Effects of Fe0 and Ni0 nanoparticles on hydrogen production from cotton stalk hydrolysate using Klebsiella sp. WL1316: Evaluation of size and concentration of the nanoparticles

Abstract

Fe0 and Ni0 nanoparticles (NPs) of certain size were synthesized and added to the hydrogen production system from cotton stalk hydrolysate using Klebsiella sp. WL1316. Fe0 and Ni0 NPs with a size of 50 nm at all concentrations effectively improve hydrogen production during mid to late fermentation stages; particularly, the highest daily hydrogen production obtained following treatment with 50 nm Fe0 NPs at 30 mg/L fermented for 96 h significantly increased by 61% comparing to the control treatment. The reducing sugar consumption in cotton stalk hydrolysate and ΔOD600 could be improved to some extent by Fe0 and Ni0 NPs supplementation. Addition of Fe0 or Ni0 NPs of 50 nm at a concentration of 30 mg/L resulted in enhanced cumulative hydrogen production with improvement of hydrogen yield reached higher than 20%, and the values of Y(H2/S) were all higher than 90 mL/g substrate, reflecting good hydrogen production and substrate consumption. The analysis of the main soluble metabolites profile revealed that supplementation with Fe0 and Ni0 NPs of suitable size and concentration may decrease the metabolic flux in the competitive branch of hydrogen production and increase the metabolic flux of the key node that leads to hydrogen generation, thus promoting biohydrogen synthesis.