Site-specific xylitol dicaprate ester synthesized by lipase from Candida sp. 99-125 with solvent-free system

Xylitol capric acid esters are widely applied due to their surfactant properties. In this study, site-specific xylitol dicaprate ester was obtained in a solvent-free system in the presence of lipase Candida sp. 99-125. UPLC-MS, and NMR analysis revealed that diesters were substituted at the C-1, C-5 positions. A series of experiments defined the optimum conditions of temperature, water content, loading of lipase, molar ratio and time course. The yield of xylitol esters reached 70% after 4 successive additions of xylitol. A subsequent coupling reaction and separation was introduced and significantly increased the yield of esters and also reduced the cost of the process. The lipase could be reused for 5 times with the yield of esters still reaching 50%.