Littérature scientifique sur le sujet « Limnospira »

Cyanobacteria from the genus Arthrospira/Limnospira are considered haloalkalotolerant organisms with optimal growth temperatures around 35 °C. They are most abundant in soda lakes in tropical and subtropical regions. Here, we report the comprehensive genome-based characterisation and physiological investigation of the new strain O9.13F that was isolated in a temperate climate zone from the winter freezing Solenoye Lake in Western Siberia. Based on genomic analyses, the Siberian strain belongs to the Arthrospira/Limnospira genus. The described strain O9.13F showed the highest relative growth index upon cultivation at 20 °C, lower than the temperature 35 °C reported as optimal for the Arthrospira/Limnospira strains. We assessed the composition of fatty acids, proteins and photosynthetic pigments in the biomass of strain O9.13F grown at different temperatures, showing its potential suitability for cultivation in a temperate climate zone. We observed a decrease of gamma-linolenic acid favouring palmitic acid in the case of strain O9.13F compared to tropical strains. Comparative genomics showed no unique genes had been found for the Siberian strain related to its tolerance to low temperatures. In addition, this strain does not possess a different set of genes associated with the salinity stress response from those typically found in tropical strains. We confirmed the absence of plasmids and functional prophage sequences. The genome consists of a 4.94 Mbp with a GC% of 44.47% and 5355 encoded proteins. The Arthrospira/Limnospira strain O9.13F presented in this work is the first representative of a new clade III based on the 16S rRNA gene, for which a genomic sequence is available in public databases (PKGD00000000).

Global food shortages make it necessary to look for alternative renewable bioresources. In the south of Western Siberia, the filamentous cyanoprokaryote Limnospira fusiformis triggers seasonal algae bloom in hypergaline alkaline Lake Solenoye. The species has valuable nutritional properties, and its phytomass is a potential source of proteins and biologically active substances. The O9.13F strain of L. fusiformis has a good potential as a bioadditive in animal feeding. The article offers a technology for cultivating O9.13F of L. fusiformis, isolated from Lake Solenoye. The research objectives were to establish the optimal cultivation conditions, medium, and periodicity. The study featured strain O9.13F of filamentous cyanoprokaryote L. fusiformis. The micropipette method made it possible to isolate pure culture from water samples taken from Lake Solenoye, Omsk, Russia, at the end of algae bloom. The cultivation involved a UT-6070 climatic chamber under uniform illumination with light intensity 10–30 μmol photons/m2s and 12-h light-dark circle at 20 ± 2°C on various media: natural habitat – water from the Solenoye Lake; mineral medium – liquid Zarrouk’s medium; agarized Zarrouk’s medium; composite variants, where the ratio of mineral medium vs. water varied from 1:9 to 9:1. Lake water inhibited the culture growth: the trichomes died and sank on day 10–15. Zarrouk’s agarized medium stopped the culture growth as early as on day 2. The most intensive growth and development of the culture was observed in the samples with Zarrouk’s mineral liquid medium and a composite mix of Zarrouk’s medium and sterilized water at a ratio of 5:5. Without stirring, full-fledged trichomes had no time to develop, and the increase in phytomass volume slowed down. O9.13F showed the highest rate of phytomass growth at a cultivation temperature of 20 ± 2°C and a light intensity of 10–30 μmol photons/m2s. The recommended light-dark circle was12:12 h. Zarrouk’s mineral liquid medium and a composite medium of Zarrouk’s medium and sterilized water proved to be optimal in a UT-6070 environmental chamber. Europolitext KV-06 or mechanical mixing could prevent sedimentation of phosphates after 20 days of cultivation. The optimal recultivation frequency was once every 5–7 days. The new cultivation technology made it possible to obtain a significant volume of L. fusiformis phytomass in a short time and with low financial expenses.

Commercially produced cyanobacteria preparations sold under the name spirulina are widely consumed, due to their traditional use as a nutrient-rich foodstuff and subsequent marketing as a superfood. Despite their popularity, the microbial composition of ponds used to cultivate these bacteria is understudied. A total of 19 pond samples were obtained from small-scale spirulina farms and subjected to metagenome and/or virome sequencing, and the results were analysed. A remarkable level of prokaryotic and viral diversity was found to be present in the ponds, with Limnospira sp. and Arthrospira sp. sometimes being notably scarce. A detailed breakdown of prokaryotic and viral components of 15 samples is presented. Twenty putative Limnospira sp.-infecting bacteriophage contigs were identified, though no correlation between the performance of these cultures and the presence of phages was found. The high diversity of these samples prevented the identification of clear trends in sample performance over time, between ponds or when comparing successful and failed fermentations.

