Purification and Characterization of Metalloprotease from Serratia marcescens PPB-26 and Its Application for Detergent Additive

Abstract

In this study, the extracellular metalloprotease from Serratia marcescens PPB-26 was purified to homogeneity via ethanol fractionation and DEAE-cellulose column chromatography. Thus, a 3.8-fold purification was achieved with a 20% yield and specific activity of 76.2 U/mg. The purified protease was a 50-kDa monomer whose optimum pH and temperature for activity were 7.5 and 30℃ respectively; however, it was found to remain active in the 5-9 pH range and up to 40℃ for 6 h. The protease had a half-life of 15 days at 4℃, an optimum reaction time of 10 min, and an optimum substrate (casein) concentration of 0.25%. Furthermore, the Michaelis constant (Km) and reaction velocity (Vmax) of the protease were calculated to be 0.28% and 111.11 μmoles/(min·mg)-1, respectively. The protease was stable when subjected to metal ions (2 mM), showing increased activity with most (especially CoCl2 and MgSO4 (30.54% increase)). It was also stable when exposed to oxidizing agents, bleaching agents, and detergents (5% v/v for 60 min). It retained 93% of its activity in non-ionic detergents (Tween-20, Tween-80, and Triton X-100). Moreover, wash performance analysis in commercial detergents (Ariel and Tide) showed that not only was the protease capable of protein stain removal, but also reduced cleaning time by 80% when added to detergents. Thus, the Serratia marcescens PPB-26 metalloprotease appears to be a promising new candidate as a laundry additive in the detergent industry.