Interaction Effects of Salinity, High Light Intensity and Acetate on Growth and Pigment Production on Scenedesmus obliquus

Abstract

The aim of the present study was to examine the effects of salinity, high light intensity, and their interactions with acetate on the growth and changes taking place in the pigment, protein, and carbohydrate contents of Scenedesmus obliquus. Algal growth was inhibited by 300 mM NaCl, high light intensity, and their combination. Adding acetate to the culture medium considerably increased the fresh weight S. obliquus, even in cultures under stresses. The amounts of chlorophylls and total carotenoids decreased by stresses and acetate; however, addition of acetate to the cultures under stresses improved the reducing effect of stresses. Among carotenoids, the amount of astaxanthin, as a secondary carotenoid, increased, while the amount of β-carotene and lutein, as primary carotenoids, decreased under salinity and light stresses. The effects of acetate addition on two types of carotenoids under stress conditions were diverse. By adding acetate under stress condition, the amount of astaxanthin decreased; while the amount of β-carotene and lutein considerably increased. Stresses caused a decrease in protein and carbohydrate contents. Application of acetate alone stimulated biosynthesis of protein and carbohydrate in S. obliquus. Moreover, acetate improved the effects of stresses on reduction of protein and carbohydrate contents. The obtained results revealed that application of acetate was the most effective factor to enhance the biomass and astaxanthin production.