TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The microorganisms form a biofilm on the biomass. The biofilm is irreversibly or reversibly immobilized on the biomass. The microorganisms can hydrolyze and ferment hemicellulosic or lignocellulosic material. The microorganisms comprise bacteria, a yeast and/or a non-yeast fungus. The microorganisms comprise Clostridium phytofermentans, Clostridium algidixylanolyticum, Clostridium xylanolyticum, Clostridium cellulovorans, Clostridium cellulolyticum, Clostridium thermocellum, Clostridium josui, Clostridium papyrosolvens, Clostridium cellobioparum, Clostridium hungatei, Clostridium cellulosi, Clostridium stercorarium, Clostridium termitidis, Clostridium thermocopriae, Clostridium celerecrescens, Clostridium polysaccharolyticum, Clostridium populeti, Clostridium lentocellum, Clostridium chartatabidum, Clostridium aldrichii, Clostridium herbivorans, Acetivibrio cellulolyticus, Bacteroides cellulosolvens, Caldicellulosiruptor saccharolyticus, Ruminococcus albus, Ruminococcus flavefaciens, Fibrobacter succinogenes, Eubacterium cellulosolvens, Butyrivibrio fibrisolvens, Anaerocellum thermophilum, Halocella cellulolytica, Thermoanaerobacterium thermosaccharolyticum, and/or Thermoanaerobacterium saccharolyticum. The microorganism is a Clostridium strain. The Clostridium strain is Clostridium phytofermentans, Clostridium sp. Q.D, or its variant. The Clostridium strain is a C phytofermentans American Type Culture Collection 700394T or a strain assigned the NRRL deposit accession number NRRL B-50351, NRRL B-50361, NRRL B-50362, NRRL B-50363, NRRL B-50364, NRRL B-50436, NRRL B-50437, NRRL B-50498, NRRL B-50511, NRRL B-50512, NRRL B-50447, NRRL B-50448, NRRL B-50449, and NRRL B-50450.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The gas comprises carbon dioxide, carbon monoxide, nitrogen, hydrogen, helium, neon, argon, nitrogen dioxide, and/or deoxygenated air.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The system further comprises: a compressor downstream of the fermenter and upstream of the condenser; a scrubber downstream of the condenser; a sterile filter downstream of the scrubber; a gas separator downstream of the scrubber and upstream of the sterile filter; and a distillation column, where the condensate is directed from the condenser to the distillation column, and the fermentation end-products are further purified.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The step of sparging is accomplished by a gas distribution member in fluid contact with the slurry in the fermenter. The step of recovering comprises directing the gas comprising the fermentation end-products to a condenser to form a condensate comprising the fermentation end-products. The step of directing is accomplished by a compressor. In the method, all or a part of the gas leaving the condenser is recycled to the fermenter. The gas leaving the condenser passes through a sterile filter prior to being recycled to the fermenter. The gas leaving the condenser is directed to a gas separator prior to the sterile filter. The gas passes through a scrubber prior to the gas separator. The biomass comprises sawdust, wood flour, wood pulp, paper pulp, paper pulp waste streams, grasses, such as, switchgrass, biomass plants and crops, such as, Crambe, algae, rice hulls, bagasse, jute, leaves, grass clippings, corn stover, corn cobs, corn grain, corn grind, distillers grains and/or pectin. The fermentation end-product has a boiling point below that of water. The microorganism is genetically modified. The fermentation end-product is maintained at a concentration in the fermenter that is below an inhibitory concentration for the microorganisms. The biomass comprises cellulose, hemicellulose and/or lignocellulose. The biomass comprises C5 sugars (pentose sugars), and/or C6 sugars (hexose sugars). Preferred Components: The compressor is downstream of the fermenter and upstream of the condenser. The compressor maintains a first pressure between the fermenter and the compressor that is below atmospheric pressure, and a second pressure between the compressor and the condenser that is at or above atmospheric pressure. The condensate is directed to a distilling column. The biomass is present at 15 (preferably 30) wt.%. EXAMPLE - Fermentation medium (xylose 24 g/l, glucose 21 g/l, cellobiose 20.6 g/l, and arabinose 2.6 g/l) was inoculated with 10% or 20% inoculums of C. phytofermentans strain. The culture was incubated at 35 degrees C with continuous agitation at 175 rpm, pH was adjusted and samples taken over the course of 100 hours and worked up to afford the ethanol.