Recursos microbianos ligninolíticos: potencial para deslignificação e produção de ligninases
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2016-11-18
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Universidade Estadual Paulista (Unesp)
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A degradação biológica da lignina pode ser realizada por fungos de podridão branca, parda e mole, os quais produzem enzimas oxidativas especialmente lacases, manganês peroxidase (MnP) e lignina peroxidase (LiP). Neste trabalho, foi investigada a interação entre diferentes fungos filamentosos para formar consórcios capazes de remover a lignina de resíduos agroindustriais. Após triagens enzimáticas realizadas para LiP, MnP, Lacase e glioxal oxidase (GLOX), 8 isolados apresentaram potencial para aplicação de degradação lignocelulósica e 5 fungos foram selecionados como os melhores produtores das enzimas estudadas. As capacidades de interação e inibição de crescimento dos isolados selecionados foram estudadas para posterior montagem dos consórcios. Desta maneira, 6 diferentes consórcios foram estruturados e submetidos a testes de degradação de lignina utilizando três diferentes resíduos derivados da agroindústria: sabugo de milho, casca de arroz e bagaço de cana. Dados de seletividade (celulose/lignina) foram também utilizados como parâmetro de avaliação dos consórcios. Os consórcios C5 (Tinctoporellus sp. e Marasmiellus sp. e Aspergillus sect. flavi) e C6 (Tinctoporellus sp. e Marasmiellus sp. Fusarium sp.) apresentaram resultados mais coerentes de degradação de lignina, seletividade e atividades enzimáticas no bagaço de cana após 7 dias a 28ºC. A casca de arroz apresentou menor degradabilidade devido a uma maior resistência ao ataque microbiano. O sabugo de milho foi melhor degradado por consórcios que apresentaram habilidade em reduzir a lignina e os polissacarídeos. Sendo assim, os consórcios C5 e C6 foram submetidos aos experimentos de degradação do bagaço de cana por 15 dias. Os resultados revelaram que o consórcio C5 foi mais eficiente no processo de deslignificação e apresentou melhores resultados de seletividade. Para aumentar o rendimento da deslignificação, 3 experimentos de otimização do processo foram realizados utilizando o planejamento experimental do tipo Plackett-Burman (PB). Aumentos sequenciais da deslignificação foram observados a cada experimento, onde as duas melhores condições de cultivo encontradas (PB3) apresentavam: i) inóculo fúngico (7), 8 mM de CuSO4, 0,4 g/L de KH2PO4 e 2,5 g de bagaço de cana (ensaio 10) e ii) inóculo fúngico (7), 20 g/L de glicose, 2 g/L de extrato de levedura, 8 mM de CuSO4 e 2,5 g de bagaço de cana (ensaio 5). As condições de cultivo dos ensaios 10 e 5 permitiram uma porcentagem de deslignificação correspondente a 57,65% e 49,73%, respectivamente. Os melhores resultados de seletividade (celulose/lignina e xilana/lignina) foram, de maneira geral, condizentes com os melhores resultados de deselignificação. Experimentos adicionais foram conduzidos visando avaliação da influência do sulfato de cobre no crescimento dos fungos dos consórcios e nos fungos de maneira isolada, e avaliação da deslignificação em cultivos contendo extrato de malte e bagaço de cana. Os resultados revelaram que a presença do sulfato de cobre não interferiu na eficiência dos consórcios frente à deslignificação. Na presença do sulfato de cobre a porcentagem de seletividade da lignina do bagaço de cana pelo consórcio C5 (53,18%) foi muito próxima à obtida no PB3. Neste teste, houve produção de LiP e MnP, enquanto a lacase foi detectada na ausência do sulfato de cobre. Os resultados da deslignificação dos experimentos em meio malte e bagaço de cana foram inferiores aos resultados com o meio otimizado, destacando a importância da aplicação do planejamento experimental para a otimização de processos. Os resultados do presente trabalho evidenciam o potencial do consórcio C5 para a deslignificação do bagaço de cana em 7 dias de cultivo.
