Influência anatômica da cana-de-açúcar em processos de extração de hemiceluloses e uso como substrato em atividade enzimática
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2018-07-27
Autores
Melati, Ranieri Bueno [UNESP]
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Universidade Estadual Paulista (Unesp)
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Materiais como o bagaço de cana-de-açúcar, são fartos na natureza e representam fontes renováveis para a extração de moléculas de interesse econômico, como as hemiceluloses. Entretanto, os métodos de extração dessas macromoléculas precisam ser melhor desenvolvidos para aplicação industrial. Deste modo, o objetivo principal do trabalho foi o desenvolvimento de uma metodologia de extração de hemicelulose com alto rendimento e pureza utilizando frações da biomassa de cana-de-açúcar: folha e colmo: entrenó, nó e fração externa. Foram avaliadas duas estratégias: uma prévia deslignificação da biomassa; e deslignificação da hemicelulose extraída de material não deslignificado. As hemicelulose extraídas foram avaliadas como substrato para determinação de atividade enzimática de xilanase. O método de extração de hemicelulose empregou 10g de cada biomassa tratadas com peróxido de hidrogênio em concentrações de 3 e 6% (m/v), em volume reacional de 200mL, por 4h, a 75 rpm, a 25˚C. Após a reação, o pH foi corrigido com HCl 6 mols/L até 6, e cerca de 4 lavagens com etanol foram aplicadas. As reações de deslignificação das biomassas ocorreram em condições específicas para cada reagente: clorito de sódio (5, 10 e 20% m/m a 80°C/1 a 3h), peróxido de hidrogênio (5, 10 e 20% m/m a 25°C/4h) e sulfito de sódio (5,10 e 20% m/m a 121°C/30 min). A deslignificação da hemicelulose seguiu a mesma metodologia da deslignificação da biomassa, no entanto com concentração de 10% do reagente de deslignificação. A atividade enzimática de xilanase, foi realizada com extrato comercial utilizando as hemiceluloses extraídas e deslignificadas como substrato. As hemiceluloses extraídas foram monitoradas quanto a sua solubilidade e condutividade em solução. Os resultados de extração com 3 e 6% de peróxido mostraram valores entre 7 a 29% de rendimento. Os teores de lignina residual se mostraram coerentes com a literatura, ficando entre 4 a 10%. A deslignificação da biomassa previamente a extração de hemicelulose apresentou melhores resultados, rendendo entre 26,22% a 47,09%, com teor de lignina residual de 0,6% a 17,09%. A deslignificação da hemicelulose apresentou melhores resultados com o emprego de peróxido de hidrogênio, com redução de 58,44% do teor inicial de lignina. As maiores atividades enzimáticas foram obtidas com as hemicelulose provenientes da biomassa deslignificada com peróxido de hidrogênio 5 e 10% (174,97 e 166,12 UI mL-1). Os testes de solubilidade e pureza (baixa presença de sal) apontam que as hemiceluloses extraídas apresentaram características semelhante ou melhor que a xilana comercial. Na deslignificação das biomassas, o peróxido de hidrogênio foi o reagente que apresentou melhor resultado ao rendimento, pureza e solubilidade da hemicelulose. Este reagente também foi melhor na deslignificação das hemiceluloses, resultando menor teor de lignina residual. Para produzir um substrato para atividade enzimática a estratégia de deslignificação da biomassa previamente a extração de hemicelulose foi mais adequada, apresentando maior atividade enzimática.
