Effect of light and temperature on the cyanobacterium Arthronema africanum -: a prospective phycobiliprotein-producing strain

The effect of light intensity (50-300 mu mol photons m(-2) s(-1)) and temperature (15-50 C) on chlorophyll a, carotenoid and phycobiliprotein content in Arthronema africanum biomass was studied. Maximum growth rate was measured at 300 mu mol photons m(-2) s(-1) and 36 C after 96 h of cultivation. The chlorophyll a content increased along with the increase in light intensity and temperature and reached 2.4% of dry weight at 150 mu mol photons m-2 s-1 and 36 C, but it decreased at higher temperatures. The level of carotenoids did not change significantly under temperature changes at illumination of 50 and 100 mu mol photons m(-2) s(-1). Carotenoids were about 1% of the dry weight at higher light intensities: 150 and 300 mu mol photons m(-)2 s(-1). Arthronema africanum contained C-phycocyanin and allophycocyanin but no phycoerythrin. The total phycobiliprotein content was extremely high, more than 30% of the dry algal biomass, thus the cyanobacterium could be deemed an alternative producer of C-phycocyanin. A highest total of phycobiliproteins was reached at light intensity of 150 mu mol photons m(-2) s(-1) and temperature of 36 C, C-phycocyanin and allophycocyanin amounting, respectively, to 23% and 12% of the dry algal biomass. Extremely low (< 15 C) and high temperatures (> 47 C) decreased phycobiliprotein content regardless of light intensity.