Provided herein is process and system for the production of high-quality lignin by treating the post-fermentation solids. In one aspect, the present disclosure relates to a novel process comprising: providing a solid material remaining at the end of a fermentation process, wherein the fermentation process utilizes a lignocellulosic biomass feedstock; extracting lignin from the solid material into a liquid phase; and recovering lignin from liquid phase. In some embodiments, the fermentation process produces one or more of ethanol, n-butanol, iso-butanol, lactic acid, polyhydroxyalkanoates, succinic acid, 1,3-propanediol and 1,4-butanediol. In one embodiment's, the fermentation process produces ethanol.