproteobacteria, Betaproteobacteria, Flavobacteria, and Sphingobacteria. The dominant classes were found in all four dairies, although every dairy had its own unique “bacterial profile.” Most but not all bacterial isolates had either lipolytic or both lipolytic and proteolytic activities. Only a few isolates showed proteolytic activity alone. The dominant genera, Pseudomonas and Acinetobacter (Gammaproteobacteria), showed mainly lipolytic activity, Microbacterium (Actinobacteria) was highly lipolytic and proteolytic, and the lactic acid bacteria (Lactococcus and Leuconostoc) displayed very minor enzymatic ability. Hence, the composition of psychrotrophic bacterial flora in raw milk has an important role in the determination of milk quality. Monitoring the dominant psychrotrophic species responsible for the production of heat-stable proteolytic and lipolytic enzymes offers a sensitive and efficient tool for maintaining better milk quality in the milk industry.
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Przemieniecki, Sebastian Wojciech, Tomasz Paweł Kurowski, Karol Korzekwa, and Anna Karwowska. "The effect of psychrotrophic bacteria isolated from the root zone of winter wheat on selected biotic and abiotic factors." Journal of Plant Protection Research 54, no. 4 (December 30, 2014): 407–13. http://dx.doi.org/10.2478/jppr-2014-0061.
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Abstract The roots of winter wheat plants, cv. Mikon, grown in 45-year monoculture, were analysed in the study. Twenty-two bacterial isolates obtained from the rhizosphere, rhizoplane, and endorhizosphere that were capable of growth at 8°C and at 28°C, were selected for further analysis. The isolated psychrotrophs accounted for 25% of all bacteria present in the wheat rhizosphere and capable of growth at 8°C. Psychrotrophic bacteria were analysed at a temperature of 10°C and 28°C to determine their ability to inhibit the growth of pathogenic fungi, solubilise mineral phosphates, and to determine their ability to degrade chitin and cellulose. Similarity between the isolates was determined by Enterobacterial Repetitive Intergenic Consensus – Polymerase Chain Reaction (ERIC-PCR) and Random Amplification of Polymorphic DNA – Polymerase Chain Reaction (RAPD-PCR). The majority of isolated psychrotrophs inhibited the growth of pathogenic fungi and solubilised mineral phosphates at both incubation temperatures. Psychrotrophic bacteria exerted a two-fold stronger inhibitory effect on mycelial growth at 10°C than at 28°C. The growth of Fusarium culmorum and F. oxysporum was inhibited to the highest extent at 10°C and at 28°C, respectively. Phosphate solubilisation rates were higher at 28°C, particularly in the rhizosphere. Regardless of temperature, the bacteria exhibited low chitin-degrading potential, and none of the isolates was capable of degrading cellulose. A high similarity between the selected psychrotrophs was revealed by ERIC-PCR and RAPD- -PCR analyses. Based on RAPD-PCR, the analysed population was divided into a group of isolates obtained from the rhizosphere, and two groups comprising representatives of both the rhizoplane and the endorhizosphere. Due to their ability to grow over a wide temperature range and increase phosphorus availability to plants, and their antagonism against pathogens, psychrotrophic bacteria can be used to improve the growth and yield of cereal crops.
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Ahmed, S., S. MMR Sumon, MD Hossain, ABM Rubayet Bostami, and MM Rahman. "Prevalence of Psychrotrophic Bacteria During Frozen Storage of Raw Milk." Annals of Bangladesh Agriculture 24, no. 1 (February 8, 2021): 65–76. http://dx.doi.org/10.3329/aba.v24i1.51936.
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The study was aimed to enumerate the load of psychrotrophic bacteria in raw milk stored in freezer. Raw milk was collected from 18 different sized dairy farms located in Gazipur and Mymensingh district. From each location equal number (three of each) of small, medium or large farms were randomly selected. The raw milk samples were stored in freezer (-18 to -22 oC) for 28 days and analyzed for psychrotrophic bacterial load at every 7 days interval. For total viable count, bacteria was grown onto plate count agar at 70C for 10 days. Bacteria grown under such conditions referred as psychrotrophs. However, to determine the type of psychrotrophs selected colonies were grown further onto pseudomonas agar base and gram staining, oxidase, catalase and methyl red test for each isolate were perfomed. The psychrotrophic bacterial load in all the samples were low until 14 days of storage. However, from the third week of storage the bacterial load was observed to increase which reached to as high as 1.1 ± 2.3×107 cfu/mL at the end of the storage period (28 days). The milk samples obtained from large farms were lower (1.3×105 to 6.6×106) than that of medium (1.7×105 to 8.8×106) and small (2.0×105 to 1.1×107) type farms. The bacterial load was significantly (P<0.01) varied among the samples suggesting the heterogeneous management practices in dairy farms. All the morphological and biochemical tests confirmed the isolates as pseudomonas. Based on the present findings, it could be suggested that raw milk can store in the freezer maximum for two weeks in terms of psychrotrophic bacterial load.
Ann. Bangladesh Agric. (2020) 24(1) : 65-76
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Verhegghe, M., J. De Block, S. Van Weyenberg, L. Herman, M. Heyndrickx, and E. Van Coillie. "Effect of a pre-milking teat foam and a liner disinfectant on the presence of mesophilic and (proteolytic) psychrotrophic bacteria prior to milking." Journal of Dairy Research 86, no. 4 (November 2019): 432–35. http://dx.doi.org/10.1017/s0022029919000700.
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AbstractContamination of raw milk by psychrotrophs can lead to the production of heat-resistant proteases and subsequent spoilage of UHT milk. Therefore, this research communication evaluated the effect of a pre-milking teat disinfectant (active components: L-(+)-lactic acid and salicylic acid) and a liner disinfectant (active components: peracetic acid and hydrogen peroxide) on the number of mesophilic and (proteolytic) psychrotrophic bacteria prior to milking. The teat orifices of 10 cows were sampled using a swabbing procedure before and after treatment with a pre-milking teat disinfectant on six subsequent days. On the teat orifices, there was a small but statistically significant decrease in the psychrotrophic bacterial counts between pre and post dipping. No differences were observed for the mesophilic bacterial counts and proteolytic active counts. Liners were also sampled using swabs pre and post disinfection. No statistically significant decrease in the bacterial counts was observed post liner disinfection, although there was a numerical decrease. Sixty-two percent of the proteolytic psychrotrophs were pseudomonads: 16.5% of which were P. fragi, 14.3% P. lundensis, 10.0% P. fluorescens and 2.9% P. putida. Trinitrobenzenesulfonic acid (TNBS) analysis revealed a wide variety in proteolytic activity (from 0 to 55 µmol glycine/ml milk) and the presence of high producers. It can be concluded that there was only a minor effect of teat and liner disinfection on the psychrotrophic bacterial counts indicating that the measures presented did not result in a reduction of the targeted bacteria on teat orifices and liners.
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Schmiedt, Jhennifer Arruda, Leonardo Ereno Tadielo, Thiago Henrique Bellé, Carolina Dias Rodrigues, Maike Tais Maziero Montanhini, Vinicius Cunha Barcellos, and Luciano Dos Santos Bersot. "Influence of time and storage temperature on raw milk deteriorating microbiota." Brazilian Journal of Veterinary Research and Animal Science 57, no. 1 (April 24, 2020): e156883. http://dx.doi.org/10.11606/issn.1678-4456.bjvras.2020.156883.
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The quality of raw milk depends on initial microbial contamination and conditions of storage until industry processing. Considering the influence of time and storage temperature on raw milk microbiota, the objective of this work was to quantify and monitor the multiplication of these groups under different conditions. For this purpose, 41 samples of raw milk were collected immediately after milking, stored in the following storage conditions: 25 °C/2 h; 35 °C/2 h; 7 °C/24 h; 7 °C/48 h and 7 °C/60 h and analyses of aerobic mesophilic, psychrotrophic and proteolytic psychrotrophic microorganisms. The milk samples analyzed in the study had an initial mean count of mesophilic aerobes of 5.38 Log CFU/mL at Time Zero. The milk stored at 25 °C/2 h and 35 °C/2 h kept the mesophilic aerobic counts within the limits established by the legislation (5.48 Log CFU/mL), with an increase in counts of psychrotrophic and proteolytic microorganisms. When stored at 7 °C/24 h and 7 °C/48 h, the count of mesophiles exceeded the established parameters. A significant increase in the count of proteolytic psychrotrophs and psychrotrophs was also observed during storage at 7 °C from 24 h. The results of this study indicate that the temperature of 7 °C is not suitable for the milk conservation, since it was not able to control the microbial multiplication. Thus, the results contribute to the change in milk storage temperature proposed by the new Brazilian legislation.
