An integrated process to produce ethanol, vanillin, and xylooligosaccharides from Camellia oleifera shell

• An integrated process was to produce ethanol, vanillin, and xylooligosaccharides.
• NaOH pretreatment was to obtain the solid residue and the liquid fraction.
• The residue after enzymatic hydrolysis was further fermented to produce ethanol.
• The liquid was firstly hydrolyzed with xylanase to produce xylooligosaccharides.
• The liquid after xylanase hydrolysis was further oxidized to produce vanillin.

This study aims to present an integrated process that can be used to produce ethanol, vanillin, and xylooligosaccharides from Camellia oleifera shell. After the shell was pretreated with NaOH, two fractions were obtained: solid and liquid fractions. The solid fraction was hydrolyzed with cellulase and then fermented with Pichia stipitis to produce ethanol. The liquid fraction was subjected to oxidation to prepare vanillin or hydrolysis with xylanase to prepare xylooligosaccharides. The optimal pretreatment conditions of an orthogonal test were as follows: 12% NaOH concentration; 120 °C; 150 min; and liquid–solid ratio of 10.0. After pretreatment, the solid fraction containing cellulose and a small part of xylan at 10% substance concentration via enzymatic hydrolysis and glucose–xylose cofermentation could obtain 17.35 g/L of ethanol, 80.90% of the theoretical yield. The liquid fraction was initially hydrolyzed with xylanase to produce 1758.63 mg/L of xylooligosaccharides (DP2–6) and then oxidized to produce 322.07 mg/L of vanillin.

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