Induction of cellulase and hemicellulase activities of Thermoascus aurantiacus by xylan hydrolyzed products

Abstract

Thermoascus aurantiacus is able to secrete most of the hemicellulolytic and cellulolytic enzymes. To establish the xylanase inducers of T. aurantiacus, the mycelia were first grown on glucose up until the end of the exponential growth phase, followed by washing and re-suspension in a basal medium without a carbon source. Pre-weighed amounts of xylose (final concentration of 3.5 mg/ml), xylobiose (7 mg/ml) and hydrolyzed xylan from sugarcane bagasse (HXSB) which contained xylose, xylobiose and xylotriose (6.8 mg/ml) were evaluated as inducers of xylanase. It was observed that xylose did not suppress enzyme induction of T. aurantiacus when used in low concentrations, regardless of whether it was inoculated with xylobiose. Xylobiose promoted fast enzyme production stopping after 10 h, even at a low consumption rate of the carbon source; therefore xylobiose appears to be the natural inducer of xylanase. In HXSB only a negligible xylanase activity was determined. Xylose present in HXSB was consumed within the first 10 h while xylobiose was partially hydrolyzed at a slow rate. The profile of α-arabinofuranosidase induction was very similar in media induced with xylobiose or HXSB, but induction with xylose showed some positive effects as well. The production profile for the xylanase was accompanied by low levels of cellulolytic activity. In comparison, growth in HXSB resulted in different profiles of both xylanase and cellulase production, excluding the possibility of xylanase acting as endoglucanases.

Production of xylanase by a new strain of Thermoascus aurantiacus: obtainment of enzymatic extract with reduced cellulolytic activity for application in pulp and paper industries

“…Thus, the T. aurantiacus strain recently isolated from the region of Dourados-MS has considerable potential for the production of xylanase in low-cost culture media (agro-industrial residues). Previous studies have confirmed the potential to produce xylanase by different strains of the same species isolated from other regions (KALOGERIS et al, 1998;DA-SILVA et al, 2005;BRIENZO et al, 2012).…”

“…However, the highest enzyme production was obtained using wheat bran as substrate, producing 1301.1 U g -1 of dry substrate (or 130.11 U mL -1 ). The production of microbial enzymes by solid-state fermentation is directly related to the nutritional composition and accessibility of the substrate (BRIENZO et al, 2012;STROPARO et al, 2012). Wheat bran is a substrate with good water absorption capacity, and its composition favors microbial cultivation for enzymes production (OLIVEIRA et al, 2015).…”

“…This necessary characteristic limits the ability to obtain xylanase by microbial cultivation on complex substrates, such as agro-industrial residues, that are capable of inducing the production of several enzymes, particularly cellulases (BRIENZO et al, 2012).…”

“…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). However, the biobleaching of kraft pulp during the processing of cellulose for paper production is the more widespread and desired use of xylanolytic enzymes, due of the economic importance of this industrial segment (MASUI et al, 2012;MITTAL et al, 2013).…”

“…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). Approximately 40% of the final cost of an enzyme is derived from the medium used for microorganism cultivation (ROMERO et al, 2007).…”