TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The hydrolysis of (a) is conducted at 120 - 220degreesC 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 solid residue of the step (iv) comprising (b), is divided into a main stream and a secondary stream. The main stream is passed directly into the fermentation stage, but the secondary stream of polysaccharide residue is passed into an enzyme production stage, in which the enzyme is generated by allowing fungi to act on the polysaccharide residue, resulting in the formation of enzyme and converts (b) into its component sugars, then the enzyme and resulting sugars are passed into the fermentation stage. The enzyme acts on (b) in the fermentation vessel and hydrolyses (b) to the component sugars. The solid residue of the step (iv) comprising (b), is passed to an enzyme treatment stage in which enzyme is generated by allowing fungi to grow on the polysaccharide. The enzyme hydrolyses the polysaccharide into the component sugars and then passing the resulting sugars into the fermentation stage in which the sugars are converted into the fermentation product. 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 an 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 or analog materials. EXAMPLE - Milled wood chips steamed with low pressure steam to approximately 100degreesC. After steaming concentrated sulfuric acid was diluted and added to the mixture until the mixture contains 0.52% acid and the solids in the reactor were 22 wt.%. The mixture was then steam heated to 175degreesC for 15 minutes. The mixture was then flash cooled for 15 minutes to remove 6.5% of the acetic acid and 61% of the furfural and hydroxymethyl furfural. The 26% insoluble solids present in the pre-hydrolyzed slurry (containing 0.38% sulfuric acid) was then separated on a filter press. Prior to pressing solutions of flocculant or flocculants (at 0.2 - 0.5% solids) and/or particulate suspensions were added into the feed stream with necessary agitation at a dose of 0.22 - 2 kg/tonne of solids. Flocculants increase the rate of free drainage by gravity through a porous belt, before preparation of a filter cake in a wedge zone and subsequent further dewatering in a pressure zone. A method of reducing the toxins remaining in the liquid portion was to wash with water. After ion exchange for the removal of acetic acid, the liquid portion of the hydrolysate was acidified to pH 2 by the addition of sulfuric acid. Lime was then added to raise the pH to 10 and the liquor was then heated to 50degreesC. The liquid was then adjusted to the fermentation pH of 4.5 for 4 hours allowing gypsum crystals to form for separation by filtration. Detoxified and diluted hydrolyzed solids was split to cellulose fermentations, Z. mobilis seed production and simultaneous saccharification and co-fermentation (SSCF) fermenters. The hydrolysate feed stream was 22% combined soluble and insoluble solids. The portion of hydrolyzed solid residue was split off for Z. mobilis seed production was approximately 10%. For cellulose production pre-hydrolyzed solids-conditioned hydrolysate liquor, recycled water, corn steep liquor and nutrients and corn oil were combined to give a final cellulose concentration of 4%. The batch was then run for 160 hours at 28degreesC to produce cellulose. For SSCF, detoxified hydrolysate slurry was cooled to 30degreesC and added to the fermenter together with a 10 vol./vol.% seed inoculum. Corn steep liquor was added to 0.25% and cellulose to give a final concentration of 15 FPU/g cellulose and an initial cellulose concentration of 22%. The SSCF fermentation in which cellulose was converted to fermentable sugars by cellulose and the fermentable sugars converted to ethanol by Z. mobilis took 7 days.