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Articles de revues sur le sujet "Lignocellulosic inhibitor"
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Sjulander, Nikki, et Timo Kikas. « Origin, Impact and Control of Lignocellulosic Inhibitors in Bioethanol Production—A Review ». Energies 13, no 18 (11 septembre 2020) : 4751. http://dx.doi.org/10.3390/en13184751.
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Bioethanol production from lignocellulosic biomass is still struggling with many obstacles. One of them is lignocellulosic inhibitors. The aim of this review is to discuss the most known inhibitors. Additionally, the review addresses different detoxification methods to degrade or to remove inhibitors from lignocellulosic hydrolysates. Inhibitors are formed during the pretreatment of biomass. They derive from the structural polymers-cellulose, hemicellulose and lignin. The formation of inhibitors depends on the pretreatment conditions. Inhibitors can have a negative influence on both the enzymatic hydrolysis and fermentation of lignocellulosic hydrolysates. The inhibition mechanisms can be, for example, deactivation of enzymes or impairment of vital cell structures. The toxicity of each inhibitor depends on its chemical and physical properties. To decrease the negative effects of inhibitors, different detoxification methods have been researched. Those methods focus on the chemical modification of inhibitors into less toxic forms or on the separation of inhibitors from lignocellulosic hydrolysates. Each detoxification method has its limitations on the removal of certain inhibitors. To choose a suitable detoxification method, a deep molecular understanding of the inhibition mechanism and the inhibitor formation is necessary.
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Vanmarcke, Gert, Quinten Deparis, Ward Vanthienen, Arne Peetermans, Maria R. Foulquié-Moreno et Johan M. Thevelein. « A novel AST2 mutation generated upon whole-genome transformation of Saccharomyces cerevisiae confers high tolerance to 5-Hydroxymethylfurfural (HMF) and other inhibitors ». PLOS Genetics 17, no 10 (8 octobre 2021) : e1009826. http://dx.doi.org/10.1371/journal.pgen.1009826.
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Development of cell factories for conversion of lignocellulosic biomass hydrolysates into biofuels or bio-based chemicals faces major challenges, including the presence of inhibitory chemicals derived from biomass hydrolysis or pretreatment. Extensive screening of 2526 Saccharomyces cerevisiae strains and 17 non-conventional yeast species identified a Candida glabrata strain as the most 5-hydroxymethylfurfural (HMF) tolerant. Whole-genome (WG) transformation of the second-generation industrial S. cerevisiae strain MD4 with genomic DNA from C. glabrata, but not from non-tolerant strains, allowed selection of stable transformants in the presence of HMF. Transformant GVM0 showed the highest HMF tolerance for growth on plates and in small-scale fermentations. Comparison of the WG sequence of MD4 and GVM1, a diploid segregant of GVM0 with similarly high HMF tolerance, surprisingly revealed only nine non-synonymous SNPs, of which none were present in the C. glabrata genome. Reciprocal hemizygosity analysis in diploid strain GVM1 revealed AST2N406I as the only causative mutation. This novel SNP improved tolerance to HMF, furfural and other inhibitors, when introduced in different yeast genetic backgrounds and both in synthetic media and lignocellulose hydrolysates. It stimulated disappearance of HMF and furfural from the medium and enhanced in vitro furfural NADH-dependent reducing activity. The corresponding mutation present in AST1 (i.e. AST1D405I) the paralog gene of AST2, also improved inhibitor tolerance but only in combination with AST2N406I and in presence of high inhibitor concentrations. Our work provides a powerful genetic tool to improve yeast inhibitor tolerance in lignocellulosic biomass hydrolysates and other inhibitor-rich industrial media, and it has revealed for the first time a clear function for Ast2 and Ast1 in inhibitor tolerance.
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Piva, Victor de Freitas, Vanessa Souza Reis Melo, Bruna Vieira Cabral et Diego Andrade Lemos. « Extraction of furfural inhibitor from biomass hydrolysate of rice husk ». Ciência e Natura 44 (18 avril 2022) : e15. http://dx.doi.org/10.5902/2179460x68832.
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The production of second generation ethanol (E2G) has proven to be an alternative to non-renewable fuels, through transforming lignocellulosic waste into renewable fuel. In turn, rice husk has great potential due to its availability and composition. The conversion of lignocellulosic biomass to biofuel comprises a fundamental pre-treatment step, however, at this stage, the formation of degradation products (inhibitory compounds) occurs, among them, furfural, which cause negative effects on the viability of fermentative cells, making the production of E2G unfeasible. Given the above, the objective of this work was to remove the furfural inhibitor present in the lignocellulosic broth after the pre-treatment process, using oleic acid, through liquid-liquid extraction. The quantification of total reducing sugars in the hydrolyzate did not show significant variation between the pre and post extraction stages. Regarding the furfural inhibitor, in tests performed with a solution made in the laboratory, removal of up to 62.30% was obtained when the initial concentration was 5.00 g.L-1. With respect to the tests with the hydrolyzate from the rice husk pre-treatment, the maximum removal observed was 10.40%, but the initial concentration of furfural was 1.64 g.L-1. The results obtained indicate the possibility of using oleic acid as an extracting agent of the furfural inhibitor from lignocellulosic hydrolysates.
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Elgharbawy, Amal A. M., Md Zahangir Alam, Muhammad Moniruzzaman et Hamzah Mohd Salleh. « Hydrolysis Kinetics of Oil Palm Empty Fruit Bunch in Ionic Liquids and Cellulase Integrated System ». International Journal of Chemistry 11, no 2 (26 juillet 2019) : 95. http://dx.doi.org/10.5539/ijc.v11n2p95.
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Ionic liquids (ILs) are developing as potential solvents in lignocellulose solvation, which enables cellulase accessibility into the substrate. Nevertheless, ILs could result in enzyme deactivation because of the high polarity. Therefore, developing a system of ILs-compatible cellulase (IL-E) to promote lignocellulose conversion into sugars is a challenge in ILs applications. This study used an IL-E to attain high conversion yield of sugars from oil palm empty fruit bunch (EFB). Cellulase (Tr-Cel) from Trichoderma reesei was stable in the ILs, 1-ethyl-3-methyl imidazolium diethyl phosphate [EMIM]DEP and choline acetate [Cho]OAc. The inhibition and deactivation of cellulase were evaluated using the model substrate, carboxymethyl cellulose (CMC) and EFB as a lignocellulosic material to assess the hydrolytic activity. The enzyme kinetics revealed that [Cho]OAc acted as a noncompetitive inhibitor. Additionally, [EMIM]DEP may not be considered as an inhibitor as it increases the Vmax and does not significantly affect the KM. In both cases, the study proved that IL did not result in a severe loss of cellulase activity, which is a promising outcome for one-pot hydrolysis of lignocellulosic materials.
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Westman, Johan O., Valeria Mapelli, Mohammad J. Taherzadeh et Carl Johan Franzén. « Flocculation Causes Inhibitor Tolerance in Saccharomyces cerevisiae for Second-Generation Bioethanol Production ». Applied and Environmental Microbiology 80, no 22 (29 août 2014) : 6908–18. http://dx.doi.org/10.1128/aem.01906-14.
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ABSTRACTYeast has long been considered the microorganism of choice for second-generation bioethanol production due to its fermentative capacity and ethanol tolerance. However, tolerance toward inhibitors derived from lignocellulosic materials is still an issue. Flocculating yeast strains often perform relatively well in inhibitory media, but inhibitor tolerance has never been clearly linked to the actual flocculation abilityper se. In this study, variants of the flocculation geneFLO1were transformed into the genome of the nonflocculating laboratory yeast strainSaccharomyces cerevisiaeCEN.PK 113-7D. Three mutants with distinct differences in flocculation properties were isolated and characterized. The degree of flocculation and hydrophobicity of the cells were correlated to the length of the gene variant. The effect of different strength of flocculation on the fermentation performance of the strains was studied in defined medium with or without fermentation inhibitors, as well as in media based on dilute acid spruce hydrolysate. Strong flocculation aided against the readily convertible inhibitor furfural but not against less convertible inhibitors such as carboxylic acids. During fermentation of dilute acid spruce hydrolysate, the most strongly flocculating mutant with dense cell flocs showed significantly faster sugar consumption. The modified strain with the weakest flocculation showed a hexose consumption profile similar to the untransformed strain. These findings may explain why flocculation has evolved as a stress response and can find application in fermentation-based biorefinery processes on lignocellulosic raw materials.
