A process for producing a bio-based surfactant comprising an alkyl disulphate salt comprises the steps of methanolysis of medium chain length polyhydroxyalkanoic acid (mcl-PHA) to provide hydroxy fatty acid methyl ester monomers (HFAME's), reduction of the HFAME's to provide 1,3 alkyl diols, sulphation of the 1,3 alkyl diols to provide 1,3 alkyl disulphates, and neutralisation of the alkyl disulphates to provide a bio-based surfactant comprising 1,3 alkyl disulphate salt. A bio-based surfactant comprising a mixture of medium chain length 1,3 alkyl disulphate salts is also described.