Two novel surfactant-stable alkaline proteases from Vibrio fluvialis TKU005 and their applications

An alkaliphilic protease-producing bacterium was isolated and identified as Vibrio fluvialis TKU005. Two surfactant-stable alkaline metalloproteases (FI and FII) were purified from the culture supernatant of shrimp shell powder containing medium (pH 10). The molecular masses of FI and FII were 41 kDa and 39 kDa, respectively, assayed by SDS-PAGE. The optimum pH, optimum temperature, pH stability, thermal stability, Km, and Vmax of FI and FII were (9, 60 °C, 7–9, 50 °C, 2.21 mg/mL, 0.26 U/mL) and (9, 60 °C, 6–9, 60 °C, 3.92 mg/mL, 0.27 U/mL), respectively. The protease activities of FI and FII could be activated by the surfactant SDS (1%). The fifth day culture supernatant enhanced the growth of Chinese cabbage (Brassica campestris). The enhancing effect was due to hydrolyzates of the metabolites rather than the proteases.