Gotta oxidise them all: efficient whole-cell conversion of benzyl alcohols to acids

Abstract: Acetic acid bacteria (AAB) are Gram-negative microorganisms able to oxidise a wide variety of sugars, alcohols, and polyols with outstanding stereo- and regio- specificity, using dehydrogenases located in the periplasmic space [1]. Therefore, AAB have been thoroughly used to prepare several aldehydes and carboxylic acids, making them considerable biocatalysts in a plethora of different bioprocesses. Interestingly, the substrate specificity and the overall oxidative efficiency strictly depend on the strains used and on the reaction conditions. In previous works, the oxidation of benzyl alcohol by different AAB strains resulted very poor [2]. Our group selected three different strains of AAB, two of them isolated from the gut microbiota of Drosophyla suzukii, and tested them with several aromatic alcohols, including benzyl derivatives, to broaden the substrate scope accepted by AAB. All reactions have been performed using 1 g/L substrate using both growing and resting cells in phosphate buffer. The conversions show promising results with the majority of alcohols completely converted into their corresponding acid within 24 hours. Moreover, aldehydes can be accumulated by using a water/isooctane two-liquid phase system. This sheds some light on a new possible industrial application of AAB for the synthesis of relevant building blocks in organic chemistry.