TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation (claimed): Production of the recombinant photoautotroph microorganism (G1) that converts a CO2 as carbon source to a suitable substrate or metabolic intermediate to isobutanol, involves transforming a microorganism with at least one recombinant nucleic acid sequence encoding polypeptides comprising the activity of acetohydroxy acid synthase, acetohydroxy acid isomeroreductase, dihydroxy-acid dehydratase, 2-keto-acid decarboxylase, and alcohol dehydrogenase. Preferred Microorganism: The 2-keto acid is selected from 2- ketobutyrate, 2-ketoisovalerate, 2-ketovalerate, 2-keto-3-methylvalerate, 2-keto 4-methyl-pentanoate, and phenylpyruvate. The recombinant photoautotroph microorganism (G1) comprises elevated expression or activity of a 2-keto-acid decarboxylase and an alcohol dehydrogenase, as compared to a parental microorganism. The 2-keto-acid decarboxylase is selected from phosducin (Pdc6), an aromatic decarboxylase (Aro10), thiamin transport (Thi3), Kivd, Pdc, or their homologs. The 2-keto-acid decarboxylase is encoded by a nucleic acid sequence derived from a gene selected from PDC6, ARO10, THI3, alpha-ketoisovalerate decarboxylase (kivd), and pdc, or their homologs (preferably kivd gene, or its homolog). The alcohol dehydrogenase is Adh2, or its homolog. The 2-alcohol dehydrogenase is encoded by a nucleic acid sequence derived from the ADH2 gene, or its homolog. The recombinant photoautotroph microorganism further comprises an elevated level of pyruvate as compared to a parental microorganism. The microorganism further comprises the deletion or inhibition of expression of an ethanol dehydrogenase (adhE), myo-inositol dehydrogenase (idhA), functional replacement of D-lactate dehydrogenase (frdBC), fibronectin receptor (fnr), pyruvate formate lyase B (pflB), or phosphotransacetylase (pta) gene and/or their homologs (preferably adhE, IdhA, frdBC gene or their homologs). The microorganism further comprises a deletion of adhE, idhA, frdBC, pta, fnr and/or their homolog (preferably the deletion of adhE, IdhA, frdBC, pta or their homolog; or deletion of adh, IdhA, frdBC, fnr and/or their homolog; or a deletion of adhE, IdhA, frdBC, pta, and pflB). The acetohydroxy acid synthase is encoded by a nucleic acid sequence derived from an ilvIH operon, or its homolog. The ilvI gene of the ilvIH operon encodes an acetohydroxy acid synthase large subunit polypeptide, or small subunit polypeptide. The acetolactate synthase is alsS from B. subtilis. The acetohydroxy acid isomeroreductase is encoded by a nucleic acid sequence derived from an ilvC gene, or its homolog. The dihydroxy-acid dehydratase is encoded by a nucleic acid sequence derived from an ilvD gene, or its homolog. The 2-keto-acid decarboxylase is encoded by a nucleic acid sequence derived from a kivd gene, ARO10 gene, or their homolog. The alcohol dehydrogenase is encoded by a nucleic acid sequence derived from an ADH2 gene, or its homolog. EXAMPLE - No suitable example is given.