Effect of inoculum source, electron donors, and substrates on medium-chain fatty acid production from palm oil mill effluent

Abstract

Selecting an appropriate inoculum source and electron donor for chain elongation is crucial to optimizing medium-chain fatty acid (MCFA) production from organic waste. The investigation examined the impact of various factors, including inoculum source, electron donors, and substrate composition, on MCFA production from palm oil mill effluent (POME). The substrate containing a mixture of ethanol, lactic acid, and acetic acid exhibited the highest MCFA production, reaching 0.4–0.5 g-COD/L. Among the cultures tested, the compost (CP)-enriched culture demonstrated the highest MCFA production (0.5 g-COD/L) and was characterized by the dominance of Sporanaerobacter sp., Clostridium sp., and Oscillibacter sp. The mesophilic condition (35 °C) has higher MCFA production than the thermophilic condition (55 °C), with the mesophilic system favoring caproic acid, heptanoic acid, and caprylic acid, while the thermophilic was more suitable for propionic acid production. The highest MCFA yield obtained from POME was 0.2 g-COD/g-COD, with a selectivity of 13.6 % for MCFA production. Lactobacillus sp., Caproiciproducens sp., and Clostridium sp. were dominant microbial species and played important roles in specific MCFA production. These findings provide valuable insights for optimizing MCFA production processes from POME and highlight the importance of selecting appropriate conditions and microbial communities to enhance MCFA yields.