Conversion of squid pen by Serratia ureilytica for the production of enzymes and antioxidants

Two proteases (P1 and P2) and a chitinase (C1) were purified from the culture supernatant of Serratia ureilytica TKU013 with squid pen as the sole carbon/nitrogen source. The molecular masses of P1, P2 and C1 determined by SDS–PAGE were approximately 50 kDa, 50 kDa and 60 kDa, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of P1, P2 and C1 were (pH 10, 40 °C, pH 7–11, and <50 °C), (pH 10, 40 °C, pH 8–11, and <40 °C) and (pH 6, 50 °C, pH 5–8, and <50 °C), respectively. P1 and P2 were inhibited by Mg2+, EDTA and C1 was inhibited completely by Cu2+. The antioxidant activity of TKU013 culture supernatant was 72% per mL (DPPH scavenging ability). With this method, we have shown that squid pen wastes can be utilized and have revealed its hidden potential in the production of functional foods.