Pretreatment of extracted olive pomace for bioethanol production


Extracted olive pomace (EOP) is an abundant lignocellulosic agro-industrial residue with a considerable cellulose content that can be potentially converted into soluble sugars and subsequently fermented to ethanol. In this work, enzymatic hydrolysis of hydrothermal (autohydrolysis) pre-treated EOP was carried out and Separate Hydrolysis and Fermentation (SHF), and Simultaneous Saccharification and Fermentation (SSF) were compared. Autohydrolysis pretreatment of EOP was highly selective towards hemicellulose, whose removal is essential to increase the efficiency of the subsequent enzymatic hydrolysis of cellulose. The ethanol concentrations attained by SHF and SSF, 22 and 26 g/L, respectively, were, according to the best of our knowledge, the higher reported in the literature for this raw material This can be explained mainly by the efficiency of the pretreatment and the high glucan content of the pretreated material. SSF operation proves to be more efficient than SHF. Residues from olive oil industry such as extracted olive pomace (EOP) are a potential feedstock for ethanol production especially in regions with great olive oil production like the Alentejo region in Portugal. In this work, enzymatic hydrolysis of EOP pre-treated by dilute acid hydrolysis (DAH) was assessed, and a comparison of separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) was performed. DAH led to a significant removal of the hemicellulosic fraction, but the subsequent enzymatic treatments showed that the resulting residue was still partially recalcitrant to cellulase action. SSF process presented higher fermentation efficiency (24%) when compared to SHF process. EOP-DAH conversion to glucose was increased up to 60% by sequential delignification with sodium chlorite, indicating that lignin may be the remaining factor influencing cellulose digestibility in DAH pre-treated EOP


Dilute acid hydrolysis and autohydrolysis


Fernandes, M. C., Dores, V., Lourenço, P. M., Viegas, M., Carvalheiro, F., & Duarte, L. C

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