Bacterial outer membrane vesicles (OMVs) are small unilamellar proteoliposomes, involved in various functions including cell-to-cell signalling and protein excretion. We have engineered the OMVs of Escherichia coli to nano-scaled bioreactors for the biotransformation of fatty acids by targeting a fatty acid double bond hydratase of Stentrophomonas maltophilia (SmOhyA) and/or a photoactivated fatty acid decarboxylase from Chlorella variabilis NC64 A (CvFAP) into OMVs. Engineered OMVs containing both SmOhyA and CvFAP were able to catalyse the transformation of oleic acid ((Z)-octadec-9-enoic acid) into 9-hydroxyheptadecane via (R)-10-hydroxyoctadecanoic acid. The specific biotransformation rates of oleic acid reached 8.0×10⁻¹² μmol/min per OMV.