NOVELTY - An expression vector (V1) comprising (i) a nucleic acid molecule encoding a polypeptide having Acyl-CoA reductase (LuxC) activity, (ii) a nucleic acid molecule encoding a polypeptide having acyl transferases (LuxD) activity; (iii) a nucleic acid molecule encoding a polypeptide having acyl-protein synthetase (LuxE) activity; and (iv) a nucleic acid molecule encoding a polypeptide having decarbonylase activity, is new.    USE - In the production of an alkane of a defined chain length, where the alkane has a carbon chain length of 13-17C, preferably 13C, 15C and 17C; and for making a biofuel (claimed).    ADVANTAGE - The method enables bacteria that require minimal nutrient requirements to be utilized to produce biofuel; and enables photosynthetic bacteria to directly convert CO2 to biofuels consisting of defined and fixed 13-17C alkanes.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) new genetically modified fatty acid biogenic cell (C1) comprising the nucleic acid molecules (i)-(iv), where the cell is transformed with at least one of the nucleic acid molecules of (i) to (iv);    (2) producing (M1) an alkane of a defined chain length involving culturing a fatty acid biogenic cell comprising the nucleic acid molecule (i)-(iii) under conditions that allow expression of each of the polypeptides having LuxC, LuxD, and LuxE activity respectively, in the presence of a carbon source and a decarbonylase;    (3) use of (M2) a LuxCDE expression construct in a recombinant expression system for the production of an alkane of a defined chain length;    (4) reaction vessel (A1) containing the fatty acid biogenic cell (C1) and medium sufficient to support growth of the cell;    (5) making (M3) a biofuel involving culturing the fatty acid biogenic cell comprising a nucleic acid molecules (i)-(iii) under conditions that allow expression of each of the polypeptides having LuxC, LuxD, and LuxE activity respectively, in the presence of a carbon source and a decarbonylase.