The lytic genes of phage λ with S amber mutation(S-RRz) were introduced into the recombinant E. coli VG1(pTU14) producing poly-β-hydroxybutyrate(PHB)to attain controllable lysis of cells. The results of EDTA/Tris(pH8.0)buffer treatment showed that S-RRz were successfully expressed in VG1(pTU14)

and cell lysis was realized due to the action of EDTA on cytoplasm membrane.Here the function of EDTA was similar to that of S gene product.When PHB content was 85%—90％，membrane permeability would be increased by the abundantly accumulated in-cell PHB granules

and then the autolysis of recombinant cells occurred. After studies on different projects for direct separation of PHB from fermentation broth

a new technique

in which temperature treatment was introduced to simulate the function of S gene product

was presented

and the autolysis of cells was then easily realized based on the successful expression of S-RRz.By this simple technique

the final purity of PHB product could be up to 95%.