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Roscini, Luca, Lorenzo Favaro, Laura Corte, Lorenzo Cagnin, Claudia Colabella, Marina Basaglia, Gianluigi Cardinali et Sergio Casella. « A yeast metabolome-based model for an ecotoxicological approach in the management of lignocellulosic ethanol stillage ». Royal Society Open Science 6, no 1 (janvier 2019) : 180718. http://dx.doi.org/10.1098/rsos.180718.
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Lignocellulosic bioethanol production results in huge amounts of stillage, a potentially polluting by-product. Stillage, rich in heavy metals and, mainly, inhibitors, requires specific toxicity studies to be adequately managed. To this purpose, we applied an FTIR ecotoxicological bioassay to evaluate the toxicity of lignocellulosic stillage. Two weak acids and furans, most frequently found in lignocellulosic stillage, have been tested in different mixtures against three Saccharomyces cerevisiae strains. The metabolomic reaction of the test microbes and the mortality induced at various levels of inhibitor concentration showed that the strains are representative of three different types of response. Furthermore, the relationship between concentrations and FTIR synthetic stress indexes has been studied, with the aim of defining a model able to predict the concentrations of inhibitors in stillage, resulting in an optimized predictive model for all the strains. This approach represents a promising tool to support the ecotoxicological management of lignocellulosic stillage.
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Padmapriya, G., V. Dhivya, M. Vishal, Y. A. J. Roshni, T. Akila et S. Ramalingam. « Development of tolerance to aldehyde-based inhibitors of pretreated lignocellulosic biomass sugars in E. coli MG1655 by sequential batch adaptive evolution ». Journal of Environmental Biology 42, no 5 (27 septembre 2021) : 1239–48. http://dx.doi.org/10.22438/jeb/42/5/mrn-1812.
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Aim: The current study involved carrying out adaptive evolution to inculcate tolerance to hydrolysate-derived aldehyde-based inhibitors, furfural, vanillin, syringaldehyde and 4-hydroxybenzaldehyde (4-HB) for the valorization of pretreated lignocellulosic biomass. Methodology: The growth-inhibitory effects of the aforementioned inhibitors on E. coli MG1655 were investigated. The percentage of inhibition was calculated from the initial growth, followed by extrapolating the IC50 values for each inhibitor. Based on these findings, adaptation experiments were conducted for individual inhibitors at a concentration lesser than or closer to IC50. Results: The specific growth rate of cells was lowered by 2.2-, 3-, 1.3- and 5- fold when grown in the presence of furfural, vanillin, syringaldehyde and 4- hydroxybenzaldehyde (4-HB), respectively. The adapted strains which were grown in the presence of furfural (9mM), vanillin (9mM), syringaldehyde (8mM) and 4- HB (6mM) individually showed around 1.5 -2.5- fold increase in the specific growth rate as compared to the wild-type with decreased lag phases and increased final cell densities. Interpretation: The strains, subjected to adaptive evolution, resulted in increased tolerance to single inhibitors and these will further be sequentially adapted to other three inhibitors for their utilization in the valorization of pretreated lignocellulosic biomass.
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Chanda, Kakoli, Atifa Begum Mozumder, Ringhoilal Chorei, Ridip Kumar Gogoi et Himanshu Kishore Prasad. « A Lignocellulolytic Colletotrichum sp. OH with Broad-Spectrum Tolerance to Lignocellulosic Pretreatment Compounds and Derivatives and the Efficiency to Produce Hydrogen Peroxide and 5-Hydroxymethylfurfural Tolerant Cellulases ». Journal of Fungi 7, no 10 (22 septembre 2021) : 785. http://dx.doi.org/10.3390/jof7100785.
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Fungal endophytes are an emerging source of novel traits and biomolecules suitable for lignocellulosic biomass treatment. This work documents the toxicity tolerance of Colletotrichum sp. OH toward various lignocellulosic pretreatment-derived inhibitors. The effects of aldehydes (vanillin, p-hydroxybenzaldehyde, furfural, 5-hydroxymethylfurfural; HMF), acids (gallic, formic, levulinic, and p-hydroxybenzoic acid), phenolics (hydroquinone, p-coumaric acid), and two pretreatment chemicals (hydrogen peroxide and ionic liquid), on the mycelium growth, biomass accumulation, and lignocellulolytic enzyme activities, were tested. The reported Colletotrichum sp. OH was naturally tolerant to high concentrations of single inhibitors like HMF (IC50; 17.5 mM), levulinic acid (IC50; 29.7 mM), hydroquinone (IC50; 10.76 mM), and H2O2 (IC50; 50 mM). The lignocellulolytic enzymes displayed a wide range of single and mixed inhibitor tolerance profiles. The enzymes β-glucosidase and endoglucanase showed H2O2- and HMF-dependent activity enhancements. The enzyme β-glucosidase activity was 34% higher in 75 mM and retained 20% activity in 125 mM H2O2. Further, β-glucosidase activity increased to 24 and 32% in the presence of 17.76 and 8.8 mM HMF. This research suggests that the Colletotrichum sp. OH, or its enzymes, can be used to pretreat plant biomass, hydrolyze it, and remove inhibitory by-products.
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Greetham, Darren, Abdelrahman Saleh Zaky et Chenyu Du. « Exploring the tolerance of marine yeast to inhibitory compounds for improving bioethanol production ». Sustainable Energy & ; Fuels 3, no 6 (2019) : 1545–53. http://dx.doi.org/10.1039/c9se00029a.
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Lam, Felix H., Burcu Turanlı-Yıldız, Dany Liu, Michael G. Resch, Gerald R. Fink et Gregory Stephanopoulos. « Engineered yeast tolerance enables efficient production from toxified lignocellulosic feedstocks ». Science Advances 7, no 26 (juin 2021) : eabf7613. http://dx.doi.org/10.1126/sciadv.abf7613.
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Lignocellulosic biomass remains unharnessed for the production of renewable fuels and chemicals due to challenges in deconstruction and the toxicity its hydrolysates pose to fermentation microorganisms. Here, we show in Saccharomyces cerevisiae that engineered aldehyde reduction and elevated extracellular potassium and pH are sufficient to enable near-parity production between inhibitor-laden and inhibitor-free feedstocks. By specifically targeting the universal hydrolysate inhibitors, a single strain is enhanced to tolerate a broad diversity of highly toxified genuine feedstocks and consistently achieve industrial-scale titers (cellulosic ethanol of >100 grams per liter when toxified). Furthermore, a functionally orthogonal, lightweight design enables seamless transferability to existing metabolically engineered chassis strains: We endow full, multifeedstock tolerance on a xylose-consuming strain and one producing the biodegradable plastics precursor lactic acid. The demonstration of “drop-in” hydrolysate competence enables the potential of cost-effective, at-scale biomass utilization for cellulosic fuel and nonfuel products alike.
Thèses sur le sujet "Lignocellulosic inhibitor"
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Gasperoni, Alessia. « Removal of inhibitors from birch pretreatment liquor by nanofiltration : Mechanisms of separation and influence of operational variables and mode ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15147/.
