Abstract
The uptake hydrogenase gene disrupted (ΔhupL) mutant of Nostoc sp. PCC 7422 has high hydrogen production activity, and accumulates hydrogen to about 30% (v/v) under a starting gas phase of Ar + 5% CO2. The mutant cells cultured under 10% nitrogen accumulated hydrogen 2 and 10 times of those cultured under 20% and 50%, respectively. We studied the effects of nitrogen concentration (1%, 5% and 10%) of the first (heterocyst induction period) and the second (hydrogen accumulation period) gas phase on hydrogen accumulation. After 2 days (2nd phase), nitrogenase activity of 10% (2nd) nitrogen cells were lower than those of 1% and 5% cells. Irrespective of the above first gas conditions, 1% (2nd) nitrogen cells produced hydrogen about 1.5 times of 5% (2nd) cells. With 5% (1st) nitrogen cells, hydrogen production activity of 1% and 5% (2nd) cells were 9 and 5 times that of 10% cells, respectively.
