Production of Alcaligenes xylosoxydans EMS33 in a Bench-scale Fermenter

Abstract

Optimization of medium composition and pH for chitinase production by the Alcaligenes xylosoxydans mutant EMS33 was carried out in the present study and the optimized medium composition and conditions were evaluated in a fermenter. The medium components screened initially using Plackett–Burman design were (NH4)2SO4, MgSO4 7H2O, KH2PO4, yeast extract, Tween 20 and chitin in shake flask experiments. The significant medium components identified by the Plackett–Burman method were MgSO4 7H2O, Tween 20 and chitin. Central composite response surface methodology was applied to further optimize chitinase production. The optimized values of MgSO4 7H2O, Tween 20, chitin and pH were found to be 0.6 g/l, 0.05 g/l, 11.5 g/l and 8.0, respectively. Chitinase and biomass production of Alcaligenes xylosoxydans EMS33, was studied in a 2-l fermenter containing (g/l): chitin, 11.5; yeast extract, 0.5; (NH4)2SO4, 1; MgSO4 7H2O, 0.6; KH2PO4, 1.36 and Tween 20, 0.05. The highest chitinase production was 54 units/ml at 60 h and pH 8.0 when the dissolved O2 concentration was 60%, whereas the highest biomass production was achieved at 36 h and pH 7.5 without any dissolved O2 control.