Effect of Triglyceride Addition on Oxygen Uptake, Carbon Metabolism, and Polyhydroxyalkanoate Accumulation in Aerobic Granules

The effect of triglyceride on polyhydroxyalkanoate (PHA) accumulation in aerobic granules used for treating palm oil mill effluent (POME) is unaddressed to date. Triglyceride was added (between 3.7 and 18.5 g/L) to a batch reactor containing aerobic granules and POME. The chemical oxygen demand (COD) removal, PHA content, and PHA composition were analyzed at different triglyceride concentrations. The COD removal decreased to 19% when 18.5 g/L triglyceride was added. Meanwhile, the PHA content decreased from 0.62 to 0.16 g PHA/g cell dry weight (CDW) as the triglyceride concentration increased from 0 to 18.5 g/L. The composition of PHA did not change significantly with the increase in triglyceride concentrations. Accumulated PHA was composed of hydroxybutyrate (HB) and hydroxyvalerate (HV) with a ratio of approximately 77:23. Eventually, the triglyceride was found to limit oxygen uptake, carbon metabolism, and PHA accumulation, in aerobic granules.