Establishment of control parameters for in situ, automated screening of sustained hydrogen photoproduction by individual algal colonies.

An apparatus was constructed which allowed automated screening of individual microalgal colonies for sustained ability to photoevolve H(2) during anaerobic photosynthesis. The main components of this apparatus were a microcomputer, a He-Ne laser mounted on a computer-controlled X-Y translation stage, a flow-through chamber which contained an agar plate of colonies, and a H(2) detector which interfaced with the microcomputer for data collection. The system was capable of detecting a minimum production rate of 1 nanomole of H(2) per hour per colony and provided an efficient means of screening relatively large numbers of algal colonies. Examination of the effect of the spacing of colonies on the agar plate, light intensity, stability of colonies within a screening period, colony age, chlorophyll content, and colony size on H(2) yield indicated that, under optimum conditions, yields from genetically uniform colonies varied by no more than a factor of 2 in their H(2)-producing ability. Therefore, colonies of algae whose H(2) yields lie outside this intrinsic twofold variability can be identified and selected as natural variants or mutants. A description of the construction and of the apparatus is presented, and the experimental results used to establish the control parameters for Chlamydomonas reinhardtii colonies are discussed.