SIMULTANEOUS PHOTOPRODUCTION OF HYDROGEN AND AMMONIA BY A NON-HETEROCYSTOUS CYANOBACTERIUM PLECTONEMA BORYANUM

Abstract

Filamentous, non-heterocystous diazotrophic cyanobacterium Plectonema boryanum simultaneously photoproduced hydrogen (0.30μmol mg^-1 dry wth^-1) and ammonium (8.2nmol mg^-1 dry wth^-1) under microaerobic (A:CO₂, 96:4, v/v) conditions in the presence of 1mM sulfide. Nitrogen in the gas phase (A:CO₂:N₂, 72:4:24, v/v) enhanced the process more than two fold. A glutamine synthetase inhibitor, MSX, stimulated ammonium excretion and H₂-production and pulses of MSX rather than a single dose favoured both the processes. A higher dose (15μM) in comparison to lower dose (5μM) of MSX, although it stimulated H₂-evolution and NH₄⁺-excretion, shortened the duration of both the processes. The stability of both the processes was prolonged in alginate-immobilized cyanobacterial cells besides enhancement in H₂-evolution and NH₄⁺-excretion. MSX was less toxic under immobilized state than the free cells.