Identification Of Polycaprolactone Degrading Strain And Characterization Of Its Depolymerase

Polycaprolactone(PCL)is a kind of thermoplastic polyester which is polymerized byε-caprolactone. PCL has many excellent characteristics,such as the low melting point, thermal stability and hydrolysis stability, the compatibility with various polymers is very good. Compared with other aliphatic polyesters, PCL has broad application prospect. However, there are few researches about the biodegradation of PCL, this paper focuses on isolate a bacterial strain to biodegrade PCL from the environment, numbered it DS0801. Purify and identify this strain DS0801 through the colony morphology, physiological and biochemical testes and 16SrDNA technology. In addition, isolate and purify extracellular PCL depolymerases from the strain DS0801 with the means of protein purification, study the fundamental characteristics of the PCL depolymerases. The main results obtained from this work are as follows:1. The isolation and identification of PCL degradation bacterium. The PCL degradation strain was isolated from the environment wastes. Identify the strain preliminary. Through the colony morphology, physiological and biochemical testes and 16SrDNA technology, we can determine that the bacteria belongs for Pseudomonas aeruginosa.2. The depolymerase of PCL were purified, and the properties of its crude enzyme were discussed. The results of the experiments show that, the optimum fermentation time of the strain DS0801 is 36 hours, the optimum temperature of crude enzyme is 40℃, and the optimum pH is 8.0.3. The PCL film is scanned by electron microscopy. After three days of degradation, the surface of PCL film changed small. On the fifth day, the film surface of PCL began to fracture and turn out severe erosion. After seven days'degradation, the weight loss rate of the PCL film is close to 100%, the film sample has broken into pieces, it's degraded basically.4. The degradation products of the crude enzyme are analyzed by mass spectrographic. The crude enzyme's degradation products of PCL depolymerase have generated the monomerε-caprolactone. When the inactivation crude enzyme is mixed with the PCL, we can't find the monomer in the degradation products. The results show that the PCL depolymeraseade crude enzyme can degrade PCL, and the PCL could be degraded intoε-caprolactone.