The biocatalytic preparation of trans-hex-2-enal from trans-hex-2-enol using a novel aryl alcohol oxidase from Pleurotus eryngii (PeAAOx) is reported. As O₂-dependent enzyme PeAAOx-dependent reactions are generally plagued by the poor solubility of O₂ in aqueous media and mass transfer limitations resulting in poor reaction rates. These limitations were efficiently overcome by conducting the reaction in a flow-reactor setup reaching unpreceded catalytic activities for the enzyme in terms of turnover frequency (up to 38 s^-1) and turnover numbers (more than 300000) pointing towards preparative usefulness of the proposed reaction scheme.