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Henry, J. G., and D. Prasad. "Microbial Aspects of the Inuvik Sewage Lagoon." Water Science and Technology 18, no. 2 (February 1, 1986): 117–28. http://dx.doi.org/10.2166/wst.1986.0021.
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A facultative sewage lagoon in Inuvik, N.W.T. was studied in August (ice free) and November (ice covered) 1984. Emphasis was placed on the microbiological aspects and their relation to lagoon performance. Analyses performed included, pH, total alkalinity, total solids, suspended solids, volatile solids, COD and BOD5 determinations. The microbiological tests included total plate counts (20°C) and psychrotrophic counts (1°C). Results indicated that the Inuvik sewage lagoon system achieved removal efficiencies, ranging from 90% BOD5 removal in summer to about 80% in winter. The total bacterial count was found to decrease in the liquid of the primary cells in the winter, but the bacterial count in the secondary cell was similar under both winter and summer conditions. No significant difference existed in bacterial counts in the sludge samples between primary and secondary cells. The total bacterial number decreased by one order of magnitude in the winter in sludges from all cells. A shift from mesophilic to psychrotrophic bacteria occurred in the winter. The percentage of psychrotrophs increased from less than 1% to over 80% with the change in season. The role of psychrotrophs in lagoon performance is discussed.
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Picard, Catherine, Isabelle Plard, Dominique Rongdaux-Gaida, and Jean-Claude Collin. "Detection of proteolysis in raw milk stored at low temperature by an inhibition ELISA." Journal of Dairy Research 61, no. 3 (August 1994): 395–404. http://dx.doi.org/10.1017/s0022029900030818.
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SummaryAn inhibition ELISA (enzyme-linked immunosorbent assay) was developed for the determination of caseinomacropeptide (CMP) in order to estimate the proteolysis of κ-casein due to the enzymes of psychrotrophic bacteria in bulk raw milk. The CMP present in milk was quantified specifically by an antibody. The limit of detection was ∽ 0·1 μg/ml and the CV was < 10%. This method was used to study the proteolytic activity of three strains of psychrotrophic Pseudomonas fluorescens in raw milk and to analyse different raw milk samples supplied by four dairy plants. The proteolytic activity for different strains of psychrotrophs and for different milk samples varied considerably, but no correlation was established between the level of microbial flora and κ-casein proteolysis. It is thus not possible to determine the extent of proteolysis from the bacterial count alone. However, by CMP determination in bulk raw milk samples after 6 d storage at 4°C, the mean κ-casein proteolysis was ∽ 4%. Among the milk samples analysed that contained < 107 cfu psychrotrophs/ml, 30% exhibited a proteolysis of κ-casein < 0·5%, i.e. < 5μg CMP/ml.
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Berthelot, Deborah, L. G. Leduc, and G. D. Ferroni. "Temperature studies of iron-oxidizing autotrophs and acidophilic heterotrophs isolated from uranium mines." Canadian Journal of Microbiology 39, no. 4 (April 1, 1993): 384–88. http://dx.doi.org/10.1139/m93-056.
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Iron-oxidizing autotrophs and acidophilic heterotrophs were quantified at an incubation temperature of 18 °C in several samples obtained from the bioleaching areas of two uranium mines in Ontario, Canada. All samples were mine-water samples with temperatures in the range 13–18 °C. Iron-oxidizing autotrophs ranged from 2683 ± 377 to 245 000 ± 20 205 colony-forming units∙mL−1 and were always numerically superior to acidophilic heterotrophs, which ranged from 40 ± 8 to 9650 ± 161 colony-forming units∙mL−1. For each sample, approximately 20 isolates of each nutritional group were examined for the ability to grow at temperatures of 4, 18, 21, and 37 °C, respectively; overall, 559 isolates of iron-oxidizing bacteria (predominantly Thiobacillus ferrooxidans) and 252 acidophilic heterotrophic isolates were examined and categorized as 'broader temperature range psychrotrophs,' 'narrower temperature range psychrotrophs,' 'intermediates,' or mesophiles. Although psychrotrophic representatives of both groups were abundant, no psychrophiles were recovered from any of the samples. For the iron oxidizers, the temperature growth profiles of the isolates were similar from sample to sample. For the acidophilic heterotrophs, the temperature growth profiles varied considerably among samples.Key words: psychrotrophs; Thiobacillus ferrooxidans; uranium mines.
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RUAS-MADIEDO, PATRICIA, JUAN CARLOS BADA-GANCEDO, ESTRELLA FERNANDEZ-GARCIA, DOLORES GONZALEZ DE LLANO, and CLARA G. de los REYES-GAVILAN. "Preservation of the Microbiological and Biochemical Quality of Raw Milk by Carbon Dioxide Addition: A Pilot-Scale Study." Journal of Food Protection 59, no. 5 (May 1, 1996): 502–8. http://dx.doi.org/10.4315/0362-028x-59.5.502.
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Carbon dioxide treatment of refrigerated raw milk was evaluated as a method for extending storage life by inhibiting growth of psychrotrophic bacteria and other bacterial groups in raw milk. The effect of CO2 acidification followed by degasification and pasteurization on biochemical and microbiological properties of cold stored milk was studied on a pilot scale, Two CO2 treatments (acidification to pH 6.2 and to pH 6.0) were compared with a control (untreated) milk during 4 days of storage at 4°C. Total bacterial counts in the categories of milk established in this study were mainly determined by the proteolytic psychrotroph levels. The inhibitory capability of CO2 was greater in the low-quality than in the high-quality milk category. Acidification at pH 6.0 was more inhibitory than that at pH 6.2, especially against proteolytic psychrotrophs. Neither caseins nor whey proteins were affected by CO2 treatment and pasteurization. Organic acid (orotic, citric, uric, formic, acetic, propionic, and hippuric) concentrations did not change after CO2 treatment, cold storage, or the pasteurization process; the lactic acid content of CO2-treated milks remained constant during the refrigeration time but increased slightly in the control. In general, lower amounts of volatile compounds were produced in CO2-treated milks during refrigeration than in control milk. Ethanol and 2-propanol levels were most affected by degasification and pasteurization. Sensory evaluation revealed no significant differences between CO2-treated milk after degasification and pasteurization and the untreated milk used as control. It was concluded that degasification and pasteurization on a pilot scale eliminated CO2 from milk with minimum detrimental effects on its biochemical and sensory properties, making this process acceptable for milk preservation.
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TATINI, S. R., P. MEKALA, A. EL-HABAZ, and M. W. GRIFFITHS. "Rapid Detection of Psychrotrophic Bacteria In Manufacturing Grade Raw Milks." Journal of Food Protection 54, no. 11 (November 1, 1991): 861–67. http://dx.doi.org/10.4315/0362-028x-54.11.861.
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Methods to rapidly assess the bacteriological quality of raw milk were investigated. Whereas direct microscopic count, modified psychrotrophic plate count, and direct epifluorescent filter technique (DEFT) did not correlate well with initial psychrotrophic bacterial count of raw milk, improvements were obtained after preincubation of the milk samples. The best preincubation conditions were identified as 30°C for 6 h, 21°C for 10 h, 13°C for 15 h, 13°C for 20 h, or 7°C for 37 h. The “square root” equation was applied to the data, and a model was produced for predicting growth of the native microflora of raw milk. Using this equation, a DEFT count after preincubation of the milk at 21°C for 10 h could accurately predict the initial psychrotroph count and the count after storage of the milk at 6°C for 48 h.
