Optimization of xylanase production from Aspergillus tamarii SCBH2 using response surface methodology

Abstract

Xylanases are enzymes that catalyze the degradation of β(1–4) bonds of xylan, which is present in the hemicellulose contained in lignocellulosic residues. Currently, xylanases have a biotechnological potential in the process of hydrolysis of lignocellulosic residues for bioalcohol production of second generation and other products of industrial interest. The hydrolysis step is limiting in these processes, since the enzyme is expensive, and its availability is very limited. The objective of this research was to optimize xylanase production evaluating nitrogen concentration, agitation, type, and concentration of carbon source. From different lignocellulosic residues, 9 strains of the genus Aspergillus were isolated, where SCBH2 strain was the one with the highest xylanase activity and was identified as Aspergillus tamarii. Sugarcane bagasse proved to be the best carbon source over corn stubble and sorghum bagasse, possibly due to its high cellulose content and low lignin content; in addition, ammonium sulfate increased xylanase production over other sources of nitrogen such as yeast extract and urea. The optimal conditions obtained from xylanase production by A. tamarii SCBH2 using a central compound design were as follows: 15 gL−1 of sugarcane bagasse, 0.7 gL−1 of ammonium sulfate, and 200 rpm, during 72 h of fermentation increasing the xylanase activity from 1.91 to 10.9 U/mL. These results show feasibility to produce xylanases using low-cost substrates and optimizing operating conditions.