The optimization system for preparation of TG1 competent cells and electrotransformation

An efficient electrotransformation system that includes electrocompetent cells is a critical component for the success of large‐scale gene transduction and replication. The conditions of TG1 competent cell preparation and optimal electrotransformation were evaluated by investigating different parameters. Certain parameters for preparation of TG1 competent cells (≥8 × 10(10) colony forming units (cfu)/μg DNA) include optimum culture time of monoclonal bacteria (8–10 hr), amplification growth concentration (approximately OD(600) = 0.45), and culture volume (400 ml in 2 L conical flask). With increased storage of competent cells at −80°C, electrotransformation efficiency gradually decreased, but it remains greater than ≥ 10(10) cfu/μg DNA 3 months later. Moreover, the recovery time of electrotransformation also influenced electrotransformation efficiency (1.5–2 hr for optimization). The optimized transformation efficiency of TG1 (≥8 × 10(10) cfu/μg DNA) was observed under suitable electric voltage (2.5 kV), electric intensity (15 kV/cm), and electric time (3.5 ms) of electricity for plasmid transformation. Optimized DNA amount (0.01–100 ng) dissolved in water led to the high efficiency of plasmid transformation (≥8 × 10(10) cfu/μg DNA), but had low efficiency when dissolved in T4 ligation buffer (≤3 × 10(10) cfu/μg DNA). These results indicated that an optimized TG1 transformation system is useful for high electrotransformation efficiency under general laboratory conditions. The optimized TG1 transformation system might facilitate large‐scale gene transduction for phage display library construction.