Synergy between chemical additives and pretreatments of sugarcane biomass favoring enzymatic hydrolysis and production of fuel ethanol
Carregando...
Data
2020-11-26
Autores
Schmatz, Alison Andrei [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O bagaço de cana-de-açúcar é matéria-prima na produção de etanol de segunda geração (2G) e produtos de valor agregado com potencial biotecnológico. No entanto, a biomassa precisa de pré-tratamentos para quebrar o complexo celulose-hemicelulose-lignina. Durante os pré-tratamentos ácido e hidrotérmico, pode ocorrer a formação de produtos de degradação de açúcares (tóxico para microrganismos fermentadores), que podem se condensar com fragmentos de lignina formando a pseudo-lignina, prejudicial à hidrólise enzimática. Portanto, este estudo teve como objetivo avaliar a remoção de hemicelulose e lignina da biomassa da cana-de-açúcar durante o pré-tratamento ácido diluído e organosolv com adição de antioxidantes de baixo custo, e suas influências na supressão da formação de inibidores e produção de açúcares fermentáveis na fermentação e sacarificação simultânea (SSF). Diferentes frações da cana-de-açúcar apresentaram diferentes recalcitrâncias. A fração externa apresentou menores rendimentos na hidrólise enzimática e 5 g L-1 de ácido acético no hidrolisado do pré-tratamento ácido. O conteúdo de extrativos e lignina foram identificados como fatores chave contribuindo para a formação de pseudo-lignina. A biomassa parcialmente deslignificada e pré-tratada com ácido apresentou rendimentos de aproximadamente 90% de conversão de celulose na hidrólise enzimática (até 12 g L-1). O hidroxibutil tolueno (BHT) demonstrou potencial efeito na remoção de lignina da biomassa no pré-tratamento ácido (121 ° C). Com 50% etanol (v/v), o BHT induziu 10 g 100 g-1 a mais de remoção de lignina. A adição de BHT no pré-tratamento ácido resultou em menor formação de inibidores na fração líquida (0,01 g L-1 de furfural, 0,01 g L-1 de HMF e 0,68 g L-1 de ácido acético) e baixo teor residual de hemicelulose e lignina na biomassa pré-tratada. Todos os 6 compostos químicos (terc-butil hidroquinona; 3-terc-butil-4-hidroxianisol; 3,4,5-trihidroxi benzoato de metila; Tween 20; Tween 80 e dimetilsulfóxido) melhoraram individualmente a remoção de lignina e o rendimento da hidrólise enzimática. O 3-terc-butil-4-hidroxianisol apresentou 71% de remoção de lignina, enquanto o Tween 80 utilizado no pré-tratamento resultou em um material com alta digestibilidade, 98,9% de rendimento de glicose na hidrólise enzimática. Após 48 h de SSF, 17,06 g L-1 de glicose e 15,17 g L-1 de etanol foram observados na biomassa deslignificada e pré-tratada com ácido (DL-PT). A remoção de hemicelulose e lignina resultou em maiores rendimentos de conversão de açúcares. Antioxidantes e surfactantes foram identificados como potenciais removedores de lignina, indicando que podem ser aplicados em processos biotecnológicos.
