Comparative evaluation of acid and alkaline sulfite pretreatments for enzymatic saccharification of bagasses from three different sugarcane hybrids

Abstract

Sugarcane bagasses from three experimental sugarcane hybrids and a mill-reference sample were used to compare the efficiency and mode of action of acid and alkaline sulfite pretreatment processes. Varied chemical loads and reaction temperatures were used to prepare samples with distinguished characteristics regarding xylan and lignin removals, as well as sulfonation levels of residual lignins. The pretreatment with low sulfite loads (5%) under acidic conditions (pH 2) provided maximum glucose yield of 70% during enzymatic hydrolysis with cellulases (10 FPU/g) and β-glucosidases (20 UI/g bagasse). In this case, glucan enzymatic conversion from pretreated materials was mostly associated with extensive xylan removal (70-100%) and partial delignification occurred during the pretreatment. The use of low sulfite loads under acidic conditions required pretreatment temperatures of 160°C. In contrast, at a lower pretreatment temperature (120°C), alkaline sulfite process achieved similar glucan digestibility, but required a higher sulfite load (7.5%). Residual xylans from acid pretreated materials were almost completely hydrolysed by commercial enzymes, contrasting with relatively lower xylan to xylose conversions observed in alkaline pretreated samples. Efficient xylan removal during acid sulfite pretreatment and during enzymatic digestion can be useful to enhance glucan accessibility and digestibility by cellulases. Alkaline sulfite process also provided substrates with high glucan digestibility, mainly associated with delignification and sulfonation of residual lignins. The results demonstrate that temperature, pH, and sulfite can be combined for reducing lignocellulose recalcitrance and achieve similar glucan conversion rates in the alkaline and acid sulfite pretreated bagasses. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:944-951, 2018.

β‐Glucosidase produced by Moniliophthora perniciosa: Characterization and application in the hydrolysis of sugarcane bagasse

“…The initial mass of sugarcane bagasse used in the pretreatment for delignification with NaOH + Na 2 SO 3 (3 + 6% w/w of bagasse) was 15.00 g. After pretreatment, the recovered biomass was 11.17 g, obtaining a biomass yield of 74.47% and a total of macromolecular compounds removed of 25.53%. Monte et al 45 obtained a total recovery of 73-87% of solids after alkaline and acid pretreatment of sugarcane bagasse in the presence of sulfite ions. This reduction in biomass mass is a result of the solubilization of the cell wall components in the pretreatment solution.…”

“…Zhang et al 47 carried out enzymatic hydrolysis of sugarcane bagasse and obtained the highest glucose yields in the samples treated with 0.5% NaOH solu-F I G U R E 5 Pareto chart for optimization of the hydrolysis of delignified sugarcane bagasse tion in ethanol, with 72% of glucose after 72 h of hydrolysis. Monte et al 45 compared the efficiency of sulfite-acid and sulfite-alkaline pretreatments for sugarcane bagasse, obtaining a conversion of about 65% in the sulfite-alkaline pretreatment carried out with a 7.5% sulfite load.…”

Cultivo de Mycothermus thermophilus e Trichoderma reesei RP698 em resíduos agroindustriais: consórcio microbiano no desenvolvimento de um coquetel enzimático para sacarificação de cana-de-açúcar

“…Segundo Buckeridge, Grandis e Tavares (2019) (27), isto ocorre devido à hidratação das paredes que possibilita a quebra de algumas ligações covalentes e, assim, torna a biomassa lignocelulósica mais acessível às enzimas responsáveis pela hidrólise do material. Dentre os pré-tratamentos disponíveis, os mais conhecidos são: alcalino (85,147,152,154,176); ácido (107,177); organosolv (88,116,175) e autohidrólise (27,91,178), que foram objeto de estudo deste trabalho. Buckeridge, Grandis e Tavares (2019) relataram que esses distintos pré-tratamentos possuem mecanismos de ação diferentes, como por exemplo, o alcalino que libera a lignina e disponibiliza celulose e hemicelulose para hidrólise, enquanto que a autohidrólise é responsável pela remoção da hemicelulose (27).…”