Effect of auxin and its synthetic analogues on the biomass production and biochemical composition of freshwater microalga Ankistrodesmus falcatus CMSACR1001

Abstract

Exogenous supplementation of phytohormones to promote the selective enrichment of biomolecules without hampering biomass production is regarded as a promising approach to improve the techno-economic feasibility of biofuels and other value-added products derived from microalgae. The present work outlines the influence of natural auxin, indole-3-acetic acid (IAA) and two synthetic analogues, 1-naphthalene acetic acid (NAA), and 2,4-dichlorophenoxyacetic acetic acid (2,4-D) on the growth pattern and biochemical productivity of the green alga Ankistrodesmus falcatus CMSACR1001. A maximum biomass production of 431 mg L−1 with a concomitant increase in the protein and carbohydrate content (20.2% and 49.6% DCW respectively) was achieved under supplementation of 10 μM IAA. Biomass productivity at 1 μM concentration was found to be comparable for both IAA and NAA (32.8 mg L−1 day−1 and 32.4 mg L−1 day−1). At higher supplemented concentrations 2,4-D induced a 30–40% increase in carotenoid production and exhibited an increased lipid content of 41–47% DCW as compared with control (34.2% DCW). The current study also reports a substantial increase in the neutral lipid proportion as much as 73.9% and 79% under supplementation of NAA and 2,4-D respectively at 100 μM. The results indicate that the auxin and its analogues under the study could increase the biomass production and favourably modulate the biochemical composition of A. falcatus.