Production of α-tocopherol biomolecules using various cultivation strategies of diverse microalgal species: Purification, characterization and assessment of antioxidant properties

Tocopherols are valuable biomolecules with antioxidant and anticancer properties, synthesized by photosynthetic organisms. Their presence in microalgae remains underexplored due to a lack of specific extraction and purification techniques. This study examines the potential of three microalgae species, Tetraselmis indica (TS), Chlorella vulgaris (CV), and Picochlorum sp. (PC) through heterotrophic, phototrophic, and mixotrophic cultivation methods, focusing on their influence on biomass production and α-tocopherol yield, an important antioxidant. The results demonstrated maximum biomass production by TS, CV, and PC, reached 1.92 ± 0.08, 1.97 ± 0.13, and 1.99 ± 0.02 g/L, respectively, under mixotrophic conditions with supplementation of 7.5 g/L sodium acetate for TS and PC, and 1 g/L glucose for CV. The yield of α-tocopherol biomolecules obtained from TS, PC, and CV was 2.82 ± 0.12, 1.57 ± 0.06, and 0.51 ± 0.01 mg/L, respectively. Microalgal α-tocopherol was purified using column chromatography and used for antioxidant activity, e.g., DPPH, ABTS, and OH^●scavenging activity. The DPPH and ABTS radical scavenging activities of purified α-tocopherol from TS, PC, and CV biomass were 79.63 ± 1.22, 76.42 ± 2.42, and 78.17 ± 2.01 %, and 30.20 ± 1.52, 28.86 ± 0.59, and 29.66 ± 1.72 %, respectively. The characterization of purified α-tocopherol was performed using FTIR, LC-HRMS, and ¹H and ¹³C NMR spectroscopy. The production of high-purity α-tocopherol from microalgae is beneficial for industrial and pharmaceutical applications and supports the concept of a bio-circular economy.