Green synthesis of magnetite nanoparticle and its regulatory effect on fermentative hydrogen production from lignocellulosic hydrolysate by Klebsiella sp.

Abstract

This study describes the synthesis and characterization of magnetite nanoparticles (NPs) from water hyacinth (WH) extract and its regulatory effect on fermentative hydrogen production from lignocellulosic hydrolysate by Klebsiella sp. Characterization of WH-magnetite-NP revealed that it was a pure magnetite NP in a spherical shape with an average particle size of 13.5 ± 3.7 nm. The maximum cumulative hydrogen production with an increment of 23.49% and an optimum Y(H2/S) of 83.20 ± 2.19 mL/gsubstrate was obtained with WH-magnetite-NP at 20 mg/L. Monitoring of key node metabolites further established the potential of WH-magnetite-NP to increase the flux distribution of the hydrogen synthesis pathway. The hydrogenase activity was enhanced via WH-magnetite-NP addition, with peak value 2.1 times of the control. The expression of functional genes in key pathways assessed via RT-PCR highlighted the effect of WH-magnetite-NP on the evident promotion of hydrogenase and formate-hydrogen lyase. This is the first attempt to detect the expression of multiple functional genes in key metabolic pathways to explain the regulatory mechanism upon NP addition.