RESUMO
Aims: To investigate the effect of cell immobilization on amylase production by the moderately halophilic bacterium, Bacillus sp. strain TSCVKK and to compare the properties of the amylase produced under immobilized conditions with the enzyme produced by the free cells. Study Design: Cell immobilization. Place and Duration of Study: Department of Chemistry, Biochemistry Lab, Indian Institute of Technology (IIT Madras), Chennai, Tamil Nadu, between Jan 2009 and March 2009. Methodology: Bacillus sp. strain TSCVKK was immobilized in alginate, agar, polyacrylamide and gelatin. Production of amylase was determined using 3, 5- dinitrosalicylic acid (DNS). Effect of NaCl, pH, temperature on the activity of amylase was determined and compared with the amylase produced by the free cells. Results: Maximum production of 832 mU/ml was achieved with an initial cell load of 1.2% (w/v; wet weight) of 24 h grown cells immobilized in 2% agar of 4 mm3 block size using GSL-2 medium containing 10% NaCl and 1.5% dextrin at pH 8.0 at 30ºC after 36 h of growth. Amylase production was lower when the cells were immobilized in alginate (211 mU/ml) or with the free cells of same biomass concentration as used for immobilization (333 mU/ml). Amylase was not produced when gelatin or polyacrylamide was used as the immobilization matrix. The immobilized cells in 2% agar could be used up to 5 cycles without much reduction in amylase production. Amylase produced through cell immobilization retained all the properties that were shown by amylase produced under submerged fermentation. Conclusion: Agar was the suitable matrix to immobilize Bacillus sp. strain TSCVKK for amylase production. Amylase produced under immobilization conditions retained its temperature, salt and pH requirements. Immobilized cells were used for 5 cycles without much decrease in production.