Dark Fermentation (DF) holds great potential for biomass valorization since it is a method that allows obtaining products of industrial interest such as hydrogen (H2). There are many parameters that affect yields and productivities in these processes. Some of them, such as temperature, stirring or substrate concentration have been extensively studied. However, the impact of Oxidation-Reduction Potential (ORP) remains unclear. To study the influence of the initial ORP on the hydrogen production by DF using two different inoculum and substrates during DF for biohydrogen production. DFs to the study of the influence of the initial ORP are carried out on two media containing either glucose or Synthetic Depackaging Food Waste (SDFW) as substrate. Two different types of inoculums, one coming from a biogas plant and one from Depackaging Food Waste (DFW) are used to inoculate, respectively. Batch fermentations are performed in Stirred Tank Reactors (4.3L), utilizing different initial ORPs. Real-time monitoring of the ORP, pH, temperature, gas flow are performed. Moreover, metabolites and hydrogen produced, hydrogen yields and productivities, and kinetic parameters throughout the modified Gompertz and the Cone model are determined, and a bacterial population analysis is conducted throughout the determination of the bacterial richness and diversity and the relative abundances from the data obtained from a 16S rRNA gene sequencing.