NOVELTY - Producing product alcohol (M1) involves: contacting fermentation broth comprising recombinant microorganism that produce product alcohol with fermentable carbon source where the recombinant microorganism consumes fermentable carbon source and produces product alcohol; and contacting the fermentation broth with fatty acids derived from biomass at a step in fermentation process, where at least one of growth rate and fermentable carbon consumption of microorganism is greater in presence of fatty acids than growth rate or fermentable carbon consumption in absence of fatty acids.    USE - For producing a product alcohol (selected from butanol) (claimed) which is used as e.g. a beverage (i.e. ethanol), fuel, reagents, solvents, and antiseptics; and as a fuel additive; as a feedstock chemical in the plastics industry and as a good-grade extractant in the food and flavor industry    ADVANTAGE - The method is efficient and environmentally friendly. At least one of growth rate and fermentable carbon consumption of the microorganism is greater in the presence of the fatty acids than the growth rate and the fermentable carbon consumption of the microorganism in the absence of the fatty acids. The addition of the fatty acids increases glucose consumption, and improves microorganism biomass production (cell growth/density) and growth rate, thus reducing production time and increasing productivity of the fermentation process. The method achieves improved alcohol productivity in which the fermentative growth of recombinant microorganisms is in the presence of fatty acids derived from biomass at a step in the fermentation process. The fatty acid supplementation during the fermentative growth of the microorganism increases the fermentable carbon consumption of the microorganisms, growth rate, and biomass production, particularly with regard to recombinant microorganisms that have reduced or eliminated pyruvate decarboxylase activity.    DETAILED DESCRIPTION - Production (M1) of a product alcohol involves:    (A) providing a fermentation broth comprising a recombinant microorganism that produces a product alcohol from a fermentable carbon source, where the recombinant microorganism comprises a reduction or elimination of pyruvate decarboxylase activity;    (B) contacting the fermentation broth with a fermentable carbon source where the recombinant microorganism consumes the fermentable carbon source and produces the product alcohol; and    (C) contacting the fermentation broth with fatty acids derived from biomass at a step in the fermentation process, where at least one of growth rate and fermentable carbon consumption of the recombinant microorganism is greater in the presence of the fatty acids than the growth rate and/or the fermentable carbon consumption of the recombinant microorganism is in the absence of the fatty acids.    INDEPENDENT CLAIMS are included for the following:    (1) producing (M2) a product alcohol involving: a) providing biomass comprising a fermentable carbon source and oil; b) converting at least a portion of the oil into fatty acids to form a biomass comprising the fatty acids; c) contacting the biomass with the fermentation broth; and d) contacting the fatty acids with the fermentation broth;    (2) producing (M3) a product alcohol involving: a1) providing a feedstock; b1) liquefying the feedstock to create a feedstock slurry; c1) separating the feedstock slurry to produce a product comprising an aqueous layer comprising a fermentable carbon source, an oil layer, and solids layer; d1) obtaining an oil from the oil layer and converting at least a portion of the oil into fatty acids; e1) feeding the aqueous layer of c1) to a fermentation vessel containing the fermentation broth; f1) fermenting the fermentable carbon source of the aqueous layer to produce the product alcohol; and g1) contacting the fermentation broth with the fatty acids; and    (3) a composition comprising a recombinant microorganism comprising a reduction or elimination of pyruvate decarboxylase activity and fatty acids.