Biological lignin degradation can be performed by white rot, brown, and soft fungi, which are able to produce oxidative enzymes such as lignin peroxidase (LiP), manganese peroxidase (MnP) and Laccase. In this work, the interaction between different filamentous fungi (isolated from different environments) was investigated aiming to the structuration of consortia able to remove the lignin from agro-industrial wastes. After the enzymatic screening accomplished to LiP, MnP, laccase, and glyoxal oxidase (GLOX), 8 isolates presented potential application to lignocellulose degradation and 5 were selected as the best producers of the studied enzymes. The interaction and inhibition growth ability of the selected isolates was investigated for the subsequent consortia assembling. In this way, 6 different consortia were pooled and subjected to lignin degradation tests using 3 different waste materials derived from agro-industry: corn cobs, rice husks, and sugarcane bagasse. Data related to selectivity (cellulose/lignin) were also used for the consortia´s evaluation. The consortia C5 (Tinctoporellus sp., Marasmiellus sp., and Aspergillus sect. Flavi) and C6 (Tinctoporellus sp., Marasmiellus sp., and Fusarium sp.) presented more coherent results of lignin degradation, selectivity, and enzymatic activities in sugarcane bagasse after 7 days incubation at 28°C. The rice husk showed lower degradability due to the higher resistance to the microbial attack. The corncob was better degraded by the consortia that showed ability to reduce the amount of lignin and polysaccharides (cellulose and xylan). In this sense, the consortia C5 and C6 were subjected to the experiments related to sugarcane bagasse degradation during 15 days. Results showed that the consortium C5 was more efficient during the delignification process and showed better results of selectivity. In order to increase the delignification efficiency, three experiments related to the process optimization were conducted using Plackett-Burman (PB) experimental design. Sequential improvements in delignification were observed to each experiment and the two better culture conditions found comprised: i) inoculum disks (7), 8 mM CuSO4, 0.4 g/L of KH2PO4, and 2.5 g of sugarcane bagasse (assay 10), and ii) inoculum (7), 20 g/L glucose, 2 g/L yeast extract, 8 mM CuSO4, and 2.5 g of sugarcane bagasse (assay 5). The culture conditions of assay 10 and 5 allowed a delignification corresponding to 57.65% and 49.73%, respectively. In general, the better results of selectivity (cellulose /lignin and xilan/lignin) were consistent with the better results of delignification. Additional experiments were conducted in order to evaluate the effect of copper sulfate on the growth of the consortia fungal strains and the each single fungus, and to evaluate the delignification in cultures containing malt extract and sugarcane bagasse. Results reveal that the presence of copper sulphate did not interfere in the consortia delignification efficiency. In the presence of copper sulphate the percentage of sugarcane bagasse delignification by the consortium C5 (53.18%) was almost the same that one obtained in the PB3. In general, in the presence of copper sulphate LiP and MnP were produced, while laccase was detected in the absence of this compound. Results related to the delignification in medium containing malt extract and sugarcane bagasse were lower than that ones with the optimized medium, highlighting the relevance of the experimental design to the process optimization. Results from the present study show the potential of the consortium C5 for the delignification of sugarcane bagasse in 7 days of cultivation.
Biological lignin degradation can be performed by white rot, brown, and soft fungi, which are able to produce oxidative enzymes such as lignin peroxidase (LiP), manganese peroxidase (MnP) and Laccase. In this work, the interaction between different filamentous fungi (isolated from different environments) was investigated aiming to the structuration of consortia able to remove the lignin from agro-industrial wastes. After the enzymatic screening accomplished to LiP, MnP, laccase, and glyoxal oxidase (GLOX), 8 isolates presented potential application to lignocellulose degradation and 5 were selected as the best producers of the studied enzymes. The interaction and inhibition growth ability of the selected isolates was investigated for the subsequent consortia assembling. In this way, 6 different consortia were pooled and subjected to lignin degradation tests using 3 different waste materials derived from agro-industry: corn cobs, rice husks, and sugarcane bagasse. Data related to selectivity (cellulose/lignin) were also used for the consortia´s evaluation. The consortia C5 (Tinctoporellus sp., Marasmiellus sp., and Aspergillus sect. Flavi) and C6 (Tinctoporellus sp., Marasmiellus sp., and Fusarium sp.) presented more coherent results of lignin degradation, selectivity, and enzymatic activities in sugarcane bagasse after 7 days incubation at 28°C. The rice husk showed lower degradability due to the higher resistance to the microbial attack. The corncob was better degraded by the consortia that showed ability to reduce the amount of lignin and polysaccharides (cellulose and xylan). In this sense, the consortia C5 and C6 were subjected to the experiments related to sugarcane bagasse degradation during 15 days. Results showed that the consortium C5 was more efficient during the delignification process and showed better results of selectivity. In order to increase the delignification efficiency, three experiments related to the process optimization were conducted using Plackett-Burman (PB) experimental design. Sequential improvements in delignification were observed to each experiment and the two better culture conditions found comprised: i) inoculum disks (7), 8 mM CuSO4, 0.4 g/L of KH2PO4, and 2.5 g of sugarcane bagasse (assay 10), and ii) inoculum (7), 20 g/L glucose, 2 g/L yeast extract, 8 mM CuSO4, and 2.5 g of sugarcane bagasse (assay 5). The culture conditions of assay 10 and 5 allowed a delignification corresponding to 57.65% and 49.73%, respectively. In general, the better results of selectivity (cellulose /lignin and xilan/lignin) were consistent with the better results of delignification. Additional experiments were conducted in order to evaluate the effect of copper sulfate on the growth of the consortia fungal strains and the each single fungus, and to evaluate the delignification in cultures containing malt extract and sugarcane bagasse. Results reveal that the presence of copper sulphate did not interfere in the consortia delignification efficiency. In the presence of copper sulphate the percentage of sugarcane bagasse delignification by the consortium C5 (53.18%) was almost the same that one obtained in the PB3. In general, in the presence of copper sulphate LiP and MnP were produced, while laccase was detected in the absence of this compound. Results related to the delignification in medium containing malt extract and sugarcane bagasse were lower than that ones with the optimized medium, highlighting the relevance of the experimental design to the process optimization. Results from the present study show the potential of the consortium C5 for the delignification of sugarcane bagasse in 7 days of cultivation.
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Palavras-chave
Biomassa lignocelulósica, Consórcio fúngico, Otimização, Planejamento experimental, Tratamento biológico, Lignocellulosic biomass, Biological treatment, Fungal consortia, Optimization, Experimental design