Processing of extracted olive oil pomace residue by hydrothermal or dilute acid pretreatment and enzymatic hydrolysis in a biorefinery context

In this work, a residue from olive oil industry, i.e., extracted dry olive pomace (EOP) is studied for valorization into fermentable sugars and other added-value compounds. EOP processing is based on a first water extraction step at 100 °C during 30 min, followed by Liquid Hot Water (170,190 °C and 210 °C) or dilute acid (DA) pretreatment [same temperatures in sulfuric acid 1% and 2% (w/v)], and enzymatic hydrolysis (EH) at laboratory scale using commercial enzymes. The results show that the water-extraction step allows extracting valuable compounds as mannitol and phenols that can contribute significantly to EOP valorization. The pretreatments tested are found to be effective to fractionate EOP biomass and facilitate sugar by EH, although DA performs comparatively better, providing the maximum overall process yield considering both glucose and xylose sugars (85 and 62% of sugar content in raw EOP) at 170 °C and 2% acid.