Hydrothermal treatment on depolymerization of hemicellulose of mango seed shell for the production of xylooligosaccharides

Abstract

Hydrothermal processing is an interesting biorefinery technology for converting lignocellulosic biomass into biofuels and biocompounds. This process is based on the selective solubilization and depolymerization of hemicellulose fraction (xylan) and may be considered beneficial, due to the possibility of obtaining xylooligosaccharides (XOS) with a degree of polymerization (DP) suitable for prebiotic applications. This study evaluated the effect of pressure (2.5 and 10 MPa) in a kinetic study (30 min) of hydrothermal treatment (180 °C) to optimize the extraction of XOS from mango seed shell. Total reducing sugars (TRS) values were close to the maximum in 15 min showing a slower rate for both pressures after this time, but at 10 MPa the value was 20 % lower than at 2.5 MPa. Based on these results, a new extraction was performed at 2.5 MPa and 15 min, and the extracted XOS were quantified, yielding 393.44 mg XOS/g xylan. XOS with a degree of polymerization between X2-X6 corresponded to 82.24 mg/g and XOS with X > 6 (or soluble xylan) corresponded to 311.20 mg/g. A low amount of xylose (8.81 mg/g xylan) was released, resulting in a hemicellulose conversion of 40.2 %. In general, approximately 8.1 kg of total XOS was produced from 100 kg of dried mango seed shell (X2-X6−1.7 kg and X > 6–6.4 kg).