Supplementary file 1_A comparative screening of freshwater and marine microalgae for salinity-induced intracellular mannitol accumulation.docx

In contrast, intracellular mannitol accumulated exclusively in the marine species, reaching maximum concentrations of 28 mg g⁻¹ DW in D. tertiolecta and 34 mg g⁻¹ DW in N. oculata under moderate salinity. Moderate salinity promoted the highest intracellular mannitol accumulation in both marine species. Although biomass-specific mannitol yields decreased under high salinity, volumetric mannitol concentration remained relatively stable in N. oculata but declined markedly in D. tertiolecta.

Salinity stress also induced distinct species-specific changes in carbohydrate, protein, and pigment composition, as well as nitrogen assimilation.</p>Discussion<p>These findings demonstrate that intracellular mannitol accumulation is a species-specific response to salinity stress rather than a universal microalgal adaptation. The comparative screening identifies D. tertiolecta and N. oculata as promising candidates for future optimization of stress-induced intracellular mannitol accumulation and provides a framework for strain selection in sustainable microalgal biotechnology.</p>