High-level xylanase production by an alkaliphilic Bacillus sp. by using solid-state fermentation

Abstract

Bacillus sp. AR-009 produced up to 720 U/g dry bacterial bran xylanase activity when grown by using solid-state fermentation with wheat bran serving as a substrate. Xylanase production was highest at a wheat bran-to-moisture ratio of from 1:0.5 to 1:1.5 and an Na 2CO 3 concentration of 10% (w/w). Strong repression of xylanase production was observed in the presence of 5% (w/w) xylose and lactose, whereas sucrose and glucose at the same concentration slightly affected enzyme production. The effect of glucose was concentration-dependent, inducing less than 10% of the maximum xylanase production at a concentration of 15% (w/w). No significant effect was observed on xylanase production upon addition of peptone and tryptone, whereas yeast extract slightly stimulated enzyme production. The ability of the organism to produce high-titer xylanase activity at alkaline pH and lower wheat bran-to-moisture ratio could have a potential advantage in minimizing the risk of contamination. In addition, because the enzyme could be extracted by using a minimum volume of liquid, the cost of downstream processing during product upgrading and the cost of waste treatment steps can be greatly reduced. The use of solid-state fermentation for the production of xylanase by Bacillus sp. AR-009 could, therefore, lead to substantial reduction in the overall cost of enzyme production.