Psychrophilic α-amylase from Aeromonas veronii NS07 isolated from farm soils

Among 120 isolates examined in this study, three isolates were selected for amylase production on starch agar plates following incubation at 10 degrees C. Identification by 16SrRNA on selected bacterium disclosed the highest similarity for protean regions of this gene as Aeromonas veronii NS07. A 63 kDa psychrophilic amylase enzyme from NS07 strain was purified by two-steps chromatography. The enzyme had the highest specific activity at pH 4 and was active at the range of temperatures from 0 to 50 degrees C, although the optimum temperature for enzyme activity was found at 10 degrees C. Analysis of the N-terminal amino acid sequencing disclosed 20 amino acids from purified amylase which had no similarity with other known alpha-amylases, indicating that the presented enzyme was novel. Amylase activity was enhanced in relation to optimum activity with the presence of sodium sulphate (161%), MnCl2 (298%), CaCl2 (175%), FeCl2 (182%), MgCl2 (237%), ZnCl2 (169%), NiCl2 (139%), NaCl (158%), each at 5 mM, while EDTA, phenylmethane sulphonylfluoride (PMSF) (3 mM), urea (8 M) and SDS (1%) inhibited the enzyme up to 5%, 2%, 80% and 18%, respectively. NS07 strain seems to be suitable as biocatalyst for practical use in liquefaction of starch at low temperatures, detergent and textile industries. (C) 2012 Elsevier Ltd. All rights reserved.