TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The enzymatic carbon chain elongation is carried out by microorganisms under reductive anaerobic conditions at redox potential lower than -350 (preferably lower than -400, more preferably lower than -450) mV. The microorganisms (preferably fermentive bacteria, especially clostridia) originate from an inoculum from anaerobic sewage sludge. The 6-18C fatty alcohol and/or 8-18C fatty acid are separated by extraction, precipitation, flotation, sedimentation and/or absorption. During the enzymatic carbon chain elongation, methane formation is inhibited, where the method (M1) involves heat pretreatment; and addition of methane formation inhibiting agent, such as 2-bromo-ethanosulfonic acid. The pH is maintained to 4-8, preferably 4-6, especially 5-6. The separation of the 6-8C fatty alcohol and/or 8-18C fatty acid is carried out at pH of 4-7 (preferably 4-6, especially 5-6). The enzymatic carbon chain elongation is carried out at pH of 6-8 (preferably 6.5-7.5, especially 7). The method (M3) additionally involves subjecting the product of the step (iv) to the method (M2). Preferred Components: The organic 2-6C compounds comprise organic 2-6C carbon acids and/or 2-6C alcohols (preferably acetate, n-propionate, iso-propionate, n-butyrate, iso-butyrate, succinate, n-valerate, iso-valerate, n-caproate, iso-caproate, n-butanol, and iso-butanol, especially acetate, n-propionate, iso-propionate, n-butyrate, ethanol and/or n-butanol). The organic 2-6C compounds are provided in the form of biomass, pretreated biomass, fermented biomass and/or their fractions. The electron donor is selected from hydrogen, formate, carbon monoxide, organic 1-6C compounds with a degree of reduction higher than 4 and/or mixtures of the electron donors (preferably hydrogen, ethanol and/or n-butanol). EXAMPLE - Fermentation was carried out using vials with volume of 125 ml were filled with 37, 5ml medium. The medium per liter comprises substrate (50 mM), (NH4)H2PO4 (3600 mg), magnesium chloride hexahydrate (500 mg), calcium chloride dihydrate (200 mg), potassium chloride (500 mg), trace metals (1 ml), B-vitamins (1 ml), zinc sulfate heptahydrate (100 mg), manganese chloride tetrahydrate (30 mg), boric acid (300 mg), cobalt chloride hexahydrate (200 mg), copper chloride hydrate (10 mg), nickel chloride hexahydrate (20 mg), Na2MoO4.7H2O (30 mg), iron chloride tetrahydrate (1500 mg), aluminum chloride hexahydrate (45 mg), sodium selenite (10 mg), biotin (106), folic acid (5), pyridoxal-HCl (2.5), lipoic acid (270), riboflavin (13), thiamine-HCl (13), Ca-D-pantothenate (414), cyanocobalamin (13), para-aminobenzoic acid (11), and nicotinic acid (15). The acetate (50 mM) was added and further 2-bromo-ethanosulfonic acid. The pH of the medium was adjusted to 5.5. The gas phase in the fermentation bottles consisted of nitrogen and hydrogen at partial hydrogen pressure. An inoculum originated from an anaerobic reactor was used for the conversion of acetate and ethanol. The vials were incubated at 30 degrees C and agitated at 200 rpm. Over a time period of 99 days, the pH was measured and adjusted to 5.35-6.65; and n-hexanol and n-caprylate were obtained with an amount of 84.1 plus minus 22.1 mg/ml and 605 plus minus 46 mg/ml respectively.