Bioethanol production from extracted olive pomace: dilute acid hydrolysis

Residues from olive oil industry such as Extracted Olive Pomace (EOP) are potential substrates for bioethanol production. In this work, enzymatic hydrolysis of EOP pretreated by dilute acid hydrolysis (DAH) was assessed, and the enzymatic hydrolysis and bioconversion were carried out both by separate hydrolysis and fermentation (SHF) and pre-saccharification followed by simultaneous saccharification and fermentation (PSSF). DAH led to a significant removal hemicellulose, but the subsequent enzymatic treatments showed that the resulting residue was still partially recalcitrant to cellulase hydrolysis. Size reduction and further treatment of EOP-DAH with an alkaline solution were also tested. Alkaline post-treatment allowed a decrease in lignin content, but had little effect on enzymatic saccharification comparing to size reduction. Hence fermentation study was performed with ground EOP-DAH. The PSSF process showed a relatively higher bioethanol fermentation yield (0.46 gg-1) when compared to the SHF process.