OPTIMIZATION OF A CULTURE-MEDIUM FOR INCREASED XYLANASE PRODUCTION BYA WILD STRAIN OF SCHIZOPHYLLUM-COMMUNE

A culture medium for a wild strain of Schizophyllum commune was optimi zed with regard to xylanase production by means of response surface me thods. The medium components having the strongest influence on xylanas e production were chosen for optimization and included microcrystallin e cellulose (Avicel), yeast extract, and NH4NO3. The optimal region of the medium composition was approached by factorial designs and by the path of steepest ascent. The optimum concentrations were determined b y a central composite design and were found to be 73.4 g l-1 Avicel, 5 5.4 g l-1 yeast extract, and 1.38 g l-1 NH4NO3. Additional factorial d esigns for the medium components that were found to have less influenc e 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 act ivity was reached within 11 days. A laboratory fermentation (9.5 l wor king volume) was performed with the optimized medium and yielded a max imum xylanase activity of 4,839 IU ml-1 (80,650 nkat ml-1). Other enzy me activities assayed during this cultivation included filter paper an d carboxymethyl cellulase, beta-glucosidase, beta-xylosidase, beta-man nanase, acetyl esterase, acetyl xylan esterase, alpha-arabinofuranosid ase, and alpha-galactosidase.