Application of statistical experimental design to optimize culture requirements of Aspergillus sp. Zh-26 producing xylanase for degradation of arabinoxylans in mashing

Abstract

The objective of this study was to isolate and characterize a strain of Aspergillus capable of producing xylanase. According to the morphology and comparison of ITS (Internal Transcribed Spacer) rDNA gene sequence, the strain Aspergillus sp. ZH-26 was identified as a strain of Aspergillus awamori. Statistically based experimental designs were applied for the optimization of xylanase production from A. awamori ZH-26. The considered medium components included 17 components as follows: yeast extract, tryptone, urea, NH(4)Cl, (NH(4))(2)SO(4), NaNO(3), KH(2)PO(4), K(2)HPO(4), NH(4)NO(3), MgSO(4), CaCl(2), CuSO(4), ZnCl(2), FeSO(4), MnSO(4), vitamin B(1), and EDTA. Yeast extract, tryptone, (NH(4))(2)SO(4), KH(2)PO(4), and CaCl(2) were identified to have significant effects on xylanase production using the Plackett-Burman experimental design. These 5 major components were subsequently optimized using the Box-Behnken experimental design. By response surface methodology and canonical analysis, the optimal concentrations for higher production of xylanase were yeast extract 5.95 g/L, tryptone 6.79 g/L, (NH(4))(2)SO(4) 13.37 g/L, KH(2)PO(4) 1.14 g/L, CaCl(2) 0.81 g/L. Under optimal conditions, the xylanase activity from A. awamori ZH-26 reached 47.3 U/mL. A small-scale mashing was carried out to evaluate the performance of the xylanase on degradation of arabinoxylans in mashing. Results showed that polymeric arabinoxylan content and wort viscosity in mashing with grist containing wheat malt sharply decreased to the basal level (from 470 to 185 mg/L) with the addition of xylanase.