Supplementation of magnetic nanoparticles for enhancement of dark fermentative hydrogen production from pretreated garden wastes using Enterobacter aerogenes

Abstract

The supplementation of magnetic nanoparticles (NPs) to the dark fermentative hydrogen production system mediated by Enterobacter aerogenes using pretreated garden wastes as feedstock was investigated to determine the enhancement of biohydrogen production efficiency. The optimized pretreatment conditions of 2% sulfuric acid with sonication (AS) and 2% Viscozyme L with sonication (ES) of garden wastes yielded a maximum of 33 and 37% total reducing sugar, respectively. In addition, the supplementation of 30 mg/L of magnetic NPs to dark fermentative system of AS and ES yielded 32 and 30% increased hydrogen production compared with the control without NPs, respectively. A maximum yield of 2.43 mol H2/mol sugar utilized was achieved in the optimized system supplemented with NPs. The reusability of the magnetic NPs offers an additional advantage showing more than 90% relative hydrogen production retained after four consecutive cycles. The proposed mechanisms suggest that the optimum level of magnetic NPs supplementation increases the electron transfer rate and modifies the E. aerogenes metabolic pathway, limiting ethanol production and increasing acetate proportion in the end metabolite analysis. Overall, the addition of magnetic NPs to the dark fermentative system improved the biological hydrogen production.