Abstract
The capability of thermophilic microorganisms to flourish at high temperatures makes their enzyme systems ideal for various biotechnological applications. Based on the proteolytic and amylolytic activities, two thermophilic bacteria were isolated from hot springs in Jazan, Saudi Arabia. The antibiotic and heavy metals susceptibility patterns of the bacterial isolates were performed. According to the metabolic fingerprint, the bacterial isolates were identified as Brevibacterium linens and Bacillus subtilis. Moreover, the impact of temperature, substrate concentration, and some metal ions on the production of proteases and amylases from the bacterial strains was investigated. The maximum protease production was achieved at 50 degrees C while the greatest amylase production was recorded at 30 degrees C for both strains at a constant pH of 7.5. The highest enzyme production was recorded at 5% skimmed milk for protease of B. linens and 10% for B. subtilis while 0.6% starch was the optimum substrate concentration of amylase production of the two strains. Furthermore, Ca2+ showed a simulative influence on protease production from the two strains whereas Mg2+ and Mn2+ demonstrated minor effect. On the other hand, Ca2+, Mg2+ and Mn2+ demonstrated a positive effect on the amylase production from both strains.