Prompt Description

The constructed recombinant plasmid is introduced into E. coli host strains. Common host strains such as BL21(DE3) or DH5α are used, and the recombinant plasmid is introduced into the bacterial cells via heat shock or electroporation. After the plasmid enters the cells, the bacterial solution is cultured, and resistant colonies are selected to confirm successful transformation. Subsequently, the recombinant strain is cultured on a large scale in a nutrient medium. During the expression phase, an inducer is added to initiate protein expression. For example, the commonly used IPTG can induce the efficient expression of genes carrying the T7 promoter; early production methods also used the tryptophan promoter (trp promoter), which automatically expresses the insulin precursor after tryptophan depletion. In summary, by optimizing expression conditions and culture medium formulations, high levels of insulin A-chain and B-chain (or precursor protein) can be obtained in E. coli.