This study systematically investigated the concentration-dependent effects of four metal oxides (Fe3O4, NiO, Al2O3, and CoO) on anaerobic fermentative biohydrogen production. Batch experiments were conducted using sucrose as the sole carbon source. All metal oxides exhibited Gaussian type–response patterns, indicating stimulation at low concentrations and inhibition at higher concentrations. These non-linear relationships were successfully quantified using a 3-parameter Gaussian model (R2≥0.79, p-value ≤ 0.0218). NiO showed the highest maximum cumulative hydrogen production (2629.30 mL/L) at an optimal concentration of 55.80 mg/L, followed by Fe3O4 (2194.34 mL/L), CoO (1876.57 mL/L), and Al2O3 (1696.82 mL/L). Gaussian-derived standard deviations indicated that NiO was the most concentration-sensitive, whereas Fe3O4 exhibited a broader tolerance range. Metabolite analysis revealed a strong positive correlation between hydrogen production and the butyric acid/acetic acid (B/A) ratio, reflecting a metabolic shift toward butyrate type fermentation. Enhanced hydrogen production was primarily observed in cultures dominated by anaerobic or facultative anaerobic bacteria such as Clostridium sp. or Klebsiella sp. which play a leading role in biological hydrogen production in the presence of NiO or Fe3O4. In contrast, cultures containing CoO and Al2O3 were characterized by the prevalence of the Enterobacteriaceae family, including Escherichia, Enterobacter, and Citrobacter. Overall, this study demonstrates that control of metal oxide type and dosage is critical for optimizing fermentative biohydrogen production.
Kim et al. (Thu,) studied this question.