Abstract

Screening and isolation of proteolytic bacteria were carried out from soil samples of Ikogosi warm spring (SW, Nigeria). Eighteen isolates were positive on skim milk agar (10%) of which fifteen produced protease in culture broth. Three isolates, identified as Bacillus macerans IKBM-11, B. licheniformis IKBL-17 and B. subtilis IKBS-10, were selected for further study. These Bacillus species could grow up to 65°C within a broad pH range of 5 to 10 with an optimal growth temperature and pH at 60°C and 8.0, respectively. For the three Bacillus species, protease production occurred between 37°C and 65°C and pH 5 to 10. Maximum growth and maximum enzyme production was observed at 48 h when grown in 50 ml medium (pH 8.0) under shaking condition at 60°C. The results showed thatBacillus species under study are good producers of extracellular protease at high temperature. This might be an indication that proteases produced would be thermostable.

Key words: Protease, proteolytic bacteria, Bacillus macerans, Bacillus licheniformis, Bacillus subtilis.