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Santana, Elsa Helena Walter de, Lucas Lima Luiz, Pamela da Silva Pasquim, Leticia de Fatima Bertachi Pinto, Flavia de Almeida Bergonse Pereira, Gisele Bombardi Freitas Barone Gasparini, Elis Lorenzetti, Samera Rafaela Bruzaroski, and Josiane Ito Eleodoro. "Psychrotrophic microorganisms in raw milk and the cheese quality." Research, Society and Development 9, no. 9 (August 14, 2020): e127997217. http://dx.doi.org/10.33448/rsd-v9i9.7217.
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Psychrotrophic microorganisms, especially Pseudomonas spp., are present in the microbiota of refrigerated milk as they can grow at refrigeration temperatures irrespective of their optimal growth temperature. Psychrotrophic counts ranging from 105 to 108 CFU/mL in refrigerated raw milk effect cheese quality, since the synthesized thermoresistant enzymes affect the nutritional value, sensory properties, and texture. Cheese is the dairy product with the highest growth rate in the food industry in Brazil in recent years and meets the current consumption trends of nutritious and practical foods. The objective of this review was to address the importance and influence of the psychrotrophic raw milk microbiota on the quality and sensory properties of cheese. The enzymes produced by psychrotrophic microorganisms lead to taste changes, undesirable clotting times, increased concentrations of free fatty acids and free amino acids, and a reduced shelf-life, in addition to negatively affecting cheese yields. Proteases from psychrotrophs are also associated with slicing problems and progressive loss of the elasticity of cheese, a bitter taste, and increased clotting times of cheese produced with pasteurized milk. On the other hand, their lipases increase the clotting time and have a negative effect on the sensory properties by providing a rancid, soap, metallic, or oxidized smell and taste. The control of the psychrotrophic population found in refrigerated raw milk contributes to better cheese production yields and desirable texture and sensory properties, which extends the shelf-life of cheese and improves consumer acceptance.
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Ruas-Madiedo, Patricia, Juan Carlos Bada-Gancedo, Teresa Delgado, Miguel Gueimonde, and Clara G. de los Reyes-Gavilán. "Proteolysis in rennet-coagulated Spanish hard cheeses made from milk preserved by refrigeration and addition of carbon dioxide." Journal of Dairy Research 70, no. 1 (February 2003): 115–22. http://dx.doi.org/10.1017/s0022029902005952.
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On-farm refrigeration of milk reduces the growth rate of mesophilic bacteria so allowing longer storage time of raw milk before processing. However, refrigeration creates a selective pressure favouring the multiplication of psychrotrophic bacteria present as normal contaminants in raw milk. Psychrotrophs are killed by most of the currently employed pasteurization and sterilization treatments of milk but they can produce extracellular heat-stable proteinases and lipases, which are capable of degrading various milk components, affecting the storage-life of heat-processed milk and the quality of dairy products (Champagne et al. 1994; Shah, 1994).
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WANG, S. Y., T. R. DOCKERTY, R. A. LEDFORD, and J. R. STOUFFER. "Shelf-Life Extension of Vacuum Packaged Frankfurters Made from Beef Inoculated with Streptococcus lactis." Journal of Food Protection 49, no. 2 (February 1, 1986): 130–34. http://dx.doi.org/10.4315/0362-028x-49.2.130.
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Fresh beef, containing .5% dextrose, was inoculated with Streptococcus lactis, incubated for 3, 5 and 7 d at 7±1°C, and then used to manufacture frankfurters. The frankfurters were vacuum-packaged and stored for 1, 2, 4 and 6 weeks at 3±1°C. Microbial quality was evaluated by examining frankfurters for aerobic and psychrotrophic counts at the end of each storage period. The level of nisin, an antibiotic substance produced by this strain of S. lactis, was also monitored in fresh meat and processed products. During the incubation period, no appreciable reduction in pH occurred in fresh meat. Growth of psychrotrophs was slower in treated than untreated fresh meat, but whether this was due to presence of nisin or competition resulting from the heavy inoculation with S. lactis is unclear. Before and after processing, nisin levels in the 5- and 7-d incubation-treated groups were higher than in the 3-d group, and all treated groups had higher nisin levels than untreated groups. Little difference in aerobic and psychrotrophic growth was noted with storage time between treated and untreated groups for the 3-d incubation period, but well defined differences were noted in the 5- and 7-d incubation groups, with aerobic growth in treated groups being significantly slowed through the 6-week storage period, and psychrotrophs being 1 to 1.5 log cycles lower at the 6-week evaluation. The growth patterns suggest that nisin played a role in the reduced growth rate of bacteria in treated groups.
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SEGNER, WAYNE P. "Spoilage of Pasteurized Crabmeat by a Nontoxigenic Psychrotrophic Anaerobic Sporeformer." Journal of Food Protection 55, no. 3 (March 1, 1992): 176–81. http://dx.doi.org/10.4315/0362-028x-55.3.176.
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Microbial spoilage occurred in machine picked, pasteurized crabmeat of the Blue Crab that had been canned in Maryland in the fall of 1989 and later in 1990. Spoilage in 1989 was first detected after hurricane Hugo, although the relationship between the onset of spoilage and the hurricane, if any, is unclear. The sole spoilage organism was identified as a nontoxigenic psychrotrophic anaerobic sporeformer. The pattern of spoilage suggested a build-up of this organism in machine picking operations. Spoilage was noticeably absent from hand picked pasteurized crabmeat from the same plant. While the psychrotrophic anererobic sporeformer, in some respects, culturally resembles the psychrotroph Clostridium arcticum, the crabmeat spoilage organism may be an unrecognized species. Spores of the crabmeat isolate heated in neutral phosphate buffer gave a thermal resistance curve from survivor data characterized by a D185 (85°C) equal to 15.6 min and a z-value equal to 17.8°F (9.9°C). In crabmeat, D-values calculated from fractional survivor endpoint data gave a thermal resistance curve characterized by an extrapolated D185 equal to 35 min and a z-value equal to 11.6°F (6.5°C). From these data, a process equivalent to = = 31 was incapable of destroying even a reasonably low number of spores of the psychrotrophic anaerobe in pasteurized crabmeat.
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CARR, T. P., and J. A. MARCHELLO. "Microbial Changes of Precooked Beef Slices as Affected by Packaging Procedure." Journal of Food Protection 49, no. 7 (July 1, 1986): 534–36. http://dx.doi.org/10.4315/0362-028x-49.7.534.
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Precooked beef slices from top round roasts were used in replicate trials to determine the effects of packaging treatment upon microbial growth during retail storage. Roasts were dry roasted to an internal temperature of 60°C, cooled for 1 h, then sliced (3 to 4 mm) and packaged in vacuum or an atmosphere containing 15% CO2/40% O2/45% N2. Slices were stored either at 2, 6 or 10°C for up to 21 d. Enumeration of psychrotrophs, mesophiles, thermophiles and molds was determined after 0, 7, 14 and 21 d of storage. At 6 and 10°C storage, psychrotrophic organisms did not increase (P<0.05) on vacuum packaged beef slices during the 21-d storage period, but did increase (P<0.05) on slices stored in the gas mixture. Conversely, at 2°C storage, psychrotrophs increased (P<0.05) in vacuum at day 21 but not under gas atmosphere storage. Mesophiles did not increase significantly at 2 or 6°C storage within either packaging treatment during 21 d of storage. Mold growth did not occur on slices stored at 2°C.
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GONZÁLEZ, CÉSAR-JAVIER, TERESA-MARÍA LÓPEZ-DÍAZ, MARÍA-LUISA GARCÍA-LÓPEZ, MIGUEL PRIETO, and ANDRÉS OTERO. "Bacterial Microflora of Wild Brown Trout (Salmo trutta), Wild Pike (Esox lucius), and Aquacultured Rainbow Trout (Oncorhynchus mykiss)." Journal of Food Protection 62, no. 11 (November 1, 1999): 1270–77. http://dx.doi.org/10.4315/0362-028x-62.11.1270.