Recent advances in research techniques have enabled rapid progress in the study of spirulina, an ancient edible cyanobacteria. Nowadays, spirulina species are classified into three genera: Spirulina, Arthrospira, and Limnospira. The latter now refers to industrially manufactured spirulina strains. Whole-genome sequencing revealed gene clusters involved in metabolite production, and the physiology of spirulina. Omics technologies demonstrated the absence of hazardous compounds in spirulina cells, confirming the safety of this biomass as a food product. Spirulina is a good source of different chemicals used in food manufacturing, food supplements, and pharmaceuticals. Spirulina’s enrichment with inherent biologically active substances makes it a potential supplier of natural products for dietary and pharmaceutical applications. Spirulina is also a prospective component of both terrestrial and space-based life support systems. Here, we review current breakthroughs in spirulina research and clarify fallacies that can be found in both professional literature and public media.

Phycocyanin denotes a photosynthetic pigment discovered in Rhodophyta and cyanobacteria, which has been used in medical, industrial, and agricultural applications. In general, phycocyanin production by cyanobacteria depends on many environmental conditions, mainly light during the cultivation period. The goal of this research was to see how various light intensities of 47, 52, as well as 60 µmol m-2 s-1, affected the Phycocyanin production of cyanobacterium Limnospira fusiformis cultured in Zarrouk medium with a maximum temperature of 28°C. The outcomes revealed that with mild light intensity (52 µmol m-2 s-1), increased phycocyanin production of 11.94 ng/mg took place. With regard to greater light intensity (60 µmol m-2 s-1), the lesser phycocyanin production of 0.57 ng/mg took place. These results give a good impression that moderate lighting increases phycocyanin production, but high light intensity inhibits it. The statistical analysis results also showed that there are significant differences between the light intensities used in the study at a level of p<0.05. Therefore, this study concluded that phycocyanin was affected by light intensity. Light regime optimization gives a good yield of this pigment. In this study, high phycocyanin production by cyanobacterium Limnospira fusiformis occurred in mild light intensity (52 µmol m-2 s-1).

En respuesta al artículo “Aplicaciones de la espirulina - planta marina: revisión panorámica” de Ochoa y Moyano (2022), quisiéramos señalar que la palabra “planta” en el título del artículo (pues se trata de una cianobacteria o, en términos más generales, un alga), podría no ser adecuada. Además nos gustaría sugerir algunas observaciones de formato en la nomenclatura (no se usa cursiva) y una actualización sobre el nombre científico de la espirulina (género Limnospira).

Contaminations are challenging for monocultures, as they impact the culture conditions and thus influence the growth of the target organism and the overall biomass composition. In phycology, axenic cultures comprising a single living species are commonly strived for both basic research and industrial applications, because contaminants reduce significance for analytic purposes and interfere with the safety and quality of commercial products. We aimed to establish axenic cultures of Limnospira fusiformis, known as the food additive “Spirulina”. Axenicity is strived because it ensures that pathogens or harmful microorganisms are absent and that the harvested biomass is consistent in terms of quality and composition. For the axenic treatment, we applied sterile filtration, ultrasonication, pH treatment, repeated centrifugation, and administration of antibiotics. For testing axenicity, we considered the most common verification method plate tests with Lysogeny Broth (LB) medium, which indicated axenicity after treatments were performed. In addition, we included plate tests with Reasoner’s 2A (R2A) agar and modified Zarrouk+ medium, the latter comparable to the biochemical properties of L. fusiformis’ cultivation medium. In contrast to LB plates, the other media, particularly Zarrouk+, indicated bacterial contamination. We conclude that LB-agar plates are inappropriate for contamination screening of extremophiles. Contamination was also verified by cultivation-independent methods like flow cytometry and 16S rRNA genome amplicon sequencing. We detected taxa of the phyla Proteobacteria, Bacteriodota, Firmicutes and to a lesser extent Verrucomicrobiota. Contaminants are robust taxa, as they survived aggressive treatments. Sequencing data suggest that some of them are promising candidates for in-depth studies to commercially exploit them.

