Microbial exopolysaccharide pullulan-based seed priming combined with Chlorella vulgaris enhances salinity tolerance...

Salinity is a major abiotic stress limiting global maize (Zea mays L.) production. This study evaluated the biostimulant potential of pullulan, an exopolysaccharide produced by Aureobasidium pullulans ATCC 42,023, applied alone or in combination with the microalga Chlorella vulgaris, to enhance seed sprouting and initial growth under saline environments. Pullulan was biosynthesized in a 5-L bioreactor using glucose as the carbon source, achieving a concentration of 19.23 g/L (0.25 g/g sugar of yield) at an initial glucose level of 100 g/L. Seed priming with pullulan concentrations (2.5-5.0 g/L) significantly promoted coleoptile and root elongation, whereas higher levels (10 g/L) inhibited growth. Notably, the combined application of 5 g/L of pullulan + 20 mg of C. vulgaris alleviated salinity stress (EC: 3.63 dS/m) by reducing oxidative damage, sustaining root activity, and improving plant height and chlorophyll content. Overall, the combined use of pullulan and Chlorella vulgaris enhanced maize performance, highlighting their potential as sustainable seed-priming agents and a promising strategy for managing salt-affected soils in resilient and sustainable agricultural systems.