You Lijun is a full professor at the School of Food Science and Engineering of the South China University of Technology (SCUT) in China. SHe was a visiting scholar in the Department of Food Science at Cornell University in the USA. Now, She is an editorial board member for two journals named “eFood” and “Food Frontiers” and now serves as the guest editor for this Special Issue of Molecules. In recent years, the main focus of her research interest has been the influence of conventional, acid-, enzyme-, microwave-, ultrasound-, and pulsed electric field-assisted extraction on the structural characteristics and biological activities of polysaccharides during isolation from marine algae sources (e.g. brown algae Sargassum fusiforme, red algae Gracilaria Lemaneiformis, and others). The structure and bioactivities of algae polysaccharides such as anti-hyperlipidemia, anti-UV radiation, anti-inflammation, and their role in regulating gut microbiota have been investigated, and the structure–function relationship of these polysaccharides is preliminarily revealed. The degradation of polysaccharides and their effects on structural properties and biological functions are also studied by her group.