(594i) A Novel Organic Solvent Stable Serine Protease From a Newly Isolated Serratia sp

Microorganisms secrete a wide variety of proteolytic enzymes, a group of hydrolytic enzymes constituting about 50% of the total worldwide enzyme market and having applications in diverse areas including detergent, leather, food, pharmaceutical  and textile processing industries and in bioremediation processes. It constitutes a complex group of enzymes whose common feature is that they catalyze the cleavage of peptide bonds but may differ in some of their properties, such as substrate specificity, active site or catalytic mechanism. Though, microbial proteases have been extensively studied since the advent of enzymology because of their importance in physiological field and industrial applications, screening of alkalophiles from naturally occurring habitats in different parts of the world is expected to result in isolation of new protease producing organisms potentially useful for many novel applications. Enzymatic conversions in non-aqueous media are drawing attention due to its various potential applications in food and pharmaceuticals to specialty chemicals and hence, search for solvent stable proteases has been an important area of research.

During our screening for novel proteases, a Serratia sp. was isolated from alkaline soils the Himlayas, a biodiversity rich hotspot and identified on the basis of morphological and physiological characteristics, biochemical tests and 16 S rRNA sequence analysis. The protease was purified to homogeneity by acetone precipitation followed by gel filtration using Sephacryl S-100. The intact molecular mass of purified protease was determined by MALDI TOF and SDS-PAGE. The enzyme was highly active in the pH range of 6.0 to 11.0 and the optimum pH and temperature were found to be 7.5 and 50^oC, respectively. The protease was characterized as serine protease based on the studies on class specific inhibitors and retained 92 % and 99 % of its activity in the presence of sodium perborate (0.5 %, w/v) and dodecyl benzene sulphonate (0.1 %, w/v), respectively. High stability in presence of detergents such as sodium dodecyl sulphate (0.1 %, w/v), Tween 80 (1.0 %, w/v), Triton X-100 (1.0 %, w/v) and organic solvents such as dimethyl sulfoxide, ethyl acetate and hexane (25 % and 50 % v/v) and its performance in stain removal makes this Serratia protease as an ideal choice for industrial applications such as in detergent, leather, food, pharmaceutical and chemical synthesis industries. The results in detail will be presented.