The efficient ethanol production from dried oil palm trunk treated by hydrothermolysis and subsequent enzymatic hydrolysis

Among the promising lignocellulosic biomasses, oil palm trunk has been spotlighted not only as a valuable energy resource, but also by its abundant production in Malaysia and Indonesia. The oil palm plant is recommended to be replanted at intervals of 20-25 years for the economic harvest of fresh palm fruits, so the efficient utilization of the oil palm trunk as a by-product of palm oil production is needed. The dried oil palm trunk is composed of starch and cellulose (45-55%), hemicellulosic sugars (~25%), lignin (~25%) and ash (~5%) in common. The starch become amorphous by heating to 60-70 °C in water, so can be easily hydrolyzed by amylases without any pretreatment. However, if the biomass would be treated hydrothermally at high temperature, the starch could be decomposed via glucose to inhibitory products of microbial fermentation and act as a feedback inhibitor of cellulolytic enzyme during subsequent enzymatic hydrolysis. Therefore, it is important to overcome the problems with starchy material via simple procedures prior to pretreatment. The aim of this study was to maximize the utilization of starchy biomass in bioethanol production. When the hydrothermal treatment at the temperature for maximum hemicelluosic sugar yields was applied to the palm trunk, glucose yield was not satisfactory. To improve glucose and ethanol yield from the palm trunk, a variety of processing strategies with an economical perspective were investigated. Consequently, the increasing yields of them were confirmed. The efficient ethanol production process applicable for starchy lignocellulosic biomass will be presented and discussed.