The efficacy of different concentrations of gibberellic acid on physiological traits of Dunaliella salina microalgae in Guillard (f/2) medium

Dunaliella salina is a carotenoid-producing microalgae that is important for its extraordinary ability to accumulate ß-carotene. Therefore, an experiment was performed to investigate the effect of different concentrations of gibberellic acid on growth, accumulation of chlorophyll pigments, carotenoid content, and dry biomass of D. salina in f/2 medium. Experimental treatments included different concentrations of gibberellic acid (GA3): 0 (control), 0.5, 5, 10 and 20 mg/L. The measured traits in this experiment included growth rate and doubling time, chlorophyll a, chlorophyll b, total chlorophyll, total carotenoid, dry biomass, total lipid content, and endogenous gibberellic acid. The analysis of variance showed that the effect of different concentrations of gibberellic acid on all studied traits in D. salina was significant at the statistical level ρ)≤ 0.05). Gibberellic acid (GA3) at a concentration of 10 mg/l increased growth rate, chlorophyll a and b content, total chlorophyll content, dry biomass and total lipid content in the studied microalgae. While the highest amount of total carotenoid accumulation was recorded for 5 mg/L GA3 treatment. According to our findings, it is suggested that 5 mg/L GA3 concentration can be effective, if the purpose of cultivating this microalgae species is to produce carotenoid, but if the aim of production are dry biomass and total lipid content, the use of 10 mg/L GA3 concentration will stimulate and increase the production of microalgae total lipid and dry biomass.