Efficient Biovalorization of Oil Palm Trunk Waste as a Low-Cost Nutrient Source for Bioethanol Production

Abstract

This study aimed to efficiently utilize felled oil palm trunk (OPT) for bioethanol and lactic acid production. OPT was separated into two fractions: oil palm sap (OPS) and OPT fiber. OPS contained substantial amounts of sugars (38–40 g/L) and nitrogen (0.60–0.70 g/L), which can serve as a base medium for bioethanol production. As bioethanol production requires high sugar concentrations, OPS was concentrated, supplemented with OPT fiber, and used for bioethanol production through simultaneous saccharification and fermentation (SSF) by Saccharomyces cerevisiae. Repeated-batch SSF for five cycles efficiently utilized OPT fiber and achieved an average ethanol production of 35–42 g/L in each cycle. To increase the accessibility of the enzyme, OPT fiber was acid-pretreated prior to the SSF process. The combined use of acid-pretreated OPT slurry and concentrated OPS provided the maximum ethanol production of 49.63 ± 1.05 g/L. The fermented broth after ethanol recovery, containing mainly xylose, was used to produce lactic acid at a concentration of 18.85 ± 0.55 g/L. These strategies can greatly contribute to the zero-waste biorefinery of OPT and may also be applicable for the efficient biovalorization of other similar agricultural wastes.