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Initial numbers of bacteria associated with wild (brown trout and pike) and cultured (rainbow trout) freshwater fish as well as with the water in which they were caught were determined. Subsequently, a total of 979 randomly selected isolates were characterized and identified to the genus level. For all counts performed (aerobes, psychrotrophs, anaerobes, Enterobacteriaceae, and enterococci), no significant differences were observed in water samples, the highest level corresponding to psychrotrophs in pike environments (4.23 × 103 CFU/ml). Overall, the skin and intestinal content of brown trout were the most contaminated, while rainbow trout specimens (gills and gut) yielded the lowest numbers. For all bacterial groups, pike gills had the highest numbers. Counts for all of the sampling sites compare well with findings in other temperate geographical environments. Biological characteristics (feeding and skin properties) and the use of antimicrobials in aquaculture might have influenced these results. Motile and nonmotile aerobic gram-negative bacteria together with Enterobacteriaceae accounted for 50 to 70% of the psychrotrophs isolated from water. Micrococcaceae, lactic acid bacteria, Bacillus, and coryneforms were also found. The groups represented in psychrotrophic isolates from the outer surfaces do not reflected those detected in water, so it was common that those organisms recovered in significant numbers from fish were not detected in surrounding habitat of the fish. Motile aeromonads and Carnobacterium were the dominant psychrotrophs in the guts of pike and brown trout, respectively. The intestinal content of reared fish gave a high incidence of Bacillus and coryneforms, while Enterobacteriaceae was absent. Again, rearing practices could have influenced this finding. Listeria monocytogenes was not detected in any of the examined samples. Two strains of Salmonella, which belonged to the same serovar and lysotype, were recovered from pond-water samples taken from one facility on different sampling days. From the gut of a pike specimen and from the pike's environment, two Plesiomonas shigelloides strains of different serovars were recovered. These latter four strains were resistant to a considerable number of antimicrobial compounds (multiple antibiotic resistance indices > 0.2).
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Munsch-Alatossava, Patricia, and Tapani Alatossava. "The darker side of raw milk spoiling psychrotrophs." Suomen Maataloustieteellisen Seuran Tiedote, no. 21 (January 31, 2006): 1–5. http://dx.doi.org/10.33354/smst.76046.
Full textAbstract:
In general, the quality of raw milk and of dairy products has been considerably improved by the refrigeration on farms, and in processing plants. Unfortunately, the current practices for the collection and the storage of the raw milk favour the growth of psychrotrophic bacteria, able to grow below 7°C, regardless of their optimal growth temperature. Besides their rapid growth ability in refrigerated milk, psychrotrophs produce heat stable extracellular proteases, lipases, phospholipases. Pseudomonas spp. constitute the predominant microorganisms limiting the shelf life of processed fluid at 4°C. In our studies, 64 isolates, selected from 13 raw-milk samples in Finland (that originate from farm, lorry or silo tanks) were characterized by the determination of their spoilage and phenotypic features. Phenotypic characterization of the isolates was mainly performed with API 20NE and BIOLOG GN2 identification systems; the results were system-dependent, although the presence of representatives of the Pseudomonas genus (for the majority of the isolates) was suggested by both systems; moreover, a significant number of isolates were partially identified as members of Stenotrophomonas, Burkholderia and Acinetobacter genera. All three genera comprise species considered in recent reports as emerging pathogens, that carry innate resistance to antibiotics. There is a general consensus that the widespread use of antibiotics has imposed a strong selective pressure that contributed to the emergence of multidrug resistant microorganisms. In the context of the increasing prevalence of antibiotic resistant bacteria, we evaluated the distribution of antibiotic resistant traits among the group of psychrotrophs retrieved from the raw milk samples The results obtained, with the ATB®PSE system (composed of a panel of 17 β-lactams and non-β-lactams antibiotics, representatives of 5 classes), designed to investigate the pseudomonads susceptibility/resistance, revealed that the majority of raw milk psychrotrophs, besides exhibiting spoilage features, also harboured antibiotic multiresistant traits.
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SENNE, M. M., and S. E. GILLILAND. "Antagonistic Action of Cells of Lactobacillus delbrueckii subsp. lactis against Pathogenic and Spoilage Microorganisms in Fresh Meat Systems†." Journal of Food Protection 66, no. 3 (March 1, 2003): 418–25. http://dx.doi.org/10.4315/0362-028x-66.3.418.
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Cells of Lactobacillus delbrueckii subsp. lactis RM2-5 were added to various meat model systems that had been inoculated with Escherichia coli O157:H7 or Salmonella Typhimurium to determine whether these lactobacilli were antagonistic to the pathogens during storage at 5°C. Experiments in which L. delbrueckii subsp. lactis RM2-5 was directly applied to the surfaces of beefsteaks resulted in significant (P < 0.05) reductions in the growth of psychrotrophs and coliforms plus a slight decrease in the numbers of E. coli O157:H7 over time relative to those for control samples to which no lactobacilli had been added. Experiments involving the direct application of L. delbrueckii subsp. lactis RM2-5 to the surfaces of freshly slaughtered beef and pork carcass samples inoculated with either E. coli O157:H7 or Salmonella Typhimurium showed significant (P < 0.05) declines in numbers of the pathogens as well as a reduction in the growth of psychrotrophs during storage at 5°C for 6 days. The results of the experiments suggest that lactobacillus cultures have potential for use in an intervention technology for the control of foodborne pathogens, especially on the surfaces of beef and pork carcasses. The results of this study also suggest that an extension of the shelf life of meat can result from the decreased growth of psychrotrophic spoilage organisms.
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Jovanovic, Jelena, Svitlana Tretiak, Katrien Begyn, and Andreja Rajkovic. "Detection of Enterotoxigenic Psychrotrophic Presumptive Bacillus cereus and Cereulide Producers in Food Products and Ingredients." Toxins 14, no. 4 (April 16, 2022): 289. http://dx.doi.org/10.3390/toxins14040289.
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In the last decade, foodborne outbreaks and individual cases caused by bacterial toxins showed an increasing trend. The major contributors are enterotoxins and cereulide produced by Bacillus cereus, which can cause a diarrheal and emetic form of the disease, respectively. These diseases usually induce relatively mild symptoms; however, fatal cases have been reported. With the aim to detected potential toxin producers that are able to grow at refrigerator temperatures and subsequently produce cereulide, we screened the prevalence of enterotoxin and cereulide toxin gene carriers and the psychrotrophic capacity of presumptive B. cereus obtained from 250 food products (cereal products, including rice and seeds/pulses, dairy-based products, dried vegetables, mixed food, herbs, and spices). Of tested food products, 226/250 (90.4%) contained presumptive B. cereus, which communities were further tested for the presence of nheA, hblA, cytK-1, and ces genes. Food products were mainly contaminated with the nheA B. cereus carriers (77.9%), followed by hblA (64.8%), ces (23.2%), and cytK-1 (4.4%). Toxigenic B. cereus communities were further subjected to refrigerated (4 and 7 °C) and mild abuse temperatures (10 °C). Overall, 77% (94/121), 86% (104/121), and 100% (121/121) were able to grow at 4, 7, and 10 °C, respectively. Enterotoxin and cereulide potential producers were detected in 81% of psychrotrophic presumptive B. cereus. Toxin encoding genes nheA, hblA, and ces gene were found in 77.2, 55, and 11.7% of tested samples, respectively. None of the psychrotrophic presumptive B. cereus were carriers of the cytotoxin K-1 encoding gene (cytK-1). Nearly half of emetic psychrotrophic B. cereus were able to produce cereulide in optimal conditions. At 4 °C none of the examined psychrotrophs produced cereulide. The results of this research highlight the high prevalence of B. cereus and the omnipresence of toxin gene harboring presumptive B. cereus that can grow at refrigerator temperatures, with a focus on cereulide producers.
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Janiyani, Kamala L., and M. K. Ray. "Cloning, Sequencing, and Expression of the Cold-Inducible hutU Gene from the Antarctic Psychrotrophic Bacterium Pseudomonas syringae." Applied and Environmental Microbiology 68, no. 1 (January 2002): 1–10. http://dx.doi.org/10.1128/aem.68.1.1-10.2002.
