Effect of Feeding Strategies and Inoculums Applied on Two-Stage Biosynthesis of Polyhydroxyalkanoates from Palm Oil Mill Effluent

Polyhydroxyalkanoate (PHA) is a biodegradable polyoxoester, which is synthesized as carbon and energy storage by various bacteria from different substrates used. Palm oil mill effluent (POME) has been redefined as a secondary raw material for PHA production. POME is bioconverted to volatile fatty acids (VFA) via anaerobic acidogenic fermentation, and VFA is utilized to synthesis PHA aerobically. A pH of 7.0 is the optimal condition to produce the highest VFA concentration with the lowest strength of formic acid. A mixed culture of aerobic activated sludge facilitates higher PHA production yield than a pure Bacillus megaterium culture. The feast–famine (FF) feeding strategy can also generate higher PHA yield compared with batch operation. Hence, the highest PHA yield of 0.2559 ± 0.0896 g PHA/g TVFA from POME is achieved by the cultivation of aerobic activated sludge under FF regime. The PHA production can be lowered by presence of formic acid and sludge biomass residue in the fermented POME.