Conversion and degradation of shellfish wastes by Bacillus cereus TKU018 fermentation for the production of chitosanases and bioactive materials

Two chitosanases (CHSB1 and CHSB2) were purified from the culture supernatant of Bacillus cereus TKU018 with shrimp shell as the sole carbon/nitrogen source. The molecular masses of CHSB1 and CHSB2 determined by SDS–PAGE were approximately 44 kDa and 22 kDa, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of CHSB1 and CHSB2 were (pH 5, 60 °C; pH 5–7, <40 °C) and (pH 7, 50 °C; pH 4–7, <50 °C), respectively. CHSB1 and CHSB2 were both inhibited by EDTA and CHSB1 was inhibited completely by 5 mM Zn2+. CHSB1 and CHSB2 degraded chitosan with DD ranging from 60% to 95%, but did not degrade chitin. The most susceptible substrate was 60% deacetylated chitosan. Furthermore, TKU018 culture supernatant (1.5% SPP) incubated for 3–4 days has 75% relative antioxidant activity (DPPH scavenging ability). With this method, we have shown that shellfish wastes may have a great potential for the production of bioactive materials.