Production, purification, and characterization of two extremely halotolerant, thermostable, and alkali-stable alpha-amylases from Chromohalobacter sp TVSP 101

Abstract

The halophilic bacterial strain Chromohalobacter sp. TVSP 101 was shown to produce extracellular, halotolerant, alkali-stable and moderately thermophilic a-amylase activity. The culture conditions for higher amylase production were optimized with respect to NaCl, pH, temperature and substrates. Maximum amylase production was achieved in a medium containing 20% NaCl or 15% KCl at pH 9.0 and 37 degrees C in the presence of 0.5% rice flour and tryptone. Addition of 50 mM CaCl2 to the medium increased amylase production by 29%. Two kinds of amylase activity, designated amylase I and amylase II, were purified from culture filtrates to homogeneity with molecular masses of 72 and 62 kDa, respectively. Both enzymes had maximal activity at pH 9.0 and 65 degrees C in the presence of 0-20% (w/v) NaCl but amylase I was much more stable in the absence of NaCl than amylase II. The enzymes efficiently hydrolyzed carbohydrates to yield maltotetraose, maltotriose, maltose, and glucose as the end products. (C) 2008 Elsevier Ltd. All rights reserved.