Can 2, 4-dichlorophenoxyacetic acid alter growth performance, biochemical composition, and fatty acid profile of the marine microalga Isochrysis galbana?

ABSTRACT

The application of plant growth regulators is a new strategy for industrial cultivation of microalgae to enhance growth performance and synthesis of bio-products. In this study, changes in some growth indices, biochemical content, and fatty acid (FA) profile of Isochrysis galbana were investigated in response to 2, 4-dichlorophenoxyacetic acid (2, 4-D) at 0, 1, 2, 4 and 6 mg l⁻¹. Based on the results, 2 mg l⁻¹ 2, 4-D significantly improved biomass, growth rate, and doubling time; however, 6 mg l⁻¹ 2, 4-D inhibited growth. Maximum chlorophyll a was observed at 2 mg l⁻¹ 2, 4-D. The highest crude protein content was calculated in 2 mg l⁻¹ 2, 4-D. Lipid accumulation was significantly increased at 1 and 2 mg l⁻¹ 2, 4-D compared to the control group (P < 0.05). The highest and lowest concentrations of polyunsaturated FAs were observed in 6 mg l⁻¹ (47.32% of total FAs) and 1 mg l⁻¹ (35.72% of total FAs), respectively. However, maximum levels of saturated and monounsaturated FAs were obtained at 1 mg l⁻¹. Overall, the current study showed that addition of 2, 4-D at 2 mg l⁻¹ can improve both growth performance and lipid accumulation in I. galbana.

KEYWORDS:

• Auxin
• Fatty acids
• Growth promoter
• Phytohormone

Acknowledgements

The authors thank Mr. Hamid Fathalian (Fisheries Laboratory, University of Science and Research Branch) for preparing the purified initial stock of I. galbana.

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