Abstract
The enzyme biosynthesis using agricultural wastes by solid state fermentation (SSF) and the study of their physicochemical properties are meaningful approaches to improve the biomass hydrolysis. Among them, β-glucosidases and β-xylosidases are key enzymes at the lignocellulose depolymerization, which act in the cleavage of oligosaccharides in monosaccharides. In this study, the production of hemicellulases and cellulases by Pleurotus ostreatus and Aspergillus niger monocultures or in consortium was investigated, using raw sugarcane bagasse (SB) and wheat bran (WB) as substrates. The highest enzymatic activities were observed in the crude extract produced by P. ostreatus PLO6 and A. niger SCBM4 consortium with 98.5, 62.9, 3.8, 12.4, 13.3 and 20.2 U/g for β-glucosidase (β-glu), β-xylosidase (Bxyl), filter paper cellulase (FPase), xylanase (Xyl), exoglucanase (Exgl) and endoglucanase (Engl), respectively. The pH and temperature effects on β-glu and β-xyl were characterized. Optimal activities were obtained at pH 4.0 and 45 °C for β-glu and 3.5 and 55 °C for β-xyl. Both enzymes were stable at acid pH and presented thermostability. The results indicated that the enzymatic cocktail demonstrated potential characteristics for future applications in saccharifications. The use of sugarcane bagasse and wheat bran for microbial growth contributed to aggregate value to these byproducts.
Highlights
Lignocellulosic wastes from agroindustry can be viable and low-cost raw materials of great potential for the production of enzymes, biofuels and biorefineries
The present study evaluated the production of enzymes by the cultivation of the strains Pleurotus ostreatus PLO6 and Aspergillus niger SCBM4, in monocultures and in consortium, by solid state fermentation (SSF) with sugarcane bagasse (SB) and wheat bran (WB) as substrates
3.1 Chemical Composition of the Substrates Sugarcane bagasse was composed of 54.36% of cellulose, 13.52% of hemicelluloses and 26.14% of lignin (Table 1), indicating that the evaluated sample presents a lignocellulosic structure similar to those reported in previous studies (Rodrigues et al, 2017; Lamounier et al, 2020)
Summary
Lignocellulosic wastes from agroindustry can be viable and low-cost raw materials of great potential for the production of enzymes, biofuels and biorefineries. Cellulosic ethanol can be synthesized from the depolymerization of lignocellulose in fermentable sugars (Toquero and Bolado, 2014). Hemicellulases and cellulases are lignocellulose-degrading enzymes responsible for the synergistic breakdown of biomass into free monosaccharides, with wide industrial application such as biofuels, pulp and paper industry, textile sector, detergents, feed, beverages, among others (Verma et al 2020). The cellulose depolymerization occurs through the action of three kinds of cellulases: endoglucanases or endo-1,4-β-D-glucanases (EC 3.2.1.4), exoglucanases or exo-β-1,4-glucanases or cellobiohydrolases (EC 3.2.1.91) and β-1,4-glucosidases or cellobiases (EC 3.2.1.21). Xylanases or endo-β-1,4-xylanases (EC 3.2.1.8) and β-xylosidases or xylan β-1,4-xylosidases (3.2.1.37) are commonly employed for the xylan hydrolysis, the main polysaccharide in the hemicelluloses group, with a wide commercial application (Gomes et al, 2016)
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