Characterization of Moderately Thermostable α-Amylase-producing Bacillus licheniformis from Decaying Potatoes and Sweet Potatoes

Muhammad Adnan Ashraf, Muhammad Imran Arshad, Sajjad Ur Rahman, Ahrar Khan


Bacillus licheniformis is an endospore-forming bacterium that is commonly present in soil. The aim of the present study was to isolate and characterize local strains of α-amylase producing B. licheniformis. Soil samples were collected from the decaying surfaces of potatoes and sweet potatoes. The samples were identified by Gram staining, spore staining, and motility testing under aerobic conditions. Twenty-three isolates were found to be from the Bacillus genus and six of those (26%) were found to be B. licheniformis. Two representative samples were run on API 20E and API 50 CH biochemical kits, and 16S rDNA polymerase chain reaction. The isolates were confirmed to be B. licheniformis by the API-web program and molecular detection. Partially purified α-amylase was characterized to determine the effect of the incubation period, temperature tolerance, and pH stability. The activity peaked at 740 mU/mL after 42 h of culturing. The relative activity reached a maximum at 55 °C and a pH of 8.0. The decaying surfaces of potatoes and sweet potatoes are promising sources of α-amylase-producing strains of B. licheniformis that can tolerate both a high temperature and drastic pH level.


Bacillus licheniformis; Microbial amylase; Physico-chemical stability

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