Enhancing cellulose accessibility in oil palm empty fruit bunches (OPEFB) through optimized maleic acid pretreatment for improved glucose-to-ethanol bioconversion

Abstract

Pretreatment of lignocellulosic biomass remains a limiting stage in sustainable energy production. Studies are still needed to understand the principles and find an efficient process for converting lignocellulosic biomass into bioethanol. This study aims to improve the accessibility of the cellulose contained in oil palm empty fruit bunch by improving pretreatment parameters. The impact of maleic acid concentration, pretreatment temperature and pretreatment time on each stage of the process is investigated. First the biomass is pretreated, then enzymatic saccharification is performed on the remaining solid, and finally fermentation of the resulting hydrolysate is carried out using Saccharomyces cerevisiae F118, an engineered yeast. Pretreatment with 75% maleic acid for 60 minutes at 180°C resulted in more efficient removal of lignin and hemicellulose, and therefore greater accessibility of the cellulose. However, the cellulose obtained at the end of pretreatment has a crystallinity of 74.8%, which slows down enzymatic attack during saccharification. Biomass pretreated with maleic acid at a concentration of 50% for 60 minutes at 180°C gives a higher glucose yield of 77.1%. Finally, greater ethanol production is obtained with the hydrolysate obtained from enzymatic saccharification of biomass pretreated with maleic acid at 1% concentration for 60 minutes at 180°C. Ethanol yield is affected by the presence of maleic acid adsorbed on the solid matrix.