Redox-centric metabolic rewiring for dark-fermentative hydrogen production in Enterobacter aerogenes.

Authors

Gengran Zhai, Qingyao Jiang, Yilin Ding, Ruoxuan Bai, Jiale Chen, Fangxu Xu, Hongxin Zhao, Hongwei Fu

Published in

Bioprocess and biosystems engineering. Jul 07, 2026. Epub Jul 07, 2026.

Abstract

Dark-fermentative hydrogen is promising but constrained by acidification, mixed-acid by-products, and competition for reducing equivalents. Enterobacter aerogenes IAM1183, a rapidly growing and substrate-flexible facultative anaerobe, was used as the H₂-producing chassis. A unified benchmark was then established to systematically redirect flux along three levers: deleting the pyruvate formate-lyase-associated pflAB locus (ΔpflAB), enlarging reducing power/electron transfer by overexpressing pntA or fdx, and deleting phosphoenolpyruvate carboxylase ppc (Δppc) to probe pyruvate-node pressure. In 20 h glucose fermentations, H₂ yield increased by 38.0% in Ea/pntA, 32.8% in Ea/fdx, and 31.3% in ΔpflAB, whereas Δppc lowered H₂ yield by 10.5%. Intracellular NADH/NAD⁺ increased by 137% in Ea/pntA and by approximately 51% in ΔpflAB. In ΔpflAB, formate fell below HPLC detection, endpoint pH was 6.06 versus 4.70 in WT, and final biomass increased by approximately 50%, consistent with a strong apparent shift away from detectable formate-associated H₂ production under the present batch condition. Shifts toward acetoin and 2,3-butanediol across engineered strains indicate residual NADH sinks accompanying redox gains. Together, these side-by-side data distill actionable rules: alleviate acid load, expand reducing capacity, and constrain NADH sinks. They also nominate ΔpflAB combined with pntA or fdx overexpression as a promising design for future validation under pH-controlled and gas-removal conditions. This integrated evaluation clarifies how de-acidification, redox reinforcement, and carbon redistribution jointly reshape endpoint H₂ phenotypes in E. aerogenes, providing a coherent platform for future strain-and-process co-optimization of dark-fermentative biohydrogen production.

PMID:
42410197
Bibliographic data and abstract were imported from PubMed on 07 Jul 2026.

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