Anodic electro-fermentation of 3-hydroxypropionic acid from glycerol by recombinant L17 in a bioelectrochemical system.

BACKGROUND

3-Hydroxypropionic acid (3-HP) is an important platform chemical which can be produced biologically from glycerol. is an ideal biocatalyst for 3-HP because it can grow well on glycerol and naturally synthesize the essential coenzyme B. On the other hand, if higher yields and titers of 3-HP are to be achieved, the sustained regeneration of NAD under anaerobic conditions, where coenzyme B is synthesized sustainably, is required.

RESULTS

In this study, recombinant L17 overexpressing aldehyde dehydrogenase (AldH) was developed and cultured in a bioelectrochemical system (BES) with the application of an electrical potential to the anode using a chronoamperometric method (+0.5 V vs. Ag/AgCl). The BES operation resulted in 1.7-fold enhancement of 3-HP production compared to the control without the applied potential. The intracellular NADH/NAD ratio was significantly lower when the L17 cells were grown under an electric potential. The interaction between the electrode and overexpressed AldH was enhanced by electron shuttling mediated by HNQ (2-hydroxy-1,4-naphthoquinone).

CONCLUSIONS

Enhanced 3-HP production by the BES was achieved using recombinant L17. The quinone-based electron transference between the electrode and L17 was investigated by respiratory uncoupler experiments. This study provides a novel strategy to control the intracellular redox states to enhance the yield and titer of 3-HP production as well as other bioconversion processes.