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, in which the liquor has been subjected to a temperature of at least 50.degree. C., wherein the solids-liquid separation stage is assisted by a treatment system, characterised in that the treatment system comprises an anionic polymer selected from natural polymers and modified natural polymers having a high anionic charge such that the equivalent weight is below 300, and synthetic polymers formed from at least 50% by weight anionic monomer units.