Processes for fermentation of lignocellulosic glucose to aliphatic alcohols or acids

A process for producing an organic aliphatic product from lignocellulosic biomass, said process comprising:

• (a) fractionating a feedstock comprising lignocellulosic biomass in the presence of 10-50 wt % of a solvent for lignin, 3-30 wt % of a hydrolysis catalyst, and water, to produce a liquor containing hemicellulose, cellulose-rich solids, and lignin;
• (b) washing said cellulose-rich solids and separating said cellulose-rich solids from said liquor;
• (c) enzymatically hydrolyzing said cellulose-rich solids to generate a hydrolysate comprising glucose;
• (d) detoxifying said hydrolysate by neutralizing said hydrolysate, removing insoluble solids, and removing or oxidizing residual hydrolysis catalyst, thereby generating a purified hydrolysate;
• (e) fermenting said purified hydrolysate using a suitable microorganism in a fermentor to produce a dilute organic aliphatic product, wherein said microorganism is recycled with a membrane, and wherein said membrane is configured to bleed microorganisms to control cell density in said fermentor;
• (f) extracting said dilute organic aliphatic product into a water-immiscible extractant, to generate an intermediate organic aliphatic product;
• and
• (g) distilling said intermediate organic aliphatic product to generate a concentrated organic aliphatic product.