Enhancing the biomass and docosahexaenoic acid-rich lipid accumulation of Schizochytrium sp. in propionate wastewater

Extraction, separation and purification of fatty acid ethyl esters for biodiesel and DHA from Thraustochytrid biomass

A novel approach for in situ transesterification, extraction, separation, and purification of fatty acid ethyl esters (FAEE) for biodiesel and docosahexaenoic acid (DHA) from Thraustochytrid biomass has been developed. The downstream processing of Thraustochytrids oil necessitates optimization, considering the higher content of polyunsaturated fatty acids (PUFA). While two-step methods are commonly employed for extracting and transesterifying oil from oleaginous microbes, this may result in oxidation/epoxidation of omega-3 oil due to prolonged exposure to heat and oxygen. To address this issue, a rapid single-step method was devised for in situ transesterification of Thraustochytrid oil. Through further process optimization, a 50% reduction in solvent requirement was achieved without significantly impacting fatty acid recovery or composition. Scale-up studies in a 4 L reactor demonstrated complete FAEE recovery (99.98% of total oil) from biomass, concurrently enhancing DHA yield from 16% to nearly 22%. The decolorization of FAEE oil with fuller's earth effectively removed impurities such as pigments, secondary metabolites, and waxes, resulting in a clear, shiny appearance. High-performance liquid chromatography (HPLC) analysis indicated that the eluted DHA was over 94.5% pure, as corroborated by GC-FID analysis.