Cultural conditions for xylanase production by Pleurotus ostreatus SYJ042 were screened in shake flask cultures. The results indicated that various factors including carbon and nitrogen source, air, pH, and inoculum size influence xylanase secretion. The optimum fermentation medium contained a carbon source (2.5% corn cob + 2.5% wheat bran), nitrogen (0.8% peptone), inoculation level (four disks, 0.5 cm in diameter), aeration rate (1/3 fermentation liquid volume) and initial pH 6.0. Under these culture conditions, the maximum level of xylanase activity (24.98 U ml(-1)) was reached in 7 days. The enzyme was stable up to 40degreesC, with 99.3% of the activity remaining after the enzyme had been incubated for 15 min. The enzyme appeared to be stable over a broad pH range (3.0-9.0) under assay conditions. The majority of the metal ions tested had little effect on enzyme activity with the exception of MnO42- (strong inhibitor) and Ag+ (modest inhibitor). (C) 2003 Elsevier Ltd. All rights reserved.