Abstract

BIOCHEMICAL AND PHYTOCHEMICAL CHARACTERIZATION OF CHLORELLA VULGARIS AND EVALUATION OF ITS ANTIBACTERIAL ACTIVITY

M. Kalaivani*, S. Sivanantham, S. Suja, M. Sasidharan, N. Sivanesan, Y. Subaazeer, V. Sudarsan, N. Rithika

Abstract

Chlorella vulgaris is a fast-growing freshwater microalga with considerable potential as a source of proteins, carbohydrates, lipids, pigments, and biologically active metabolites. The present study investigated the biochemical and phytochemical characteristics of a C. vulgaris culture isolated from a freshwater pond at Kuppandapalayam, Erode District, Tamil Nadu, India, together with its preliminary antimicrobial and biorefinery potential. The culture was maintained in BG-11 medium under continuous aeration and cool-white illumination and developed dense green biomass within 7–10 days. Microscopic examination revealed healthy unicellular, spherical to slightly oval cells with a distinct cell wall and prominent chloroplast. Acetone-extracted pigments contained 11.45 mg L⁻¹ chlorophyll a, 0.34 mg L⁻¹ chlorophyll b, and 11.79 mg L⁻¹ total chlorophyll. Qualitative phytochemical screening detected alkaloids, carbohydrates, flavonoids, glycosides, proteins, steroids, tannins, and terpenoids in both aqueous and acetone extracts, whereas saponins were detected only in the aqueous extract. The estimated carbohydrate content was 1.01 mg g⁻¹ dry biomass, while the protein assay yielded approximately 0.46 mg mL⁻¹ in the tested sample. Soxhlet extraction recovered 1.327 g lipid from 10 g dry biomass, corresponding to a lipid yield of 13.27%. Both aqueous and acetone extracts exhibited antibacterial activity against Escherichia coli, producing inhibition zones of 20 and 15 mm, respectively. Preliminary antifungal activity was also observed against Fusarium sacchari and Fusarium incarnatum. Following acid hydrolysis and fermentation with Saccharomyces cerevisiae, the resulting distillate gave a positive qualitative test for ethanol. Collectively, the findings demonstrate that C. vulgaris biomass contains multiple biochemical and phytochemical constituents with preliminary antimicrobial activity and potential for integrated biomass valorization. Further studies incorporating replicated quantitative analyses, molecular authentication of the strain, standardized antimicrobial assays, detailed metabolite profiling, and optimization of fermentation and downstream processing are required to establish its biotechnological and industrial potential.

Keywords: Antimicrobial activity, BG-11; Bioethanol; Chlorella vulgaris, Phytochemicals; Wastewater treatment.