The conversion of pretreated cellulose into fuel-ethanol by SSF with the thermotolerant yeast S. cerevisiae IR2-9a was strongly affected by the substrate particle size, especially after hydrothermal
pretreatments. Among the pretreatments assessed, the mixture of dilute sulphuric acid (1.5 g acid per 100 g of olive stone) and ethanol (50% v/v) was the most effective in improving SSF stage, providing
fuel-ethanol concentrations above 45 kg m3, simultaneous saccharification and fermentation yields close to 100%, and overall ethanol yields between 12.8 and 13.1 kg ethanol per 100 kg of olive stones.