Effect of various metal ions: The effect of various metal ions on chitinase production by Aeromonas sp. JK.l was investigated by supplementing the medium with 5 mM of the respective cations. Results showed that chitinase production was most affected by the addition of Mg 2+ and J.1n2+, where enzyme production was approximately 60 and 54% higher than that of control, respectively (Fig. 5). Addition of Ca2+ and Cs+ resulted in a slight increase in chitinase production, while other ions were formd to inhibit enzyme production from 20 to 100%. When the concentration effect of Mg2 + was further studied, it was formd that the optimum concentration of MgCl2 for chitinase production by Aeromonas sp. JK.l was 7.5 mM.