Influence of temperature on the bioconversion of palm oil mill effluent into volatile fatty acids as precursor to the production of polyhydroxyalkanoates

BACKGROUND: The focus of wastewater management has evolved from treatment technology into resource recovery, which enables simultaneous waste minimization and value-added product generation. This study utilized palm oil mill effluent (POME) for volatile fatty acids (VFA) production by acidogenic fermentation at mesophilic (30 degrees C and 40 degrees C) and thermophilic (55 degrees C) temperatures. The viability of using the VFA produced to generate biodegradable plastics polyhydroxyalkanoates (PHA) was also determined. RESULTS: The VFA production at mesophilic temperature outperformed thermophilic temperature considerably, with a degree of acidification of 48% at both 30 degrees C and 40 degrees C but only 7% at 55 degrees C. These results were in agreement with the substrate consumption profiles whereby the percentage of substrate consumption at 55 degrees C was six times lower than those at 30 degrees C and 40 degrees C. The VFA produced from POME could be used for PHA production, achieving 17 wt% PHA of sludge dry weight. CONCLUSION: Mesophilic acidogenic fermentation of POME is preferable due to its better VFA production. Since palm oil mills are located in tropical countries, the fermentation can be conducted under ambient conditions (25-32 degrees C) and without temperature control. The potential of VFA-rich fermented POME for PHA production is recognized, but optimization of the PHA production conditions is required for higher PHA content. (C) 2013 Society of Chemical Industry