Comprehensive Biochemical Characterization and Lipid Profiling of Chlorella vulgaris with Evaluation of Its Antioxidant and Antibacterial Activities

Abstract

Chlorella vulgaris was cultivated under open-pond and closed-photobioreactor systems to evaluate its biochemical composition, lipid profile, antioxidant capacity and antibacterial efficacy. Photobioreactor cultivation significantly enhanced total pigments by 67.9% ( dry cell weight) and soluble protein by 58.5% ( dry cell weight). Conversely, open-pond biomass yielded two-fold higher carbohydrate content (dry cell weight) and higher gravimetric lipid yield (). However, higher final biomass density in the photobioreactor resulted in superior volumetric lipid productivity (). FTIR analysis confirmed characteristic functional groups. Urea inclusion crystallization effectively enriched polyunsaturated fatty acids (PUFA recovery: ), with GC–MS identifying eicosapentaenoic acid (EPA, 42.90%) and docosahexaenoic acid (DHA, 7.73%) as major omega-3 constituents. The PUFA fraction exhibited dose-dependent DPPH radical scavenging (; ). In antibacterial assays against four major pathogens, the extract displayed potent, Gram-selective activity at , the zone of inhibition against Staphylococcus aureus () surpassed the Streptomycin control (), alongside moderate inhibition of Bacillus subtilis (), Escherichia coli () and Salmonella enterica (). These results highlight the strong influence of cultivation systems on microalgal metabolism and establish C. vulgaris PUFA extract as a promising Gram-selective antimicrobial and antioxidant candidate for nutraceutical, pharmaceutical and cosmeceutical applications.