Limnospira maxima is a remarkable organism showing great potential as a versatile and sustainable food source, offering a powerful solution to address the pressing issues of malnutrition and undernourishment worldwide. L. maxima contains high amounts of proteins, vitamins, minerals, and essential fatty acids. It can be grown in both bioreactors and open systems; however, before considering industrial production, optimization studies of the cultivation must be conducted to obtain knowledge about the ideal environmental conditions. Additionally, for the molecular typing of L. maxima strains and their industrial scaling, high-quality and large quantity DNA extraction is required. Notwithstanding, DNA extraction from L. maxima can be challenging due to the low amount of DNA in cells and the presence of difficult-to-remove substances such as polysaccharides and polyphenols. In this study, the quality and quantity of DNA extracted from two types of L. maxima samples (Limnospira maxima strain SISCA accession GenBank: OR195505.1) were evaluated using three commercially available DNA extraction kits and two types of input biological material. The results showed that Pbact-P kit had the highest quantity and quality of DNA, while CTAB-P allowed for a higher quantity and quality of RNA, making them optimal protocols for nucleic acid extraction to improve PCR, rt-PCR, and genome sequencing of L. maxima compared with other extraction methods.

Cultivating Limnospira maxima, renowned for its abundant proteins and valuable pigments, faces substantial challenges rooted in the limited understanding of its optimal growth parameters, associated high costs, and constraints in the procurement of traditional nitrogen sources, particularly NaNO3. To overcome these challenges, we conducted a comprehensive 4 × 3 factorial design study. Factors considered included white, red, blue, and yellow light spectra, along with nitrogen sources NaNO3 and KNO3, as well as a nitrogen-free control, for large-scale implementation. Optimal growth, measured by Optical Density, occurred with white and yellow light combined with KNO3 as the nitrogen source. These conditions also increased dry weight and Chl-a content. Cultures with nitrogen deprivation exhibited high values for these variables, attributed to carbon accumulation in response to nitrogen scarcity. Phycocyanin, a crucial pigment for nutrition and industry, reached its highest levels in cultures exposed to white light and supplemented with KNO3, with an impressive content of 384.11 g kg−1 of dry weight. These results highlight the efficacy and cost-efficiency of using a combination of white light and KNO3 for large-scale L. maxima cultivation. This strategy offers promising opportunities to address global food security challenges and enhance the production of industrially relevant pigments.

The cyanobacterium Limnospira platensis, vulgarly Spirulina, has gained significant attention due to its high protein content, rich bioactive compounds, and health benefits, making it a valuable resource in biotechnology, nutraceuticals, food supplements, biopharmaceuticals, and cosmetics. Recent advancements in fermentation technology have considerably improved the efficiency, scalability, and cost-effectiveness of L. platensis production while addressing environmental sustainability and enhancing product quality. Based on well-recognized databases (Google Scholar, PubMed, Scopus, Web of Science), this review explores the latest developments in L. platensis fermentation, emphasizing strain improvement, bioprocess engineering, and optimization of fermentation parameters. It also examines key factors such as bioreactor design, downstream processing, and innovative monitoring technologies aimed at maximizing biomass yield and bioactive compound production. Additionally, emerging applications of fermented L. platensis in various industries and future perspectives, including large-scale production, regulatory barriers, and biosafety considerations, are discussed. These insights provide a comprehensive outlook on the future of L. platensis fermentation in biotechnological applications.

