NOVELTY - A metabolically enhanced cyanobacterium comprising at least two first production genes encoding first biocatalysts for the production of the first chemical compound, where one of the two first production genes is under transcriptional control of first promoter for first production gene and the other of the two first production genes is under transcriptional control of a second promoter for the first production gene, where first promoter and second promoter are separately inducible under different conditions and at least two first biocatalysts catalyze the same chemical reaction, is new.    USE - For producing a first chemical compound such as biofuel e.g. hydrocarbon-based biofuel or ethanol (claimed). The biofuels also include fatty acid esters or alcohols, functional foods, vitamins, pharmaceuticals such as lactams, peptides and polyketides or terpenes and terpenoids and also biopolymers such as polyhydroxyalkanoates.    ADVANTAGE - The cyanobacterium provides improved cyanobacterial hybrid strains for prolonged production of first chemical compounds. The use of a first and a second promoter for the first production gene allows for the first biocatalyst under the control of first promoter to be expressed whereas at the same time the first biocatalyst under the control of the second promoter is not expressed, and vice versa. When the first promoter is induced, the first biocatalyst is expressed and the first chemical compound is produced, where genetic alterations can occur in the corresponding first production gene. At the same time, the second promoter for the first production gene is maintained in an uninduced state and the corresponding second of the first biocatalysts is not expressed, thus better preserving the genetic integrity of the corresponding non-induced first production gene compared to the induced one. The metabolically enhanced hybrid strains of cyanobacteria can be genetically stably maintained for much longer periods under non-inducing conditions than under induced cultivation conditions.    DETAILED DESCRIPTION - A metabolically enhanced cyanobacterium for the production of a first chemical compound, comprising at least two first production genes encoding first biocatalysts for the production of the first chemical compound, where one of the two first production genes is under the transcriptional control of a first promoter for the first production gene, and the other of the two first production genes is under the transcriptional control of a second promoter for the first production gene, where the first promoter and second promoter are separately inducible under different conditions and the at least two first biocatalysts catalyze the same chemical reaction, is new. INDEPENDENT CLAIMS are included for the following:    (1) a method for producing metabolically enhanced cyanobacterium; and    (2) a method (M1) for producing a first chemical compound using the metabolically enhanced cyanobacterium involving: culturing the metabolically enhanced cyanobacterium under conditions for induction of the first promoter for the first production gene, where the cyanobacterium produces the first chemical compound; culturing the metabolically enhanced cyanobacterium under conditions for induction of the second promoter for the first production gene, where the cyanobacterium produces the first chemical compound, where the steps are temporally separated, the second promoter for the first production gene of method second step is maintained in an uninduced state during method first step.