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To produce PHA(polyhydroxyalkanoic acid) from microbe, dozens of microorganism have been screened from sewage sludge. Selected a strain HJ out of 50 strains of PHA producing bacteria has a capability of accumulating large amounts of PHB/HV copolymer when grown in batch culture with a single carbon source(glucose) that was not generally considered as precusor of hydroxyvalerate monomer unit. The strain HJ was identified as the genus Pseudomonas with respect to morphological, cultural, and biochemical characteristics. The optimal temperature and pH for cell growth were 37°C and 7.0. The optimal medium compositions for cell growth were glucose 1% as a carbon source, (NH,)2SO, 0.2% as a nitrogen source, K,HPO, 0.3%, and KH2PO, 0.45%. To investigate the optimal condition for PHA production two-step cultivation method was employed. PHA production was induced by deficiency of NH;S0,-Z, Mg". Besides carbon source, deficiency of all nutrients stimulated PHA productivity but deficiency of NH;stimulated the most HV monomer content. The highest PHA production was C/N molar ratio 95.2. Pseudomonas sp. HJ was also able to produc PHB/HV copolymer when cultivated on alkane, alkanoate, alcohol as carbon sources. The contents of PHA and the proportions of hydroxyvalerate monomer units varied depending on the carbon sources. Especially Pseudomonas sp. HJ was able to incorporate hydroxyvalerate into PHB/HV to level as high as from 49 to 74 mol% when grown in a medium containing hexadecane and propionate. The purified PHA was identified PHB/HV copolymer by ´HNMR analysis.
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