Provided is a host cell comprising a rhlA gene or an ortholog thereof, under the control of a heterologous promoter and a rhlB gene or an ortholog thereof, under the control of a heterologous promoter. The host cell is capable of achieving a carbon yield of more than 0.18 Cmol rhamnolipid/Cmol substrate. Provided is also a method of producing rhamnolipids, employing such a host cell.