Acetoin is an important four-carbon compound that has many applications in foods, chemical
synthesis, cosmetics, cigarettes, soaps, and detergents. Its stereoisomer (S)-acetoin, a high-value chiral
compound, can also be used to synthesize optically active drugs, which could enhance targeting properties
and reduce side effects. Recently, considerable progress has been made in the development of biotechnological
routes for (S)-acetoin production. In this review, various strategies for biological (S)-
acetoin production are summarized, and their constraints and possible solutions are described. Furthermore,
future prospects of biological production of (S)-acetoin are discussed.