The present invention provides a microbial cell capable of producing at least one terminal alkene from at least one short chain fatty acid, wherein the cell is genetically modified to comprise at least a first genetic mutation that increases the expression relative to the wild type cell of an enzyme (E1) selected from the CYP152 peroxygenase family, and at least a second genetic mutation that increases the expression relative to the wild type cell of at least one NAD(P)+ oxidoreductase (E2) and the corresponding mediator protein, wherein the short chain fatty acid is a C4-C10 fatty acid.