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ABSTRACT A promoter-fusion study with a Tn 5-based promoter probe vector had earlier found that the hutU gene which encodes the enzyme urocanase for the histidine utilization pathway is upregulated at a lower temperature (4° C) in the Antarctic psychrotrophic bacterium Pseudomonas syringae. To examine the characteristics of the urocanase gene and its promoter elements from the psychrotroph, the complete hutU and its upstream region from P. syringae were cloned, sequenced, and analyzed in the present study. Northern blot and primer extension analyses suggested that the hutU gene is inducible upon a downshift of temperature (22 to 4°C) and that there is more than one transcription initiation site. One of the initiation sites was specific to the cells grown at 4°C, which was different from the common initiation sites observed at both 4 and 22°C. Although no typical promoter consensus sequences were observed in the flanking region of the transcription initiation sites, there was a characteristic CAAAA sequence at the −10 position of the promoters. Additionally, the location of the transcription and translation initiation sites suggested that the hutU mRNA contains a long 5′-untranslated region, a characteristic feature of many cold-inducible genes of mesophilic bacteria. A comparison of deduced amino acid sequences of urocanase from various bacteria, including the mesophilic and psychrotrophic Pseudomonas spp., suggests that there is a high degree of similarity between the enzymes. The enzyme sequence contains a signature motif (GXGX2GX10G) of the Rossmann fold for dinucleotide (NAD+) binding and two conserved cysteine residues in and around the active site. The psychrotrophic enzyme, however, has an extended N-terminal end.
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Chan, Yiu-Kwok. "Temperature response of an associative N2-fixing Pseudomonas species in pure culture." Canadian Journal of Microbiology 37, no. 9 (September 1, 1991): 715–18. http://dx.doi.org/10.1139/m91-122.
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The growth rate and nitrogenase (acetylene reduction) activity of a pseudomonad isolated from the rhizosphere of the grass species Deschampsia caespitosa were investigated in the 0–35 °C temperature range. Growth was detected from 5 to 30 °C with or without provision of fixed N and its optimum growth temperature was about 25 °C, establishing its psychrotrophic response to temperature. Maximum nitrogenase activity was also found at about 25 °C. Low but significant nitrogenase activity was detected below 15 °C. This organism was confirmed to be a microaerobic diazotroph and it was sensitive to a dissolved O2 concentration of ca. 12 μM. It is probably dependent on the appropriate environment in the rhizosphere of the host plant in order to persist with sustained nitrogenase activity during cold and dormant periods. Key words: nitrogen fixation, Pseudomonas, psychrotroph, temperature.
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DELAQUIS, P. J., C. GARIÉPY, and FRANCE DUSSAULT. "Bacteriology of Hot and Cold Boned Pork Preblends." Journal of Food Protection 55, no. 11 (November 1, 1992): 910–12. http://dx.doi.org/10.4315/0362-028x-55.11.910.
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Ground pork and preblends containing 2% NaCl or 2% NaCl plus 200 ppm NaNO2 were prepared from hot (HB) and cold (CB) boned pork in a commercial slaughtering plant. Total aerobic mesophiles, psychrotrophs, Enterobacteriaceae, salt tolerant, and lactic acid bacteria were enumerated in freshly ground meat and in preblends stored for 1 week at 2°C. Boning method had no effect on mesophillic, psychrotrophic, and salt tolerant counts in freshly ground meat, but Enterobacteriaceae and lactic acid bacteria were found in higher numbers in CB than HB meat (P < 0.05). Addition of salt plus nitrite led to the inhibition of most bacterial groups, although lactic acid bacteria were found in higher numbers in HB preblends after one week of storage (P < 0.05). The data revealed that HB pork preblends of excellent bacteriological quality and stability can be produced in an industrial context.
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ŚMIECIŃSKA, KATARZYNA. "Microbiological quality of beef stored under different modified atmospheres." Medycyna Weterynaryjna 76, no. 12 (2020): 6471–2020. http://dx.doi.org/10.21521/mw.6471.
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The aim of this study was to analyze changes in the microbiological quality of Longissimus lumborum (LL) muscles collected from young Polish Holstein-Friesian Black-and-White (PHF BW) bulls and stored for 7, 14, and 21 days under different modified atmospheres (MA) (vacuum, 80% O2 + 20% CO2, 60% O2 + 30% CO2 + 10% N2, 40% CO2 + 60% N2, 30% CO2 + 70% Ar). Before and after the specified storage periods, crosssectional samples of the LL muscle were collected under aseptic conditions to determine total microbial counts, and the total counts of psychrotrophic bacteria and mesophilic lactic acid bacteria. The effects of storage time and MA composition on changes in the parameters analyzed were evaluated, and the effectiveness of argon in delaying microbial growth in cold-stored beef was determined. Between days 7 and 14 of storage, total microbial counts were lowest in meat packaged under the MA composed of 30% CO2 + 70% Ar, whereas between days 14 and 21 they were lowest in both MA packages containing O2. The greatest increase in total microbial counts between days 7 and 14 of storage was noted in the MAs containing O2, and between days 14 and 21 of storage in the MA containing Ar. Beef stored for 7 days in the MA containing 60% O2 was characterized by the lowest total microbial counts, whereas the highest total microbial counts were noted in samples stored for 14 days in the MA containing 80% O2. Between days 7 and 14 of storage, the counts of psychrotrophic bacteria increased significantly in all MAs. Between days 14 and 21 of storage, the counts of psychrotrophic bacteria did not increase in meat samples packaged under vacuum or the MA composed of 80% O2 + 20% CO2. The counts of psychrotrophs were significantly lower in beef stored for 7 days in the oxygen-free MAs than they were in both MA packages containing O2. The counts of psychrotrophic bacteria were significantly lower in beef stored for 14 days in the MA containing Ar, compared with samples packaged under vacuum and the MA containing 80% O2. Gas composition in MA packaging had no significant effect on total microbial counts or the counts of psychrotrophic bacteria in meat stored for 21 days. Between days 14 and 21 of storage, the counts of lactic acid bacteria did not increase significantly only in meat packaged in the MAs composed of 60% O2 + 30% CO2 + 10% N2 and 40% CO2 + 60% N2. After 7 days of storage, the counts of lactic acid bacteria were higher in beef packaged in oxygen-free MAs than they were in both MA packages containing O2. After 14 days of storage, the counts of lactic acid bacteria were higher in meat packaged in the MA composed of 80% O2 + 20% CO2 than they were in the other MAs. Beef samples stored for 21 days under the MA composed of 80% O2 + 20% CO2 were characterized by significantly lower counts of lactic acid bacteria, compared with samples stored under the other MAs, except for the MA composed of 40% CO2 + 60% N2. It can be concluded that beef can be stored in the MA composed of 30% CO2 + 70% Ar for shorter periods of time (up to 14 days). The modified atmosphere composed of 30% CO2 + 70% Ar contributed to slower microbial growth in meat and resulted in lower counts of psychrotrophs and lactic acid bacteria, relative to the other samples. However, there is a need for further research on different concentrations of argon in MA packages to confirm that this gas can effectively delay microbial growth in beef. Meat stored for 14 days in the MA composed of 80% O2 + 20% CO2 was characterized by the lowest microbiological quality. The composition of MAs had a minor influence on the growth rates of the microbial groups analyzed in beef stored for 21 days; certain changes were observed only in the counts of lactic acid bacteria.
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Sallam, Khaled, Samir Abd-elghany, E. Youssef, and A. Zein. "ANTIBACTERIAL AND ANTIOXIDANT EFFECT OF BLACK SEED OIL AND BLACK SEED POWDER ON BEEF MINCED MEAT." Mansoura Veterinary Medical Journal, no. 19 (July 7, 2018): 27–37. http://dx.doi.org/10.35943//mvmj.2018.19.1515.
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he aim of this study is to determine the effect of the addition of different levels of black seed oil and black seed powder to beef meat ball on the quality and shelf life of beef patties. During the studies lipid oxidation, number of aerobic bacteria, psychrotrophes and entero bactriacea of raw minced beef stored under refrigeration conditions for 24days were determinated. Results showed that the addition of BSO, BSP have significant decrease in APC for 10 days after that no significant decrease in count, treatment of meat balls with black seed oil (at concentrations 1, 2, 3%) induce significant decrease in enterobacteriaceae count at different period of storage, however a ddition of black seed powder (at concentrations 2, 4, 6%) induced significant increase in psychrotrophs count at different period of storage. The outcomes of this research is that addition of black seed oil and black seed powder to beef meat does not increase shelf life of meat. However, This addition has antioxidant effect.
