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EXTRACELLULAR ENZYME PRODUCTION BY INDIGENOUS THERMOPHILIC BACTERIA: PARTIAL PURIFICATION AND CHARACTERIZATION OF α-AMYLASE BY BACILLUS SP. WA21

WAJEEHA ASAD, MARIA ASIF AND SHEIKH AJAZ RASOOL^*

Abstract: Thermostability is a characteristic of most of the enzymes available for bulk industrial usage. Thermophilic microorganisms are of special interest as a source of novel thermostable enzymes. A total of 50 bacterial strains, isolated from local hot springs and ash samples were screened for the extracellular enzyme production including amylase, lipase, esterase, cellulase and β-galactosidase. As a follow up, studies on α-amylase were carried out with a bacterial strain identified as Bacillus sp. WA21 (from hot spring) on the basis of maximum zone of starch hydrolysis in agar plate medium. Bacillus WA21 showed growth over a wide range of temperature (35-55ºC) and pH (3-11) with optimum being 45ºC and pH 6. Maximum enzyme production was observed after 144 hours. The enzyme was found optimally active at 55ºC and pH 6. Temperature stability profile revealed that enzyme α-amylase retained more than half of its activity at 85ºC and between pH 5-9. Thus, Bacillus WA21 may be regarded as a promising source of α-amylase for biotechnological and industrial applications. 

Department of Microbiology, University of Karachi, Karachi, Pakistan.