The biomass of the cyanobacteria, Spirulina maxima 2342, was autotrophically obtained in a 201 bioreactor under illumination and air bubbling and analyzed for its photobiological hydrogen production capability. A volume of 250 ml of Spirulina sp. taken from the reactor was used as culture sample for performing the experiments. An illumination-agitation process was employed to induce the hydrogen photoproduction reaction. The hydrogen produced in this process was quantified by gas chromatography technique using Molesieve 5 angstrom (16 ft x 1/8 in) column and a thermal conductivity detector (with a detector temperature of 110 degrees C and a column temperature of 60 degrees C. The culture samples were finally observed in an electron microscope to evaluate the effect of vacuum on the Spirulina sp. cells. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.