Transformation of silage-making Lactobacillus strains by electroporation with plasmid vectors

Several newly isolated strains of Lactobacillus for silage fermentation wer e transformed with plasmid vectors, pGK12 and pSA3, by electroporation. Tra nsformation efficiency depended on the electric field strength, time-consta nt, polyethyleneglycol (PEG) molecular weight in electroporation buffer and the incubation temperature after exposition of pulses. Transformation of L . pentosus NGRI0225 resulted in the maximum transformation efficiency of 5. 7 x 10(5) transformants per mu g DNA of pGK12 with an electric field streng th of 7.0 kV/cm, time-constant of 6.2 ms and 30% (W/V) of PEG 1000. Plasmid DNAs isolated from all transformants did not show any detectable rearrange ments or deletions under these conditions.