Metabolic response of Pseudomonas putida to increased NADH regeneration rates

Pseudomonas putida efficiently utilizes many different carbon sources without the formation of byproducts even under conditions of stress. This implies a high degree of flexibility to cope with conditions that require a significantly altered distribution of carbon to either biomass or energy in the form of NADH. In the literature, co-feeding of the reduced C1 compound formate to Escherichia coli heterologously expressing the NAD⁺-dependent formate dehydrogenase of the yeast Candida boidinii was demonstrated to boost various NADH-demanding applications. Pseudomonas putida as emerging biotechnological workhorse is inherently equipped with an NAD⁺-dependent formate dehydrogenase encouraging us to investigate the use of formate and its effect on P. putida's metabolism. Hence, this study provides a detailed insight into the co-utilization of formate and glucose by P. putida. Our results show that the addition of formate leads to a high increase in the NADH regeneration rate resulting in a very high biomass yield on glucose. Metabolic flux analysis revealed a significant flux rerouting from catabolism to anabolism. These metabolic insights argue further for P. putida as a host for redox cofactor demanding bioprocesses.