A novel low molecular weight extracellular protease from a moderately halophilic bacterium Salinivibrio sp. strain MS-7: production and biochemical properties

Abstract

A B S T R A C T Kinetics of bacterial growth and protease production were monitored on a novel isolated moderately halophilic bacterium, Salinivibrio sp. strain MS-7, and maximum growth and protease activity was achieved after 48 hours at 30°C and 180 rpm. To determine the effect of various carbon sources on protease production, glucose, lactose, sucrose and maltose were investigated and maximum production of the enzyme was obtained in a basal medium (pH 8.0) containing maltose as a carbon source (494 U/ml). The protease was isolated from a stationary phase culture, purified 3.6 -fold with 56% yield by a simple procedure and characterized biochemically. The enzyme revealed a monomeric structure with a relative molecular mass of 21 KDa by running on SDS-PAGE. Maximum caseinolytic activity of the enzyme was observed at 50°C, pH 8.0 and 0€ 0.5 M NaCl with a high tolerance to salt concentrations of up to 3 M. The effect of various metal ions and inhibitors on caseinolytic activity of the purified protease revealed that it probably belongs to the subclass of serine metalloproteases. These finding s suggest that the protease secreted by Salinivibrio sp. strain MS-7 can be introduced as a candidate for biotechnological applications based on its haloalkaline properties.