Microalgal proteins as sustainable alternatives: CRISPR opportunities and challenges.

Against the backdrop of risinggrowing global demand for high-quality protein and increasing constraints on natural resources and the environment, microalgae are regarded as a promising alternative protein source, owing to their nutritional value, resource efficiency, and relatively low environmental footprint. However, their market adoption remains constrained by the limited availability of industrially robust strains combining high protein productivity with desirable processing traits. Recent advances in CRISPR-based genome engineering offer new opportunities for targeted microalgal strain improvement. This review systematically summarizes the comparative advantages, application prospects, and industrialization challenges of microalgal protein as an alternative protein source. It also reviews recent advances in using CRISPR technologies to improve microalgal protein. Particular emphasis is placed on CRISPR-based modulation of key pathways involved in nitrogen uptake and assimilation, amino acid biosynthesis, carbon-nitrogen allocation, light-energy utilization, and stress responses. These efforts aim to improve protein yield and quality, engineering compatibility, biomass production, and stress tolerance. We also discuss targeted improvement of cell-wall properties, colour and flavour to reduce production costs and enhance consumer acceptance, as well as protein-oriented multi-product biorefineries to further lower protein production costs. Finally, we analyse current challenges related to CRISPR delivery efficiency, multi-gene regulation, safety, market access and regulatory oversight, and highlight future directions that integrate multi-omics-driven design, precise genome editing and intelligent biomanufacturing. Collectively, this review provides an integrated framework for the low-cost, scalable, and sustainable production of microalgal alternative protein.