TECHNOLOGY FOCUS - BIOLOGY - Preferred Method: The microorganism produces a liquid product. Preferred Components: The microorganisms comprise a mono-culture or a co-culture of at least one of Clostridium ragsdalei, Butyribacterium methylotrophicum, Clostridium ljungdahlii, Clostridium coskatii or Clostridium carboxidivorans.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The feed gas passes serially into contact with multiple asymmetric membranes and carbon dioxide is removed from the feed gas as it passes between the asymmetric hollow fiber membranes. The liquid product passes into and through the lumens of the asymmetric membrane and the feed gas passes across the asymmetric membrane countercurrent to the axial direction of the lumens. The pressure of the liquid on the liquid contacting side is temporarily raised relative to the pressure on the gas contacting side by a sufficient amount to permeate liquid into the bio-pores and on the gas contacting side to flush microorganisms and/or biological material from the bio-pores. Preferred Components: The liquid product is at least one of ethanol (preferred), propanol, n-butanol, hexanol, acetic acid or butyric acid. The feed gas is synthesis gas having an oxygen concentration of less than 1000 ppm. The fermentation liquid has a redox potential of less than -200mV. The asymmetric membrane comprises many hollow fiber membranes.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The asymmetric membrane comprises the hydration layer in the form of a semipermeable skin on a porous polymer that provides the biolayer, where the skin has a thickness of less than 10 mu m and defines the gas contact side of the member and the porous polymer layer has a thickness of at least 50 mu m which defines the gas contact side of the membrane. The skin is rated at a nominal molecular weight cutoff of less than 300 kDa and a porous polymer defines bio-pores with effective diameters that do not exceed 100 mu m. The semipermeable skin comprises regenerated cellulose cast on the polymer comprising a microporous polyethylene substrate or the membrane comprises essentially of skin and polymer, where both have polysulfone or polyethersulfone. The biolayer and hydration layer have same chemical composition. The membrane comprises a composite having a biolayer and a hydration layer of two different materials. The hydration layer comprises a skin that occludes an end of the pores which are at opposite the open end of the bio-pores. The hollow fibers comprise the inner skin made of a semipermeable skin cast on the inside of the porous polymer layer. EXAMPLE - Membrane cartridge was connected to a fermentor (7.5 l) having fermentation medium (comprising 25 ml/l of mineral solution (having (in g/l) sodium chloride (80), ammonium chloride (100), potassium chloride (10), potassium dihydrogen phosphate (10), heptahydrate epsomite (20) and calcium chloride dihydrate (4)), 10 ml/l of trace metal solution (having (in g/l) nitrilotriacetic acid (2), manganese sulfate monohydrate (1), ammonium iron(II) sulfate hexahydrate (0.8), cobalt chloride hexahydrate (0.2), zinc sulfate heptahydrate (1), nickel chloride hexahydrate (0.2), sodium molybdate dihydrate (0.02), sodium selenium oxide (0.1), and sodium tungsten oxide (0.2)), 10 ml of vitamin solution (having (in g/l) pyridoxine (10), thiamine hydrochloride (5), riboflavin (5), calcium pantothenate (5), thioctic acid (5), p-aminobenzoic acid (5), nicotinic acid (5), vitamin B12 (5), mercaptoethanesulfonic acid (5), biotin (2), and folic acid (2)), yeast extract (0.5 g/l), sodium hydroxide (6.1 g/l), 2.5 ml/l of reducing agent (comprising cysteine (free base) (40 g/l) and sodium sulfide nonahydrate (g/l)). The fermentation medium (3 l) was agitated at 37 degrees C and pH of 5.9 with sodium chloride and hydrogen chloride under anaerobic conditions. The membrane cartridge was inoculated with Clostridium ragsdalei (150 ml). A gas (containing carbon monoxide (40%), hydrogen (30%) and carbon dioxide (30%)) was fed into cartridge. The cartridge was first operated in batch mode and then, switched to continuous operation for product recovery. The gas feed was stopped and the liquid circulation rate is increased (2000 ml/minute) and reduced back (500 ml/minute) and the gas feed was resumed finally to give ethanol (concentration increases to 15 g/l).