Ethanol production from olive oil extraction residue pretreated with hot water.

The olive pulp fraction contained in the residue generated in olive oil extraction by a two-step centrifugation process can be upgraded by using the cellulose fraction to produce ethanol and recovering high value phenols (tyrosol and hydroxytyrosol). Olive pulp was pretreated in a laboratory scale stirred autoclave at different temperatures (150-250 degrees C). Pretreatment was evaluated regarding cellulose recovery, enzymatic hydrolysis effectiveness, ethanol production by a simultaneous saccharification and fermentation process (SSF), and phenols recovery in the filtrate. The pretreatment of olive pulp using water at temperatures between 200 degrees C and 250 degrees C enhanced enzymatic hydrolysis. Maximum ethanol production (11.9 g/L) was obtained after pretreating pulp at 210 degrees C in a SSF fed-batch procedure. Maximum hydroxytyrosol recovery was obtained in the liquid fraction when pretreated at 230 degrees C.