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Lignocellulosic biomass has attracted considerable attention as an alternative feedstock for the production of fuels, energy and chemicals, due to its renewability, abundance and reduced cost. Pretreatment and hydrolysation of lignocellulose releases sugars that are subsequently converted by fermentation. However, by-products such as aliphatic acids and furans could be generated during the upstream processes, which could inhibit enzymes and fermenting microorganisms. In addition, fermentation of low-concentrated sugars would lead to low products concentration and, consequently, to higher recovery and purification costs. Therefore, it is beneficial to reduce the concentration of the inhibitors and to concentrate the fermentable sugars in the liquor, prior to the fermentation process. This study was focused on the identification of the operating conditions to effectively remove aliphatic acids and furans from birch pretreatment liquor by nanofiltration. Two commercial NF membranes (NF90 and TS40) were employed. Effects of main operating parameters such as pH, feed concentration, temperature, pressure and tangential velocity on the separation performances were investigated, in both dead-end and cross-flow modes. The membrane performances were compared in terms of retention of sugars and inhibitors, permeate flux and permeability loss. It was found that NF90 membrane was more suitable than TS40 for simultaneous sugars concentration and beneficial removal of the inhibitors. Better separation performances were achieved at pH 1.5, 8 bar, room temperature and 3000 rpm. Dilution of 5 times of the liquor promoted the rejection of the sugars and kept low the retention of the inhibitory compounds. Water permeability loss was recovered by flushing with NaOH and water. The protocol and the operating conditions proposed in this study are suitable to perform the filtration process not only on laboratory scale, but also on industrial scale.
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BERTAGNOLI, STEFANO. « Improving robustness and metabolic profile of saccharomyces cerevisiae for industrial bioprocesses ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/28926.
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The fossil energy resources decrease and climate changes, caused by carbon dioxide (CO2) emissions, have led most industrialized countries to undertake policies aimed at the development and use of renewable energy sources. Among the renewable energies, vegetal biomasses play a key role because widely available and potentially able to cover up to 200% of the global energy demand. Vegetal biomasses can be used mainly as raw materials for the production of chemicals, biofuels and energy, in the increasingly important green economy concept based on biorefineries creation. Although the vegetal biomasses result widely available, rising costs of food raw material such as wheat, corn and sugar beet have raised a serious ethical problem using these resources. To avoid the use of such raw materials, the exploitation of lignocellulosic biomasses plays a fundamental role in the industry. However, for an efficient utilization of lignocellulosic biomasses, new technologies are required in order to transform the starting biomass into simple molecules, such as pentoses and hexoses sugars, more easily to use by the microrganism, which will have the task of producing both fine chemicals and bulk chemicals in an economically and environmentally sustainable processes. In this regard, industrial biotechnologies should be able to develop new microrganisms capable to face the harsh environmental conditions that occur during an industrial production process. For many of these productions the yeast Saccharomyces cerevisiae is largely used, not only because of its naturally ability to produce large ethanol amount, but also is widely known both at genetic and metabolic level, outlining a good starting point for the development of producers strains with high tolerance against different stresses occur during an industrial process. This is the view adopted by NEMO project (Novel high performance Enzymes and Microrganisms for conversion of lignocellulosic biomass to ethanol), belonging to the European Union seventh framework program, where it become of primary importance the development of microrganisms, especially S.cerevisiae, for the second generation ethanol production. Microrganisms must be, on the one hand able to efficiently utilize all the sugars released from lignocellulosic biomass pre-treatment, on the other hand should be more tolerant against process conditons, such as inhibitory compounds and environmental stresses.
A point of relevant importance is the ability to utilize pentose sugars, like D-xylose, released in large amount after lignocellulose pre-treatment. Currently, worldwide researches are focused on the development of yeast strains engineered with xylose degradation pathways involving the pentose phosphate pathway. In fact the fungal pathway exploits xylose reductase and the xylitol dehydrogenase while the bacterial pathway exploits xylose isomerase; both pathways degrade D-xylose into D-xylulose, which will enter into pentose phosphate pathway.
In addition to these two pathways studied since the ‘80s of the last century, there also two other poorly known metabolisms, described for the first time in the ‘70s, which produce alpha-ketoglutarate or pyruvate and glycolaldehyde through an oxidative xylose degradation. These pathways are composed of 5 enzymatic reactions by the Weimberg’s pathway and of 4 enzymatic reactions by the Dahms’ pathway, however they share the first 3 enzymatic reactions. After bioinformatics we were identified the presence of Weimberg’s pathway into Burkholderia xenovorans, while the reaction that characterizes the Dahms’ pathway has been identified in Escherichia coli. The encoding genes for these enzymatic activities were expressed in S.cerevisiae, and the capacity to grow on D-xylose as carbon source are evaluated. The reconstruction of these two pathways showed a poorly growth capacity on xylose. Such growth limitation seems to be related to several factors: the presence of bottlenecks associated to enzymes functionality, like D-xylonate dehydratase activity; the yeast ability to internalize xylose efficiently; the involved genes optimization.
Another important aspect is the yeast ability to face and overcome environmental stresses encountered during an industrial process. The cytoplasmic membrane plays a key role in cellular homeostasis, being at the interface between the cell and the external environment, and reacting at environmental changes. The plant membrane protein TIL gives particular strength to the yeast cells when these are subjected to environmental stresses of industrial relevance, such as the presence of oxidative agents or during temperature changes. However, when TIL is expressed in an industrial and/or in an engineered laboratory strains, for industrial use, the protective effect against prolonged stress exposure and process conditions disappear.
Finally, a further important aspect during an industrial process is the S.cerevisiae ability to tolerate the growth inhibitory compounds presence into pre-treated lignocellulose. In fact has been largely described how chemical compounds like aldehydes, organic acids and phenolic compounds, released during lignocellulose pre-treatment process, are toxic at certain concentration, inhibiting S.cerevisiae growth or causing yeast death. The growth performance of different wild type or engineered yeast strains are evaluated on spruce and giant cane lignocellulose pre-treated: in addition the same strains were tested on minimal formulated medium according to the spruce pre-treated composition. The results showed that the combination of low pH and the presence of organic acids, especially acetic acid and formic acid, are dramatically harmful for growth of both industrial strain, naturally more tolerant, and engineered strain, for the production and recycle of L-ascorbic acid. However, the behavior of engineered strain for production and recycle of L-ascorbic acid is interesting at low pH, because showed higher tolerance than other strains in terms of growth rate and ethanol production and productivity.
Despite the positive results obtained by engineering microrganisms, especially S.cerevisiae, in laboratory, their industrial uses still remain limited. Therefore, appears extremely important the construction of more robustness strains, able to withstand different environmental conditions along an entire industrial process, with consequent influence on yields, production and productivity. For these reasons, the research is aimed to combine these aspects to provide the best microrganism possible to industry productions.
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Leung, Ka Kay. « Analysis of yeast resistance to lignocellulosic-derived inhibitors ». Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/32589/.
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The rapid depletion of fossil fuel reserves and concurrent increase in global temperatures has resulted in global demand for the production of alternative environmentally friendly fuels. First-generation biofuels that utilise cash crops for the extraction of fermentable sugars currently exist, but are highly controversial due to socioeconomic and environmental reasons such as diverting food production or deforestation. Therefore, second-generation biofuels that utilise lignocellulosic waste materials are a more attractive prospect. In Europe, lignocellulosic biomass wastes such as wheat straw, display great potential for the production of alternative energy sources such as bioethanol for transportation. Conversion to this biofuel requires microorganisms that will effectively utilise the constituent sugars to produce a high yield of product. Saccharomyces cerevisiae (S. cerevisiae) strains possess the most desirable phenotypes for this objective. However, the components of wheat straw are difficult to break down, therefore pretreatment is required. Pretreatment methods vary but often utilise various chemicals that produce compounds that are inhibitory to yeast. This affects the efficiency of fermentations. The focus of this work is on formic acid and a synthetic media containing the main inhibitor compounds released during pre-treatment of steam exploded wheat straw. Six pair-wise F1 crosses between four distinct parental S. cerevisiae clean lineage populations have been generated previously by Cubillos et al., 2009. The 96 F1 progeny from each cross have been assayed for tolerance phenotypes in order to determine QTLs (Quantitative Trait Loci), which will enable us to map genes contributing to the multi-genic trait of inhibitor tolerance. Overall, three QTLs were identified for formic acid and five QTLs were identified from the synthetic inhibitor mix. Candidate genes were selected from the QTL analysis and were tested by performing reciprocal hemizygosity assays to determine which genes are responsible for inhibitor resistance to enable the development of yeast strains suitable for second-generation biofuel production.
