Ethanol production from alkali-pretreated oil palm empty fruit bunch by simultaneous saccharification and fermentation with mucor indicus

Oil palm empty fruit bunch (OPEFB) is a potential raw material for production of lignocellulosic bioethanol. The OPEFB was pretreated with 8% sodium hydroxide (NaOH) solution at 100 degrees C for 10 to 90 min. Enzymatic digestion was carried out using cellulase and -glucosidase at 45 degrees C for 24 h. It was then inoculated with Mucor indicus spores suspension and fermented under anaerobic conditions at 37 degrees C for 96 h. Sodium hydroxide pretreatment effectively removed 51-57% of lignin in the OPEFB and also its hemicellulose (40-84%). The highest glucan digestibility (0.75 g/g theoretical glucose) was achieved in 40-min NaOH pretreatment. Fermentation by M. indicus resulted in 68.4% of the theoretical ethanol yield, while glycerol (16.2-83.2 mg/g), succinic acid (0-0.4 mg/g), and acetic acid (0-0.9 mg/g) were its by-products. According to these results, 11.75 million tons of dry OPEFB in Indonesia can be converted into 1.5 billion liters of ethanol per year.