MULTIFACTORIAL EXPERIMENTAL-DESIGNS FOR OPTIMIZING TRANSFORMATION - ELECTROPORATION OF STREPTOCOCCUS-THERMOPHILUS

A multifactorial process was used to optimize transformation of Strept ococcus thermophilus by electroporation. Simple experimental designs w ere applied to study three, four, or five factors in eight experiments . Four qualitative factors, growth and recovering media, and plasmid a nd bacterial strains, were studied empirically. Eight quantitative fac tors, including electrical, physiological, and chemical parameters, we re studied by fractional factorial designs. Effects of individual para meters as well as interactions between them were investigated and opti mized. Optimization was performed for one S. thermophilus strain, ST11 , and proved to work for all other tested strains of the same species. Transformation efficiencies of 9 x 10(2) to 6 x 10(5) transformants p er microgram DNA were achieved, depending on the strains and vectors u sed. (C) 1994 John Wiley and Sons, Inc.