Synthesis of poly(3-hydroxybutyrate/3-hydroxyvalerate) from propionate-fed activated sludge under various carbon sources.

This study investigated the potential of a propionate-fed PHAs accumulating sludge, which was submitted to aerobic dynamic feeding (ADF) condition, for producing poly (3-hydroxybutyrate/3-hydroxyvalerate), P(HB/HV). Results of batch P(HB/HV) production tests indicated that propionate-ADF sludge with propionate or valerate exhibited better PHAs production performance than with acetate in terms of kinetics and stoichiometry. However, acetate-ADF sludge obtained a superior PHAs production capability from acetate than from propionate. Choice of carbon source for PHAs production therefore relied significantly on the cultivating substrate of PHAs accumulating sludge. Furthermore, mixture of acetate and valerate in molar ratio of 50:50 achieved higher P(HB/HV) content than in molar ratio of 75:25, and obtained a P(HB/HV) copolymer with optimum HV fraction of 45 mol%. The above findings propose that elevating the applicability of P(HB/HV) production require simultaneously two conditions: cultivating a propionate-fed sludge and providing the sludge with mixture of odd- and even-number carbon sources.