exceptionally cold-adapted alpha-amylase from a metagenomic library of a cold and alkaline environment

A cold-active α-amylase, AmyI₃C₆, identified by a functional metagenomics approach was expressed in Escherichia coli and purified to homogeneity. Sequence analysis showed that the AmyI₃C₆amylase was similar to α-amylases from the class Clostridia and revealed classical characteristics of cold-adapted enzymes, as did comparison of the kinetic parameters Kₘand kcₐₜto a mesophilic α-amylase. AmyI₃C₆was shown to be heat-labile. Temperature optimum was at 10–15 °C, and more than 70 % of the relative activity was retained at 1 °C. The pH optimum of AmyI₃C₆was at pH 8–9, and the enzyme displayed activity in two commercial detergents tested, suggesting that the AmyI₃C₆α-amylase may be useful as a detergent enzyme in environmentally friendly, low-temperature laundry processes.