Characterisation of an amylase from a psychrotrophic Vibrio isolated from a deep-sea mud sample

A psychrotrophic bacterium which produced amylase was isolated from a deep-sea mud sample collected at a depth of 1200 m from Sagami Bay, Japan. The isolate was identified as Vibrio sp. from its taxonomic characteristics. The amylase produced by the bacterium was purified and its characteristics were examined. The molecular mass of the amylase was estimated to be 66 kDa by SDS-PAGE and 70 kDa by gel filtration chromatography. The enzyme had maximum activity at neutral pH and the activity was inhibited by 1 mM Hg²⁺, 5 mM EDTA or 0.1% SDS. The amylase hydrolysed amylopectin and glycogen as well as soluble starch but did not hydrolyse cyclodextrins. Complete inactivation of the enzyme activity occurred after 1 h incubation at 45°C. The enzyme showed an optimal temperature for activity at 35°C and retained 10% of the maximum activity at 0°C.