Chemical-free fractionation of palm empty fruit bunch and palm fiber by hot-compressed water technique for ethanol production

Abstract

The purpose of this study was to valorize oil palm empty fruit bunch (EFB) and palm fiber (PF) from palm oil mills to produce fuel ethanol. Chemical-free fractionation of EFB and PF using hot-compressed water (HCW) pretreatment at temperatures ranging from 150 to 200ºC at 30 bars and reaction times for 5, 15, 25 min was applied to remove most of hemicellulose and partial lignin fractions into liquid phase. Comparison of the effects of different commercial cellulase enzyme complexes (Accellerase 1500, Cellic® Ctec2, Cellic® Htec2 and Ctec2＋Htec2) on HCW pretreated materials were investigated. Finally, an inhibitory effect of using the whole slurry from HCW pretreatment of EFB and PF on enzyme hydrolysis and ethanol production by Saccharomyces cerevisiae TISTR5606 was studied. The finding suggested using solely solid fraction from HCW pretreatment for ethanol fermentation, otherwise some additional tannic acid, furfural and acetic acid removal steps are required to prevent the inhibition on yeast growth. Keywords: Hot-compressed water, Palm empty fruit bunch, Palm fiber, Separate hydrolysis and fermentation (SHF), Enzyme hydrolysis, Ethanol fermentation