Preparation and properties of microencapsulated genetically engineered bacteria cells for oral therapy of uremia

Microencapsulated genetically engineered bacteria cells are a novel approach of oral therapy for uremia. Klebsiella aerogenes urease genes (UreaDABCEFG) are transformed into E. coli DH5α cells through plasmid pKAU17. The transformant can use urea or ammonia as its sole nitrogen source through strain training. The urease genetically engineered bacteria cells are entrapped in polyvinyl alcohol (PVA) microcapsules, which can be used to remove urea from uremia patients. The mechanical strength of PVA microcapsules is significantly higher than that of APA microcapsules. This suggests that the problem of friability of APA can be solved in this way. The optimal conditions for the preparation of PVA microencapsulated genetically engineered bacterial cells are: polyvinyl alcohol (PVA, 2450±50) used as the carrier at a concentration 6%, the pH value of boric acid as crosslinking reagent 6.5, crosslinking time 24 h, entrapment ratio of bacteria 8%, air flow rate of the encapsulate device 3 L/min and liquid flow rate at 1 mL/10 min. The average diameter of microcapsules prepared under these optimal conditions is 20–40 mesh. Experiments in vitro showed that one hundred milligrams of wet bacterial cells in PVA microcapsules could remove 18.4 mg of urea in 4 h.