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KMID : 1094720110160020312
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Biotechnology and Bioprocess Engineering
2011 Volume.16 No. 2 p.312 ~ p.319
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Isozymes of α-amylases from newly isolated Bacillus thuringiensis CKB19: Production from immobilized cells
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Maity Chiranjit
Samanta Saptadip
Halder Suman K.
Mohapatra Pradeep K. Das
Pati Bikas R.
Jana Malabendu
Mondal Keshab C.
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Abstract
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The aim of this study was to produce two isozymes of α-amylase by immobilization of a newly isolated soil bacterium. The bacterium was identified as Bacillus thuringiensis CKB19 on the basis of its 16S rRNA profile. Enzyme production by free cells increased linearly with cell growth up to 34 h in starch containing enriched liquid media. The active bacterial cells were immobilized in Caalginate beads, and operational stability of the entrapped cell was optimized for amylase production. Enzyme production was optimal at an alginate concentration of 2 g% (w/v), calcium chloride concentration of 1 M, and with 300 beads (each bead contained 2 × 107 cells)/250 mL flask. Amylase production by the immobilized cells was about 3 times higher than free cell fermentation after 34 h of incubation. It was observed that the immobilized bacterium secreted two different amylases (Am-I and Am-II) into the culture fluid. The molecular masses of Am-I and Am-II were 59.6 and 44.7 kd, respectively, and showed optimum activity at pH 5.0 and 9.0. Both amylases showed optimum activity at 40°C and were stable at the same temperature, with losses of only 10 and 20% (for Am I and Am II, respectively) of their original activities after 24 h of incubation. Further, both amylases were salt tolerant (up to 4 M NaCl) and hydrolyzed raw starchy foods into glucose. All these characteristics make this enzyme mixture suitable for use as a digestive aid and for the improvement of digestibility of animal feed ingredients.
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KEYWORD
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isozyme, α-amylase, Bacillus thuringiensis, immobilization
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