Physicochemical characterization, antioxidant and antifreeze properties of Porphyra haitanensis polysaccharide fractions.

This study aims to reveal the antifreeze and antioxidant properties of Porphyra haitanensis polysaccharide (PHP) fractions, and to elucidate their relationship with the chemical composition of PHP. With the decrease of alcohol precipitation concentration (75%-45%), the content of sulfate groups (SG) in PHP fractions increased, and their antifreeze effect increased. Specifically, the frozen yeast cells viability increased from 4.38% to 82.20%, and the fermentation capacity of frozen yeast cells increased from 1.92 cm to 2.53 cm. Through correlation analysis, it was found that SG was positively correlated with antifreeze properties, but not with antioxidant activity. Additionally, molecular dynamics simulations showed that polysaccharides with higher SG content enhanced ice crystal inhibition and antifreeze activity by changing the arrangement of the polysaccharide water interface. These results illustrate that the composition of PHP fractions is related to their antifreeze protection effect, and they have potential as cell and food antifreeze agents.