Recovery of catalyst used in oxalic acid pretreatment of empty fruit bunch (EFB) and bioethanol production

Abstract

In this study, oxalic acid pretreatment of empty fruit bunch (EFB) was performed at different pretreatment temperatures. Also, we evaluated oxalic acid recovery from hydrolysate by electrodialysis. The fermentable sugar concentration in hydrolysate was high at more than 20 g/l, when pretreatment was carried out at 150°C. At the same time, ethanol production was 3.78 g/l after 72 h which correspond to the ethanol yield of 0.21 g/g. On the other hydrolysate (160, 170°C), fermentable sugar was not consumed by Pichia stipitis during fermentation. Most of the oxalic acid was recovered and some of the fermentation inhibitors were removed by electrodialysis. For the electrodialysis treated hydrolysate, ethanol production was increased compared to the original hydrolysate. The highest ethanol production was 5.38 g/l after 24 h which correspond to the yield of 0.33 g/g. The ethanol production by simultaneous saccharification and fermentation (SSF) under all pretreatment conditions was more than 15 g/l after 96 h. The highest ethanol production was 20.54 g/l, when pretreatment was performed at 170°C. In particular, ethanol production was increased, when electrodialysis treated hydrolysate was used for SSF.