Continuous hydrogen production from molasses by fermentation using urethane foam as a support of flocks

Abstract

Continuous hydrogen production by fermentation was tried using molasses as a substrate. In the fermenter, pieces of urethane foam were suspended to make them suports for cells or cell flocks of a bacterium, Enterobacter aerogenes strain E.82005. The suspended cell density was ca 0.8 g dry cell 1 −1 during cultivation, while the probability of adhesion of cells on or in the urethane foam was ensured from two different view points: the increment in the uptake rate of sugar, and the hydrogen evolution rate per unit cell mass. Lactate, butyrate and acetate were the main products of the fermentation, especially lactate which formed ca 70% of all products. The maximum and the available yields of hydrogen from sugar were ca 3.5 and ca 2.2 mol H 2 mol sugar −1, estimated in terms of sucrose, respectively. The available yield was nearly equal to the yield predicted from the sugar composition of molasses. The pathway of hydrogen evolution of the bacterium was determined to be the NADH pathway, from balance accounts of NADH.