In general, compounds lacking a C=C‐spacer between the carboxylate and the aromatic system were not converted (compound 38–44, Figure 1). Conjugated 2,4‐di‐unsaturated acids 36 a (sorbic acid) and 37 a were excellent substrates, which were quantitatively decarboxylated into the corresponding 1,3‐dienes by whole cells and only a minor decrease in rates were observed with isolated enzymes.