Composition, structural features, and multifunctional properties of extracellular polysaccharides from the non-toxic green alga Parachlorella sp.

Microalgae are promising biorefineries because of their rapid growth and carbon fixation abilities. However, the functional applications of microalgal extracellular polysaccharides (EPS), particularly those from edible strains, remain underexplored, limiting their potential use in health-related and cosmetic industries. In this study, we investigated the EPS produced by the edible green alga Parachlorella sp. BX1.5 (bxEPS). The bxEPS was extracted from nitrogen-depleted BG11 (BG11-N) medium and identified as an acidic rhamnan (rhamnose: xylose: glucuronic acid = 55.1:35.4:9.5 mol%) without sulfate groups. The bxEPS solution exhibited high stability due to its low cation reactivity, suggesting its potential for cosmetic applications. Additionally, bxEPS showed antioxidant, angiotensin-converting enzyme-inhibitory (anti-hypertensive), and tyrosinase activity-enhancing (anti-gray hair) effects in vitro, indicating its potential as a functional ingredient in health foods and pharmaceuticals. Furthermore, a 0.2 % (w/v) bxEPS solution promoted hair growth in mice, accompanied by hair follicle enlargement. These findings demonstrate the safety and multifunctional properties of bxEPS and support its application as a novel biopolymer for sustainable microalgal biorefineries.