Regioselective hydration of geraniol by Escherichia coli fumarases in whole-cell biotransformations

The regioselective hydration of carbon–carbon double bonds to generate alcohols is a fundamental reaction in synthetic organic chemistry, offering pathways to valuable secondary and tertiary alcohols. Biocatalysis using hydratase enzymes, which add water to a double bond, provides a selective and sustainable alternative to traditional chemical methods. This study investigates the potential of Escherichia coli to hydrate the monoterpene geraniol in whole-cell biotransformation systems. Through a targeted knockout approach using the Keio collection, fumarases were identified as key contributors to geraniol hydration. Overexpression studies further revealed that FumA and FumB overexpression substantially enhanced geraniol hydration activity at the terminal alkene, suggesting promiscuity towards this non-native substrate. This result indicates an expanded substrate scope of class I fumarases beyond their established role in fumarate metabolism. By establishing a link between geraniol hydration and specific genes, we aim to extend the enzymatic toolbox for monoterpene transformations. Utilizing the inherent regioselectivity and atom economy of fumarases, the potential of fumarases as efficient biocatalysts in terpene modification could open new avenues to advance applications in green chemistry and biocatalysis.