Characterisation and Recovery of a Bacterial Amylase Liberating Maltotriose and Maltose

An amylase which produces maltotriose and maltose from starch as the main products was isolated from the culture filtrate of an Arthrobacter species showing the ability to lyse yeast cell walls. The enzyme was purified to almost complete homogeneity from the concentrated culture medium by acetone precipitation and gel chromatography. The enzyme (specific activity 70 U/mg protein) showed an IEP of 5.4, a pH optimum of 7.5 and a molecular weight of 48 kD. Its temperature optimum was 40–45°C and there was only low stability of enzyme solutions at room temperature. Furthermore, enzyme activity was strongly inhibited by Hg2+-ions. Di- and trisaccharides identified as maltose and matotriose were exclusively formed in a molar ratio of 1:5 from soluble starch, amylopectin and amylose, and even 1:11 from glycogen; pullulan was not cleaved. A stable solid enzyme preparation was recovered by cross-flow ultrafiltration and spray-drying at air temperature of 65-72°C with KCl added as a stabilizer.