ماندانا زارعی

Chitinases have received attention because of their wide applications in the medicine, biotechnology, agriculture, waste management and industrial applications such as food quality enhancer and biopesticide. The ability of chitinase for digesting insect chitin raises the idea of using it for controlling insects. In this research Temperature, pH profile and temperature, pH stability of Serratia marcescens B4A (isolated from soil) chitinase were compared by chitinase produced by Bacillus cereus p-1 that isolated from an insecticide tablet for probable capacity of S. marcescens chitinase for using in insecticide. chitinase activity was examined by incubating the enzyme in 1% w/v colloidal chitin as substrate at various temperatures (10-90 ?C) for 15 min at pH 7.9 (optimum pH); after that the residual activity of the chitinase was measured at once. To determine the temperature stability, chitinase initially was pre-incubated at the different temperatures (10-90 ?C). Every 10 min (up to 90 min) samples were placed in ice for 30 min and then colloidal chitin was added and enzyme assay was done at 25 ?C. To examine the optimum pH of the chitinase, 1% w/v colloidal chitin was prepared as the substrate at different pHs (2-10) by 50 mM phosphate- sodium acetate- glycine buffer and the chitinase was added to the substrate and then incubated in 45 ?C for 15 min. The optimum temperature of Bacillus cereus p-1 and Serratia marcescens B4A for chitinase production was 50 ?C and 45 ?C, respectively.the optimum pH for activity of the Bacillus cereus p-1 chitinase is 5 and for Serratia marcescens B4A is also 5. Both chitinases were stable at pH 3 to 10 for 90 min at 25 ?C. The similarity between temperature and pH profile and stability of these two strains determined that chitinase extracted from Serratia marcescens B4A has potential use in insecticide.