Study On The Degredation Of PHB For Biological Rececling

PHA is a family of biopolyesters produced by many microorganisms. As a kind as PHA, PHB has properties similar with thermoplastic plastic and polypropylene, and is biodegradable and biocompatible, as well. Nowadays, the production of PHB depolymerases has been the focus of the world, but its application for recycling of PHB is rarely repaired.The aim of this thesis is to achieve basic result for biological recycling of PHB. Separate into three parts: 1. Using PHB depolymerases degraded PHB, study the optimized condition for high level production of PHB degradation enzyme to obtain the high yield of 3-hydroxybutyrate; 2. Using PHB depolymerization strains degraded PHB, from study of optimized condition of enzyme production and the optimized condition of enzyme reaction, achieve the highest yield and activity of the enzyme. Then, using the degradation enzyme obtain the high yield of 3-hydroxybutyrate.The main results obtained from this work are as follow:1. Degradation by bacterium DSWY0601Pseudomonas mendocina DSWY0601 can grow in normal medium with PHB as sole carbon source, indicated that this stain would secret PHB depolymerase degradation of PHB as a carbon source utilization. According to the mass spectrum analysis the degraded products of enzymes was 3-hydroxybutyrate. The optimum condition for high lever production of PHB degradation products according to the results of the orthogonal experiment is: cultivation time is 24 hours ,carbon source is 0.6g/100ml, initial pH of culture medium is 6, the inoculation is 3ml/100ml.2. Degradation by PHB depolymerasesThe optimum of enzyme production is: fermentation time 24 hours, pH 7, carbon source 0.3g/100ml, and the inoculation 1ml/100ml.The optimum of enzyme reaction temperature is 40℃. When in the range of 10-40℃for 5h the depolymerases was still stable. The optimum reaction time is 7min. The reaction pH is 7.5, when pH in the range of 6.5-8.5the stability of the enzyme was still good .3. The high yield rate of 3-hydroxybutyrateThe high yield rate of 3-hydroxybutyrate degradation by PHB depolymerases is 24.2%,and the high yield rate of 3-hydroxybutyrate degradation by bacterium of DSWY0601 is 45.4%.