Process for the production of fermentation products and lignin

A process for the production of one or more fermentation products and lignin comprising:

• (a) contacting lignocellulosic biomass or steamed lignocellulosic biomass with a pretreatment liquor at an elevated temperature under pressure;
• wherein the pretreatment liquor comprises sulfur dioxide, volatile alcohol, and water;
• thereby releasing and/or dissolving lignin and hemicelluloses from the lignocellulosic biomass into the pretreatment liquor, resulting in a mixture comprising lignin and hemicelluloses dissolved in the pretreatment liquor and a solid fraction comprising mainly cellulose, which mixture is referred to as the pretreated material;
• (b1) recovering sulfur dioxide and alcohol, thereby precipitating lignin and producing a first mixture comprising cellulose, lignin, and monosaccharides;
• (b2) optionally retaining the first mixture at a desired temperature and at a desired pressure and mixing rate or recirculating rate, whereby the chemically bound volatile alcohol is released and optionally recovered, providing a second mixture comprising cellulose, lignin, and monosaccharides;
• (c) adjusting the pH of the first or second mixture to an appropriate level for enzymatic hydrolysis;
• (d) contacting the pH-adjusted first or second mixture with a cellulase, a glucosidase, a hemicellulase, or a combination thereof, to provide a third mixture comprising glucose derived from cellulose and monosaccharides derived from hemicelluloses as well as lignin;
• and
• (e) subjecting the third mixture to fermentation;
• to produce the one or more fermentation products.