Detoxifying and recycling of washing solution used in pretreatment of lignocellulose-containing materials

A process for producing a fermentation product, comprising:

• (a) subjecting a lignocellulose-containing material to a pretreatment;
• (b) washing the pretreated lignocellulose-containing material in an aqueous washing solution;
• (c) separating the pretreated and washed lignocellulose-containing material from the used aqueous washing solution;
• (d) removing an enzyme inhibitor and an inhibitor of a fermenting organism from the used aqueous washing solution obtained in step (c) by contacting the used aqueous washing solution obtained in step (c) with a column comprising a resin directly after washing and separating, and recycling the used aqueous washing solution with less enzyme inhibitor and less inhibitor of a fermenting organism to step (b);
• (e) enzymatically hydrolyzing the separated lignocellulose-containing material obtained in step (c) to produce a hydrolyzate comprising fermentable sugars;
• (f) continuously repeating steps (a) to (e);
• and
• (g) fermenting the hydrolyzate produced in step (e) with the fermenting organism to produce the fermentation product.