Green synthesis of nickel ferrite nanoparticles for efficient enhancement of lignocellulosic hydrolysate-based biohydrogen production

To improve the lignocellulosic hydrolysate-based production of biohydrogen, bimetallic nickel ferrite nano -particles (NPs) with small particle size, cubic shape, high stability, and biocompatibility are synthesized using an Eichhornia crassipes extract at a low annealing temperature of 400 degrees C and added to the lignocellulosic hydrolysate fermentation by Klebsiella sp. WL1316. The optimal addition of 30 mg/L gsNiFe2O4 NPs accounts for the highest cumulative hydrogen production of 5544.86 +/- 37.03 mL/L and improvement of 112.32% +/- 1.86% at 24 h, while also resulting in the highest improvement of hydrogenase and formate-hydrogen lyase activities up to 102.11% +/- 13.73% and 62.99% +/- 4.66% compared to the Control treatment, respectively. Moreover, the conversion efficiencies of glucose, xylose, and substrate are enhanced upon addition of gsNiFe2O4 NPs, reaching values higher than 96% in the presence of 30 mg/L gsNiFe2O4 NPs. At the same time, the hydrogen yield converted from the substrate (Y(H2/S)) and biomass converted from the substrate (Y(B/S)) are also improved. In addition, the alteration of soluble metabolic products, especially significant changes in formic acid and ethanol concentrations compared to the control, increases the flux in the formate-hydrogen lytic pathway for hydrogen evolution, thereby promoting the substrate conversion level to hydrogen gas.