Dark fermentation of hydrogen from waste glycerol using hyperthermophilic eubacterium Thermotoga neapolitana

Waste glycerol from bio-diesel manufacturing is currently held to be a new, attractive, and abundant resource for future bio-fuel. Bio-hydrogen production via the fermentation route was examined for the first time from pure glycerol and discharged waste glycerol as the sole substrate by the hyperthermophilic eubacterium Thermotoga neapolitana. The bacterium, directly fermenting pure glycerol and crude waste glycerol in the medium, showed respective retarded growth and low H ₂ production 447 ± 22 mL H ₂ L ^-1 and 437 ± 21 mL H ₂ L ^-1. Attempting to improve the growth and H ₂ production, small amount (1.5 g L ^-1) of itaconic acid was added into the culture medium. In this case, H ₂ production from fermentation was approximately 620 ± 30 mL H ₂ L ^-1 for both pure glycerol and pre-treated waste glycerol as main substrate, an increase of 36.6% compared with cultures grown without itaconic acid, respectively. Further optimization of the glycerol concentration and culture conditions revealed enhancements in growth, H ₂ production, and glycerol utilization. The H ₂ fermentation from waste glycerol is of potential importance as wastes from bio-diesel processes can be utilized to produce bio-hydrogen.