TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation (Disclosed): The microbial host cell is produced by standard recombinant methods. Preferred Polypeptide: The polypeptide that catalyzes a substrate to product conversion of pyruvate to acetolactate is acetolactate synthase. The polypeptide that catalyzes a substrate to product conversion of acetolactate to 2,3-dihydroxyisovalerate is acetohydroxy acid isomeroreductase. The polypeptide that catalyzes a substrate to product conversion of 2,3-dihydroxyisovalerate to alpha -ketoisovalerate is acetohydroxy acid dehydratase. The polypeptide that catalyzes a substrate to product conversion of isobutyraldehyde to isobutanol is branched-chain alcohol dehydrogenase. The polypeptide that catalyzes a substrate to product conversion of alpha -ketoisovalerate to isobutyraldehyde is branched-chain alpha -keto acid decarboxylase. The polypeptide that catalyzes a substrate to product conversion of alpha -ketoisovalerate to isobutyryl-coenzymeA is branched-chain keto acid dehydrogenase. The polypeptide that catalyzes a substrate to product conversion of isobutyryl-coenzymeA to isobutyraldehyde is acylating aldehyde dehydrogenase. The polypeptide that catalyzes a substrate to product conversion of alpha -ketoisovalerate to valine is transaminase. The polypeptide that catalyzes a substrate to product conversion of alpha -ketoisovalerate to valine is valine dehydrogenase. The polypeptide that catalyzes a substrate to product conversion of valine to isobutylamine is valine decarboxylase. The polypeptide that catalyzes a substrate to product conversion of isobutylamine to isobutyraldehyde is omega -transaminase. The acetolactate synthase comprises a 559, 571, or 554 amino acid sequence (SEQ ID NO: 2, 179 or 180) fully defined in the specification. The acetohydroxy acid isomeroreductase comprises an amino acid sequence of SEQ ID NO: 43 which is defined as a 19 base pair sequence (sic) fully defined in the specification, or comprises a 395, 330, or 342 amino acid sequence (SEQ ID NO: 181, 183 or 185) fully defined in the specification. The acetohydroxy acid dehydratase comprises a 616, 585, 550, or 558 amino acid sequence (SEQ ID NO: 6, 186, 188, or 190) fully defined in the specification. The branched-chain alcohol dehydrogenase comprises a 387, 312, 360, 389, or 390 amino acid sequence (SEQ ID NO: 10, 199, 201, 203, or 204) fully defined in the specification. The branched-chain alpha -keto acid decarboxylase comprises a 548, 547, 550, or 554 amino acid sequence (SEQ ID NO: 8, 193, 195, or 197) fully defined in the specification. The branched-chain keto acid dehydrogenase comprises four subunits comprising a 410, 352, 423, 459, 424, 327, 330, or 457 amino acid sequence (SEQ ID NO: 214, 216, 218, 220, 210, 208, 206, or 212) fully defined in the specification. The acylating aldehyde dehydrogenase comprises a 468, 862, 800, 307, or 307 amino acid sequence (SEQ ID NO: 222, 224, 226, 228, or 230) fully defined in the specification. The transaminase comprises a 417, 425, 309, 376, or 330 amino acid sequence (SEQ ID NO: 232, 234, 236, 238, or 240). The valine dehydrogenase comprises a 364 amino acid sequence (SEQ ID NO: 242, or 244) fully defined in the specification. The valine decarboxylase comprises a 594 amino acid sequence (SEQ ID NO: 246) fully defined in the specification. The omega -transaminase comprises a 440, 443, 446, or 448 amino acid sequence (SEQ ID NO: 248, 250, 252, or 254) fully defined in the specification. Preferred Cell: The host cell is chosen from bacterium, cyanobacterium, filamentous fungus, and yeast. The cell is a member of a genus chosen from Clostridium, Zymomonas, Escherichia, Salmonella, Rhodococcus, Pseudomonas, Bacillus, Lactobacillus, Enterococcus, Alcaligenes, Klebsiella, Paenibacillus, Arthrobacter, Corynebacterium, Brevibacterium, Pichia, Candida, Hansenula, and Saccharomyces, preferably E.coli, A.eutrophus, B.licheniformis, P.macerans, R.erythropolis, P.putida, B.subtilis, L.plantarum, E.faecium, E.gallinarium, E.faecalis, and S.cerevisiae. The host cell is a facultative anaerobe.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The fermentable carbon substrate is chosen from monosaccharides, oligosaccharides, and polysaccharides. The carbon substrate is chosen from glucose, sucrose, and fructose. Preferred Method: The conditions for producing isobutanol are anaerobic or microaerobic conditions. The host cell is contacted with the carbon substrate in a minimal medium. aaaataccagcgcctgtcc (SEQ ID NO: 43). EXAMPLE - No suitable example given.