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Frazão, Cláudio José Remédios. « Challenges of ethanol production from lignocellulosic biomass ». Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13657.
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Mestrado em Biotecnologia - Biotecnologia Industrial e AmbientalThe present work aimed to tackle two of the major challenges in bioethanol production from lignocellulosic feedstocks: (i) high tolerance of microorganisms to lignocellulosic inhibitors, and (ii) microbial contamination avoidance. Lignocellulosic inhibitors are an important fraction of spent sulphite liquor (SSL), a by-product of the pulp and paper industries. Hardwood SSL (HSSL) is rich in pentose sugars, mainly xylose, which can be converted to ethanol by the yeast Scheffersomyces stipitis. In this work, a population of S. stipitis previously adapted to 60 % (v/v) of HSSL was used, and its stability on the absence of inhibitors during ten sequential transfers was investigated at single-clone level. During the screening trials, all the isolated clones showed higher xylose and acetate uptake rates and lower ethanol productivities than the parental strain. The clone exhibiting higher xylose uptake rate (0.558 g L-1 h-1) was named isolate C4. The effect of short-term adaptation on isolate C4 fermentation performance was evaluated by pre-cultivating the clone in the presence or absence of 60 % (v/v) of HSSL. The uptake rates of glucose and xylose were similar under both conditions, but a higher acetate consumption rate (0.101 g L-1 h-1) and maximum ethanol concentration (4.51 g L-1) were achieved without pre-adaptation step, suggesting the robustness of isolate C4. The industrial bioethanol production is mostly carried out under non-sterile conditions, which favours microbial contamination. In this work, the mechanism that triggers Lactobacillus pentosus contamination in SSL plants was investigated. A simulated synthetic hydrolysate mimicking the average composition of sugars and inhibitors of softwood SSL (SSSL) was used and the impact of different factors in bacterial and Saccharomyces cerevisiae viability was analysed. The presence of yeast extract led to an increase in lactate production (9-fold higher) and L. pentosus viability when only bacteria was inoculated. Using different inoculation ratios of yeast/bacteria, the ethanol production rates were not affected after 48 h, and L. pentosus failed to overtake S. cerevisiae. The presence of inhibitors delayed yeast growth, but the bacteria did not outcompete S. cerevisiae. When the pH was optimal to L. pentosus in co-culture experiments, the bacterial cell viability decreased slower. The results indicate that L. pentosus was unable to overtake S. cerevisiae. The presence of yeast extract and favourable pH to bacteria are important factors that can play a role in the mechanism that triggers the bacterial contamination in ethanol plants.
A presente dissertação tem como objetivo abordar dois dos maiores desafios na produção de bioetanol a partir de biomassa lenhocelulósica: (i) elevada tolerância de microrganismos a inibidores, e (ii) prevenção de contaminação microbiana. Os inibidores lenhocelulósicos são uma fração relevante do licor de cozimento ao sulfito ácido (SSL), um subproduto das indústrias do papel e pastas. O SSL de folhosas (HSSL) é rico em pentoses, principalmente xilose, que podem ser fermentadas em etanol pela levedura Scheffersomyces stipitis. Neste estudo, utilizou-se uma população de S. stipitis previamente adaptada a 60 % (v/v) HSSL, e avaliou-se a sua estabilidade na ausência de inibidores durante dez transferências sequenciais. Comparando com a estirpe original, todos os clones isolados exibiram taxas de consumo de xilose e ácido acético superiores e produtividades em etanol inferiores. O clone que demonstrou a maior taxa de consumo de xilose (0,558 g L-1 h-1) foi designado isolado C4, e o efeito de adaptação de curta duração no seu desempenho fermentativo foi investigado através do seu pré-cultivo na presença ou ausência de 60 % (v/v) HSSL. Nas duas condições, as taxas de consumo de glucose e xilose foram idênticas, contudo, atingiu-se maior taxa de consumo de ácido acético (0,101 g L-1 h-1) e maior concentração máxima de etanol (4,51 g L-1) foram atingidas na ausência do processo de adaptação de curta duração. Tais resultados demonstram a robustez do isolado C4. A maioria dos processos de produção industrial de bioetanol é realizada na ausência de esterilidade, favorencendo a contaminação por microrganismos. Neste estudo, investigou-se o mecanismo responsável pela contaminação com Lactobacillus pentosus na indústria de SSL. Para tal, utilizou-se um hidrolisado sintético mimetizando a composição média de açúcares e inibidores de SSL de resinosas (SSSL) e averiguou-se o impacto de vários fatores na viabilidade de L. pentosus e S. cerevisiae. A presença de extrato de levedura foi responsável pelo aumento da produção de ácido lático (9 vezes) e da viabilidade bacteriana quando L. pentosus foi cultivado na ausência de levedura. Diferentes proporções de inóculo de levedura/bactéria não afetaram a produção de etanol após 48 h de fermentação, e L. pentosus foi incapaz de ser a estirpe dominante durante os ensaios de co-cultura. A presença de inibidores retardou o crescimento da levedura, mas a bactéria foi de novo incapaz de se a espécie dominante. Ajustando o valor de pH para o ótimo de L. pentosus nos ensaios de co-cultura, a viabilidade celular da bactéria diminuiu mais lentamente. Os resultados demonstram que L. pentosus não foi a espécie dominante nos ensaios de co-cultura. A presença de extrato de levedura e de valores de pH favoráveis a L. pentosus podem desempenhar um papel importante no mecanismo responsável pela contaminação bacteriana nas indústrias de produção de bioetanol.
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Du, Bowen Chambliss C. Kevin. « Effect of varying feedstock-pretreatment chemistry combinations on the production of potentially inhibitory degradation products in biomass hydrolysates ». Waco, Tex. : Baylor University, 2009. http://hdl.handle.net/2104/5319.
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Boukari, Imen. « Définition des critères d'efficacité d'une hémicellulase pour l'hydrolyse de substrats lignocellulosiques complexes et insolubles ». Reims, 2010. http://ebureau.univ-reims.fr/slide/files/quotas/SCD/theses/sciences/2010REIMS011.pdf.
