Enhancement of specific activity of Xylanase produced by Ca-alginate entrapped cells of Aspergillus candidus: Optimization by Box-Behnken design

Calcium -alginate entrapment method for the production of xylanase by Aspergillus candidus was optimized by statistical design. Influential parameters like xylan concentration, bead loading and alginate concentration were optimized by Box-Behnken design and subsequent analysis and model validation by second order regression equation. The level of three variables such as xylan concentration, 19.0 g/l; number of bead loading, 112 and alginate concentration, 3.09% were found to be the optimum for maximum xylanase production. Under optimized condition maximum xylanase activity observed 100.23 IU/ml, which was 9% higher than predicted by the model. Organic nitrogen sources were found suitable for xylanase biosynthesis and mixture of yeast extract and peptone was emerged as best among all nitrogen sources tested. Specific activity of xylanase produced under immobilized condition was found 2.8 times higher than that produced under free cells. In repeated batch process maximum xylanase produced at second cycle and it retained more than 50% operational efficiency at the end of 4th cycle. Operational efficiency was found to increase when reused bead loading was reduced up to 50% after the end of 4th cycle.