Low-temperature plasma technology: comprehensive applications in microalgae cultivation, mutagenesis, and downstream processing.

Microalgae can produce fuels, nutraceutical ingredients, and materials useful in environmental remediation, but their wider use still depends on better strains and cheaper processing. Low-temperature plasma (LTP) technologies, including atmospheric and room-temperature plasma (ARTP), are emerging as versatile tools for microalgal biotechnology. This review critically examines dose-dependent LTP-microalgae interactions across the cultivation-to-biorefinery continuum. At low doses, plasma-derived reactive oxygen and nitrogen species (ROS/RNS) act as signaling molecules, modulating phytohormone pathways and epigenetic marks to enhance biomass formation and secondary metabolite accumulation. Moderate-to-high doses induce DNA damage and error-prone repair, enabling generation of mutant libraries with improved lipid, protein, pigment, and stress-tolerance traits. Under severe conditions, plasma facilitates cell disruption, product recovery, sterilization, and harmful algal bloom mitigation. Key advances in ARTP mutagenesis have produced strains with 44-75% higher lipid productivity and 40-78% enhanced carbohydrate content. This review identifies critical knowledge gaps, including the lack of standardized plasma dosimetry, limited understanding of plasma-induced epigenetic mechanisms, and insufficient pilot-scale validation. Future integration of plasma technologies with omics-guided screening, continuous-flow reactor design, and life-cycle assessment will be essential for industrial translation.