Texte intégralRésumé :
Le développement de technologies enzymatiques constitue un enjeu majeur pour le fractionnement maîtrisé et la valorisation des ressources lignocellulosiques (biocarburants, biopolymères, synthons…). L’efficacité de ces biocatalyseurs est cependant limitée par de multiples facteurs liés à la fois à leurs caractéristiques structurales et fonctionnelles, mais également à la nature complexe de la biomasse lignocellulosique (riche en parois secondaires lignifiées). Dans le but d’identifier les paramètres clés pour une conversion efficace des hémicelluloses, constituants majeurs des lignocelluloses, nous avons centré notre étude sur l’endoxylanase (Tx-Xyl) de Thermobacillus xylanilyticus appartenant à la famille 11 des glycoside- hydrolases (GH11). Dans une approche biomimétique, nous avons étudié, l’action de la xylanase (Tx-Xyl) sur des substrats différents et de complexité croissante (hétéroxylanes isolés, assemblages de copolymères reconstitués in vitro. . . ). L’emploi de nano-composites hétéroxylanes extraits - lignines de synthèse (DHPs) nous a permis de souligner l’impact de l’agencement tridimensionnel des complexes covalents (LCC) sur la limitation de l’accessibilité des hétéroxylanes à l’enzyme. Une corrélation directe a pu, également, être établie entre l’augmentation du contenu en lignines des nano-composites et la baisse de l’activité de l’enzyme, suggérant des interactions non spécifiques directes enzyme-lignines. Par ailleurs, l’étude des interactions de Tx-Xyl avec divers acides hydroxycinamiques (p-coumarique, férulique, cafféique…) a permis de mettre en évidence un phénomène d’inhibition non compétitif de l’enzyme par ces composés phénoliques. Moyennant des outils de biologie moléculaire, nous avons développé une stratégie qui vise à modifier l’architecture protéique et/ou la spécificité de fixation de Tx-Xyl en la fusionnant via des séquences "linker" à des modules protéiques différents: le CBM1 de la cellulase Cel7A de Trichoderma reesei fixant spécifiquement la cellulose cristalline et la GFP (Green Fluoerescent Protein). Les protéines chimériques Tx-Xyl-CBM1 et Tx-Xyl-GFP obtenues sont moins efficaces sur les xylanes solubles (faible kcat) comparées à Tx-Xyl. Cependant, leurs modes d’action sur des substrats lignocellulosiques (tels que les coproduits du blé : paille et son de blé) semblent différents. En effet, des rendements d’hydrolyse légèrement augmentés sont obtenus dans le cas de Tx-Xyl-CBM1, suggérant un impact positif du CBM1 sur l’action de l’enzyme in situ, contrairement à Tx-Xyl-GFP dont la taille serait un facteur limitant sa diffusion/pénétration au sein des parois végétalesThe development of enzymatic technologies offers an alternative, environmentally-friendly interesting strategy for controlled fractionation and upgrading of lignocellulosic biomass (biofuels, biopolymers, industrially-relevant chemicals. . . ). The effectiveness of these biocatalysts is, nevertheless, limited by multiple factors related to their structural and functional characteristics, but also to the complex nature of the lignocellulosic biomass (rich in lignified secondary cell walls). In order to identify the key parameters for an effective bioconversion of hemicelluloses, the major components of lignocelluloses, we have focused our study on the endoxylanase (Tx-Xyl) of Thermobacillus xylanilyticus, a family 11 glycoside- hydrolase (GH11). In a biomimetic approach, we have studied the action pattern of Tx-Xyl on different substrates displaying increasing complexity (isolated heteroxylans, in vitro reconstituted copolymer assemblies. . . ). The use of nano-composites of heteroxylans - lignins (DHPs) synthesized in vitro has enabled us to reveal that supramolecular organization of the covalent complexes (LCC) would severely hamper the enzyme's access to carbohydrates. Otherwise, a direct correlation has been established between the increase in the lignin content of the nano-composites and the decrease of the enzyme activity suggesting direct nonspecific lignins-enzyme interactions. In addition, the study of the interactions of Tx-Xyl with various hydroxycinamic acids (p-coumaric, ferulic, caffeic acids. . . ) has revealed a non-competitive inhibition of the enzyme by these phenolic compounds. Using protein engineering, we have developed a strategy which aims at modifying the Tx-Xyl architecture and/or specificity by grafting, through "linker" sequences, different protein modules: the CBM1 of the cellulase Cel7A from Trichoderma reesei binding specifically crystalline cellulose and the GFP (Green Fluoerescent Protein). The chimeric fusion proteins Tx-Xyl-CBM1 and Tx-Xyl-GFP obtained have been less effective on soluble xylans (low kcat) than Tx-Xyl. However, their efficiency on lignocellulosic substrates (such as wheat by products; straw and bran) was different. Indeed, modestly enhanced hydrolysis rates were obtained in the case of Tx-Xyl-CBM1, suggesting that the CBM1 may potentiate in situ action of the enzyme, contrary to Tx-Xyl-GFP whose size would be a factor limiting its diffusion/action within the cell wall network
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Cavka, Adnan. « Biorefining of lignocellulose : Detoxification of inhibitory hydrolysates and potential utilization of residual streams for production of enzymes ». Doctoral thesis, Umeå universitet, Kemiska institutionen, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-82486.
Texte intégralRésumé :
Lignocellulosic biomass is a renewable resource that can be utilized for the production of biofuels, chemicals, and bio-based materials. Biochemical conversion of lignocellulose to advanced biofuels, such as cellulosic ethanol, is generally performed through microbial fermentation of sugars generated by thermochemical pretreatment of the biomass followed by an enzymatic hydrolysis of the cellulose. The aims of the research presented in this thesis were to address problems associated with pretreatment by-products that inhibit microbial and enzymatic biocatalysts, and to investigate the potential of utilizing residual streams from pulp mills and biorefineries to produce hydrolytic enzymes. A novel method to detoxify lignocellulosic hydrolysates to improve the fermentability was investigated in experiments with the yeast Saccharomyces cerevisiae. The method is based on treatment of lignocellulosic slurries and hydrolysates with reducing agents, such as sodium dithionite and sodium sulfite. The effects of treatment with sodium borohydride were also investigated. Treatment of a hydrolysate of Norway spruce by addition of 10 mM dithionite resulted in an increase of the balanced ethanol yield from 0.03 to 0.35 g/g. Similarly, the balanced ethanol yield of a hydrolysate of sugarcane bagasse increased from 0.06 to 0.28 g/g after treatment with 10 mM dithionite. In another study with a hydrolysate of Norway spruce, addition of 34 mM borohydride increased the balanced ethanol yield from 0.02 to 0.30 g/g, while the ethanol productivity increased from 0.05 to 0.57 g/(L×h). While treatment with sulfur oxyanions had a positive effect on microbial fermentation and enzymatic hydrolysis, treatment with borohydride resulted in an improvement only for the microbial fermentation. The chemical effects of treatments of hydrolysates with sodium dithionite, sodium sulfite, and sodium borohydride were investigated using liquid chromatography-mass spectrometry (LC-MS). Treatments with dithionite and sulfite were found to rapidly sulfonate inhibitors already at room temperature and at a pH that is compatible with enzymatic hydrolysis and microbial fermentation. Treatment with borohydride reduced inhibitory compounds, but the products were less hydrophilic than the products obtained in the reactions with the sulfur oxyanions. The potential of on-site enzyme production using low-value residual streams, such as stillage, was investigated utilizing recombinant Aspergillus niger producing xylanase and cellulase. A xylanase activity of 8,400 nkat/ml and a cellulase activity of 2,700 nkat/ml were reached using stillages from processes based on waste fiber sludge. The fungus consumed a large part of the xylose, the acetic acid, and the oligosaccharides that were left in the stillages after fermentation with S. cerevisiae. In another study, the capability of two filamentous fungi (A. niger and Trichoderma reesei) and three yeasts (S. cerevisiae, Pichia pastoris, and Yarrowia lipolytica) to grow on inhibitory lignocellulosic media were compared. The results indicate that the two filamentous fungi had the best capability to utilize different nutrients in the media, while the S. cerevisiae strain exhibited the best tolerance against the inhibitors. Utilization of different nutrients would be especially important in enzyme production using residual streams, while tolerance against inhibitors is desirable in a consolidated bio-process in which the fermenting microorganism also contributes by producing enzymes.
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Zautsen, Remigius Reinerus Maria 1977. « Fermentação alcoólica e extração líquido-líquido simultânea de etanol e de inibidores provenientes de caldo hidrolítico de biomassa lignocelulósica ». [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256499.
