Isolation and Characterization of an Antarctic Stenotrophomonas Strain with Extracellular Protease Activity

Abstract

Proteases, being one of the largest groups of industrial enzymes, have been used in a wide range of applications including protein stain removal, food preparation, leather preparation, and so on. In particular, cold-active proteases offer a great potential as biocatalysts in various fields of biotechnology primarily due to high catalytic efficiency at low temperature and rapid enzyme inactivation by a mild heat treatment, which enable energy cost saving and selective enzyme inactivation, respectively. To unearth new microbial resources for cold-active proteases, we have screened Antarctic soils for the presence of proteolytic bacteria using casein and keratin as substrates, respectively. A total of 129 bacterial species were isolated with genera including Pseudomonas, Bacillus, Thermoleophilum, Mocrococcus, Chryseobacterium, Arthrobacter, Stenotrophomonas, Sporocarcina, Paenibacillus, Planococcus, and unclassified Bacteria after screening 100 different soil samples. Strains showing keratinase activity were further screened for caseinase enzyme activity. Among them, one Stenotrophomonas strain was chosen for further study. The azocasein assay showed that extracellular protease activity was first detected approximately 10 hours after entering stationary phase during growth in nutrient broth, reached its peak at around 60 hours, and prolonged for further 20 hours. The enzyme was found to be aer a great potential as biocatalysts in various fields of biotechnology primarily due to high catalytic efficiency at low temperature and rapid enzyme inactivation by a mild heat treatment, which enable energy cost saving and selective enzyme inactivation, respectively. To unearth new microbial resources for cold-active proteases, we have screened Antarctic soils for the presence of proteolytic bacteria using casein and keratin as substrates, respectively. A total of 129 bacterial species were isolated with genera including Pseudomonas, Bacil