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Karolenko, Caitlin, Udaya DeSilva, and Peter M. Muriana. "Microbial Profiling of Biltong Processing Using Culture-Dependent and Culture-Independent Microbiome Analysis." Foods 12, no. 4 (February 16, 2023): 844. http://dx.doi.org/10.3390/foods12040844.
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Biltong is a South African air-dried beef product that does not have a heat lethality step, but rather relies on marinade chemistry (low pH from vinegar, ~2% salt, spices/pepper) in combination with drying at ambient temperature and low humidity to achieve microbial reduction during processing. Culture-dependent and culture-independent microbiome methodologies were used to determine the changes in the microbial community at each step during biltong processing through 8 days of drying. Culture-dependent analysis was conducted using agar-based methods to recover viable bacteria from each step in the biltong process that were identified with 16S rRNA PCR, sequencing, and BLAST searching of the NCBI nucleotide database. DNA was extracted from samples taken from the laboratory meat processing environment, biltong marinade, and beef samples at three stages of processing (post-marinade, day 4, and day 8). In all, 87 samples collected from two biltong trials with beef obtained from each of three separate meat processors (n = six trials) were amplified, sequenced with Illumina HiSeq, and evaluated with bioinformatic analysis for a culture-independent approach. Both culture-dependent and independent methodologies show a more diverse population of bacteria present on the vacuum-packaged chilled raw beef that reduces in diversity during biltong processing. The main genera present after processing were identified as Latilactobacillus sp., Lactococcus sp., and Carnobacterium sp. The high prevalence of these organisms is consistent with extended cold-storage of vacuum-packaged beef (from packers, to wholesalers, to end users), growth of psychrotrophs at refrigeration temperatures (Latilactobacillus sp., Carnobacterium sp.), and survival during biltong processing (Latilactobacillus sakei). The presence of these organisms on raw beef and their growth during conditions of beef storage appears to ‘front-load’ the raw beef with non-pathogenic organisms that are present at high levels leading into biltong processing. As shown in our prior study on the use of surrogate organisms, L. sakei is resistant to the biltong process (i.e., 2-log reduction), whereas Carnobacterium sp. demonstrated a 5-log reduction in the process; the recovery of either psychrotroph after biltong processing may be dependent on which was more prevalent on the raw beef. This phenomenon of psychrotrophic bloom during refrigerated storage of raw beef may result in a natural microbial suppression of mesophilic foodborne pathogens that are further reduced during biltong processing and contributes to the safety of this type of air-dried beef.
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CARR, T. P., and J. A. MARCHELLO. "Growth of Aerobic Psychrotrophs and Color Changes of Precooked Beef Slices as Affected by Packaging Procedure1." Journal of Food Protection 50, no. 9 (September 1, 1987): 733–36. http://dx.doi.org/10.4315/0362-028x-50.9.733.
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Precooked beef slices from top round roasts were used in replicate trials to determine the effects of packaging treatment upon shelf-life characteristics (microbial growth and color attributes) during retail storage. Roasts were dry-roasted to an internal temperature of 60°C, cooled for 1 h, then sliced (3–4 mm). Slices were packaged in: (a) vacuum; (b) 15% CO2, 40% O2, 45% N2; (c) 15% CO2, 20% O2, 65% N2; or (d) 15% CO2, 10% O2, 75% N2 and held at 4°C for up to 18 d. Enumeration of microorganisms and determination of color attributes were done at 0, 3, 6, 9, 12, 15, and 18 d of storage. Psychrotrophic counts were higher (P<.05) on slices stored 9–18 d in atmospheres containing ambient (20%) oxygen level as compared to the other packaging treatments. Vacuum packaging exhibited a greater lag phase for psychrotrophs. Vacuum packaged slices maintained a superior cooked beef color for 18 d and had greater (P<.05) chroma readings, indicating a greater color intensity.
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FERNANDES, CUSTY F., GEORGE J. FLICK, JUAN L. SILVA, and THOMAS A. McCASKEy. "Influence of Processing Schemes on Indicative Bacteria and Quality of Fresh Aquacultured Catfish Filletst†." Journal of Food Protection 60, no. 1 (January 1, 1997): 54–58. http://dx.doi.org/10.4315/0362-028x-60.1.54.
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Fresh aquacultured catfish fillets were obtained from three processors using different processing protocols in summer, autumn, winter, and spring and evaluated for microbial quality. Twenty freshly processed fillets were randomly selected and each fillet was placed in a sterile polyethylene bag. The fillets were transported on ice-pack overnight by air immediately after processing. Five fillets were randomly selected for microbial assays. Each fillet was weighed and an equal volume of sterile 0.1 % peptone water at 0 to 1°C was added aseptically. The fillet was massaged (or rinsed) for 120 s and the rinse was used to determine microbial quality. Aerobes (incubation at 35°C for 48 h) and psychrotrophs (incubation at 20°C for 96 h) were enumerated using 3M Petrifilm™ Aerobic Count plates. Escherichia coli (incubation at 35°C for 24 to 48 h) and total coliforms (incubation at 35°C for 24 to 48 h) were enumerated on 3M Petrifilm™ E. coli Count plates. Staphylococcus aureus counts were determined on Baird-Parker agar (incubation at 35°C for 48 h). Significant differences (P ≤ 0.05) in aerobic, psychrotrophic, total coliform, E. coli, and S. aureus counts due to temperature effects during production and variations in processing protocols were observed. E. coli and S. aureus counts were significantly different during the four seasons. E. coli and S. aureus counts were high during summer and low during winter weather. There was a significant difference (P ≤ 0.05) in aerobic, psychrotrophic, and total coliform counts among the three processors during warm weather; however, these differences were significantly (P≤ 0.05) reduced in cold weather.
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Ercolini, Danilo, Federica Russo, Antonella Nasi, Pasquale Ferranti, and Francesco Villani. "Mesophilic and Psychrotrophic Bacteria from Meat and Their Spoilage Potential In Vitro and in Beef." Applied and Environmental Microbiology 75, no. 7 (February 5, 2009): 1990–2001. http://dx.doi.org/10.1128/aem.02762-08.
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ABSTRACT Mesophilic and psychrotrophic populations from refrigerated meat were identified in this study, and the spoilage potential of microbial isolates in packaged beef was evaluated by analyzing the release of volatile organic compounds (VOC) by gas chromatography-mass spectrometry (GC/MS). Fifty mesophilic and twenty-nine psychrotrophic isolates were analyzed by random amplified polymorphic DNA-PCR, and representative strains were identified by 16S rRNA gene sequencing. Carnobacterium maltaromaticum and C. divergens were the species most frequently found in both mesophilic and psychrotrophic populations. Acinetobacter baumannii, Buttiauxella spp. and Serratia spp. were identified among the mesophilic isolates, while Pseudomonas spp. were commonly identified among the psychrotrophs. The isolates were further characterized for their growth at different temperatures and their proteolytic activity in vitro on meat proteins extracts at 7°C. Selected proteolytic strains of Serratia proteamaculans, Pseudomonas fragi, and C. maltaromaticum were used to examine their spoilage potential in situ. Single strains of these species and mixtures of these strains were used to contaminate beef chops that were packed and stored at 7°C. At time intervals up to 1 month, viable counts were determined, and VOC were identified by GC/MS. Generally, the VOC concentrations went to increase during the storage of the contaminated meats, and the profiles of the analyzed meat changed dramatically depending on the contaminating microbial species. About 100 volatiles were identified in the different contaminated samples. Among the detected volatiles, some specific molecules were identified only when the meat was contaminated by a specific microbial species. Compounds such as 2-ethyl-1-hexanol, 2-buten-1-ol, 2-hexyl-1-octanol, 2-nonanone, and 2-ethylhexanal were detectable only for C. maltaromaticum, which also produced the highest number of aldehydes, lactones, and sulfur compounds. The highest number of alcohols and ketons were detected in the headspace of meat samples contaminated by P. fragi, whereas the highest concentrations of some alcohols, such as 1-octen-3-ol, and some esters, such as isoamyl acetate, were produced by S. proteamaculans. In conclusion, different microbial species can contribute to meat spoilage with release of different volatile compounds that concur to the overall quality decrease of spoiling meat.
