Isolation and Identification of a Bacterial Strain Producing Thermostable α- Amylase

Abstract

This study was aimed at isolating and identifying thermostable α-amylase producing bacteria, and characterization of α- amylase produced by the selected strains. A total of 72 bacterial strains were isolated from different sources such as soil containing decaying materials (42), gruel of rice (09), soil receiving kitchen waste (06), bakery waste (08), flour mill waste (04) and tea waste (03) by incubating at 37°C for 24 h in a medium containing nutrient agar (25.0 g/L) and starch (3.0 g/L). Bacterial colonies (72) capable of hydrolyzing starch were purified and transferred to starch - nutrient agar slants for activation and then to fermentation medium. The highest α-amylase activity producing [7.0 ±0.21 Um/L at 24 h] strain (BS1) was isolated from soil receiving bakery waste. The strain BS1 was identified as Bacillus licheniformis based on genus, species analysis, morphological and biochemical characterization. Crude α-amylase showed zero order kinetics for 5 min and gave the highest activity at 90°C and pH 7.0. Michaelis constant of the crude enzyme to soluble starch was 2.85 g/L at 90°C and pH 7.0. In the absence of additives α-amylase retained 37.6% of its initial activity at 90°C at 30 min and 10.4% of its activity at 1 h, whereas at 80°C and pH 7.0 it retained 68.8% of its initial activity at 30 min and 59.1% of its initial activity at 1 h. Half life of the enzyme was 21 min at pH 7.0 and 90°C. Key words: Activity; α-Amylase; Bacillus licheniformis; Half life; Thermostable.DOI: 10.4038/tar.v22i1.2603Tropical Agricultural Research Vol. 22 (1): 1 - 11 (2010)

Keywords

• activity
• α-amylase
• bacillus licheniformis
• half life
• thermostable