Isolation and identification of bacteria degrading soy lecithin and dimethoate and comparision of enzyme activities

Objective In order to clarify degradation characteristics and enzyme activities of two organic phosphorus degrading bacteria in soy lecithin and dimethoate.

Method Bacterium strains Yj2 and Yj3 were isolated from soy soil and identified by 16S rDNA identification method. The growth conditions of Yj2 and Yj3 were optimized by orthogonal test. The enzyme activities from two strains were determined under different phosphorus sources, and organophosphate degrading enzymes were classified and purified.

Result Yj2 was identified as Acinetobacter sp., and Yj3 was identified as Bacillus sp.. The result of growth condition optimization showed that the best carbon and nitrogen source and pH values for strain Yj2 and Yj3 were glucose, ammonium sulfate, pH 8 and glucose, peptone, pH 9, respectively. The growth of Yj3 was slightly better than that of Yj2 when the phosphorus source was soy lecithin. However, the growth trend was the opposite with dimethoate as the phosphorus source. Within 72 h of dimethoate being the phosphorus source, acid phosphatase activity and alkaline phosphatase activity of Yj2 were generally higher than that of Yj3, but organophosphate degradation enzyme activiy of Yj2 was lower than those of Yj3. The organophosphorus degradation enzymes were isolated and purified respectively from strains Yj2 and Yj3 by ammonium sulfate precipitation followed with cation exchange chromatography. SDS-PAGE results showed that the purified proteins were both a single band. The purification ratio of ammonium sulfate precipitation followed with cation exchange was 7.77 times higher than that of the ammonium sulphate precipitation for Yj2, and the latter was 1.35 times higher than crude enzyme for Yj2. The corresponding purification ratios for Yj3 were 5.07 and 1.53 times respectively.

Conclusion Acinetobacter sp. Yj2 and Bacillus sp. Yj3 both can degrade soy lecithin and dimethoate. The activities of acid phosphatase, alkaline phosphatase and organophosphate degradation enzymes, which play the main roles on degrading organic phosphate, have obvious differences between two strains in soy lecithin and dimethoate degrading process. The organophosphate degradation enzymes with relatively high purity can be isolated and purified from YJ2 and Yj3, respectively.