Enhancing microalgal PUFAs through exogenous phytohormones: Mechanisms, market potential and future prospects

Polyunsaturated fatty acids (PUFAs) play an important role in maintaining normal homeostasis in humans and animals, underscoring the scientific priority of exploiting their sustainable sources. Microalgae-derived PUFAs are a sustainable source that supports carbon neutrality, renewability, and low maintenance. Thus, the present paper reviewed the potential of several freshwater and marine microalgal strains for PUFA production, focusing on factors that enhance their yield and productivity. The paper especially emphasizes the role of exogenous phytohormones in PUFA accumulation and the mechanisms underlying the same. In addition, commercial aspects such as the techno-economic assessment of microalgal PUFA production, market trends and projections have been discussed. Several marketed microalgal oil products have higher production costs compared with other marine sources, limiting their commercial feasibility. This necessitates the development of novel processes to enhance PUFA yield and productivity using physical, chemical, and additive-supplementation approaches. Among these, the use of exogenous phytohormones has emerged as an efficient strategy that can simultaneously enhance microalgal growth and PUFA levels, irrespective of other stress-mediated approaches that may otherwise hinder overall biomass content. Indole acetic acid (IAA), kinetin (KIN), gibberellic acid (GA), abscisic acid (ABA), methyl jasmonate (MeJ), and salicylic acid (SA) can modulate the transcriptional expression of genes in microalgae responsible for reactive oxygen species production, lipid remodeling, and PUFA production. Overall, using potential microalgal strains such as species of Nannochloropsis, Phaeodactylum, Scenedesmus, and Chlorella alongside phytohormone supplementation, especially auxins and jasmonic acid, validated by techno-economic and life-cycle assessment, can enhance the viability of the microalgae-based PUFA industry.