Study On Production Of Pha From Starch Fermentation Via Organic Acids

Polyhydroxyalkanoate (PHA) is an intracellular storage substance produced by a large variety of bacteria. It has attracted interest as biodegradable plastics not only because of its compatible material properties like synthetic thermoplastics but also because of it could be synthesized from renewable resource.but the expensive cost restricts the large-scale commercial exploitation. In order to decrease its cost, many researchers use the inexpensive mixed culture biomass and organic wastewater to produce PHA.In this research, PHA was produced from organic acids discharged from the acidification reator by activated sludge, the main research results was showed as follows:(1)The effect of temperature, starch concentration, pH and Reaction Time on the anaerobic acidogenesis of starchy water by anaerobic sludge was researched. The optimal acidification conditions were determined. The temperature was 35℃, the pH was 5.5, the starch concentration was 4g/L and the REACTION TIME was 12h. Under this condition, the maximum production of VFA was 3.11g/L, and butyric acid was the main composition.(2) During process of PHA synthesis, the using rate of butyric acid by activated sludge was the fastest. After 8h synthesis reaction, the maximum production of PHA was 1.6g/L and 34.7% PHA of sludge was acquired.(3) The PHA in the sludge was extracted and its structure and thermal character were analyzed by Nuclear Magnetic Resonance (NMR), themogravimetric (TG) and Differential Scanning calorimeter (DSC). The results of NMR showed that the PHA was composed of HB and HV and the PHA and HV content of 8.9 mol%. The results of thermal analysis showed that the melting point was 150℃and the thermal degradation temperature was 270℃.Therefore, feeding by the acidified starchy, the copolymer of 3HB and 3HV was produced by activated sludge, and the PHBV had the character of lower melting-temperature and good thermal stability.