Interdependence of Escherichia coli formate dehydrogenase and hydrogen-producing hydrogenases during mixed carbon sources fermentation at different pHs

The impact of the four membrane-bound [NiFe]-hydrogenases (Hyd) of Escherichia coli on total H-2-oxidizing activity during fermentation of a mixture of glucose, glycerol and formate at different pHs was examined. It was shown that Hyd-2 had a major contribution to total Hyd activity at pH 7.5 in early-stationary phase (24 h) cells, while the main contribution was made by Hyd-3 in late-stationary phase (72 h). Hyd-4-dependent Hyd activity could be demonstrated at pH 6.5 in cells lacking Hyd-1, Hyd-2 and Hyd-3. at pH 7.5 Hyd-4-dependent formate dehydrogenase (FDH-H) activity was demonstrated. Growth properties and fermentation end product patterns during 72 h demonstrated that the cells retained viability deep into stationary phase. Our findings emphasize the importance of formate in modulating H-2 metabolism, presumably by contributing to maintain redox, pH and pmf balance. This is important for regulating and enhancing H-2 production when a mixture of carbon sources is applied. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study examined the impact of four membrane-bound [NiFe]-hydrogenases of Escherichia coli on total H-2-oxidizing activity during fermentation with a mixture of glucose, glycerol, and formate at different pHs. The findings indicated that different hydrogenases played varying roles at different pH levels and stages of fermentation. Formate was emphasized as an important factor in modulating H-2 metabolism.