Hydrogen production efficiency and microbial community of ethanol-type fermentation

The hydrogen production efficiency and microbial community of ethanol-type fermentation were investigated in this experiment. An internal circulation (IC) reactor was used to produce hydrogen with molasses wastewater as a substrate. The IC system was started up at the organic load rate of 8 kg COD/m(3) day and the hydraulic retention time of 6 h. The stable ethanol-type fermentation was achieved on Day 32; a maximum hydrogen production rate of 1.72 l/l day was obtained on Day 39 with the hydrogen content of 65.42%. The microbial diversity of the microorganisms in the enrichment phase (L1) and the ethanol-type fermentation phase (L5) was analyzed based on the high-throughput sequencing of the V3 region of the 16S rRNA gene. A total of 14 009 effective sequences and 426 operational taxonomic units (OTUs) were obtained from L1, which were classified into 226 genera from 19 phyla. The dominant genus was Propionibacterium with the relative abundance of 50.62%, and the dominant microorganism was Propionibacterium_unclassified with the relative abundance of 44.5%. In the L5, a total of 12 206 effective sequences and 416 OTUs were obtained, including 20 phyla, of which Firmicutes accounted for 55%; 230 genera, of which Propionibacterium accounted for 50.26% of the total abundance; and 338 species, of which Lactobacillus_unclassified accounted for 20.32% of the total abundance. Published under license by AIP Publishing.