Magnesium improves hydrogen production by a novel fermentative hydrogen-producing bacterial strain B49

Batch experiments were conducted to investigate the effects of magnesium on glucose metabolism, including growth and hydrogen-producing capacity of fermentative hydrogen-producing bacterial strain B49. These abilities were enhanced with an increase in magnesium concentration. At the end of fermentation from 10 g/L glucose, for 10 mg/L MgCl₂·6H₂O the cell growth in terms of optical density (OD) at 600 nm was 0.46, the ratio of ethanol amount (mg/L) to acetate amount (mg/L) was 1.1, and the accumulated hydrogen volume was 934.9 mL H₂/L culture; for 200 mg/L of MgCl₂·6H₂O OD_{600 nm} was increased to 1.34. The accumulated hydrogen volume was increased to 2360.5 mL H₂/L culture, the ratio of ethanol amount (mg/L) to acetate a-mount (mg/L) was increased to 1.3 and polysaccharide was decreased to 2.5 mg/L. Moreover, the magnesium solution addition to the medium at different fermentation times affected hydrogen-producing ability. However, the later the addition time was postponed, the less the effect was on hydrogen evolution. Further experiments confirmed the enhancement was dependent on magnesium ions and not on the other inorganic ions such as SO₄^2- or Cl^-, which constituted the magnesium salts.