Strain Improvement Through Genetic Engineering and Synthetic Biology for the Creation of Microalgae with Enhanced Lipid Accumulation, Stress Tolerance, and Production of High-value

Microalgae are microscopic, unicellular or simple colony-forming photosynthetic organisms found mainly in freshwater and marine environments. Unlike multicellular macroalgae, microalgae lack complex structures such as roots, stems, and leaves. They perform photosynthesis using pigments like chlorophyll, producing oxygen and serving as primary producers in aquatic ecosystems. Microalgae have emerged as a promising platform for sustainable production of biofuels, high-value biochemicals, and nutraceuticals due to their rapid growth and ability to accumulate lipids. However, natural strains often exhibit limitations in lipid yield, stress tolerance, and metabolic versatility that restrict their industrial application. Strain improvement of microalgae through genetic engineering and synthetic biology involves precise modification of genetic and metabolic pathways to enhance desirable traits such as lipid accumulation, stress tolerance, and production of high-value compounds. This review highlights recent advances in genetic engineering and synthetic biology approaches aimed at enhancing microalgal strains for improved lipid accumulation, stress tolerance, and biosynthesis of high-value compounds. Emphasis is placed on novel transformation methods, genome editing tools such as CRISPR/Cas9, metabolic pathway optimization, and transcriptional regulation strategies. We discuss challenges in strain development, including stability and scalability, as well as future perspectives integrating multi-omics and systems biology to accelerate industrial applications of microalgae for sustainable biofuel and bioproducts production.