Effective production of β-sitosteryl oleate using a highly thermal-tolerant immobilized lipase in a solvent-free system

β-Sitosteryl oleate, renowned for its diverse beneficial bioactivities, holds significant promise as a potential ingredient in functional foods. This study reports the superior performance of β-sitosteryl oleate facilitated by lipase UM1 (lipase from marine Streptomyces sp. W007, immobilized on XAD1180 resin) as a biocatalyst in a solvent-free system, in comparison to commercial enzymes Novozym 435 (lipase B from Candida antarctica, immobilized on a macroporous acrylic resin), Lipozyme TL IM (lipase from Thermomyces lanuginosus, immobilized on a non-compressible silica gel carrier), and Lipozyme RM IM (lipase from Rhizomucor miehei, immobilized on a macroporous acrylic resin). Remarkably, an over 98% yield was achieved under the optimal conditions: a substrate molar ratio of β-sitosterol to oleic acid of 1:4, lipase loading of 150 U, and a reaction temperature of 60°C. The process exhibited substantial resilience and effectiveness, maintaining a degree of esterification above 95% even after five recycles. Following this, the synthesis was successfully scaled up by 100-fold, with the product isolated through molecular distillation and confirmed using ultra-performance liquid chromatography mass spectrometry (UPLC-MS) and Fourier transform infrared spectroscopy (FT-IR) analytical techniques. These results underscore lipase UM1 as a promising catalyst for the industrial-scale synthesis of β-sitosteryl oleate, fostering expanded avenues for its utilization in the functional food industry.