A Study on the Effect of Nitrate and Phosphate Concentrations on the Production of Mycosporine-Like Amino Acids by Chlorella Vulgaris

Cyanobacteria can produce compounds absorbing ultraviolet irradiation. Mycosporine like amino acids (MAAs) are some of these important metabolites, which can be potentially considered as a sunscreen agent in the pharmaceutical and cosmetic industry. Different factors have been reported that can affect the biosynthesis of MAA. In this study, the influence of different concentrations of phosphate and nitrate under different environmental conditions on MAA production by Chlorella vulgaris was investigated using an experimental design method, in order to enhance MAAs production in this specious. A 23 full factorial design (FFD) using Design-Expert v7.0.0 software was used to optimize simultaneously all the three factors of nitrate and phosphate concentration and condition of incubation environment on the MAA production by this species of C. vulgaris. Two milliliter of organism stock were grown in 200 mL BG11 medium and after 21 days, the biomasses of all samples were separated. Then, the MAA was extracted from dried biomass using methanol extraction. The extracts were analyzed by reverse-phase high performance liquid chromatography (RP-HPLC). After complete analysis, four samples were then cultured at the optimized conditions and analyzed by liquid chromatohraphy coupled to mass spectrometry (LC/MS). The results showed that this microalga could produce compounds with λmax of 330 nm and a retention time of about 2 min. According to the central composite analysis, phosphate at 0.51 g.L-1 and nitrate at 2.5 g.L-1 can be considered as the optimum concentrations, resulting to the preferable conditions concerning the culture in germinator. Based on LC/MSS analysis, the major compound had a m/z of 332 at the optimum condition. Thus, this species is expected to have the capability of MAA production (maybe Shinorine) or one of its glycosylated derivatives.