THE EFFECT OF GROWTH TEMPERATURE ON THE BIOENERGETICS OF PHOTOSYNTHETIC ALGAL CULTURES

Two photosynthetic algal cultures, one Chlorella vulgaris, and the other a Chlorogonium sp. , were cultured under light limitations in chemostats. The effects of growth temperature on their energy yield and maintenance energy requirement were studied. It was observed that a lowering in temperature resulted in a lower maximum growth yield from the light energy, Y//G. This was attributed to two reasons. First, at low temperatures there was a change in the algal cell composition with more energy being expended to synthesize a higher biomass protein content. Secondly, at low temperatures, a cyanide-resistant respiratory pathway became operative which led to a decrease in the number of ATP being generated. The maximum specific growth rate dropped with decreasing temperature, and can be described by an Arrhenius type rate-temperature model up to the optimal temperature for growth; i. e. , activation energy remained constant.