Academic literature on the topic 'Lignocellulosic micro'

Made available in DSpace on 2017-07-10T18:08:19Z (GMT). No. of bitstreams: 1 Fabiano Bisinella Scheufele.pdf: 1716907 bytes, checksum: fee6288858ac3d92f0d2e7f9f8d02ba2 (MD5) Previous issue date: 2012-02-15<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Lignocellulosic biomass has high yields of cellulose which can be hydrolyzed to fermentable carbohydrates. Global generation of agro-industrial wastes grows simultaneously with the sector development resulting at the accumulation of lignocellulosic residues leading environmental pollution and loss of potential materials for the bioconversion to a wide range of high added value products, such as biofuels. Recently, the search of renewable sources of energy has grown, due to the depleting of fossil fuels, increasing the possibility at the conversion of the lignocellulosic biomass via hydrolytic enzymes. The aim of this work was evaluate cellulases production by lignocellulolytic fungi from the Amazonic biome aiming at the bioconversion of the agro-industrial residues. Submerged and solid-state fermentations were performed to select the microorganism with superior cellulase productive capacity. The influence of parameters such as pH, surfactant induction (Tween 80), aeration and agitation, besides the alkaline oxidative treatment of the sugarcane bagasse. Statistical design were carried out to estimate the influence of the moisture and the initial pH at cellulases production by solid-state fermentation. Trichoderma sp. and Aspergillus niger performed the best production of enzymes, where the highest yields of total cellulase were obtained by agitated submerged fermentation with sugarcane bagasse pretreated with H2O2 (1%) reaching 0.265 U.mL-1 (12.915 U.g-1) by Trichoderma sp. at the sugarcane bagasse, and 0.155 U.mL-1 (7.549 U.g-1) by Aspergillus niger. Through solid state fermentations with the pretreated sugarcane bagasse the influence of initial pH and the moisture were evaluated by statistical design. In the case of the Trichoderma sp. both parameters were significant at the cellulase production, as well as the synergistic interaction, within the confidence interval of 95%, yielding 0.167 U.mL-1 (2.695 U.g-1), at the pH 7.0 and 1:9 solid-liquid ratio. For Aspergillus niger only pH was significant and the cellulase content obtained was 0.098 U.mL-1 (1.695 U.g-1) at pH 7.0. Finally, a cellulase produced by Trichoderma sp. at solid state fermentation and a commercial enzyme were used at enzymatic hydrolysis tests. The parameters hydrolysis time, enzyme dilution, concentration of Tween 80 and solid-liquid ratio of sugarcane bagasse were evaluated. The significant variables were then optimized by a central composite rotational design. The strain of Trichoderma sp. from the Amazon biome showed potential at the cellulase production and the treated sugarcane bagasse was a fine substrate for the enzymatic production.<br>A biomassa lignocelulósica contêm altos teores de celulose e outros polissacarídeos em sua constituição química, podendo ser hidrolisados em açúcares fermentescíveis. A geração de resíduos agroindustriais anual tem crescido resultando no acúmulo de resíduos que contribuem para a poluição do meio ambiente e na perda de materiais que possuem potencial na bioconversão a produtos de alto valor agregado, como por exemplo, biocombustíveis. Recentemente, há a necessidade de fontes energéticas de origem renovável, devido à diminuição dos combustíveis fósseis, viabilizando a conversão das biomassas lignocelulósicas via enzimas hidrolíticas. O objetivo deste trabalho foi avaliar a produção de enzimas celulases por fungos lignocelulolíticos provenientes do bioma amazônico visando a bioconversão de resíduos agroindustriais. Diferentes fermentações foram realizadas, tanto em meio submerso quanto em estado sólido, através das quais selecionou-se os micro-organismos com melhor capacidade produtiva de celulases. Estudou-se a influência de parâmetros como pH, utilização de surfactante como indutor (Tween 80), aeração e agitação, além do tratamento alcalino oxidativo do bagaço de cana. Os micro-organismos que apresentaram melhor desempenho na produção das enzimas foram o Trichoderma sp. e o Aspergillus niger, sendo que os maiores níveis de celulase total foram obtidos por fermentação submersa nos ensaios agitados com bagaço de cana pré-tratado com H2O2 (1%), com 0,265 U.mL-1 (12,915 U.g-1) pelo Trichoderma sp., e 0,155 U.mL-1 (7,549 U.g-1) com Aspergillus niger. A partir de fermentações em estado sólido com o bagaço de cana pré-tratado avaliou-se a influência dos parâmetros pH inicial e umidade por planejamentos experimentais, verificando-se que para o Trichoderma sp. ambos os parâmetros, bem como a interação sinergética entre si, foram significativos dentro do intervalo de confiança de 95%, obtendo-se 0,167 U.mL-1 (2,695 U.g-1) no pH 7,0 e relação sólido-líquido 1:9. No caso do Aspergillus niger apenas o pH foi significativo e o teor de celulase obtido foi de 0,098 U.mL-1 (1,695 U.g-1) para um pH 7,0. Finalmente, a partir de uma celulase produzida por fermentação em estado sólido do Trichoderma sp. e uma enzima comercial foi realizada a avaliação da influência dos parâmetros tempo de hidrólise, diluição da enzima, concentração de Tween 80 e razão sólido-líquido do bagaço de cana sobre a hidrólise do mesmo. As variáveis significativas foram, posteriormente, otimizadas por um delineamento composto central rotacional. A cepa Trichoderma sp. proveniente do bioma amazônico apresentou potencial na produção de celulases e o o bagaço de cana submetido ao tratamento alcalino oxidativo apresentou-se como um bom substrato para a produção enzimática.

Lignocellulosic biomass is a sustainable resource with abundant reserves. Compared to petroleum ‐ based products, the biomass ‐ derived polymers and chemicals give better environmental profiles. A lot of research interest is focused on understanding the lignocellulose structures. Lignin, among the three major wood components, represents most difficulty for microbial degradation because of its complex structure and because cross ‐ linking to hemicellulose makes wood such a compact structure. Nevertheless, wood is naturally degraded by wood ‐ degrading micro ‐ organisms and modified and partly degraded residual of lignin goes into soil. Therefore soil serves as a good environment in which to search for special lignin ‐ degraders. In this thesis, different types of lignin have been used as sole carbon sources to screen for lignin ‐ degrading soil micro ‐ organisms. Eleven aerobic and three anaerobic microbe strains have been isolated and identified as able to grow on lignin. The lignin degradation patterns of selected strains have been studied and these partly include an endwise cleavage of  β‐ O ‐ 4 bonds in lignin and is more complex than simple hydrolytic degradation. As lignin exists in wood covalently bonded to hemicellulose, one isolated microbe strain, Phoma herbarum, has also been studied with regards to its ability to degrade covalent lignin polysaccharide networks (LCC). The results show that its culture filtrate can attack lignin ‐ polysaccharide networks in a manner different from that of the commercial enzyme product, Gammanase, possibly by selective cleavage of phenyl glucoside bonds. The effects on LCC of Phoma herbarum also enhance polymer extractability. Hot ‐ water extraction of a culture filtrate of Phoma herbarum ‐ treated fiberized spruce wood material gave an amount of extracted galactoglucomannan more than that given by the Gammanase ‐ treated material and non ‐ enzyme ‐ treated material. Over millions of years of natural evolution, micro ‐ organisms on the one hand develop so that they can degrade all wood components to get energy for growth, while plants on the other hand also continuously develop to defend from microbial attack. Compared with lignin and cellulose, hemicelluloses as major components of plant cell walls, are much more easily degraded, but hemicelluloses differ from cellulose in that they are acetylated to different extents. The biological functions of acetylation are not completely understood, but it is suggested is that one function is to decrease the microbial degradability of cell walls. By cultivation of soil micro ‐ organisms using mannans acetylated to deffernent degrees as sole carbon source on agar plates, we were able to see significant trends where the resistance towards microbial degradation of glucomannan and galactomannan increased with increasing degree of acetylation. Possible mechanisms and the technological significance of this are discussed. Tailoring the degree of acetylation of polysaccharide materials might slow down the biodegradation, making it possible to design a material with a degradation rate suited to its application.<br><p>QC 20160223</p>