| Abstract: | The three representative cyanobacteria, Synechococcus PCC7942, Anabaena variabilis, and Nostoc muscorum, were studied for their ability to asymmetrically reduce the prochiral ketones 2′‐3′‐4′‐5′‐6′‐pentafluoroacetophenone, ethyl 4‐chloroacetate, 4‐chloroacetophenone, and ethylbenzoylacetate to the corresponding chiral alcohols. Photosynthesis as well as respiration was applied for intracellular regeneration of the NAD(P)H cofactor. It was shown for the first time that all cyanobacteria were able to reduce the prochiral ketones asymmetrically without light for cofactor regeneration. By comparison of the cell specific product formation capacities of cyanobacteria with typical heterotrophic whole cell biocatalysts in batch processes, it is shown that comparable or, in some cases, better performances at high enantiomeric excess (ee > 99.8 %) are obtained. As a consequence of a generally strong product inhibition, in situ product removal must be applied in order to restore process efficiency when using cyanobacteria as biocatalysts. |
