Isolation and identification of an Amylolytic psychrotrophic bacterium and characterization of the Amylolytic activity of the isolate

A psychrotrophic bacterium with amylolytic activity was isolated from soil samples collected from the southwestern suburb of Tehran. Using biochemical tests and a molecular approach based on 16S rDNA sequencing this bacterial isolate was identified as closely related with Exiguobacterium genus. This bacterium designated as Exiguobacterium sp. SH3 was able to grow and produce amylolytic enzymes at 4, 30, 37, and 48 °C. The best temperature for amylase production by this bacterium was 30 °C at which the starch (1%) added as inducer to the culture medium was totally digested during 9 h of culture. The supernatant of culture medium was used as a source of crude enzyme for amylase assay. The amylolytic activity was observed over a wide range of the tested temperatures from 4 to 45 °C and a wide range of the tested pH conditions from 5 to 9. Cold adapted enzymes with high catalytic activity seem to be more efficient than their mesophilic or thermophilic counterparts for applications at ambient temperature such as laundry and food processing.