Abstract: In order to overcome the shortcomings of high purity Vitamin K₂ extraction process, such as large amount of toxic solvent, serious pollution and toxic substance residues, a green separation and purification process of high purity Vitamin K₂ was established. Natural oil, methanol, ethanol and other organic reagents were used to extract VK₂ from Bacillus natto. The results showed that medium chain triglyceride had the best extraction effect, and the maximum extraction amount was 2.7 mg/g. Seven types of macroporous resins were used to separate VK₂ from medium chain triglyceride solvent phase, and the optimal macroporous resin HC-200S was selected by static adsorption and desorption experiments. The dynamic adsorption and desorption process of macroporous resin was optimized, and the dynamic desorption curve of macroporous resin was drawn. The results showed that when the adsorption flow rate of sample solution was 2.0 mL/min, the desorption agent was anhydrous ethanol/butyl acetate mixture solution (1∶2, volume ratio) and the flow rate of desorption agent was 1.0 mL/min, the adsorption and desorption effect of HC-200S macroporous resin on VK₂ was the best. At this time, the purity of vitamin K₂ was 4 times higher than that of the before purification, reaching 87.8%, and the recovery rate reached 93.1%. VK₂ desorption solutions obtained by resin separation and purification were frozen crystallization and solvent volatilization crystallization, respectively, to obtain VK₂ crystals with purity of 96.7% and 97.1%. This study provided a method basis for the industrial production and green separation and purification of VK₂.

Key words: vitamin K₂, macroporous resin, separation and purification, green extraction, MK-7 crystal