The Role of Molecular Tools in Microalgal Strain Improvement: Current Status and Future Perspectives

Microalgae are microscopic, typically single-celled photosynthetic organisms found in freshwater, marine, and even terrestrial environments. Microalgae are crucial to global ecosystems because they are primary producers, forming the base of the aquatic food chain and producing about half of the Earth's oxygen through photosynthesis. Microalgae are vital sustainable feedstocks with applications spanning food, feed, biofuels, and high-value bioproducts. However, their industrial-scale use faces challenges due to the limited robustness and productivity of wild-type strains. Recent advancements in molecular tools and genetic engineering have ushered in a new era for microalgal strain improvement. Molecular tools, including genetic engineering, random mutagenesis, and advanced selection methods such as fluorescence-activated cell sorting (FACS), constitute powerful approaches for microalgal strain improvement. These tools enable precise genome modifications, creation of tailor-made phenotypes, and selection of mutants with enhanced productivity and stress tolerance. The scope of this review encompasses the diverse molecular techniques employed in strain optimization covering forward and reverse genetics, site-directed mutagenesis, adaptive laboratory evolution, and non-GMO random mutagenesis. The significance lies in overcoming bottlenecks in microalgal commercialization by improving strain performance and enabling sustainable bioproduct generation. This article aims to synthesize current advancements, critically analyze the integration of these molecular tools with high-throughput technologies, discuss regulatory considerations, and outline future perspectives for accelerating microalgal strain development to meet industrial and environmental demands.