Abstract: The strain Yj1 isolated and purified from the soybean soil could degrade soy lecithin and dimethoate. The 16S rDNA identification of the strain, optimization of growth conditions and examination of enzyme activities were performed and organophosphate degradation enzyme from Yj1 was separated and purified. The results revealed that the similarity of 16S rDNA in Yj1 and Serratia marcescens WW4(CP003959. 1)was 99%. The orthogonal experiment for the culture medium demonstrated that the optimal growth condition of Yj1 was the combination of mannose, peptone and pH8. The growth rate of Yj1 was poor in either of 2 phosphorus sources；however, the growth rate in soy lecithin was better than that in the dimethoate within 72 h. Moreover, the activities of acid phosphatase, alkaline phosphatase and organophosphate degrading enzyme(ODE)were higher when the soybean lecithin as the sole phosphorus source than those of dimethoate, and the activity of alkaline phosphatase was obviously greater than that of acid phosphatase and ODE within 72 h. ODE was successfully purified from Yj1 by combining ammonium sulfate precipitation and SP Sepharose Fast Flow. SDS-PAGE results showed that the purified protein was in a single band. The purified multiple by SP Sepharose Fast Flow was 5. 303 times as many by ammonium sulfate precipitation, and by the latter 1. 416 times as many by crude enzyme.

Key words: Serratia marcescens, Yj1, dimethoate, soy lecithin, organophosphate degrading enzyme