Enhanced hydrogen gas production from mixture of beer spent grains (BSG) and distiller's grains (DG) with glycerol by Escherichia coli

Escherichia coli perform mixed acid fermentation and produce hydrogen gas (H2) as one of the fermentation end products. E. coli can ferment sugars like glucose, xylose and alcohols like glycerol. It has been shown that E. coli has the ability to utilize pretreated organic waste (BSG or DG) or mixtures of it with glycerol and H2 can be produced. H2 evolution was maximum when the concentration of BSG was 4% and DG - 10% yielding 1.4 mmol L−1 H2. H2 evolution was prolonged to ~24–120 h when mixtures of glycerol and DG or BSG wastes were applied. Moreover, in hycE (lacking large subunit of Hyd-3) or hyfG (lacking large subunit of Hyd-4) single mutants H2 production was absent compared to wild type suggesting that Hyd-3 and Hyd-4 are responsible for H2 generation. In addition, multiple mutant enhanced cumulative H2 production ~3–4 fold. Taken together it can be proposed that BSG or DG wastes either together or in mixture with glycerol can be applied to obtain E. coli biomass and produce bio-H2. The novel data can be used to further control effectively the application of organic waste resources as a feedstock for developing bio-H2 production technology.