Abstract
An account is given on the state of the art of medium-engineering for bio-organic synthesis. Medium-engineering means designing (micro)environments for the biocatalyst with the objective of reaching maximal activity, stability and hence productivity. Medium-engineering therefore involves aspects such as stabilizing the essential water layer around the biocatalyst, controlling electrostatic and hydrophobic interactions between matrix, reactants and biocatalyst, as well as optimizing substrate and product fluxes through the entire biocatalytic system. Where possible, some general rules have been derived, which might be of help in designing media for bio-organic synthesis.