Patent ID: 7867400

Claim:
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 fermentation liquor comprises lignin, wherein the solids-liquid separation stage comprises treating the fermentation liquor with an anionic polymer which anionic polymer is selected from the group consisting of natural polymers and modified natural polymers having an anionic charge such that the equivalent weight is below 300, 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, wherein the cake solids contain mainly lignin, with the proviso that the solids-liquid separation stage does not include a cationic polymer having an intrinsic viscosity (IV) of at least 4 dl/g.