| Poly-β-hydroxybutyrate(PHB) 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 resources.The microorganisms in activated sludge were able to accumulate PHB in the form of intracellular storage polymers. The production of PHB from residual sludge, therefore, is a new way for PHB synthesis, which also develops a novel pathway for the reclamation of residual sludge.Anoxic–aerobic process was applied in this study to acclimate facultative anaerobes to be the dominate bacteria. Continuous aeration process was favorable for PHB synthesis and 4.5 g/L sodium acetate was proven to be the optimum carbon source. The maximum yield of PHB was 1318 mg/L(38.2% of Mixed Liquor Suspended Solid), carbon transforming ratio was 55.6% and PHB production rate was 190 mg/(L?h).Aerobic process was used to acclimate strict aerobes to be the dominate bacteria. The aeration process was optimized: 30 minutes'aeration followed by 30 minutes'intermission as intermittent aeration operation cycle, with 5.5 g/L sodium acetate the yield of PHB reached 2002 mg/L(54.9% of MLSS), and the carbon translating ratio was 69.2%. But the accumulative time of PHB was prolonged with the intermittent aeration operation cycle. The PHB production rate was only 147 mg/(L?h).PHB was extracted from residual sludge by sodium hypochlorite-chloroform. The extraction efficiency was 85.4%. Elementary analysis, infrared spectrum and nuclear magnetic resonance analysis were utilized for the structure identification of PHB. DSC and TG-DTA analysis showed that: the fusion temperature of PHB was 65.09℃; crystallization rate was 60.75%; glass transition temperature was 65.09℃; initial weight-loss temperature was 266℃.The forming technique temperature of PHB sample was predicted to be 218℃. |
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