Isolation of Chitinase Producing Bacillus Strains and Increasing of the Enzyme Production by In vitro Mutagenesis

In the present study, three chitinolytic Bacillus strains were isolated from the soil samples containing shells of crustaceans collected from the coast sediments of Erzin district of Hatay province. The isolates were entitled as Bacillus sp. DBK1, DBK2, and DBK3, respectively. The optimum enzyme activities were observed at 40 °C for all chitinases. On the other hand, optimum pH value for DBK1 chitinase was 7.0, whereas 6.0 for DBK2 and DBK3 chitinases. The specific activities of DBK1, DBK2, and DBK3 chitinases were 6.61, 13.17 and 8.65 U/mg at 40 °C, respectively. Maximum enzyme productions of isolates were observed after 48, 36, and 60 hours later from inoculation for DBK1, DBK2, and DBK3 isolates, respectively. Mutant varieties DBK1-M3 and DBK1-M4 from DBK1, DBK2-M3, DBK2-M4 and DBK2-M5 from DBK2, and DBK3-M3 and DBK3-M4 from DBK3 were obtained after ethidium bromide (EtBr) treatment. DBK1-M3, DBK1-M4, DBK2-M3, DBK2-M4, DBK2-M5, DBK3-M3 and DBK3-M4 have produced 146, 193, 192, 121, 136, 178 and 116% more chitinase according to their own wild type strains, respectively. The activators for DBK1 chitinase were MnCl2, MgCl2, CaCl2, ZnCl2, and CuSO4, for DBK2 chitinase were MnCl2, ZnCl2 and KCl, and for DBK3 chitinase were MnCl2, CaCl2 and ZnCl2. HgCl2 strongly inhibited all wild type chitinases. These properties of the enzymes indicated that they could be used as an enzyme supplement for aerobic stability of silage