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[Display omitted] • CaO 2 -metallic NP was applied for pretreatment and H 2 production from RS. • MnO 2 -CaO 2 NP addition was beneficial for biomass pretreatment and H 2 production. • MnO 2 -CaO 2 NP addition attained 16% lignin removal than hydrothermal treated RS. • MnO 2 -CaO 2 NP supplementation modulating the acetate and butyrate mediated pathway. In this study, calcium peroxide was modified and doped with metal-based nanoparticles (NP) to enhance the efficiency of pretreatment and biohydrogen generation from RS. The findings revealed that the addition of MnO 2 -CaO 2 NPs (at a dosage of 0.02 g/g TS of RS) had a synergistic effect on the breakdown of biomass and the production of biohydrogen. This enhancement resulted in a maximum hydrogen yield (HY) of 58 mL/g TS, accompanied by increased concentrations of acetic acid (2117 mg/L) and butyric acid (1325 mg/L). In contrast, RS that underwent pretreatment without the use of chemicals or NP exhibited a lower HY of 28 mL/g TS, along with the lowest concentrations of acetic acid (1062 mg/L) and butyric acid (697 mg/L). The outcome showed that supplementation of NP stimulated the pretreatment of RS and improved the formation of acetic and butyric acid through the regulation of metabolic pathways during acidogenic fermentation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lactobacillus lactis has been employed for biohydrogen production. • NiO/Fe 2 O 3 addition stimulates hydrogen production over 18% than control. • NiO/Fe 2 O 3 supplementation redirects butyrate mediated hydrogen metabolism. • Dehydrogenase activity enhances after nano-materials supplementation. • NAD+/NADH and FAD+/FADH 2 pool increases by 19% and 17%. The positive interaction between Clostridium sp. and lactic acid-producing bacteria (Lactobacillus sp) is commonly seen in various high-rate hydrogen production systems. However, the exact role of the hydrogen production ability of Lactobacillus sp in a dark fermentation production system is rarely studied. Lactobacillus delbrueckii was herein used for the first time, to the best of the author's knowledge, to demonstrate biohydrogen production under anaerobic conditions. At first, the pH condition was optimized, followed by the addition of nanoparticles for enhanced biohydrogen production. Under optimized conditions of pH 6.5, substrate concentration 10 g/L, and 100 mg/L of NiO/Fe 2 O 3 , the maximum hydrogen yield (HY) of 1.94 mol/mol hexose was obtained, which is 18 % more than the control. The enhanced H 2 production upon the addition of nanoparticles is supported via the external electron transfer (EET) mechanism, which regulates the metabolic pathway regulation with increased production of acetate and butyrate and reduced formation of lactate. [ABSTRACT FROM AUTHOR]