Influence of Inhibitors from Microwave Pretreatment of Oil Palm Frond Pulping (OPFP) on Bioethanol Production

Abstract

This research aims to analyze the influence of inhibitors from microwave pretreatment of oil palm frond pulping (OPFP) on the efficiency of bioethanol fermentation by S.cerevisiae in the simultaneous saccharification and fermentation (SSF) processes. OPFPs were achieved at different ages: 3-4, 4-7, 7-10, 10-20, and 20-25 years old. OPFP was pretreated with a microwave and sulfuric acid (MW/SF), microwave and hydrogen sulfide (MW/HP), and microwave and water (MW/W). The results showed that the main inhibitors formed during the pretreatment process of OPFP were acetic acid, furfural, 5-hydroxymethylfurfural (HMF), furfural, formic acid, and phenol. The pretreatment of OPFP with MW/W had the lowest concentrations of inhibitors compared to the other pretreatment methods. The highest bioethanol yields at all ages of OPFP were in the range of 0.41-0.42 g-bioethanol/g-glucose, corresponding to more than 80% fermentation efficiency. At these conditions, the concentrations of the acetic acid were 0.09-0.19 g/l, HMF =0, furfural =0, formic acid 0.05-0.28 g/l, and phenol 0.22-0.47 g/l. The MW/W was the suitable pretreatment of OPFP for bioethanol production due to the lowest to generate the inhibitor and high ethanol production yield.