Production of a fermentation product

A process of separating suspended solids from a fermentation liquor by subjecting the liquor to a solids-liquid separation stage,

• wherein the fermentation liquor is produced in a fermentation process for the production of a fermentation product,
• which liquor comprises water, lignin and BOD,
• wherein the solids-liquid separation stage comprises adding to the fermentation liquor,
• (ii) a cationic polymer having high intrinsic viscosity (IV) of at least 4 dl/g and at least one component selected from the group consisting of
• (iii) an anionic polymer,
• (iv) a cationic polymer of low intrinsic viscosity of below 4 dl/g and a cationic charge density of at least 3 meq/g,
• (v) inorganic coagulants and
• (vi) charged microparticulate material
• flocculating the suspended solids and lignin in the fermentation liquor and
• subjecting the fermentation liquor to a mechanical dewatering stage selected from at least one of, a centrifuge, a screw press, a filter press, a belt filter press, a horizontal belt filter or a pressure filter to separate the flocculated suspended solids and lignin as cake solids.