Sophorolipid biosurfactants application as novel approach to lipid extraction from Chlorella cultures

Algal lipids and high-value biomaterials have diverse applications in industries such as biofuels, nutraceuticals, pharmaceuticals, and cosmetics. They represent a promising alternative to traditional plant oils and animal fats. However, the high costs of extraction and recovery still pose significant challenges. In the present study, a novel method involving treatment of Chlorella sorokiniana cultures with sophorolipid (SL) biosurfactants, obtained from Starmerella bombicola yeast culture, was initially developed to facilitate the release of lipids prior to extraction with ethyl acetate (EA), a moderately polar and low toxicity organic solvent with reduced environmental impacts. Light and fluorescence microscopy analyses confirmed the proficiency of sophorolipids in enhanced cell disruption and leakage of cellular components, ultimately increasing the solvent accessibility to intracellular biomaterials. Lipid extraction efficiency was evaluated and compared with the traditional Bligh and Dyer (B&D) method, which uses hazardous solvent combinations such as chloroform and methanol. Initially, the increase in SL concentration enhanced total lipid yields. Under room conditions, EA extraction of cultures subject to 2 days nitrogen deprivation and 12 h incubation with 1 mg/mL SL, resulted in 85% total lipids compared to yields extracted from C. sorokiniana cells using the B&D method. Under these conditions, the lipid profile consisted of 65% of both saturated and monounsaturated fatty acids confirming the extract suitability as potential biodiesel feedstock. The procedure allowing recovery of high lipid yields while considerably reducing the use of organic solvents is environmentally friendly and offers high potential for industrial-scale implementation and large-scale commercialization of microalgae-based products.