TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Component: The deleted gene is phospho-transbutyrylase encoding phospho-transbutyrylase and/or butyrate kinase encoding butyrate kinase. At least one gene involved in acetone formation is attenuated in the microorganism. At least one gene from CoA-transferase encoding CoA-transferase and acetoacetate decarboxylase encoding aceto-acetate decarboxylase is deleted, or phospho-transacetylase encoding phospho-transacetylase and/or acetate kinase encoding acetate kinase. The hydrogenase gene is attenuated. The microorganism is C. acetobutylicum, C. beijerinckii, C. saccharoperbutylacetonicum, or C. saccharobutylicum.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The hydrogen flux is decreased and the reducing power redirected to butanol production. The method comprises fermentation of the microorganism producing n-butanol, elimination of n-butanol during the fermentation by gas stripping, and isolation of n-butanol from the condensate by distillation. EXAMPLE - An n-butanol producing strain was analyzed in chemostat cultures in the synthetic medium. An overnight culture at 35 degrees C was used to inoculate a 300 ml fermentor. The fermentor was filled with 250 ml synthetic medium, sparged with nitrogen for 30 minutes, and inoculated with 25 ml preculture to an optical density of 0.05-0.1. After 12 hours of batch culture at 35 degrees C, ph 5.5, and an agitation rate of 300 rpm, the fermentor was fed with oxygen free synthetic medium at a dilution rate of 0.05/hour while the volume was kept constant by removal of fermentated medium. Stability of the culture was followed by product analysis. Upon deletion of the gene coding for butyrate kinase, the maximum butyrate concentration detected in the medium decreased from 3.13 g/l after 2 days of culture in the C. acetobutylicum strain to 0.43 g/l after 5 days of culture in the C. acetobutylicum strain. The alcohol/glucose yield was increased (38.07%) and the acetone/glucose yield was decreased (4.64%).