Enhancing biomass production of Dunaliella salina via optimized combinational application of phytohormones.

Abstract Dunaliella salina is an important source of natural β-carotene. Phytohormones have growth-promoting and other physiological effects on many microalgae. However, there are only few systematic studies on the screening and optimization of key phytohormones for D. salina production. To enhance the biomass production of D. salina , the growth and physiological effects of seven phytohormones, myo-inositol (MI), 6-benzylaminopurine (6-BA), naphthyl acetic acid (NAA), indoleacetic acid (IAA), 2,4-dichlorophenoxyacetic acid (2,4-D), gibberellic acid (GA), and abscisic acid (ABA), on D. salina were investigated. The results showed that the seven selected phytohormones exerted significant effects on growth, photosynthesis, respiration and β-carotene biosynthesis at specific concentrations and time points. Three significant variables affecting biomass production were revealed via a Plackett–Burman design. The statistical model for maximum biomass production was constructed via response surface methodology using a Box-Behnken design. Statistical analysis showed that MI, IAA, and ABA have a stronger promoting effect on D. salina growth than the other four phytohormones, and their optimum concentrations were found to be 552 mg·L−1, 0.14 mg·L−1 and 0.22 mg·L−1, respectively. Validation experiments showed that the biomass increased by 19% using this optimized combination of phytohormones. Highlights • Phytohormones significantly promote Dunaliella salina cell growth. • Phytohormones affect photosynthesis and respiration of Dunaliella salina. • Phytohormones affect β-carotene biosynthesis of Dunaliella salina. • Three variable effects were found to be significant. • A second-order quadratic model was developed to predict biomass production. [ABSTRACT FROM AUTHOR]