The present invention relates to a composition or combination for the production of butanol and isopropanol, comprising an acetone-butanol-ethanol (ABE)-producing Clostridium strain and a genetically engineered B. subtilis strain, wherein said genetically engineered B. subtilis strain has been transformed by at least one polynucleotide molecule; the at least one polynucleotide molecule comprising a secondary alcohol dehydrogenase gene operably linked to at least one promoter. The invention also relates to methods of producing butanol and isopropanol in a co-culture, methods of producing butyrate, isopropanol and butanol in a co-culture and methods of producing esters.