Bioremediation of textile dye Direct Blue 129, by green alga Chlorella vulgaris Beijerinck and cyanobacter Spirulina (Arthrospira) platensis Gomont, and influence of dye on their physiological and biochemical indices

 Removal of undesirable pollutants from aquatic ecosystems, which is caused by discharge of large amounts of industrial and urban pollutants into water resources, requires efficient, cost-effective and environmentally friendly technologies, such as phycoremediation. In this biological process, the physiological ability of some algal and cyanobacterial species in detoxifying pollutants such as textile dyes is used. In the present study, the ability of eukaryotic green alga Chlorella vulgaris and prokaryotic cyanobacter Spirulina platensis for decolorization of Direct Blue 129 (DB129) dye at zero (control), 20 and 60 mg. L-1 was studied during one week. Evaluations of physiological indices were performed on 1, 3 and 7 days of growth. C. vulgaris showed a higher percentage in removal efficiency than S. platensis. Dye treatment increased growth indices; Xm (maximum cell concentration), Px (cell productivity) and µm (maximum specific growth rate) and decreased td (doubling time) in C. vulgaris, compared to the control, but astaxanthin showed a higher increase in S. platensis. Chl a, Chl b and total carotenoid contents were increased in C. vulgaris alga at both concentrations of dye, and at 20 mg. L-1 in S. platensis, compared to control. Phycobilins were also increased in treated S. platensis. The highest concentration of dye (60 mg. L-1) caused the highest soluble carbohydrate production in both microorganisms. Along with an increase in dye concentration (unlike S. platensis) protein content was also increased in C. vulgaris. In general, it seems that C. vulgaris has a higher ability in decolrization and is more tolerant to DB129 dye stress than S. platensis.