INFLUENCE OF THE DEGREE AND MODE OF LIGHT LIMITATION ON GROWTH-CHARACTERISTICS OF THE RHODOBACTER-CAPSULATUS CONTINUOUS CULTURES

The influence of the degree and mode of light limitation on growth cha racteristics of turbidostat cultures of Rhodobacter capsulatus was inv estigated using mass and energy balance regularities. Light limitation was achieved by increasing the steady-state biomass concentration at constant incident light intensity (similar to 100 W/m(2)) or by decrea sing the incident light intensity at constant steady-state biomass con centration (similar to 500 mg of dry biomass/L). It was shown that und er conditions of light limitation of Rh. capsulatus, the content of P and N in the biomass as well as the biomass degree of reduction were d etermined by the growth rate of the cultures. The energetic yield of b iomass of Rh. capsulatus and total bacteriochlorophyll a content incre ased when light limitation increased. These parameters were higher in the cultures, in which light limitation was achieved by lowering the i ncident light intensity at low biomass concentration. This seems to be due to different distribution of lightwithin the photobioreactor when dissimilar modes of light limitation were used. (C) 1996 John Wiley & Sons, Inc.