HYDROGEN PHOTOPRODUCTION BY 3 DIFFERENT NITROGENASES IN WHOLE CELLS OF ANABAENA-VARIABILIS AND THE DEPENDENCE ON PH

Mo, V and Fe nitrogenases were induced in Anabaena variabilis. The inf luence of neutral and alkaline pHs on nitrogenase activity and rates o f H-2 photoproduction by whole cells was investigated to establish the optimum activity for H-2 evolution under varying growth and H-2 produ ction conditions. Growth rates in batch cultures at pH 7 with Mo- or V -nitrogenases were three times higher than the Fe-nitrogenase cultures . The Mo-nitrogenase activity decreased from pHs 7 to 9, and at pH 10, the culture was unable to grow. Fe-nitrogenase cells (no Mo or V) sho wed similar behaviour over pH 7-8. Cultures expressing V-nitrogenase e xhibited the highest resistance to alkaline pHs and grew even at pH 10 ; H-2 evolution was practically independent of the culture at pH 7-9. With cells grown under more alkaline conditions, the pH optimum for th e H-2 production was more alkaline; the maximal rates of H-2 photoprod uction were observed with V-nitrogenase containing cells. (C) 1997 Int ernational Association for Hydrogen Energy.