Abstract
Xylanases are useful in several industrial segments, including pulp and paper bleaching, animal feed, and bread-making processes. However, the industrial use of these enzymes is closely related to its production cost and its catalytic properties. The process of solid state fermentation enables the use of agro-industrial residues as substrates for microbial cultivation and enzymes production, reducing costs. In the present study, different cultivation parameters were evaluated for the xylanase production by the thermophilic fungus Thermoascus aurantiacus , by solid state fermentation, using agro-industrial residues as substrates. High production of xylanase (1701.9 U g -1 of dry substrate) was obtained using wheat bran containing 65% of initial moisture, at 120 h of cultivation, and 45°C. The xylanase showed optimal activity at pH 5.0 and 75°C; its stability was maintained at pH 3.0–11.0. The enzyme retained its catalytic potential after 1 h, at 75°C. The enzymatic extract produced under optimized conditions showed reduced activities of endoglucanase and FPase. Our results, including the xylanase production by T. aurantiacus in low-cost cultivation medium, high structural stability of the enzyme, and reduced cellulolytic activity, encourage the application of this enzymatic extract in pulp and paper bleaching processes.
Highlights
Hemicellulose is the second-most abundant polysaccharide in nature, as it is a structural constituent of plant cell wall, disposed between cellulose and lignin
Xylanases are enzymes responsible for hydrolyzing the β-1,4-xylan bonds to release xylose oligosaccharides, reducing the degree of polymerization of the main hemicellulose chain and disrupting the plant cell wall (HADDAR et al, 2012; GOWDHAMAN et al, 2014). This catalytic property enables these enzymes to be used in the hydrolysis of vegetal biomass for the production of biofuels, the formulation of animal feed, or even in bread-making processes to improve the quality of dough, hydrolyzing xylooligosaccharides that are disadvantageous to the formation of gluten and impairs the crumb structure (BECKER et al, 2009; BRIENZO et al, 2012; OLIVEIRA et al, 2014; PIROTA et al, 2015; TERRASAN and CARMONA, 2015)
An alternative for reducing the final cost of these biomolecules involves the use of agro-industrial residues in solidstate fermentation to produce microbial enzymes (BRIENZO et al, 2012; MASUI et al, 2012; SILVA et al, 2013; TERRASAN and CARMONA, 2015)
Summary
Hemicellulose is the second-most abundant polysaccharide in nature, as it is a structural constituent of plant cell wall, disposed between cellulose and lignin. Xylanases are enzymes responsible for hydrolyzing the β-1,4-xylan bonds to release xylose oligosaccharides, reducing the degree of polymerization of the main hemicellulose chain and disrupting the plant cell wall (HADDAR et al, 2012; GOWDHAMAN et al, 2014) This catalytic property enables these enzymes to be used in the hydrolysis of vegetal biomass for the production of biofuels, the formulation of animal feed, or even in bread-making processes to improve the quality of dough, hydrolyzing xylooligosaccharides that are disadvantageous to the formation of gluten and impairs the crumb structure (BECKER et al, 2009; BRIENZO et al, 2012; OLIVEIRA et al, 2014; PIROTA et al, 2015; TERRASAN and CARMONA, 2015). The enzyme produced under optimized conditions was characterized biochemically to evaluate its structural stability for future application in the pulp and paper industry
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