Microbial reclamation of shellfish wastes for the production of chitinases

Shrimp and crab shell powder (SCSP), prepared by treating shellfish processing waste with boiling and crushing, was used as a substrate for isolating chitinolytic microorganisms. Three potential strains (E1, J1, and J1-1) were isolated and identified as Bacillus cereus, B. alvei, and B. sphaericus, respectively. Three extracellular chitinases (FB1, FB2, and FB3) were purified from the culture supernatants of Bacillus cereus E1, B. alvei J1, and B. sphaericus J1-1, respectively. The molecular weights of FB1, FB2, and FB3 were 71,000, 71,000, and 65,000, respectively, by SDS-PAGE. The pIs for FB1, FB2, and FB3 were 7.1, 7.2, and 7.4, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of FB1 were pH 9, 50°C, pH 7 to 10, and 70°C; those of FB2 were pH 9, 60°C, pH 5 to 9, and 70°C; and those of FB3 were pH 7, 50°C, pH 5 to 9, and 60°C. The activities of all enzymes were strongly inhibited by Hg2+ and completely inhibited by glutathione, dithiothreitol, and 2-mercaptoethanol.