Isolation and characterization of thermoactive extracellular protease-producing geobacillus caldoproteolyticus sp. nov. from sewage sludge

Abstract

A proteolytic thermophilic bacterial strain, designated as strain SF03, was isolated from sewage sludge in Singapore. Strain SF03 is strictly aerobic, rod-shaped, Gram- positive, catalase positive, oxidase positive, and forms endospores. Strain SF03 grew at temperatures ranging from 35 to 65 OC, pH ranging from 6.0 to 9.0 and salinities ranging from 0 to 2.5%. Phylogenetic analyses revealed that strain SF03 was most similar to Saccharococcus themophilus, Geobacillus caldoxylosilyticus and Geobacillus thermoglucosidasius, with the 16s rRNA gene sequence identity of 97.6%, 97.5% and 97.2%, respectively. Based on taxonomic and 16s rRNA analysis data, strain SF03 was named Geobacillus caldoproteolyticus sp. nov. Production of extracellular protease from strain SF03 was observed in a basal peptone medium and the peptone medium supplemented with different carbon and nitrogen sources. Different levels of protease production were found with different carbon and nitrogen sources