Selection of metabolic pathways for continuous hydrogen production under thermophilic and mesophilic temperature conditions in anaerobic fluidized bed reactors

Abstract

This study evaluated the influence of hydraulic retention time (HRT) on hydrogen (H2) production in anaerobic fluidized bed reactors at mesophilic (30 degrees C, AFBR-M) and thermophilic (55 degrees C, AFBR-T) temperatures. Reactors were fed sucrose-based synthetic wastewater (5000 mg chemical oxygen demand . L-1) in the HRT of 8, 6, 4, 2, or 1 h. H-2 production rate increased from 67.8 14.8 to 194.9 57.0 ml H-2.h(-1) L (AFBR-T) and from 72.0 +/- 10.0 to 344.4 +/- 74.0 mL H-2 h(-1) .l(-1) (AFBR-M) when HRT decreased from 8 to 1 h. Maximum H-2 yields for AFBR-T and AFBR-M were 1.93 t 0.21 and 2.68 0.48 mol H-2 mol(-1) sucrose, respectively. The main metabolites were acetic acid (31.3%-41.5%) and butyric acid (10.2%-20.7%) (AFBR-M) and acetate (20.1%-39.3%) and ethanol (14.3%-29.9%) (AFBR-T). Denaturing gradient gel electrophoresis profiles revealed selective enrichment of microbial populations responsible for H2 production by the aceto-butyric route (AFBR-M) and ethanol type fermentation (AFBR-T). (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.