Enumeration and isolation of polylactic acid (PLA)-degrading bacteria from soils and wastewater sludge were performed on emulsified PLA agar. Two isolates of potent PLA-degrading bacteria, designated as CH1 and WS3, were selected and identified as Stenotrophomonas pavanii and Pseudomonas geniculata, respectively. PLA was presented as a substrate to stimulate production of protease and PLA-degrading enzyme by S. pavanii CH1 and P. geniculata WS3. The optimal pH values for both protease and PLA-degrading enzyme production by S. pavanii CH1 and P. geniculata WS3 were 7.5 and 8.0, respectively. The optimal gelatin concentrations for stimulating protease production in S. pavanii CH1 and P. geniculata WS3 were 0.3% (w/v), while those for PLA-degrading enzyme production in S. pavanii CH1 and P. geniculata WS3 were 0.1 and 0.3% (w/v), respectively. In addition, P. geniculata WS3 had a higher percentage of PLA film-weight loss than that of S. pavanii CH1, corresponding with reduced molecular weight of PLA. A significant increase of lactic acid content in culture broth was directly correlated with the increasing percentage of PLA film-weight loss. Our results clearly demonstrated that P. geniculata WS3, a novel isolated bacterium, has played a substantial role in PLA biodegradation by producing PLA-degrading enzyme and adhering on PLA surface.

在乳化的PLA琼脂上对土壤和废水污泥中降解聚乳酸（PLA）的细菌进行计数和分离。选择了两个有效的可降解PLA的细菌，分别命名为CH1和WS3，并将其分别鉴定为Stenotrophomonas pavanii和Pseudomonas geniculata。PLA被认为是通过刺激链球菌CH1和霉假单胞菌WS3刺激蛋白酶和PLA降解酶产生的底物。帕氏链球菌CH1和产金假单胞菌WS3生产蛋白酶和PLA降解酶的最佳pH值分别为7.5和8.0。刺激蛋白酶生产的最佳明胶浓度S. pavanii CH1和P.膝WS3分别为0.3％（W / V），而那些用于PLA分解酶生产S. pavanii CH1和P.膝WS3分别（V W /），分别为0.1和0.3％。此外，与P. avanavanii CH1相比，P。geniculata WS3的PLA膜重量损失百分比更高，这与PLA的分子量降低相对应。培养液中乳酸含量的显着增加与PLA膜重量损失百分比的增加直接相关。我们的结果清楚地表明，P。geniculata WS3是一种新型的分离细菌，它通过产生PLA降解酶并粘附在PLA表面上，在PLA生物降解中发挥了重要作用。