Optimization of fermentation conditions for bioethanol production from oil palm trunk sap

Abstract

Oil palm trunk (OPT) sap, a waste product generated during the felling of Elaeis guineensis (E. guineensis) trees, has been identified as an underutilized resource with significant potential for sustainable bioethanol production. In this study, fermentation parameters were optimized to maximize bioethanol yield from felled E. guineensis OPT sap using Saccharomyces cerevisiae (S. cerevisiae) Kyokai no. 7. A combination of Plackett–Burman design (PBD), steepest ascent method, and Box–Behnken design (BBD) was employed to screen and optimize key variables, including temperature, initial pH, fermentation time, yeast extract, sodium chloride, ammonium sulfate, magnesium sulfate, peptone, urea, and corn steep liquor (CSL). Among these, initial pH, peptone, and CSL were identified as the most significant effects and were selected for further optimization. The fermentation process was conducted using a batch strategy to enhance productivity and simulate scalable operation. The optimal conditions were predicted by BBD with pH 6.50, peptone at 6.80 g/L, and CSL at 13.28 g/L, which resulted in a validated bioethanol yield of 0.4800 ± 0.0275 g/g and a validation accuracy of 94.12 %. These findings demonstrated the viability of felled E. guineensis OPT sap as a promising fermentation substrate, which has been largely overlooked in bioethanol research. The integration of sequential statistical optimization techniques enabled efficient fine–tuning of key parameters to approach theoretical conversion limits. Overall, this work supported the potential of felled E. guineensis OPT sap as a sustainable feedstock for bioethanol production and offers a foundation for process scaling, cost analysis, and further refinement through strain or co–substrate diversification.