TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In converting acetolactate to dihydroxy-isovalerate, the genetic construct encodes the polypeptide having ketol-acid reductoisomerase specific activity of greater than 1.1 mu mol/minute/mg based on purified protein as measured by the NADPH consumption assay, run under the following conditions: (i) pH of about 7.5; (ii) a temperature of about 22.5 degrees C; and (iii) greater than 10 mM potassium. In production of isobutanol, the genetic construct encoding the polypeptide having ketol-acid reductoisomerase activity is isolated from Pseudomonas. The host cell is selected from a bacterium, a cyanobacterium, a filamentous fungus and yeast. Also, the host cell is a member of a genus selected from Clostridium, Zymomonas, Escherichia, Salmonella, Rhodococcus, Pseudomonas, Bacillus, Lactobacillus, Enterococcus, Alcaligenes, Klebsiella, Paenibacillus, Arthrobacter, Corynebacterium, Brevibacterium, Pichia, Candida, Hansenula, Vibrio and Saccharomyces. The host cell is E. coli. The cell is Lactobacillus plantarum, or Saccharomyces cerevisiae. Moreover, the acetolactate synthase has an amino acid sequence of fully defined 559 amino acids (SEQ ID NO: 2), given in the specification. The polypeptide having ketol-acid reductoisomerase activity has an amino acid sequence selected from fully defined -338-494 (SEQ ID NO: 34, 35, and 36), given in the specification. The acetohydroxy acid dehydratase activity has an amino acid sequence of fully defined 616 amino acids (SEQ ID NO: 6), given in the specification. The branched-chain alcohol dehydrogenase has an amino acid sequence of fully defined 387 amino acids (SEQ ID NO: 10), given in the specification. The branched-chain alpha -keto acid decarboxylase has an amino acid sequence of fully defined 548 amino acids (SEQ ID NO: 8), given in the specification. In identifying and isolating of the genetic construct encoding the ketol-acid reductoisomerase enzyme having the specific activity of greater than 1.1 mu mol/minute/mg based on purified protein as measured by the NADPH consumption assay, the doubling time of (a) is equal to or less than 80% of the doubling time of E. coli when grown in M9 minimal medium. SPECIFIC SEQUENCES - Specifically claimed are acetolactate synthase, polypeptide having ketol-acid reductoisomerase activity, acetohydroxy acid dehydratase activity, branched-chain alcohol dehydrogenase, and branched-chain alpha -keto acid decarboxylase sequences comprising 338-616 amino acids (SEQ ID NO: 2, 6, 8, 10, and 34-36). All sequences are fully defined in the specification.    EXAMPLE - No suitable example given.