Xylo-oligosaccharides and lignin production from Camellia oleifera shell by malic acid hydrolysis at mild conditions

Camellia oleifera shell (COS), a by-product of processing woody vegetable oil, is rich in hemicellulose and lignin. In this study, we investigated the effects of acid concentration, pretreatment temperature and reaction time on the concentration and yield of xylo-oligosaccharides (XOS) and the degree of polymerization (DP) distribution of XOS when pretreating COS with malic acid (MA). Under moderate condition (2 M MA, 120 degrees C, 30 min), the maximum yield of XOS with DP 2-4 was 48.78% (based on the initial xylan) with low xylose, 5-hydroxymethylfurfural (HMF) and furfural, in which xylobiose (X2), xylotriose (X3) and xylotraose (X4) concentrations were 5.22 g/L, 2.75 g/L and 2.91 g/L, respectively. In addition, acid-insoluble lignin (AIL) in the residue after MA pretreatment and milling wood lignin (MWL) were mainly composed of guaiacyl and syringyl. AIL has higher thermal stability than MWL, which can be the stabilizer for producing flame-resistant materials.

Automated summary

The study found that under moderate conditions, xylobiose, xylotriose, and xylotraose had the highest yield and concentration, and acid-insoluble lignin in the residue could enhance the flame resistance of materials.