Abstract
Chinese hickory shell, a by-product of the food industry, is still not utilized and urgent to develop sustainable technologies for its valorization. This research focuses on the systematical evaluation of degraded products and xylooligosaccharide production with high yield from the shell via hydrothermal process. The pretreatment was carried out in a bath pressurized reactor at 140–220 °C for 0.5–2 h. The results indicated that the pretreatment condition strongly affected the chemical structures and compositions of the liquid fraction. The maximum yield of XOS (55.3 wt%) with limitation of by-products formation was achieved at 160 °C for 2 h. High temperature (220 °C) and short time (0.5 h) contributed to hydrolysis of xylooligosaccharide with high DP to yield 37.5 wt% xylooligosaccharide with DP from 2 to 6. Xylooligosaccharide obtained mainly consisted of xylan with branches according to the HSQC NMR analysis. Overall, the production of XOS with a high yield from food waste will facilitate the valorization of food waste in the biorefinery industry.Graphical
Highlights
Chinese hickory (Carya Cathayensis) is a famous nut due to its nutritional value
To understand the structural changes of hemicelluloses from lignocellulose to liquid fraction and obtain XOS with high yield, a detailed and systematic evaluation of solid and liquid fractions was conducted for the hydrothermal pretreatment of Chinese hickory shell at various temperatures and different times
Moderate temperature (160 °C) and relatively long time was preferred for the production XOS with wide degree of polymerization (DP), the maximum yield can be up to 165.5 g/kg raw material with a relatively low level of xylose and other degraded products, while relatively high temperature (220 °C) and short time (0.5 h) was in favor for preparation of XOS with DP from 2 to 6, the maximum yield was 112.2 g/kg raw material
Summary
Chinese hickory (Carya Cathayensis) is a famous nut due to its nutritional value. More than 15,000 ha of Chinese hickory trees are cultivated in the Zhejiang and Anhui provinces of China [1]. It has been reported that kernel, leaves, and green husk have abundant nutraceutical components [2]. The hickory shell is a byproduct produced in large quantities after the cracking and shelling process. Hickory shell as waste would pollute the environment [3]. As far as we know, there is no report that developing and using sustainable and green strategy is used for high value-added utilization of hickory shell. How to utilize the hickory shell into value-added chemicals, materials, or biofuels is urgent and promising
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