초록
<P><B>Abstract</B></P> <P>Pineapple peel waste was utilized as an unexplored source of hemicellulose (31.8±1.9%) for value addition. Hemicellulose was extracted by an alkali-based method, where the peels were incubated at different alkali concentrations (5%, 10% and 15% w/v) at temperatures ranging from 35°C to a maximum of 65°C for a fixed period of 16h. A maximum recovery of hemicellulose (95.9±2.0%) was observed after incubating extractive-free pineapple peels in 15% (w/v) alkali solution for 16h at 45°C. Higher incubation temperatures (65°C) for 16h, resulted in a lower yield of hemicellulose (81.7±3.7%) which can be attributed to the disintegration of the hemicellulose structure due to large severity factor (temperature–time combination). With low severity factor, it was noted that higher yields (96.6±0.3%) were obtained 65°C, 4h). Hydrothermal-assisted alkali extraction was also evaluated for maximizing the recovery of pineapple peel hemicellulose. The maximum relative recovery of ˜87.6% was obtained with 10% (w/v) alkali at the end of 1.5h of hydrothermal pretreatment (121°C and 15psi pressure). The hemicellulose extracted by hydrothermal-assisted alkali pretreatment was enzymatically hydrolyzed to produce XOS and the process was optimized in terms of enzyme dose (U), temperature (°C), pH and time (h). Direct hydrolysis of pineapple peels with dilute nitric acid produced xylose-rich liquor (˜91% xylose yield) at 0.5% nitric acid, reaction time of 1h and solid–liquid ratio of 1:20. The xylose-rich liquor could be converted to potential chemicals such as xylitol.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pineapple peel emerged out to be a rich source of hemicellulose. </LI> <LI> Maximum hemicellulose was recovered at 45°C with pre-incubation of 16h. </LI> <LI> The hydrothermal process gave maximum hemicellulose yield without pre-incubation. </LI> <LI> XOS and xylose were final products of the hemicellulose bio-refinery. </LI> <LI> XOS mixture was composed of xylobiose (˜83% of XOS) and xylotriose (˜16% of XOS). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>