Continuous hydrogen production from molasses by the bacterium Enterobacter aerogenes

Hydrogen was produced continuously for 42 days by fermentation using Enterobacter aerogenes strain E. 82005. Diluted molasses containing about 2% sugars were fed at a rate of approximately 80 ml h −1. The maximum and the available rate of hydrogen production at 38°C in a 300 ml fermenter with 250 ml molasses fluid were 36 mmol-H 2/(l-culture h) and 20 mmol-H 2/(l-culture h) respectively. Cell concentration in waste liquid was nearly constant at about 0.9 g-dry cell/l throughout the experiment, although the total cell concentration in the fermenter was about 6.2 g-dry cell/l at the final cultivation, since flocks of the cells adhered to the wall of the fermenter. The maximum yield of hydrogen was 2.5 mol-H 2/mol sugar expressed in terms of sucrose, while the available yield of hydrogen was approximately 1.5 mol-H 2/mol-sugar. The volumetric fraction of hydrogen was approximately 60% of the gaseous products. Catabolism in continuous cultivation was different from that in batchwise cultivation. Lactate was the richest catabolite at about 70% in the liquid catabolites. Butyrate and acetate amounted about 15% and 10% respectively.