NOVELTY - Producing a fatty acid or its derivative, comprises: providing a host cell which is genetically engineered to have an altered level of expression of a FadR polypeptide as compared to the level of expression of FadR polypeptide in a corresponding wild-type host cell; culturing the engineered host cell in a culture medium under conditions permissive for production of fatty acid; and isolating fatty acid from the host cell.    USE - The method is useful for producing the fatty acid or its derivative which is useful in a surfactant composition, and in a biofuel composition including biodiesel, fatty alcohol, fatty ester, triacylglyceride, diesel, gasoline or a jet fuel, where the fatty acid is an acyl-acyl carrier protein, acyl-coenzyme-A, fatty aldehyde, short chain alcohol, long chain alcohol, fatty alcohol (preferred), hydrocarbon or an ester, an ester is a wax, fatty ester or a fatty acid ester (preferred), the fatty acid ester is a fatty acid methyl ester or a fatty acid ethyl ester, and the fatty alcohol is 6C, 8C, 10C, or 12-18C fatty alcohol, or a 10C:1, 12C:1, 14C:1, 16C:1, or 18C:1 unsaturated fatty alcohol (all claimed). The fatty acid or its derivative is also as detergents, fuel additives, starting materials for production of other chemical compounds (e.g. polymers, surfactants, plastics, textiles, solvents or adhesives), personal care additives, or as feedstock for subsequent reactions e.g. hydrogenation or catalytic cracking, to make other products.    ADVANTAGE - The method increases at least one of titer (100 mg/l, preferably 100 g/l), yield (at least 10%, preferably at least 30%), or productivity (at least 3 (preferably at least 15) mg/l/OD600) of fatty acid produced by the engineered host cell when compared to that of the corresponding wild-type host cell.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) the fatty acid or its derivative produced by the method;    (2) a biofuel composition comprising the fatty acid or its derivative; and    (3) a surfactant composition comprising the fatty alcohol.