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García-Armesto, María-Rosario, Miguel Prieto, Carlos Alonso, María-Luisa GarcíLópez, María-Camino García-Fernández, and Andrés Otero. "Numerical taxonomy of psychrotrophic bacteria isolated from raw ewes' milk." Journal of Dairy Research 60, no. 3 (August 1993): 371–83. http://dx.doi.org/10.1017/s0022029900027710.
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SummaryA total of 204 psychrotrophic isolates from raw ewes' milk (hand and machine milked) were identified by conventional methods. In addition, a numerical taxonomic study was conducted on 180 of these isolates and 19 reference strains. Three of the isolates were yeasts. Using identification schemes, 54 isolates were assigned to genera of Gram-negative aerobic rods (Pseudomonas, Acinetobacter, Flavobacterium, MoraxellaandPsychrobacter), 48 were Enterobacteriaceae (Entero-bacter, Hafnia, Klebsiella, CitrobacterandSerratia) and one was identified asAeromonas hydrophila. The 98 Gram-positive isolates were identified asEnterococcus, Streptococcus, Leuconostoc, Lactococcus, Bacillus, Staphylococcus, Micrococcus, Aureobacterium, KurthiaandMicrobacterium. At the 82% similarity level (SSM), 18 clusters were formed. Cluster I included 34 strainsof Lactococcus, StreptococcusandLeuconostoc. Most of the 35 strains in cluster II wereEnterococcus. Clusters III and IV were identified asKurthiaandMicrobacteriumrespectively. Cluster V was identified asAureobacteriumand cluster VI consisted of coagulase-negative staphylococci. Gram-negative isolates formed 12 clusters:Aeromonas(one cluster), Enterobacteriaceae (two clusters),Flavobacterium(two clusters),PseudomonasandPsychrobacter immobilis(three clusters) andAcinetobacter(four clusters). Non-motile variants ofPs. fragiwere found.Enterococcusand Enterobacteriaceae did not have significant spoilage properties. As expected, Gram-negative aerobic rods were proteolytic and/or lipolytic even at low temperature. Contamination with certain types of psychrotrophs (Gram-negative aerobic rods and enterococci) seemed to be associated with the milking method. The isolate ofAes. hydrophilahad properties associated with virulence.
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Barreto de Deus, Tamiles, Ludmilla Santana Soares Barros, Ricardo Mendes da Silva, Wanessa Karine da Silva Lima, Danuza das Virgens Lima, and Adriana dos Santos Silva. "Staphylococcus aureus and Escherichia coli in Curd Cheese Sold in the Northeastern Region of South America." International Journal of Microbiology 2017 (2017): 1–6. http://dx.doi.org/10.1155/2017/8173741.
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The present study evaluated the microbiological and sanitary quality of curd cheese sold on the beaches of the Itaparica Island, Brazil, and verified whether a correlation exists between the commercialization conditions and the microbiological data. The research was performed between December 2015 and March 2017. Sixty samples of rennet-containing cheese were collected to estimate the populations of mesophylls, psychrotrophic microorganisms, mold and yeast, Staphylococcus aureus, total coliforms, and Escherichia coli. An observational analysis was performed during the collection, using a checklist to verify the sellers’ sanitary conditions and cheese marketing. A high nonconformity index was registered regarding aspects in the checklist. In the microbiological analyses, the number of mesophylls in raw and roasted samples ranged from 7,88 to 14,82 log CFU/mL, and those of psychrotrophs ranged from 2,80 to 3,84 log CFU/mL. Meanwhile, mold and yeast levels in the samples ranged from 8,06 to 5,54 log CFU/mL, S. aureus was detected at levels from 3,24 to 4,94 log CFU/mL, and the total coliform counts ranged from 4,48 to 7,18 log CFU/mL. The number of E. coli specimens ranged from 2,96 to 5,75 log CFU/mL. Microbial insecurity was noted for commercialized curd cheese, and the need for intervention was indicated.
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Chauret, Christian, Colin I. Mayfield, and William E. Inniss. "Biotransformation of di-n-butyl phthalate by a psychrotrophicPseudomonas fluoresceins(BGW) isolated from subsurface environment." Canadian Journal of Microbiology 41, no. 1 (January 1, 1995): 54–63. http://dx.doi.org/10.1139/m95-007.
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A psychrotrophic denitrifying Pseudomonas fluorescens was isolated from an unamended subsurface microcosm incubated at 10 °C for 43 days. This pseudomonad transformed di-n-butyl phthalate at 10 °C in a chemically defined medium under both aerobic and anaerobic conditions using NO3−as the terminal electron acceptor. Biotransformation of di-n-butyl phthalate by the pseudomonad appeared to take place only in the stationary and decline phases of growth and was correlated to the amount of biomass. Studies with growth inhibitors and outer membrane permeabilizers suggested that the outer membrane of the cells in the stationary and decline phases was possibly made more permeable to di-n-butyl phthalate, which would explain the biotransformation pattern. Butanol was produced and utilized by cells that transformed di-n-butyl phthalate, implying that the side chains were hydrolyzed by means of an esterase. An esterase was detected by staining after isolation by gel electrophoresis. The esterase was not induced by di-n-butyl phthalate and was present at various stages of growth. The isolated pseudomonad did not grow with phthalic acid as the sole source of carbon, indicating that di-n-butyl phthalate was not mineralized by this bacterium.Key words: biotransformation, di-n-butyl phthalate, psychrotroph, pseudomonad.
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PAL, AMIT, THEODORE P. LABUZA, and FRANCISCO DIEZ-GONZALEZ. "Evaluating the Growth of Listeria monocytogenes in Refrigerated Ready-to-Eat Frankfurters: Influence of Strain, Temperature, Packaging, Lactate and Diacetate, and Background Microflora." Journal of Food Protection 71, no. 9 (September 1, 2008): 1806–16. http://dx.doi.org/10.4315/0362-028x-71.9.1806.
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This research was conducted to study the growth of Listeria monocytogenes inoculated on frankfurters stored at different conditions as a basis for a safety-based consume by shelf life date label. Three L. monocytogenes strains were separately inoculated at 10 to 20 CFU/cm2 onto frankfurters that were previously formulated with or without high pressure and with or without added 2% potassium lactate (PL) and 0.2% sodium diacetate (SD). Inoculated frankfurters were air or vacuum packaged; stored at 4, 8, or 12°C; and L. monocytogenes and psychrotrophic plate counts were determined for 90, 60, and 45 days, respectively, or until the stationary phase was reached. The data (log CFU per square centimeter versus time) were fitted using the Baranyi-Roberts model to determine maximum growth rates and lag-phase time. The maximum growth rates and the lag time under each growth condition were used to calculate the time to reach 100-fold the initial Listeria population. In frankfurters lacking PL and SD, the count of all strains increased by 2 log after 18 to 50 days at 4°C and 4 to 13 days at 8°C. The growth was inhibited at 4 and 8°C in frankfurters containing PL and SD, but one ribotype was capable of growing, with the time to reach 100-fold the initial Listeria population ranging from 19 to 35 days at 12°C. In most cases, the time to reach 100-fold the initial Listeria population of L. monocytogenes was significantly longer in vacuum-packaged frankfurters as compared with air-packaged samples. Inclusion of PL and SD also inhibited the growth of psychrotrophs, but at all temperatures the psychrotrophic plate counts were greater than 4 log CFU/cm2 at the end of the experiments. These results indicated that despite the use of antimicrobials, certain L. monocytogenes strains could be capable of growing under storage-abuse conditions. Growth kinetics data could be useful for establishing a shelf life date label protocol under different handling scenarios.
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PHILLIPS, CHRISTIE A., and MARK A. HARRISON. "Comparison of the Microflora on Organically and Conventionally Grown Spring Mix from a California Processor." Journal of Food Protection 68, no. 6 (June 1, 2005): 1143–46. http://dx.doi.org/10.4315/0362-028x-68.6.1143.
