Effects of changes in chemical and structural characteristic of ammonia fibre expansion (AFEX) pretreated oil palm empty fruit bunch fibre on enzymatic saccharification and fermentability for biohydrogen

Oil palm empty fruit bunch (OPEFB) fibre is widely available in Southeast Asian countries and found to have 60% (w/w) sugar components. OPEFB was pretreated using the ammonia fibre expansion (AFEX) method and characterised physically by the Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The results show that there were significant structural changes in OPEFB after the pretreatment step, and the sugar yield after enzymatic hydrolysis using a cocktail of Cellic Ctec2® and Cellic Htec2® increased from 0.15 g g−1 of OPEFB in the raw untreated OPEFB sample to 0.53 g g−1 of OPEFB in AFEX-pretreated OPEFB (i.e. almost a fourfold increase in sugar conversion), which enhances the economic value of OPEFB. A biohydrogen fermentability test of this hydrolysate was carried out using a locally isolated bacterium, Enterobacter sp. KBH6958. The biohydrogen yield after 72 h of fermentation was 1.68 mol H2 per mol sugar. Butyrate, ethanol, and acetate were the major metabolites.