Safety, Bioactivity, and Application Potential of Chlorella vulgaris and Tetradesmus obliquus Hydrolysates

Microalgae are a sustainable source of bioactive peptides with promising applications in food and cosmetics. This study evaluated protein hydrolysates from Chlorella vulgaris (Chl) and Tetradesmus obliquus (Sce) for their safety, biological activity, and application potential. Neither hydrolysate showed mutagenic potential, and both were non-cytotoxic up to 5 mg/mL in Caco-2 cells, with safe concentrations of 5 mg/mL (Sce) and 2.5 mg/mL (Chl) in HaCaT cells. Both hydrolysates exhibited selective antifungal activity against Candida albicans and Candida tropicalis (MIC = 50 mg/mL) while preserving Staphylococcus epidermidis growth, supporting compatibility with skin microbiota. Significant inhibition of tyrosinase and neutrophil elastase at 5 mg/mL pointed to anti-ageing potential. Simulated gastrointestinal digestion (INFOGEST) showed higher peptide stability for Chl, whereas Sce underwent more extensive proteolytic breakdown. Both hydrolysates also stimulated the growth of Bifidobacterium and Lactobacillus strains in the presence of glucose, in a strain-dependent manner, indicating prebiotic potential. Ex vivo skin permeation assays confirmed no permeation through human skin, and histological analysis showed preserved tissue structure without irritation-related alterations. These results indicate that Chl and Sce hydrolysates are safe, multifunctional peptide-rich ingredients with antifungal, enzyme-inhibitory, and microbiota-modulating properties, combining good digestive stability and dermal safety with strong potential for next-generation nutraceutical, functional food, and cosmetic applications.