中文摘要：

从污泥中筛选出1株对聚乳酸（poly—L—lacticacid，PLA）具有降解活力的细菌DSL09，该菌株对PLA的乳化液、粉末及薄膜都具有降解作用。通过形态学、16SrDNA比对及生理生化特性的分析，鉴定该菌株属于芽胞杆菌属（Bacillus sp．）。为提高该菌株对PLA的降解活力，对其进行了紫外诱变，获得了稳定遗传的突变株DSL09-60b，该突变株的PLA降解活性提高至原始菌株的1．5倍。对该突变株产PLA降解酶的发酵条件进行了优化，经测定DSL09-60b在初始培养基pH为8．0、0．5％酪蛋白为诱导物、接种量6％（体积比）的条件下37℃培养54h时发酵液酶活性最高。

英文摘要：

A strain possessing activity to degrade poly-L-lactic acid （PLA） DSL09 was screened from sludge. The strain had the effect to degrade PLA in emulsion, powder or film. It was identified as Bacillus sp. by the analyses of morphology, 16S rDNA comparison, physiological and biochemical characteristics. In order to enhance the degradation activity it was mutated with UV and obtained a genetically stable mutant strain DSL09-60b which increased PLA- degrading activity by 1.5 times of the original strain. The fermentation conditions and medium composition for the production of PLA degradase by DSL09-60b were optimized, it was tested that medium at initial pH 8. 0, 0. 5 % casein as inducer, 6% （v/v） of inoculum and fermented at 37 ℃ for 54 h the fermentation broth had the highest enzymatic activity.