Enzymatic conversion of treated oil palm empty fruit bunches fiber into fermentable sugars: optimization of solid and protein loadings and surfactant effects

Empty palm fruit bunches fiber (EPFBF) is a lignocellulosic biomass by-product of palm oil production. In the present work, EPFBF was pretreated with sequential diluted acid/alkali to enhance the material’s enzymatic digestibility. Response surface methodology (RSM) based on Central Composite Rotatable Design (CCRD) was used to optimize solids and protein loadings to maximize both glucose release and enzymatic hydrolysis (EH) yield after 48 h. Optimum solid and protein loadings determined by RSM were 243.4 g/L and 22 mg/g of cellulose, respectively, and under these conditions 74.8 ± 0.3 g/L of glucose were obtained, corresponding to an EH yield of 64.7 ± 0.2%. Polyethylene glycol 8000 (PEG 8000), bovine serum albumin (BSA), and TWEEN 20 were supplemented separately to evaluate their influence on EH of pretreated EPFBF. The highest levels of glucose release were achieved by adding 150 mg/g of cellulose of PEG 8000, increasing EH yield to 76.6 ± 0.9%. A simultaneous saccharification and fermentation (SSF) with delayed inoculation process was used for ethanol production. A final ethanol concentration of 32.6 ± 1.0 g/L was obtained with an efficiency of 74.1% and an overall productivity of 0.6 g/(L h).