Sugarcane bagasse is a feedstock material in the production of second-generation ethanol (2G) and value-added products with biotechnological potential. However, biomass needs pretreatments to break down the cellulose-hemicellulose-lignin complex. During acid and hydrothermic pretreatments, can occur formation of sugar degradation products (toxic to fermenting microorganisms), which can condense with lignin fragments forming the pseudo-lignin, harmful to enzymatic hydrolysis. Therefore, this study aimed evaluate the hemicellulose and lignin removal from sugarcane biomass during diluted acid and organosolv pretreatment with addition of low-cost antioxidants, and their influences on the suppression the inhibitors formation and fermentable sugars production in simultaneous saccharification and fermentation (SSF). Different sugarcane fractions showed different recalcitrance. External fraction showed lower yields in the enzymatic hydrolysis, and 5 g L-1 of acetic acid in the hydrolysate from acid pretreatment. The content of extractives and lignin were identified as key factor contributing to the formation of pseudo-lignin. Partial delignified and acid pretreated biomass showed yields of approximately 90% of cellulose conversion by enzymatic hydrolysis (up to 12 g L-1). Butylated hydroxytoluene (BHT) demonstrated a potential effect on the removal of lignin from biomass in acid pretreatment (121 °C). With 50% (v/v) ethanol, BHT induced 10 g 100 g-1 more lignin removal. Addition of BHT in acid pretreatment resulted in lower formation of inhibitors in liquid fraction (0.01 g L-1 of furfural, 0.01 g L-1 of HMF and 0.68 g L-1 of acetic acid) and low residual hemicellulose and lignin content in the pretreated biomass. All the 6 chemical compounds (tert-butylhydroquinone; 3-tert-butyl-4-hydroxyanisole; methyl 3,4,5-trihydroxybenzoate; Tween 20; Tween 80 and dimethyl sulfoxide) individually improved lignin removal and enzyme hydrolysis yield. The 3-tert-butyl-4-hydroxyanisole showed 71% lignin removal, while Tween 80 used in the pretreatment resulted in a material with high digestibility, 98.9% glucose yield by enzymatic hydrolysis. After 48 h of SSF, 17.06 g L-1 of glucose and 15.17 g L-1 of ethanol were observed in delignified-acid pretreated biomass (DL-PT). Removal of hemicellulose and lignin resulted in higher yields conversion of sugars. Antioxidants and surfactants were identified as potential lignin removal effect, indicating that they can be applied in biotechnological process.
Sugarcane bagasse is a feedstock material in the production of second-generation ethanol (2G) and value-added products with biotechnological potential. However, biomass needs pretreatments to break down the cellulose-hemicellulose-lignin complex. During acid and hydrothermic pretreatments, can occur formation of sugar degradation products (toxic to fermenting microorganisms), which can condense with lignin fragments forming the pseudo-lignin, harmful to enzymatic hydrolysis. Therefore, this study aimed evaluate the hemicellulose and lignin removal from sugarcane biomass during diluted acid and organosolv pretreatment with addition of low-cost antioxidants, and their influences on the suppression the inhibitors formation and fermentable sugars production in simultaneous saccharification and fermentation (SSF). Different sugarcane fractions showed different recalcitrance. External fraction showed lower yields in the enzymatic hydrolysis, and 5 g L-1 of acetic acid in the hydrolysate from acid pretreatment. The content of extractives and lignin were identified as key factor contributing to the formation of pseudo-lignin. Partial delignified and acid pretreated biomass showed yields of approximately 90% of cellulose conversion by enzymatic hydrolysis (up to 12 g L-1). Butylated hydroxytoluene (BHT) demonstrated a potential effect on the removal of lignin from biomass in acid pretreatment (121 °C). With 50% (v/v) ethanol, BHT induced 10 g 100 g-1 more lignin removal. Addition of BHT in acid pretreatment resulted in lower formation of inhibitors in liquid fraction (0.01 g L-1 of furfural, 0.01 g L-1 of HMF and 0.68 g L-1 of acetic acid) and low residual hemicellulose and lignin content in the pretreated biomass. All the 6 chemical compounds (tert-butylhydroquinone; 3-tert-butyl-4-hydroxyanisole; methyl 3,4,5-trihydroxybenzoate; Tween 20; Tween 80 and dimethyl sulfoxide) individually improved lignin removal and enzyme hydrolysis yield. The 3-tert-butyl-4-hydroxyanisole showed 71% lignin removal, while Tween 80 used in the pretreatment resulted in a material with high digestibility, 98.9% glucose yield by enzymatic hydrolysis. After 48 h of SSF, 17.06 g L-1 of glucose and 15.17 g L-1 of ethanol were observed in delignified-acid pretreated biomass (DL-PT). Removal of hemicellulose and lignin resulted in higher yields conversion of sugars. Antioxidants and surfactants were identified as potential lignin removal effect, indicating that they can be applied in biotechnological process.
Descrição
Palavras-chave
Fermentation, Cellulosic ethanol, Sugarcane, Biomass energy, Cellulosic biodegradation, Saccharification, Bioethanol, Pseudo-lignin, Biorefinery, Lignocellulosic biomass, Sacarificação, Fermentação, Bioetanol, Pseudo-lignina, Biorrefinaria, Biomassa lignocelulósica