Lower production of ethanol (1.38 g/L) was observed after 72 h by E. aerogenes. However, E. aerogenes yielded high hydrogen production (1,416 mL/L) after 12 h of cultivation (Fig. 2b). E. aerogenes can convert various carbohydrates, such as sugars and sugar alcohols, to H2, ethanol, 2,3butanediol, lactate and acetate. Ito et al. [16] reported that E. aerogenes HU-101 mainly produces H2 and ethanol with a minimal production of other by-products when glycerol was used as substrate.