Oligosaccharides and monomeric carbohydrates production from olive tree pruning biomass

Using the severity factor, it has been possible to study cellulose and hemicellulose fractional conversion, sugar yields change and oligosaccharides variation through olive tree pruning biomass pretreatments with acid or liquid hot water under pressure. The temperatures tested were in the range 180–230 °C, operation time varying between 0 and 30 min and acid concentration used did not exceed 0.05 M. Complete hemicellulose solubilization in autohydrolysis was achieved using severity factors (log R0) close to 3.9 (most sugars are like oligomers), while if sulfuric acid 0.025 M is employed, this parameter could be smaller (≥3.4). With these treatments, we have obtained cellulose conversions between 30 and 42% from liquid hot water experiments, 40–51% with sulfuric acid 0.025 M and 42–57% when the acid concentration was 0.05 M. The best results in terms of maximum yield in total sugars, d-glucose and d-xylose, with a low amount of acetic acid and hydroxymethylfurfural, was obtained at 200 °C, 0 min (what means that there is no time of temperature maintenance, only heating and cooling) and H2SO4 0.025 M.

► Carbohydrate generation from olive tree pruning biomass is proposed.
► Severity factor is employed to study important parameters related to oligosaccharides and sugars production.
► Thermal pretreatments with acid or liquid hot water were performed.
► Pretreatments conditions were optimized to a possible liquid fermentation.