Cold-active lipolytic activity of psychrotrophic Acinetobacter sp. strain no. 6

A lipolytic bacterium, strain no. 6, was isolated from Siberian tundra soil. It was a gram-negative coccoid rod capable of growing at 4 degrees C but not at 37 degrees C and was identified as a psychrotrophic strain of the genus Acinetobacter. Strain no. 6 extracellularly produced a lipolytic enzyme that efficiently hydrolyzed triglycerides such as soybean oil during bacterial growth even at 4 degrees C; it degraded 60% of added soybean oil (initial concentration, 1% w/v) after cultivation in LB medium at 4 degrees C for 7 d. Thus, the bacterium is potentially applicable to in-situ bioremediation or bioaugumentation of fat-contaminated cold environments. We partially purified the lipolytic enzyme from the culture filtrate by acetone fractionation and characterized it. The enzyme preparation contained a single species of cold-active lipase with significant activity at 4 degrees C, which was 57% of the activity at the optimum temperature (20 degrees C). The enzyme showed a broad specificity toward the acyl group (C8-C16) of substrate ethyl esters.