Not only vinegar: Acetic Acid Bacteria as versatile biocatalysts for selective oxidation

Acetic acid bacteria (AAB) are aerobic, Gram-negative microorganisms able to oxidise a wide variety of sugars, alcohols, and polyols with high stereo- and regio-specificity, thanks to the presence of dehydrogenases located in their membrane and periplasmic space1. Moreover, several strains of AABs are also able to produce bacterial cellulose (BC), a natural polymer with high crystallinity and purity, which of particular relevance not only for its mechanical properties but also as an innovative support for enzymatic immobilization. Our research group kept an all-round view on the synthetic potentialities of AAB as biocatalysts for oxidations. Acetobacter malorum, isolated from the mother of vinegar, demonstrated good to excellent conversions (60-100%) in the oxidation of different aryl-aliphatic alcohols to their corresponding acids (Figure 1). This result was obtained either using resting cells or immobilised cells into barium alginate beads, thus allowing to maximize the productivity by using continuous-flow reactors. Among the tested compounds, regiospecific desymmetrization of 1,4-benzenedimethanol to 4-(hydroxymethyl) benzoic acid (m.c. 90%) is particularly noteworthy, since the only available procedures show low conversion (40%) and require heavy metals and harsh conditions.