Fusarium oxysporum F3 produced N-acetyl-beta-D-glucosaminidase when grown on wheat bran and chitin as carbon sources in solid-state fermentation. The initial moisture content and pH of growth medium were 65% and 6.0, respectively, and the enzyme yield 23.6 U g(-1) carbon source. Two isozymes of N-acetyl-beta-D-glucosaminidase, called N-acetyl-beta-D-glucosaminidases I and II, were isolated from the culture filtrate of F. oxysporum F3. The filtrate was subjected to ammonium sulphate fractionation followed by anion exchange, get filtration, hydrophobic interaction and cation exchange chromatography. The optimum pH of isozymes I and II was 5.0 and 6.0, respectively, whereas maximum activity of both isozymes was obtained at 40degreesC. The K-m of isozymes I and II was 49.6 and 48.6 muM and the V-max 1.24 and 0.26 mu mol mg(-1) min(-1), respectively, on p-nitrophenyl N-acetyl-beta-D-glucosaminide as substrate. The molecular mass of isozymes I and II was calculated to be 67 kDa by SDS-PAGE. (C) 2003 Elsevier Ltd. All rights reserved.