采用膜分离技术将费氏丙酸杆菌菌体细胞分离，离位合成转化维生素B12，考察了不同类型及孔径的膜对发酵液的处理能力及对菌体细胞活性的损伤情况，分析了不同浓缩条件下维生素B12的转化效果. 结果表明，卷式膜比陶瓷膜更适用于发酵液中菌体细胞的分离，用0.22 mm卷式膜处理时，细胞的生物活性几乎不受损伤，存活率达99.5%，将发酵液浓缩4倍，中间体Abo-cbi转化率达78.8%，维生素B12产量为53.9 mg/L.

The application of membrane separation of Propionibacterium freudenreichii cells was studied. The effects of membrane material and pore size on the flux and cellular activity were examined. The Vitamin B12 ex-situ transformation was also investigated. The results showed that spiral wound membrane was more suitable for on-line cell separation compared with ceramic membrane. When the fermentation broth was treated with 0.22 mm spiral wound membrane, the biological activity of cells was almost not damaged, with a survival rate of 99.5%, Abo-cbi conversion rate of 78.8% was obtained at 30℃ for 72 h with 4 times concentrated fermentation broth and the productivity of Vitamin B12 reached 53.9 mg/L.