Antifungal activity of chitinases from Trichoderma aureoviride DY-59 and Rhizopus microsporus VS-9

Two chitinolytic fungal strains, Trichoderma aureoviride DY-59 and Rhizopus microsporus VS-9, were isolated from soil samples of Korea and Vietnam, respectively. DY-59 and VS-9 crude chitinases secreted by these fungi in the 0.5% swollen chitin culture medium had an optimal pH of 4 and the optimal temperatures of 40 degrees C and 60 degrees C, respectively. Enzymatic hydrolysis products from crab swollen chitin were N-acetyl-beta-D-glucosamine (GlcNAc) by DY-59 chitinase, and GlcNAc and N, N'-diacetylchitobiose (GlcNAc)2 by VS-9 chitinases. The chitinases degraded the cell wall of Fusarium solani hyphae to produce oligosaccharides, among which GlcNAc, (GlcNAc)2, and pentamer (GlcNAc)5 were identified by high-pressure liquid chromatography. DY-59 and VS-9 chitinases inhibited F. solani microconidial germination by more than 70% and 60% at final protein concentrations of 5 and 27 microg mL(-1), respectively, at 30 degrees C for 20 h treatment.