Influence of antioxidant extraction on fermentability of olive biomass hydrolysates
Olive tree biomass has been proposed as raw material for ethanol production by means of a biochemical process. The pretreatment is one of the key steps which results in a celluloseenriched pretreated solid and a liquid fraction (hydrolysate) containing most of the hemicellulosic derived sugars, as well as degradation products from sugars and lignin and other minor components. It is of great interest the presence in these hydrolysates of compounds with antioxidant capacity, because their exploitation could affect positively the economy of the global process. This work deals with the fermentation of olive tree biomass hydrolysates by Pichia stipitis. Hydrolysates were prepared from biomass submitted to steam explosion and liquid hot water pretreatments, at different temperatures (170–240 ◦ C). Hydrolysates were further submitted to a process aimed at separating compounds with antioxidant capacity and improve fermentation results by eliminating yeast inhibitors. The fermentability of the hydrolysates before and after separation of these compounds is compared. Separation procedures include organic solvent extraction (e.g., ethyl acetate, which separates phenolic compounds) and ion exchange resins, which allow interesting compounds to be obtained, mainly hydroxytirosol. In the latter case, the process described in the patent procedure (US 2004/0102657A1) is followed, including the use of an anionic resin for retaining certain polyphenolic compounds, and then elution with water.