OPTIMIZED TRANSFORMATION BY ELECTROPORATION OF LACTOCOCCUS-LACTIS IL1403

Rolling circle replication of plasmid pGKV21 in L. lactis was a more s table replication mode than the theta replication of plasmid pIL253. W hen the plasmid pGKV21 was used to develop and optimize transformation of L. lactis by electroporation, optimum transformation was obtained using dense suspension of late-exponential phase cells subjected to a high voltage (12.5 kV/cm) and a short pulse time (0.5 ms) in the prese nce of a plasmid DNA. With plasmid vector pGKV21, a transformation fre quency of 2.2 x 10(8) transformants per mu g of DNA was obtained.