The Preliminary Study On Isolation,Identification And PHB Accumulation Of Marine Photosynthetic Bacteria

Poly-β-hydroxybutyrate (PHB) is a biodegradable polyester which is synthesized and accumulated intracellularly during unbalanced growth by a large number of bacteria. PHB crystallizes to form a polymer with similar properties to polypropylene. It is also biodegradable and biocompatible. So PHB as a new biodegradable material can substitute for petroleum-based plastic. However, the high production cost is disadvantage to its industrialization production. The photosynthetic bacteria, which is widely used in purification treatment of organic waste water, is able to utilize many kinds of organic matter for metabolism and growth under the aerobic, microaerobic and anaerobic condition. In addition, the photosynthetic bacteria can accumulate PHB granules in the cells. So it has broad application prospects for the combination of organic waste water treatment and PHB production by the photosynthetic bacteria.In this study, firstly,, the muddy substrate of Hong Dao shrimp ponds in Qingdao was considered as a sample for isolation photosynthetic bacteria. The bacterial group of muddy substrate was enriched in RCVBN medium. Then the photosynthetic bacteria strain was isolated and identified by anaerobic plate method and the molecular biology and biochemistry methods. The strain was initially identified as Rhodovulum sulfidophilum and designated as R. sulfidophilum P5.Secondly, the culture conditions were examined of the nutrient, inorganic substance and light intensity. The results were as follows:in lab conditions, the best optimal carbon source of R. sulfidophilum P5was DL-malic acid, the best optimal nitrogen source was peptone, the optimum NaCl concentration was3%, the initial optimum pH was7.5and the optimum light intensity was80μmol/m2·s. Sodium pyruvate and ammonium chloride were also suitable for the growth of the strain and had the advantages of cheap price, thereby the effect of sources concentration on the growth of strain P5was studied deeply. The experimental results indicate that the optimum concentration of sodium pyruvate was6g/L and the optimum concentration of ammonium chloride was1.5g/L. Particularly, R. sulfidophilum P5had strong tolerance to NaCl concentration and pH value, which could survive under the condition that NaCl concentration at from0%to7%at pH value was from5.0to10.0.Thirdly, the conditions of PHB accumulation were studied preliminarily by the analysis method of UV spectroscopy. Under the anaerobic culture conditions, the PHB accumulation optimum conditions of R. sulfidophilum P5were the carbon source of2-4g/L sodium pyruvate, the nitrogen source of1.5g/L ammonium chloride, the NaCl concentration of2.0%, the initial pH value of6.0and the light intensity of40μmol/m2·s.When the sodium pyruvate as the sole carbon source, the concentration of PHB in the strain reached to718.5mg/L, and PHB content accounted for66.93%of cell dry weight.In conclusion, it is possible that R. sulfidophilum P5is used for PHB production and biological treatment of mariculture wastewater and marine organic waste, which has high value in research and application.