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Considerable speculation has occurred concerning the potential for higher numbers of foodborne pathogens on organically grown produce compared with produce not grown organically. The microflora composition of spring mix or mesclun, a mixture of multiple salad ingredients, grown either by organic or conventional means was determined. Unwashed or washed spring mix was obtained from a commercial California fresh-cut produce processor who does not use manure in their cultivation practices. Fifty-four samples of each type of product were supplied over a 4-month period. Analysis included enumeration of total mesophiles, psychrotrophs, coliforms, generic Escherichia coli, lactic acid bacteria, yeasts, and molds. In addition, spring mix was analyzed for the presence of Salmonella and Listeria monocytogenes. The mean populations of mesophilic and psychrotrophic bacteria, yeasts, molds, lactic acid bacteria, and coliforms on conventionally grown spring mix were not statistically different (P > 0.05) from respective mean populations on organically grown spring mix. The mean population of each microbial group was significantly higher on unwashed spring mix compared with the washed product. Of the 14 samples found to contain E. coli, eight were from nonwashed conventional spring mix, one was from washed conventional spring mix, and four were from nonwashed organic spring mix. Salmonella and L. monocytogenes were not detected in any of the samples analyzed.
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Vida, Silviu, Sorin Daniel Dan, Alexandra Tabaran, Oana Lucia Reget, Alina Ioana Fat, and Marian Mihaiu. "Microbiological Hazards Assessment of Psychrotrophic Microflora in Bovine Carcasses Slaughtered in North West Romania." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Veterinary Medicine 73, no. 2 (November 30, 2016): 369. http://dx.doi.org/10.15835/buasvmcn-vm:12233.
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Gram negative bacteria have the greatest capacity to spoil the meat if kept under aerobic conditions, therefor the members of the genera Pseudomonas, Acinetobater, Psychrobacter and Moraxella, will form the dominant microflora. The purpose of this study was to assess the contamination level with psychrotropic microflora of bovine carcasses in order to prove how the results could be used to improve the slaughter process. The research was carried out between January-December 2015, in two slaughterhouses from North West Romania. The research material was represented by 144 meat samples (slaughterhouse A, n=72, slaughterhouse B, n=72). Weekly, 3 samples were collected from refrigerated carcasses, and examined for total psychrotrophic counts (TPC), Enterobacteriaceae, Pseudomonas, Aeromonas and Yersinia. From statistical processing of recorded data was established that mean log TPC from the surface of refrigerated carcasses has presented different values, ranged between 3.70±0.20 log CFU/cm2 and 6.90±0.43 log CFU/cm2. Initial surface microflora of bovine carcasses was represented by germs from the following genera: Staphylococcus, Micrococcus, Aeromonas, Acinetobacter, Pseudomonas, Yersinia, Serratia, Hafnia, Proteus and Escherichia. Microbiological hazard assessment reveals the key role of psychotropic microorganisms in the spoilage of meat, if the monitoring system of the slaughtering process is not functioning properly.
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Martin-Kearley, Jennifer, and John A. Gow. "Numerical taxonomy of Vibrionaceae from Newfoundland coastal waters." Canadian Journal of Microbiology 40, no. 5 (May 1, 1994): 355–61. http://dx.doi.org/10.1139/m94-058.
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Numerical analysis was used to characterize 111 Vibrionaceae strains. These included 31 reference cultures belonging to the genera Aeromonas, Listonella, and Vibrio and 80 strains isolated from the seasonally cold coastal waters of Newfoundland. The sources of the regional strains were the brown alga Alaria esculenta and the giant scallop Placopecten magellanicus. Most of the regional strains grew at temperatures associated with psychrotrophs, while a small proportion may have been psychrophilic. All of the regional strains grew at 4 °C. A routine incubation temperature of 20 °C was chosen and in tests for utilization of organic components as sole sources of carbon and energy the strains were incubated for 3 weeks rather than the more common 6-day period. The treatment of weak positive results as weak positive, positive, or negative was investigated and it was decided that the general conclusions reached in the study would not be significantly altered by the interpretation of weak positive results. Using numerical analysis it was shown that most of the strains clustered according to source. Most reference cultures were more closely related to each other than they were to the regional strains. Some strains were phenotypically similar to Vibrio splendidus biovar I, which is arginine dihydrolase positive. Although there were differences, some strains were similar to the fish pathogen Vibrio ordalii, which is negative for arginine dihydrolase. Both species are reported to grow at 4 °C. It was shown that most of the regional Vibrionaceae strains studied were different from previously described species belonging to the family Vibrionaceae.Key words: numerical taxonomy, Vibrionaceae, Vibrio, marine bacteria, psychrotroph.
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Berthelot, Deborah, L. G. Leduc, and G. D. Ferroni. "The absence of psychrophilic Thiobacillus ferrooxidans and acidophilic heterotrophic bacteria in cold, tailings effluents from a uranium mine." Canadian Journal of Microbiology 40, no. 1 (January 1, 1994): 60–63. http://dx.doi.org/10.1139/m94-009.
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Iron-oxidizing autotrophs (mainly Thiobacillus ferrooxidans) and acidophilic heterotrophs were recovered and quantified at an incubation temperature of 18 °C, in four tailings-effluent samples obtained from the environment of a uranium mine in Ontario, Canada. The samples were collected during winter when the temperatures of the effluents were in the range 0.5–5.0 °C. Iron-oxidizing autotrophs were recovered in the four samples and their numbers ranged from 3 ± 2 to 185 ± 18 colony-forming units/mL; acidophilic heterotrophs were recovered in three of the four samples and their numbers ranged from 13 ± 3 to 2517 ± 859 colony-forming units/mL. Forty-six of the iron-oxidizer isolates and 63 of the acidophilic heterotrophic isolates were examined for their ability to grow at temperatures of 4, 18, 21, and 37 °C. None of the isolates was psychrophilic, although 96% of the iron oxidizers and 54% of the acidophilic heterotrophs were psychrotrophs; less that 5% of the isolates for both nutritional types were capable of growth at 37 °C. In addition, the isolates were categorized as 'broader temperature range psychrotrophs,' 'narrower temperature range psychrotrophs,' 'intermediates,' or mesophiles, and the narrower temperature range psychrotrophs were found to be numerically predominant.Key words: psychrotrophs, psychrophiles, Thiobacillus ferrooxidans, acidophilic heterotrophic bacteria.
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Patel, T. R., and D. M. Jackman. "Susceptibility of psychrotrophic pseudomonads of milk origin to psychrotrophic bacteriophages." Applied and Environmental Microbiology 51, no. 2 (1986): 446–48. http://dx.doi.org/10.1128/aem.51.2.446-448.1986.
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He, Hongjun, Roger Gordon, and John A. Gow. "The effect of temperature on the fatty acids and isozymes of a psychrotrophic and two mesophilic species ofXenorhabdus, a bacterial symbiont of entomopathogenic nematodes." Canadian Journal of Microbiology 47, no. 5 (May 1, 2001): 382–91. http://dx.doi.org/10.1139/w01-025.
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In the first part of this study, generation times relative to temperature, together with cardinal and conceptual temperatures, were determined for four strains of Xenorhabdus bacteria that represented three geographically distinct species. The data showed that the NF strain of Xenorhabdus bovienii, like the Umeå strain of the same species, is psychrotrophic, while Xenorhabdus sp. TX strain resembles Xenorhabdus nematophila All strain in being mesophilic. In the second part, the capacity of these bacteria to adapt to changes in temperature, shown by changes in fatty acid composition, was investigated. As temperature declined, the proportions of the two major unsaturated fatty acids, palmitoleic (16:1ω7) acid and oleic (18:1ω9) acid, increased significantly in all of the strains. The proportion of the prevalent saturated fatty acid, which was palmitic acid (16:0), decreased. In the All, NF, and Umeå strains, myristic acid (14:0), margaric acid (17:0), cyclopropane (17:0c), and arachidic acid (20:0) decreased with decreasing temperature. In the third part of the study, the synthesis of isozymes in response to changing temperature was investigated. For the seven enzymes studied, the numbers for which isozyme synthesis was temperature related were as follows: five for Umeå, four for All, three for NF, and two for TX. Where the study dealt with fatty acid composition and isozyme synthesis, the results show a broad capacity for physiological temperature adaptation among strains of different climatic origin.Key words: Xenorhabdus, temperature, psychrotroph, mesophile, fatty acid, isozyme.