Isolation, Phylogeny and Characterization of New a-amylase Producing Thermophilic Bacillus sp. from the Jazan Region, Saudi Arabia

摘要

A total of 20 thermophilic, spore-forming and a-amylase producing Bacillus sp., bacteria were isolated from soil samples collected from three different regions located in the south-west of Saudi Arabia. Isolate J5, obtained from the Jazan region, showed the best production for a-amylase and therefore was investigated further. The phylogenetic analysis showed that isolate J5 had the highest homology (81%) with the Bacillus subtilis strain EMU. Therefore, isolate J5 is considered to be a new species ofthe genus Bacillus and named Bacillus sp. AMRI-01. The production of a-amylase was detected on intervals and it reached its peak after 48 h of inoculation (23.7U ml~(-1)). The optimal pH and temperature were 8.0 and 45°C, respectively. Potato starch and corn starch were the best inducers for a-amylase production, followed by maltose. The enzyme production was increased in proportion to starch concentration of up to 3%, giving a maximum a-amylase production of 48.7U ml~(-1). The optimum enzymatic activity (70.3U ml~(-1)) was exhibited at 60°C. Enzyme was thermostable for 1 h at 80°C, while at 90°C, only 4.5% of the original activity was lost. These properties make the enzyme quite suitable for biotechnological applications, especially in starch liquefaction.