Comprehensive lipid extract characterization of Chlorella vulgaris microalgae: A multi-analytical approach

This study aimed to assess lipid extracts of Chlorella vulgaris (CV) using traditional (soxhlet) and innovative extraction methods (microwave-assisted and ultrasound-assisted). The evaluation focused on antioxidant properties, fatty acid profiling, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR) of lipid extract and raw biomass. Scanning electron microscopy (SEM) of the lipid-extracted biomass (residual biomass) was also analyzed. Principal component analysis (PCA) was used to develop a correlation between the antioxidant properties of soxhlet lipid extract (SLE), microwave lipid extract (MWLE), ultrasound lipid extract (USLE), and raw biomass. The study revealed that the MWLE showed significantly higher antioxidant properties such as total phenolic content (TPC) 10.71 ± 0.15 mg GAE/g, % DPPH inhibition (37.23 ± 0.16 %), ABTS (9.86 ± 0.02 mg TE/g), and FRAP (19.67 ± 0.04 mg TE/g) whereas SLE showed highest total flavonoid content (TFC) 45.92 ± 2.33 mg QE/g. Extracted lipids also showed a suitable fatty acid profile for biodiesel and food applications. Further TGA results depicted that the residual biomass after lipid extraction could be suitable for biochar production. The FT-IR spectroscopy confirmed the presence of lipids in the extracts, while SEM images demonstrated ultrasonication's superior lipid extraction efficiency over other methods (soxhlet and microwave). The findings suggest that CV biomass and lipid extracts has potential applications in the food, feed, and medicine sectors.