Texte intégralRésumé :
Orientador: Francisco Maugeri FilhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Na fermentação de produtos como etanol, utilizando biomassa lignocelulósica como matéria-prima, existem dois fatores principais que limitam a produtividade e eficiência do processo: inibição pelo produto e inibição por substâncias no caldo hidrolítico provenientes da hidrólise. Neste trabalho, é proposta a remoção simultânea de ambos os fatores para eliminar seus efeitos negativos na fermentação alcoólica. Produtos de fermentação prejudicam muitas vezes a integridade da membrana celular do micro-organismo utilizado como fermento. Portanto, a toxidez do produto não permite que a fermentação ocorra de forma ilimitada, uma vez que o produto está presente no meio em certa concentração. O crescimento do micro-organismo, a produtividade e o rendimento são prejudicados pela presença do mesmo. Compostos como furfural, hidroximetil furfural, compostos fenólicos e ácidos, que são produzidos durante o pré-tratamento ou hidrólise da biomassa lignocelulósica, introduzem outros efeitos inibidores, como a extensão da fase lag da levedura, prejudicam o crescimento e a produção. Esta tese propõe empregar um solvente orgânico na dorna do biorreator, com o fim de extrair o produto inibidor e todos os componentes inibidores existentes no substrato, de tal forma que o processo de fermentação não seja prejudicado. Com esse objetivo, primeiramente foi definida a relação entre o tamanho molecular de agentes extrativos, bio-compatibilidade e propriedades extrativas dos mesmos. Em seguida, um solvente foi escolhido, sendo o biodiesel à base de óleo de mamona, através de características como biocompatibilidade, coeficientes de partição, seletividade, alta disponibilidade e reutilização. Foram feitas fermentações em regime batelada em fermentadores de bancada, utilizando o biodiesel como agente extrativo, demonstrando os efeitos positivos no desempenho da fermentação de um licor hidrolítico. Adicionalmente, o comportamento de uma cepa de levedura industrial foi estudado na presença de inibidores e foi construído um modelo matemático que descreve as taxas de conversão dos principais inibidores e as condições em que a levedura, ao invés de manter uma fase lag, inicia a produção de biomassa e etanol. Finalmente, foi elaborado, como exemplo da utilização da tecnologia proposta, um modelo do sistema contínuo de fermentação alcoólica com a extração líquido-líquido, incluindo a recuperação do produto e resfriamento do meio de fermentação pelo próprio solvente orgânico. Por meio desta modelagem e uma série de simulações, foram determinadas as faixas ideais das principais variáveis na produção de etanol pelo sistema bifásico, sendo elas a fração de licor hidrolítico no mosto, concentração de substrato, temperatura de fermentação, e taxa de diluição do solvente. Assim, o trabalho demonstra as vantagens, efeitos positivos e os limites da utilização de extração líquido-líquido na fermentação de substrato da segunda geração. Entre as vantagens se destacam: maior tolerância de caldo hidrolítico no mosto, elevada produtividade, maior rendimento e maior custo-benefício do substrato
Abstract: There are two main factors that limit fermentation productivity and eficiency during the production of chemicals like ethanol when using lignocelulosic biomass as raw material: product inhibition and inhibition by substances in hydrolitic liquor generated during hydrolyzis. In this work, the simultaneous removal of both factors is proposed to eliminate their negative effects on ethanol fermentation. Fermentation products often damage the cellular wall of the micro-organism that is used as ferment. As a result, the toxicicity of the product does not permit that the fermentation continues unhindered once the product concentration has reached a certain level; growth of the micro-organism, productivity and yield are effected. Substances like furfural, hydroximetil furfural, phenolic compounds and organic acids, that are produced or released during pre-treatment or hydrolyzis of ligno-celulosic biomass, introduce other inhibiting effects, like the extension of the lag phase of the ferment or decreasing growth and production. This thesis proposes the use of an organic solvent as a second liquid phase in the bioreactor, to extract both the inhibiting product and all inhibiting compounds present in the substrate, such that the fermentation process remains unhindered. With this objective, first the relation between the molecular size of an extractive agent and its biocompatibility and extractive properties was determined. Next, a solvent was chosen, being biodiesel based on castor oil, by prioritizing characteristics as biocompatibility, partition coeficients, selectivity, availability and possibilities for recycling and reuse. Batch fermentations were executed in bench-scale, using biodiesel as extractive agent, demonstrating the improvements of fermentation of hydrolytic liquor. Aditionaly, the performance of an industrial yeast strain was studied in the presence of inhibitors and a mathematical model was constructed that descibes the conversion rates of the main inhibitors and conditions at which the yeast, instead of maintaining a lag phase, starts production of biomass and ethanol. Finally, as a practical example of the proposed technology, simulations were performed for an integrated process including continuous ethanol fermentation with liquid-liquid extraction, product recovery and cooling of the fermentation broth by the extractive agent itself. The simulation results reveiled the optimal ranges for the most important variables of the two-phase ethanol production process, i.e. fraction of hydrolitic liquor in the must, substrate concentration, fermentation temperature and dilution rate of the solvent. In all, the work shows the advantages, positive effects of and limits to the use of liquid-liquid extraction in fermentation of second-generation substrate. Advantages are, among others, higher tolerance of hydrolyzate in the must, higher yield, higher productivity and higher return on investment of raw-material
Doutorado
Engenharia de Alimentos
Doutor em Engenharia de Alimentos
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Siqueira, Marcos Rechi. « Efeitos dos produtos de hidrólise de materiais lignocelulósicos sobre a produção de H2 por fermentação ». Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-13042015-114341/.
Texte intégralRésumé :
O hidrogênio é uma fonte de energia limpa, pois sua combustão gera apenas água. Porém, ainda há a necessidade de se encontrar soluções tecnologicamente eficientes, econômicas e seguras para sua geração e uso. A produção do H2 por vias biológicas, conhecido como biohidrogênio, vem ganhando grande destaque nos últimos anos, pois possibilita o uso de materiais renováveis como matéria-prima. Materiais lignocelulósicos são potenciais substratos para a produção de H2 por fermentação, no entanto se faz necessário dispor de métodos de hidrólise que disponibilizem os componentes destes materiais para a fermentação. A maior parte dos métodos disponíveis para hidrolisar materiais lignocelulósicos resulta em produtos de degradação de carboidratos, que são reconhecidamente inibidores de fermentação. Este estudo, primeiramente, avaliou o efeito de 3 diferentes grupos de inibidores sobre a produção de H2 por fermentação: (1) ácido orgânico, como o ácido acético; (2) derivados de furano, tais como o furfural e o 5-hidroximetilfurfural (5-HMF); (3) monômeros fenólicos derivados da lignina, tais como o siringaldeído, vanilina e ácido 4-hidroxibenzóico (AHB). Ensaios de fermentação para a produção de H2 em batelada utilizaram como inóculo uma cultura mista (lodo) e foram realizados na presença de glicose e diferentes concentrações dos mencionados inibidores. O modelo de Gompertz modificado foi utilizado para estimar os parâmetros cinéticos dos ensaios de fermentação, como o volume máximo de H2 (P), velocidade máxima de produção de H2 (Rm) e o tempo necessário para o início da produção de H2 (). A partir destes ensaios foi verificado como a adição de diferentes concentrações de inibidores afetou tais parâmetros cinéticos em relação a um controle (apenas contendo glicose). Desta forma foi possível estimar as concentrações dos inibidores que reduzem em 50% as velocidades máximas de produção de H2 a concentração inibitória 50 (CI 50). Em termos de CI 50, o AHB proporcionou a maior inibição (0,38 g.L-1), seguido do 5-HMF e o furfural, com valores de CI 50 de 0,48 e 0,62 g.L-1, respectivamente. A vanilina, o siringaldeído e o ácido acético apresentaram os menores efeitos inibitórios sobre a produção de H2 dentre os inibidores testados, com CI 50 de 0,71; 1,05; e 5,14 g L-1, respectivamente. Numa segunda etapa do trabalho foi avaliado o efeito inibitório da associação de 3 inibidores, representantes de cada uma das classes de inibidores, o ácido acético, o 5-HMF e o siringaldeído. Foi observado um efeito aditivo da inibição quando o ácido acético foi adicionado juntamente com o 5-HMF, porém em ensaios contendo siringaldeído o efeito inibitório tornou-se sinérgico. Por fim, foi utilizado um hidrolisado de bagaço de cana de açúcar como substrato na produção de H2 por fermentação. A produção de H2 a partir deste substrato só foi possível após o tratamento do hidrolisado com carvão ativado. Portanto, concluiu-se que os compostos inibitórios presentes em hidrolisados de materiais lignocelulósicos condicionam a viabilidade da produção de H2 com estes materiais. Este estudo permitiu concluir que os compostos estudados, exceto os monossacarídeos, resultantes da hidrólise de materiais lignocelulósicos, inibem a produção de H2 pela cultura mista utilizada em diferentes graus, sendo o AHB o mais inibidor. A combinação de compostos inibidores