TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The hydrolysis of (a) is conducted at 120 - 220 degrees C for 1 - 15 minutes. The fermentation product is separated from the broth by passing the broth containing the fermentation product into a distillation stage or a concentration stage. In the distillation stage the fermentation compound is collected as a distillate and the residue still bottoms is removed. In the concentration stage the fermentation compound is collected in the concentrate and extracted by at least one method selected from ion exchange, solvent extraction or electrodialysis.Preferred Components: The acid is sulfuric acid or hydrochloric acid; and has a pKa of below 4 and has a concentration up to 2 wt.%.    TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The plant derived material is herbaceous biomass, softwood biomass, hardwood biomass, sewage sludge, paper mill sludge the biomass fraction of municipal solid waste or cellulosic material comprising hemicellulose as (a) and cellulose as (b).    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The flocculating agent is water-soluble or water swellable natural, semi-natural and synthetic polymer; or charged microparticulate material. The polymer is polyacrylate salts, polyacrylamide, copolymers of acrylamide with dialkylaminoalky(meth)acrylate or acid addition or quaternary ammonium salts, polymers of diallyldimethyl ammonium chloride, polyamine or polyethylene imines; and formed from a water soluble monomer or blend of monomers. The charged microparticulate material is swellable clays, anionic, cationic or amphoteric microparticulate silica based materials and organic cross-linked polymeric microparticles. The flocculation is effected by employing a water soluble or water-swellable polymer and a charged microparticulate material; by introducing an anionic microparticle material into the mixture and then reflocculating by adding non ionic polymer; by introducing a cationic polymer into the mixture and then reflocculating by adding an anionic microparticulate material or anionic polymer; or by introducing an anionic polymer into the mixture and then reflocculating by adding cationic polymer. The solid-by product material is lignin.