Parameter Optimization and Regulatory Mechanism of Cold Plasma Pretreatment for Enhancing Intracellular...

The promise of intracellular polysaccharides (IPS) from Irpex lacteus as pharmaceuticals and functional foods due to the antioxidant and immunomodulatory activities, is hindered by low yield for industrial applications. Cold plasma, a non-thermal, residue-free microbial metabolism regulator, has not been used for IPS synthesis for I. lacteus. An IPS-producing strain was newly isolated and identified, sharing 99.68% identity with I. lacteus PJC74. The polysaccharide was composed of fucose, galactose, glucose, xylose, mannose, ribose, and galacturonic acid in a molar ratio of 0.62: 1.96: 75.92: 3.79: 10.89: 3.90: 2.91, as quantified by HPAEC. IPS yield was raised to 13.89% (mg/g dry mycelium) by cold plasma treatment (140 W, 15 s, and 135 Pa) optimized via single-factor and L₉(3³) orthogonal experiments, representing a 1.38-fold increase over the control (10.08%). CP treatment increased mycelial diameter (1.92 to 2.80 μm) and induced centralized vacuoles through electron microscope and enhanced membrane permeability using laser confocal scanning microscopy. Label-free proteomics illustrated that 87 differentially expressed proteins (56 upregulated, mainly in carbohydrate and energy metabolism), with enriched polysaccharide biosynthesis pathways (GO/KEGG). CP treatment enhanced I. lacteus IPS yield via morphological modification, nutrient uptake improvement, and metabolic upregulation, providing a novel, scalable method and molecular targets for future engineering. Accordingly, this study not only identifies a novel IPS-producing strain but also paves the way for enhancing IPS yield through CP treatment.