Optimization of a culture medium for increased xylanase production by a wild strain of Schizophyllum commune

Abstract

A culture medium for a wild strain of Schizophyllum commune was optimized with regard to xylanase production by means of response surface methods. The medium components having the strongest influence on xylanase production were chosen for optimization and included microcrystalline cellulose (Avicel), yeast extract, and NH 4NO 3. The optimal region of the medium composition was approached by factorial designs and by the path of steepest ascent. The optimum concentrations were determined by a central composite design and were found to be 73.4 g l -1 Avicel, 55.4 g l -1 yeast extract, and 1.38 g l -1 NH 4NO 3. Additional factorial designs for the medium components that were found to have less influence on xylanase production further improved the medium composition. When the strain was cultivated using the optimized medium in shake flasks, a maximum production of 5,740 IU ml -1 (95,670 nkat ml -1) xylanase activity was reached within 11 days. A laboratory fermentation (9.5 l working volume) was performed with the optimized medium and yielded a maximum xylanase activity of 4,839 IU ml -1 (80,650 nkat ml -1). Other enzyme activities assayed during this cultivation included filter paper and carboxymethyl cellulase, β-glucosidase, β-xylosidase, β-mannanase, acetyl esterase, acetyl xylan esterase, α-arabinofuranosidase, and α-galactosidase.