从石油污染土壤中筛选到1株具有聚丁二酸丁二醇酯降解能力的菌株PBS1302,经菌体形态特征、菌落培养特征、生理生化鉴定和16S r DNA基因序列分析,初步鉴定为铜绿假单胞菌(Pseudomonas aeruginosa)。该菌株在培养温度37℃,培养基起始p H 6.8的条件下经6 d的培养,对聚丁二酸丁二醇酯薄膜的降解率可达36.9%。经电子显微镜观察,与降解前相比,聚丁二酸丁二醇酯薄膜表面变得粗糙,出现明显的蚀刻痕迹。
An extracellular polyhydroxybutyrate（PHB） depolymerase was purified to homogeneity from the culture supernatant of a PHB-degrading bacterium, Pseudomonas mendocina DSWY0601, which was isolated from brewery sewage for the ability to form clear zones on the PHB mineral agar plates. The molecular weight of the purified PHB depolymerase as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis（SDS-PAGE） was ap- proximately 59800 at the optimal temperature and pH value being 50 ℃ and 8.5, respectively. PHB depolymerase was stable in a temperature range of 20--50 ℃ and sensitive to pH value within a pH range of 8.0-9.5. PHB depo- lymerase degraded poly-3-hydroxybutyrate-co-4-hydroxybutyrate（P3/4HB） and poly-3-hydroxybutyrate-co-3- hydroxyvalerate（PHBV） but did not degrade poly（lactic acid）（PLA）, poly（butylene succinate）（PBS） or poly- （caprolactone）（PCL）. PHB depolymerase was sensitive to phenylmethylsulfonyl fluoride（PMSF）, H202 and SDS. The main product after enzymatic degradation of PHB was indentified as 3-hydroxbutyrate monomer（3HB） by mass spectrometric analysis, suggesting that PHB depolymerase acted as an exo-type hydrolase. Analysis ofphaZpm gene reveals that PHB depolymerase is a typical denatured short-chain-length PHA（dPHAscL, PHA=polyhydroxyalkanoate） depolymerase containing catalytic domain, linker and substrate-binding domain.
WANG YanLI FanWANG Zhan-yongLIU Dong-boXIA Hong-meiLIU Ling-feiCHEN Shan