potencializa ainda mais o efeito inibitório sobre a produção de H2. O ácido acético, que pode se originar dos hidrolisados, mas que também é um metabólito da produção de H2 por fermentação aumentou ainda mais a inibição do siringaldeído. Assim, sugere-se que a hidrólise de materiais lignocelulósicos deve ser conduzida de forma a minimizar a presença dos inibidores nos hidrolisados, a fim de maximizar o aproveitamento da biomassa lignocelulósica como matéria-prima no processo fermentativo.Hydrogen is a clean energy source because its combustion produces only water. However, there is still the need to find technologically efficient, economic and safe solutions for their generation and use. The production of H2 by biological pathways, known as biohydrogen, has gained great prominence in recent years because it enables the use of renewable materials as raw material. Lignocellulosic materials are potential substrates for H2 production by fermentation, however it is necessary to have methods that provide hydrolysis of the components of these materials for fermentation. Most methods are available for hydrolyzing lignocellulosic materials results in carbohydrate degradation products are fermentation inhibitors known. This study was primarily to evaluate the effect of 3 different groups inhibitors of the H2 production by fermentation: (1) organic acid such as acetic acid; (2) furan derivatives such as furfural and 5-hydroxymethylfurfural (5-HMF); (3) phenolic derivatives of lignin monomers, such as syringaldehyde, vanillin and 4-hydroxybenzoic acid (HBA). Fermentation tests for H2 production batch used as a mixed culture inoculum (sludge) and were carried out in the presence of glucose and different concentrations of the inhibitors mentioned. The modified Gompertz model was used to estimate the kinetic parameters of the fermentation test, the maximum volume of H2 (H), maximum rate of H2 production (Rm) and the time required for the commencement of production of H2 () . From these tests it was observed how the addition of different concentrations of inhibitors affect these kinetic parameters relative to a control (containing only glucose). Thus it was possible to estimate the concentrations of inhibitors that reduce by 50% the maximum production speeds H2 - The inhibitory concentration 50 (IC 50). In terms of IC 50, the AHB provided the greatest inhibition (0.38 g L-1), followed by 5-HMF and furfural, with IC 50 values of 0.48 and 0.62 g L-1, respectively. Vanillin, syringaldehyde and the acetic acid had minor inhibitory effects on H2 production from the tested inhibitors with IC50 of 0.71; 1.05; and 5.14 g L-1, respectively. In a second stage of work, the inhibitory effect of 3 inhibitors association representatives of each class inhibitors, acetic acid, and 5-HMF syringaldehyde. An additive effect of inhibition when acetic acid was added along with 5-HMF was observed in assays containing syringaldehyde but the inhibitory effect became synergistic. Finally, we used a hydrolyzate of sugarcane bagasse as substrate in H2 production by fermentation. The production of H2 from this substrate was only possible after the hydrolyzate treatment with activated carbon. Therefore, it was concluded that the inhibitory compounds present in hydrolyzed lignocellulosic materials affect the viability of H2 production with these materials. This study concluded that the studied compounds, other monosaccharides resulting from the hydrolysis of lignocellulosic materials, inhibit the production of H2 by mixed culture used in varying degrees, being most AHB inhibitor. The combination of compounds further enhances the inhibitory effect of inhibitors on the production of H2. Acetic acid, which can originate the hydrolysates, but is also a metabolite of H2 production by fermentation further increased inhibition of syringaldehyde. Thus, it is suggested that the hydrolysis of lignocellulosic materials should be conducted to minimize the presence of inhibitors of the hydrolysates, in order to maximize the utilization of lignocellulosic biomass as a raw material in the fermentation process.
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Westman, Johan. « Ethanol production from lignocellulose using high local cell density yeast cultures. Investigations of flocculating and encapsulated Saccharomyces cerevisiae ». Doctoral thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3685.
Texte intégralRésumé :
Efforts are made to change from 1st to 2nd generation bioethanol production, using lignocellulosics as raw materials rather than using raw materials that alternatively can be used as food sources. An issue with lignocellulosics is that a harsh pretreatment step is required in the process of converting them into fermentable sugars. In this step, inhibitory compounds such as furan aldehydes and carboxylic acids are formed, leading to suboptimal fermentation rates. Another issue is that lignocellulosics may contain a large portion of pentoses, which cannot be fermented simultaneously with glucose by Saccharomyces cerevisiae. In this thesis, high local cell density has been investigated as a means of overcoming these two issues. Encapsulation of yeast in semi-permeable alginate-chitosan capsules increased the tolerance towards furan aldehydes, but not towards carboxylic acids. The selective tolerance can be explained by differences in the concentration of compounds radially through the cell pellet inside the capsule. For inhibitors, gradients will only be formed if the compounds are readily convertible, like the furan aldehydes. Conversion of inhibitors by cells close to the membrane leads to decreased concentrations radially through the cell pellet. Thus, cells closer to the core experience subinhibitory levels of inhibitors and can ferment sugars. Carbohydrate gradients also give rise to nutrient limitations, which in turn trigger a stress response in the yeast, as was observed on mRNA and protein level. The stress response is believed to increase the robustness of the yeast and lead to improved tolerance towards additional stress. Glucose and xylose co-consumption by a recombinant strain, CEN.PK XXX, was also improved by encapsulation. Differences in affinity of the sugar transporters normally result in that glucose is taken up preferentially to xylose. However, when encapsulated, cells in different parts of the capsule experienced high and low glucose concentrations simultaneously. Xylose and glucose could thus be taken up concurrently. This improved the co-utilisation of the sugars by the system and led to 50% higher xylose consumption and 15% higher final ethanol titres. A protective effect by the capsule membrane itself could not be shown. Hence, the interest in flocculation was triggered, as a more convenient way to keep the cells together. To investigate whether flocculation increases the tolerance, like encapsulation, recombinant flocculating yeast strains were constructed and compared with the non-flocculating parental strain. Experiments showed that strong flocculation did not increase the tolerance towards carboxylic acids. However, the tolerance towards a spruce hydrolysate and especially against furfural was indeed increased. The results of this thesis show that high local cell density yeast cultures have the potential to aid against two of the major problems for 2nd generation bioethanol production: inhibitors and simultaneous hexose and pentose utilisation.Akademisk avhandling som för avläggande av teknologie doktorsexamen vid Chalmers tekniska högskola försvaras vid offentlig disputation den 19 februari 2014,klockan 13.30 i KA-salen, Kemigården 4, Göteborg.
Chapitres de livres sur le sujet "Lignocellulosic inhibitor"
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Pinel, Dominic, et Vincent J. J. Martin. « Meiotic Recombination-Based Genome Shuffling ofSaccharomyces CerevisiaeandSchefferomyces Stiptisfor Increased Inhibitor Tolerance to Lignocellulosic Substrate Toxicity ». Dans Engineering Complex Phenotypes in Industrial Strains, 233–50. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118433034.ch9.
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Hurst, G., M. Peeters et S. Tedesco. « Integration of Catalytic Biofuel Production and Anaerobic Digestion for Biogas Production ». Dans Springer Proceedings in Energy, 125–31. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63916-7_16.
Texte intégralRésumé :
AbstractThe drive towards a low carbon economy will lead to an increase in new lignocellulosic biorefinery activities. Integration of biorefinery waste products into established bioenergy technologies could lead to synergies for increased bioenergy production. In this study, we show that solid residue from the acid hydrolysis production of levulinic acid, has hydrochar properties and can be utilised as an Anaerobic Digestion (AD) supplement. The addition of 6 g/L solid residue to the AD of ammonia inhibited chicken manure improved methane yields by +14.1%. The co-digestion of biorefinery waste solids and manures could be a promising solution for improving biogas production from animal manures, sustainable waste management method and possible form of carbon sequestration.
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Richardson, T. L., N. K. Harner, P. K. Bajwa, J. T. Trevors et H. Lee. « Approaches To Deal with Toxic Inhibitors during Fermentation of Lignocellulosic Substrates ». Dans ACS Symposium Series, 171–202. Washington, DC : American Chemical Society, 2011. http://dx.doi.org/10.1021/bk-2011-1067.ch007.
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T., Lakshmana Kishore, et Haribalaji V. « A Study on the Conversion of Ligninolytic Biomass to Biofuels ». Dans Human Agro-Energy Optimization for Business and Industry, 46–68. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-4118-3.ch003.
