Effect of peroxisome proliferation and salt stress on enhancing the potential of microalgae as biodiesel feedstock

Abstract

Microalgae are widely recognized as leading producers of third-generation biofuels. However, the industrialization of microalgae biodiesel faces significant challenges, primarily concerning efficiency and cost. A key bottleneck is the scarcity of energy-efficient, high-yielding, and resilient algal strains. To address this issue, this study investigated the role of the pivotal gene, Peroxin 11 (PEX11), involved in the formation of peroxisomes oxidative organelles ubiquitously present and associated with lipid metabolism and stress response. This study aimed to uncover the potential functions of PEX11 in lipid accumulation and salt stress response in Tetradesmus obliquus, utilizing PEX11-1 overexpression strains. Consistent with most reports, PEX11-1 was found to be localized in peroxisomes and potentially contributed to peroxisome proliferation in microalgae. The results revealed that overexpression of PEX11-1 positively impacted lipid accumulation, facilitated by the regulation of reactive oxygen species levels, the expression of lipid synthesis-related genes, and the redistribution of carbon precursors. The neutral lipid content in PEX11-1 overexpressing algal strains increased 2–3 times, with lipid yield escalating to 284.4 mg L⁻¹ and cellular biomass reaching 902.3 mg L⁻¹. Notably, under salt stress, the neutral lipid content per unit cell in the transformed line was nearly 4-fold higher than that of the WT. In addition, the overexpression of PEX11-1 hindered the involvement of lipid droplets in membrane remodeling and cell division, thereby diminishing the salt stress tolerance of T. obliquus. In conclusion, these findings emphasize the crucial role of PEX11 in microalgal lipid metabolism and offer insights into creating lipid-producing algal strains through genetic engineering.