Photoproduction of hydrogen by cyanobacteria under partial vacuum in batch culture or in a photobioreactor

Optimal conditions for H-2 photoproduction by the cyanobacterium Anabaena variabilis were investigated in batch experiments. Increasing light intensities during the incubation of cyanobacterial cells led to increased H-2 production which was accompanied by suppression of O-2 evolution. The batch experimental results were subsequently applied to the use of cyanobacteria in a computer-controlled photobioreactor for H-2 production. Some devices associated with the photobioreactor such as the pH electrode, CO2 cylinder and air line via proportional control gas flow valves and the vacuum and peristaltic pumps were connected via an interface card to an IBM computer. BBCBASIC (86) plus was the chosen language to write a program to control the photobioreactor. A two-phase H-2 production system is suggested as being feasible for practical demonstration. In the first phase the cyanobacterial cells photosynthesize under light intensities of 45-55 mu mol . s(-1) . m(-2) and establish conditions for subsequent H-2 production. In the second phase the cells produce H-2 under light intensities of 170-180 mu mol . s(-1) . m(-2) Photoproduction of H-2 at rates of about 12.5 ml H-2 . gcdw(-1) . h(-1) was observed. (C) 1997 International Association for Hydrogen Energy. All rights reserved.