The alteration in the biomass color observed in the alga culture
grown in the 3rd run could be attributed to elevated CO2
concentrations. It was reported that S. platensis grown on
elevated CO2 concentrations resulted in an increase in carbohydrate
content; decrease in proteins and pigments . Also, stated that some microalgae can undergo a carotenogenesis
process, in response to various environmental and cultural
stresses (e.g., light, temperature, salts, nutrients), where the
alga stops growth and changes dramatically its carotenoid
metabolism, accumulating secondary carotenoids as an
adaptation to severe environments.