Coomassie Brilliant Blue R250 stained SDS-PAGE gel demonstrating expression of β-lactamse gene with respect to increasing concentration of IPTG; Lane 1: Pre-stained Protein Ladder (Thermo Fisher Scientific); Lane 2: BL21 CodonPlus Cells transformed with pET21a without insert as control; Lane 3, 4, 5, 6, 7 shows the transformed BL21 CodonPlus (DE3) cells having recombinant pET21a induced with 0.2, 0.4, 0.6, 0.8 and 1mM concentration of IPTG, respectively.