La spiruline est le nom commun de cyanobactéries comestibles cultivées dans des exploitations aquacoles généralement industrielles. Toutefois, en France, cette production est assurée par 180 fermes paysannes. La spiruline est consommée sous forme d’aliments ou de compléments alimentaires, pour sa valeur nutritionnelle et ses effets positifs sur la santé. Cependant, certaines cyanobactéries produisent des cyanotoxines et sont susceptibles de contaminer les cultures de spiruline. Ces toxines, notamment des microcystines (MCs), avaient été détectées dans des spirulines provenant de différents marchés étrangers. De plus, une espèce de spiruline, Limnospira fusiformis, était soupçonnée de toxicité suite à deux publications portant sur des souches kényanes. Enfin, une confusion taxonomique concernait les spirulines désignées par quatre noms d’espèces réparties sur deux genres. Au regard de ces éléments, il apparait nécessaire d’apporter des connaissances sur les contaminations, par des cyanotoxines et par des cyanobactéries, des cultures françaises de spiruline. En outre, il était indispensable de caractériser les différentes souches de spiruline cultivées afin d’identifier leur espèce et de vérifier si elles peuvent produire des cyanotoxines.Les résultats de 623 analyses de MCs sur des spirulines par la méthode enzymatique Adda-ELISA et de cinq résultats de contre-analyses par la méthode LC-MS/MS ont permis de conclure que les productions de spiruline de la filière paysanne française ne présentent pas de risque sanitaire lié aux MCs. Par ailleurs, des analyses métagénétique et métagénomique réalisées sur six échantillons de culture de spiruline ont montré que ces derniers ne contiennent que des cyanobactéries halo-alcalophiles non toxiques dont le genre Sodalinema qui est un contaminant dominant. A contrario, l’échantillon environnemental de la souche de spiruline camarguaise contenait des cyanobactéries potentiellement toxiques. Ces résultats, étayés par les dénombrements de cyanobactéries réalisés sur des échantillons issus de 95 fermes, ont révélé que la salinité et l’alcalinité des milieux de cultures utilisés en France ne sont pas propices au développement des cyanobactéries connues pour produire des MCs.La comparaison des génomes de 22 souches de spiruline, dont deux cultivars utilisés en France, ainsi que la souche camarguaise, a établi qu’il n’existe que deux espèces de spiruline, Limnospira maxima et L. platensis, et que les appellations L. fusiformis et L. indica sont des synonymes hétérotypes de L. maxima. La caractéristique morphologique permettant de distinguer ces deux espèces a également été trouvée. Enfin, l’analyse de 11 génomes de chaque espèce a démontré l’absence de séquences génétiques pouvant être associée aux cyanotoxines, prouvant par là leur innocuité
Spirulina is the common name for edible cyanobacteria cultivated in aquaculture facilities, which are generally industrial. In France, however, production is carried out by 180 small-scale farms. Spirulina is consumed as a food or dietary supplement for its nutritional value and health benefits. However, certain cyanobacteria produce cyanotoxins and can contaminate spirulina culture. These toxins, notably microcystins (MCs), have been found in spirulina samples from various foreign markets. In addition, one spirulina species, Limnospira fusiformis, was suspected of toxicity following two publications on Kenyan strains. Finally, a taxonomic confusion does exist for spirulina designated by four species names, spread among two genera. It therefore appears of interest to provide information on the cyanotoxin and cyanobacteria contamination of French spirulina cultures. Moreover, it was essential to characterize the different strains cultivated by the French spirulina farmers to assess the potential risk of cyanotoxins production.In that sense, the results of 623 analyses of spirulina for MCs using the enzymatic Adda-ELISA method complemented by five duplicate analyses using the LC-MS/MS method led to the conclusion that spirulina produced by French farmers does not present a health risk related to MCs. In addition, metagenomic and metagenetic analyses of six spirulina culture samples showed that they contained only non-toxic halo-alkalophilic cyanobacteria, including the genus Sodalinema, which is the most dominant and recurring contaminant. In contrast, the environmental sample of the Camargue spirulina strain contained potentially toxic cyanobacteria. These results, supported by cyanobacterial counts carried out on samples from 95 farms, revealed that the salinity and alkalinity of the growing media used in France are not promoting the development of cyanobacteria known to produce MCs.Finally, comparing the genomes of 22 spirulina strains, including two cultivars used in France as well as the Camargue strain, showed that there are only two species of spirulina, Limnospira maxima and L. platensis, and that the names L. fusiformis and L. indica are heterotypic synonyms for L. maxima. A morphological character was also found to distinguish the two species. Finally, the analysis of 11 genomes of each species demonstrated the absence of genetic sequences that could be associated with cyanotoxins, thus proving their safety

Single Cell-Microorganism based Proteins (SCP) are obtained from microorganisms such as bacteria, yeasts, fungi and algae. These microorganisms are grown under controlled conditions and processed into end-products rich in proteins. The most common microorganisms used for SCP include Limnospira, Saccharomyces cerevisiae, Fusarium venenatum, Candida, and Chlorella species. These species are selected for their characteristics, such as rapid-growth rate, high-protein content, and ability to thrive under harsh conditions. SCPs amino acids required for the sustainable nutrition of the rapidly growing world population. SCPs can be designed and optimized through various R&D activities to meet specific nutritional requirements. SCPs are more environmentally sustainable alternatives to traditional protein sources such as industrial meat and soy, and do not require significant land, fertilizer, water or feed. As grown in controlled environments, SCPs make a promising sustainable solution to meet the growing global protein. However, there are still challenges regarding common spread utilization of SCPs such as regulatory procedures for human consumption, consumers’ perspective and acceptance, increasing large-scale production efficiency and high R&D costs. In addition, the risk of pathogens and possible toxin contamination are among the issues that need to be considered in terms of safety. This study aims to inform the public and private sectors by blending the studies on SCP research conducted at Boğaziçi University Microalgae Biotechnologies R&D Unit with existing literature studies as well as SCP samples produced in Boğaziçi University microalgae biorefinery