Studies on a N-acetyl-β-d-glucosaminidase produced by Fusarium oxysporum F3 grown in solid-state fermentation

Abstract

Fusarium oxysporum F3 produced N -acetyl-β- 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-β- d -glucosaminidase, called N -acetyl-β- 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 , gel 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 40 °C. The K m of isozymes I and II was 49.6 and 48.6 μM and the V max 1.24 and 0.26 μmol mg −1 min −1 , respectively, on p -nitrophenyl N -acetyl-β- d -glucosaminide as substrate. The molecular mass of isozymes I and II was calculated to be 67 kDa by SDS–PAGE.