FRACTIONATION OF OLIGOMERS FROM PRETREATED OLIVE TREE PRUNING AND ITS ENZYMATIC HYDROLYSIS

摘要

Olive tree pruning is a suitable raw material for ethanol production, and also an interesting biomass toobtain high value-added products such as oligosaccharides and antioxidants. It can have a positive effect on both theintegral use of this agricultural residue and the improvement of ethanol yields. The aim of this study is to characterizeand enzymatically hydrolyze the liquid fraction released during the steam explosion pretreatment of olive treepruning. Steam-exploded olive tree pruning biomass was pretreated under 190 °C for 25 minutes in a 2 L reactor. Theprehydrolysate obtained from the hydrothermal treatment was purified in a HiLoad 16/60 Superdex 30 prep gradecolumn. The three fractions collected were analyzed by high liquid size exclusion chromatography. Fraction F1shows a molecular weight distribution of oligomers up to 20000 Da, F2 from 400 to 6000 Da and F3 contained lowmolecular weight compounds, monosaccharides and compounds with molecular weight up to 600 Da. The enzymatichydrolysis of each of the fractions has been carried out with specific enzymes to depolymerize larger oligomers(glucoamylase, xylanase, cellulase) and thus to produce its selective hydrolysis. The highest proportion ofoligosaccharides is in the first fraction with 43.4 % followed by fraction 2 with 33.6 %. The rest consists ofmonosaccharides and sugars with low degree of polymerization. The addition of enzymes to fractions F1 and F2produces the oligomers hydrolysis to glucose, xylose, xylobiose, xylotriose and DP4.