Biohydrogen production from sugarcane bagasse hydrolysate: effects of pH, S / X , Fe 2+ , and magnetite nanoparticles

Abstract

Batch dark fermentation experiments were conducted to investigate the effects of initial pH, substrate-to-biomass (S/X) ratio, and concentrations of Fe²⁺ and magnetite nanoparticles on biohydrogen production from sugarcane bagasse (SCB) hydrolysate. By applying the response surface methodology, the optimum condition of steam-acid hydrolysis was 0.64% (v/v) H₂SO₄ for 55.7 min, which obtained a sugar yield of 274 mg g⁻¹. The maximum hydrogen yield (HY) of 0.874 mol (mol glucose⁻¹) was detected at the optimum pH of 5.0 and S/X ratio of 0.5 g chemical oxygen demand (COD, g VSS⁻¹). The addition of Fe²⁺ 200 mg L⁻¹ and magnetite nanoparticles 200 mg L⁻¹ to the inoculum enhanced the HY by 62.1% and 69.6%, respectively. The kinetics of hydrogen production was estimated by fitting the experimental data to the modified Gompertz model. The inhibitory effects of adding Fe²⁺ and magnetite nanoparticles to the fermentative hydrogen production were examined by applying Andrew's inhibition model. COD mass balance and full stoichiometric reactions, including soluble metabolic products, cell synthesis, and H₂ production, indicated the reliability of the experimental results. A qPCR-based analysis was conducted to assess the microbial community structure using Enterobacteriaceae, Clostridium spp., and hydrogenase-specific gene activity. Results from the microbial analysis revealed the dominance of hydrogen producers in the inoculum immobilized on magnetite nanoparticles, followed by the inoculum supplemented with Fe²⁺ concentration.

Graphical abstract

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