From substrate stress to metabolic strategy shift: Quantifying synergistic effects on lignocellulosic biohydrogen production

This is the authors' abstract. We don't add key points for this paper.

Dark fermentation of lignocellulosic hydrolysates offers a sustainable route to biohydrogen. Process efficiency depends on both total sugar concentration and composition, yet their synergistic effects are not fully quantified. This study systematically investigates this interaction using a substrate matrix based on typical straw saccharification profiles. Quantitative analysis reveals distinct functional zones and a critical transition threshold at 40-60 g/L. Beyond it, metabolism shifts from a biohydrogen production-oriented to a growth-adapted state, which involved a decoupling between the maximum production rate and the final yield. Performance depends on the sugar ratio. A glucose-dominant blend achieves peak production of 234.74 mmol/L at 40 g/L, while a xylose-dominant blend yields 276.83 mmol/L at 180 g/L. Lactate accumulation served as a key phenotypic marker of this shift, with tolerance levels varying by sugar composition. This work establishes a functional zoning framework that links substrate conditions to metabolic outcomes, offering practical guidance for process optimization.