Hydrogen production from proteins via electrohydrogenesis in microbial electrolysis cells

Microorganisms can produce hydrogen gas (H2) at high rates by fermentation of carbohydrates, but not from proteins. However, it is possible to produce H2 at high rates and yields from proteins by electrohydrogenesis in microbial electrolysis cells (MECs). Hydrogen gas was generated using bovine serum albumin (BSA, 700 mg/L) in a single-chamber MEC at a rate of Q = 0.42 ± 0.07 m3/m3/day and a yield of YH2=21.0±5.0 mmol-H2/g-CODYH2=21.0±5.0 mmol-H2/g-COD, with an energy recovery (relative to electrical input) of ηE = 75 ± 12% (applied voltage of 0.6 V). Hydrogen production was substantially reduced using a complex protein (peptone) under the same conditions, to Q = 0.05 ± 0.01 m3/m3/day, YH2=2.6±0.1 mmol-H2/g-CODYH2=2.6±0.1 mmol-H2/g-COD, and ηE = 14 ± 3%. There was good removal of organic matter for both substrates in terms of either protein (87 ± 6–97 ± 2%) or total COD (86 ± 2–91 ± 2%). Electron recycling likely occurred as Coulombic efficiencies exceeded 100% using BSA. The use of a two-chamber design, with either a CEM or AEM membrane, reduced the hydrogen production rate, but did not appreciably affect the hydrogen yield or energy efficiency. When an MEC was first acclimated to acetate, and then switched to BSA, performance was substantially reduced and was similar to that obtained using peptone. These results demonstrate that electrohydrogenesis can be used to produce H2 from proteins, and it can also be used as a method for treatment of protein-containing wastewaters.