Texte intégralRésumé :
Due to increasing power demand and the utilisation of natural resources in growing countries, the use of biomass and biofuels is emerging. The role of thermophilic ligninolytic bacterial enzymes in the biomass-to-biofuel conversion process is discussed in this chapter. Various elements of biomass feedstocks, compositions, and viabilities of lignocellulosic biomass are illustrated. The lignocellulosic biomass pre-treatment methods, inhibitors during the pre-treatment process, hydrolysis methods, and bacteria production processes have been explained. The processes for isolation, screening, and maintenance of cellulolytic bacteria are exemplified through suitable schematics. The utilization of agro-waste in the ethanal and biofuel production processes is also exemplified.
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Purkait, Mihir Kumar, et Dibyajyoti Haldar. « Formation and detoxification of inhibitors ». Dans Lignocellulosic Biomass to Value-Added Products, 61–78. Elsevier, 2021. http://dx.doi.org/10.1016/b978-0-12-823534-8.00004-1.
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« Bioconversion of Lignocellulose : Inhibitors and Detoxifi cation ». Dans New Biotechnologies for Increased Energy Security, 64–87. Apple Academic Press, 2015. http://dx.doi.org/10.1201/b18537-11.
Texte intégralActes de conférences sur le sujet "Lignocellulosic inhibitor"
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Watanabe, Kenshi, Miho Nishijima, Shinzo Mayuzumi et Tsunehiro Aki. « Utilization of sugar cane bagasse as a substrate for fatty acid production by Aurantiochytrium sp. » Dans 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/bptz2428.
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The genus Aurantiochytrium, a heterotrophic marine protist, produces significant amounts of polyunsaturated fatty acids and carotenoids and is promising as an alternative source of those lipids. This research aimed to utilize lignocellulosic biomass, which is abundant on land and does not compete with food supply, for fatty acid production by Aurantiochytrium limacinum strain SR21. Sugarcane bagasse soaked in diluted sulfuric acid was blasted by steam explosion and subsequently saccharified by the enzyme. When SR21 was cultivated in the medium containing saccharified liquid of sugarcane bagasse, the cell growth was almost abolished as compared with the control medium with the same glucose concentration, suggesting the presence of growth-inhibiting components in the saccharified liquid. The growth and fatty acid production of SR21 was significantly inhibited in the presence of furans and phenolic compounds previously reported to be generated by heat treatment of lignocellulosic biomass. Among them, furfural was detected in the bagasse saccharified liquid at the concentration that could inhibit the growth of SR21. Removal of such compounds by activated charcoal restored the cell growth and fatty acid productivity.
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BICHOT, Aurélie, Jean Philippe DELGENES, Marilena RADOIU et Diana GARCIA BERNET. « MICROWAVE PRETREATMENT OF LIGNOCELLULOSIC BIOMASS TO RELEASE MAXIMUM PHENOLIC ACIDS ». Dans Ampere 2019. Valencia : Universitat Politècnica de València, 2019. http://dx.doi.org/10.4995/ampere2019.2019.9629.
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The objectives fixed by world’s governments concerning energy transition have aroused interest on lignocellulosic biomass utilization for bioenergy and green chemistry applications. However, due to their resistant structure, deconstructive pretreatments are necessary to render possible biological conversions of these lignocellulosic residues. Microwave (MW) treatment has been reported as efficient in many biotechnology fields; biomass pretreatment for biorefinery purposes is another possible application. This work presents the effects of MW pretreatment on underexploited natural agri-food biomass of economic interest: wheat bran, miscanthus stalks and corn stalks. Various parameters were studied including solvent, power density, treatment duration, pressure. Effects were evaluated by a complete biomass characterization before and after treatment, with main focus on phenolic acids release. In the tested conditions and when compared to the high NaOH consumption reference extraction method for phenolic acids, the atmospheric pressure (open vessel) microwave treatment did not allow attaining high acid yields (Fig.1). The most important parameters for improving treatment efficiency were power density and solvent. In order to increase yields, microwave treatments under pressure were carried out to reach higher temperatures while taking care as to not exceed the acid denaturation temperature (150°C) and to avoid the formation of inhibitors. Phenolic acids yields and biomass composition are currently being processed and will be discussed.
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PROCÓPIO, D. P., F. E. CIAMPONI, M. BRANDÃO, F. V. WINK et T. O. BASSO. « Physiology and Transcriptomic analysis of Saccharomyces cerevisiae in the presence of inhibitors derived from lignocellulosic biomass ». Dans XXII Congresso Brasileiro de Engenharia Química. São Paulo : Editora Blucher, 2018. http://dx.doi.org/10.5151/cobeq2018-pt.0541.
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Mutrakulcharoen, Parita, Peerapong Pornwongthong, Kraipat Cheenkachorn, Prapakorn Tantayotai, Supacheree Roddecha et Malinee Sriarivanun. « Inhibitory Effect of Inorganic Salts Residuals on Cellulase Kinetics in Biofuel Production from Lignocellulose Biomass ». Dans 2020 International Conference and Utility Exhibition on Energy, Environment and Climate Change (ICUE). IEEE, 2020. http://dx.doi.org/10.1109/icue49301.2020.9307055.
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Mathew, Anil, Mitch Crook, Keith Chaney et Andrea Humphries. « Bioethanol Production From Canola Straw Using a Continuous Flow Immobilized Cell System ». Dans ASME 2012 6th International Conference on Energy Sustainability collocated with the ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/es2012-91061.
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Global cultivation of canola increased by approximately 22% between 2000 and 2009, due to increased demand for canola oil for biodiesel production and as an edible oil. In 2009 over 290,000 km2 of canola was cultivated globally. In contrast to oilseed, the commercial market for canola straw is minimal and it is generally ploughed back into the field. The high carbohydrate content (greater than 50 % by dry weight) of canola straw suggests it would be a good feedstock for second-generation bioethanol production. There are four major steps involved in bioethanol production from lignocellulosic materials: (i) pretreatment, (ii) hydrolysis, (iii) fermentation, and (iv) further purification to fuel grade bioethanol through distillation and dehydration. Previous research demonstrated a glucose yield of (440.6 ± 14.9) g kg−1 when canola straw was treated using alkaline pretreatment followed by enzymatic hydrolysis. Whilst bioethanol can be produced using cells free in solution, cell immobilization provides the opportunity to reduce bioethanol production costs by minimizing the extent to which down-stream processing is required, and increasing cellular stability against shear forces. Furthermore, the immobilization process can reduce substrate and product inhibition, which enhances the yield and volumetric productivity of bioethanol production during fermentation, improves operational stability and increases cell viability ensuring cells can be used for several cycles of operation. Previous research used cells of Saccharomyces cerevisiae immobilized in Lentikat® discs to convert glucose extracted from canola straw to bioethanol. In batch mode a yield of (165.1 ± 0.1) g bioethanol kg−1 canola straw was achieved. Continuous fermentation is advantageous in comparison to batch fermentation. The amount of unproductive time (e.g. due to filling, emptying and cleaning) is reduced leading to increased volumetric productivity. The higher volumetric productivity of continuous fermentation means that smaller reactor vessels can be used to produce the same amount of product. This reduces the capital costs associated with a fermentation plant. Research demonstrated a higher bioethanol yield was attained (224.7 g bioethanol kg−1 canola straw) when glucose was converted to bioethanol using immobilized cells in packed-bed continuous flow columns. On an energy generation basis, conversion of 1 kg of canola straw to bioethanol resulted in an energy generation of 6 MJ, representing approximately 35% energy recovery from canola straw. The amount of energy recovered from canola straw could be improved by increasing the amount of energy recovered as bioethanol and by utilising the process by-products in a biorefinery concept.
Rapports d'organisations sur le sujet "Lignocellulosic inhibitor"
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Mark A. Eiteman PHD et Elliot Altman Phd. A novel fermentation strategy for removing the key inhibitor acetic acid and efficiently utilizing the mixed sugars from lignocellulosic hydrolysates. Office of Scientific and Technical Information (OSTI), février 2009. http://dx.doi.org/10.2172/971996.
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