Materials such as sugarcane bagasse are abundant in nature and represent renewable sources for the extraction of molecules of economic interest, such as hemicelluloses. However, the extraction methods for these macromolecules need to be better developed for industrial application. Thus, the main objective of the work has been the development of a hemicellulose extraction method with high yield and purity using fractions of sugarcane biomass: leaf and stem: internode, node, and external fraction. Two strategies have been evaluated: a prior delignification of the biomass, and the delignification of the hemicellulose extracted from nondelignified material. The extracted hemicellulose has been evaluated as a substrate for the determination of enzymatic activity of xylanase. The hemicellulose extraction method has employed 10g of each biomass treated with hydrogen peroxide in concentrations of 3 and 6% (m/v), in a reaction with volume of 200mL, for 4h, at 75 rpm, at 25ºC. After the reaction, the pH has been corrected with HCl 6 mol/L to 6, and about 4 washes with ethanol have been applied. The biomass delignification reactions have occurred under specific conditions for each reagent: sodium chlorite (5, 10, and 20% w/w 80 °C / 1 to 3h), hydrogen peroxide (5, 10, and 20% w/w 25°C/4h), and sodium sulfite (5.10 and 20% w/w 121°C/30 min). The delignification of the hemicellulose has followed the same methodology of delignification of the biomass, however with a concentration of 10% of the delignification reagent. The enzymatic activity of xylanase has been performed with commercial extract using hemicellulose extracted and delignified as substrate. The extracted hemicelluloses have been monitored for their solubility and conductivity in solution. The results of extraction with 3 and 6% peroxide have shown yield values between 7 and 29%. The residual lignin contents have been consistent with the literature, ranging from 4 to 10%. The delignification of the biomass prior to the extraction of hemicellulose presented better results, yielding between 26.22% and 47.09%, with residual lignin contents of 0.6% to 17.09%. The delignification of hemicellulose has presented better results with use of hydrogen peroxide, with reduction of 58.44% of the initial lignin content. The highest enzymatic activities have been obtained with the hemicellulose from the biomass delignified with hydrogen peroxide 5 and 10% (174.97 and 166.12 IU mL-1). The solubility and purity tests (low salt content) indicate that the extracted hemicelluloses have presented characteristics similar to or better than commercial xylan. In the delignification of the biomasses the hydrogen peroxide has been the reagent that has presented better results referring to yield, purity, and solubility of the hemicellulose. This reagent has also been better in the delignification of the hemicelluloses, resulting in lower residual lignin content. To produce a substrate for enzymatic activity the strategy of delignification of the biomass prior to hemicellulose extraction has been more adequate, presenting higher enzymatic activity.
Materials such as sugarcane bagasse are abundant in nature and represent renewable sources for the extraction of molecules of economic interest, such as hemicelluloses. However, the extraction methods for these macromolecules need to be better developed for industrial application. Thus, the main objective of the work has been the development of a hemicellulose extraction method with high yield and purity using fractions of sugarcane biomass: leaf and stem: internode, node, and external fraction. Two strategies have been evaluated: a prior delignification of the biomass, and the delignification of the hemicellulose extracted from nondelignified material. The extracted hemicellulose has been evaluated as a substrate for the determination of enzymatic activity of xylanase. The hemicellulose extraction method has employed 10g of each biomass treated with hydrogen peroxide in concentrations of 3 and 6% (m/v), in a reaction with volume of 200mL, for 4h, at 75 rpm, at 25ºC. After the reaction, the pH has been corrected with HCl 6 mol/L to 6, and about 4 washes with ethanol have been applied. The biomass delignification reactions have occurred under specific conditions for each reagent: sodium chlorite (5, 10, and 20% w/w 80 °C / 1 to 3h), hydrogen peroxide (5, 10, and 20% w/w 25°C/4h), and sodium sulfite (5.10 and 20% w/w 121°C/30 min). The delignification of the hemicellulose has followed the same methodology of delignification of the biomass, however with a concentration of 10% of the delignification reagent. The enzymatic activity of xylanase has been performed with commercial extract using hemicellulose extracted and delignified as substrate. The extracted hemicelluloses have been monitored for their solubility and conductivity in solution. The results of extraction with 3 and 6% peroxide have shown yield values between 7 and 29%. The residual lignin contents have been consistent with the literature, ranging from 4 to 10%. The delignification of the biomass prior to the extraction of hemicellulose presented better results, yielding between 26.22% and 47.09%, with residual lignin contents of 0.6% to 17.09%. The delignification of hemicellulose has presented better results with use of hydrogen peroxide, with reduction of 58.44% of the initial lignin content. The highest enzymatic activities have been obtained with the hemicellulose from the biomass delignified with hydrogen peroxide 5 and 10% (174.97 and 166.12 IU mL-1). The solubility and purity tests (low salt content) indicate that the extracted hemicelluloses have presented characteristics similar to or better than commercial xylan. In the delignification of the biomasses the hydrogen peroxide has been the reagent that has presented better results referring to yield, purity, and solubility of the hemicellulose. This reagent has also been better in the delignification of the hemicelluloses, resulting in lower residual lignin content. To produce a substrate for enzymatic activity the strategy of delignification of the biomass prior to hemicellulose extraction has been more adequate, presenting higher enzymatic activity.
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Palavras-chave
Biomassa, Cana-de-açúcar, Hemicelulose, Lignina, Xilanase, Biomass, Sugarcane, Hemicellulose, Lignin, Xylanase