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Abstract
Extracellular chitinase production by the entomopathogenic fungus, Isaria fumosorosea IF28.2 was studied by using submerged fermentation. Maximum chitinase production (178.34±3.91 mU/mL) was obtained when fermentation was carried out at 25°C for 120 h using 72-h-old mycelium in a medium. The effect of inoculum size on chitinase activity was also observed and maximum chitinase activity (159.41±2.91 mU/mL) was obtained with an inoculum size of 3 discs while an incubation period of 96 h proved the most active inducer of chitinase production yielding a chitinase activity of 186.14±3.81 mU/mL. Colloidal chitin (1.5%, w/v) proved to be the best concentration. The optimum pH for chitinase production was 5.7 while 25°C proved to be the best temperature for chitinase production. Supplementation of additional carbon source like 1.5% N-acetylglucosamine (GlcNAc) showed further enhancement in chitinase production. The divalent metal salts, CaCl2, MgCl2 and ZnSO4, inhibited chitinase activity at 10 and 100 mM concentration, whereas inhibition of chitinase activity by KCl, FeSO4 and EDTA was observed only at higher concentrations. The results presented in this study increase the knowledge on chitinase production in I. fumosoroseus opening new avenues for the study of the role of this enzyme in virulence against different insect pests during the infection process.
Acknowledgements
This research was funded by grants from the Chinese National Basic Research Program (called 973 Program) (No. 2006CB102005), the Eleventh Five Year Forest Support Program of China (No. 2006BAD08A1903) and Public sector specific research projects (No. 200803005)