Ethanol production from olive cake biomass substrate

The inexpensive production of sugars from lignocellulose is an essential step for the use of biomass to produce fuel ethanol. Olive cake is an abundant by-product of the olive oil industry and represents a potentially significant lignocellulosic source for bioethanol production in the Mediterranean basin. Furthermore, converting olive cake to ethanol could add further value to olive production. In the present study, olive cake was evaluated as a feedstock for ethanol production. To this end, the lignocellulosic component of the olive cake was dilute-acid pretreated at a 13.5% olive-cake loading with 1.75% (w/v) sulfuric acid and heating at 160A degrees C for 10 min. This was followed by chemical elimination of fermentation inhibitors. Soluble sugars resulting from the pretreatment process were fermented using E. coli FBR5, a strain engineered to selectively produce ethanol. 8.1 g of ethanol/L was obtained from hydrolysates containing 18.1 g of soluble sugars. Increasing the pretreatment temperature to 180A degrees C resulted in failed fermentations, presumably due to inhibitory by-products released during pretreatment.