Bio-hydrogen production from glycerol by immobilized Enterobacter aerogenes ATCC 13048 on heat-treated UASB granules as affected by organic loading rate

•Enterobacter aerogenes immobilized on heat-treated UASB granules was used as inoculum.•Optimum OLR of 50 g/L d was found when waste glycerol was used as substrate.•Maximum HPR of 6.24 mmol H2/L h was achieved using waste glycerol as substrate.•Maximum hydrogen content of 24.19% was obtained using waste glycerol as substrate.•Hydrogen producers were E. aerogenes, Clostridium, Bacillus, and Dialister sp.

Bio-hydrogen production from glycerol by immobilized Enterobacter aerogenes ATCC 13048 on heat-treated upflow anaerobic sludge blanket (UASB) granules was examined in a UASB reactor. The organic loading rate (OLR) was optimized in order to maximize the hydrogen production rate (HPR). The maximum hydrogen content (37.1% and 24.2%) and HPR (9 and 6.2 mmol H2/L h) were achieved at the optimum OLR of 50 g/L d using pure and waste glycerol as the substrate, respectively. The major soluble metabolite products (SMPs) were ethanol, 1,3-propanediol (1,3-PD), formic acid, and acetic acid. The microbial community and microbial structure, analyzed by fluorescent in situ hybridization (FISH) and scanning electron microscopy (SEM), revealed that the predominant hydrogen producers were E. aerogenes ATCC 13048 and firmicutes bacteria including Clostridium, Bacillus, and Dialister sp.