Study on exogenous plasmids transformed into Lactobacillus casei Zhang by electroporation.

Two donors of exogeneous plasmids: pMG36e and pMG36c were introduced into Lactobacillus casei Zhang which isolated from traditional fermented milk in China by electroporation.We systemly investigated that the impact of transformation parameters and culture dif-ferent periods of the host cells on efficiency.By comparing different conversion parameters with two plasmids,we acquired the optimum con-ditions as follows: 2.0 ms,the voltage was 1.5 kV,The transformant quantity and the conversion rate of different periods in log phase growth were: early-term:4.04×106 mL-1 and 89.78%;medium-term:1.97×107 mL-1 and 21.88%;late-term:1.6×107 mL-1 and 4.0%;the transformant quantity in sodium phosphate buffer was 1.97×107 mL-1,4.8×104 mL-1 in 10% glycerol,3.2×107 mL-1 in 0.5% glycine,5.6×106 mL-1 in 1% glycine,2.8×105 mL-1 in 2% glycine;the conversion rate reduced from 35.56% to 0.31% with increase of the glycerol concentration.The trans-formant quantity of pMG36c is obviously higher than pMG36e.The reliability of transformation was successfully confirmed by PCR identifi-cation of the transformant,L.casei Zhang that contain the plasmid pMG36e.The results have provided reliable reference bases for foreign gene introduced into Lactobacillus casei.