Recombinant protein expression in Escherichia coli has become a widely used method for producing heterologous proteins due to the organism's fast growth, ease of manipulation, and availability of molecular tools. This review discusses recent advances and challenges in the field, focusing on the selection of host organisms, plasmids, promoters, and strategies for protein expression and purification. The choice of host organism is crucial, as it determines the technology and reagents needed for the project. While various microorganisms are available, E. coli is the most commonly used due to its fast growth, high cell density, and ability to produce large quantities of recombinant proteins. However, the expression of some proteins can be problematic due to inclusion body formation, protein inactivity, or failure to produce the protein. The selection of an appropriate plasmid is also important, as it determines the expression level and solubility of the recombinant protein. Commonly used plasmids include the pET series, which uses the T7 promoter for high-level expression, and the pMAL series, which uses the tac promoter for controlled expression. The choice of promoter is also critical, as it affects the level of expression and the solubility of the protein. Promoters such as the lac promoter and its derivatives, the tac promoter, and the araP_BAD promoter are commonly used, each with its own advantages and limitations. Affinity tags are often used to facilitate the purification of recombinant proteins. These tags can be added to the protein to allow for easy purification using chromatography techniques. However, the use of affinity tags can sometimes interfere with the structure or activity of the protein, so care must be taken in their selection and use. The choice of host strain is also important, as different strains have different abilities to express recombinant proteins. Strains such as BL21(DE3) and Origami are commonly used, each with its own advantages and limitations. The use of plasmid addiction systems can also be beneficial in large-scale production, as they allow for the selection of cells that carry the plasmid. In addition to the selection of host, plasmid, and promoter, the optimization of growth conditions is also important for successful expression. Factors such as medium composition, aeration, and temperature can all affect the expression and solubility of the recombinant protein. Autoinduction media have been developed to simplify the process of induction, allowing for the timely addition of inducer without the need for manual monitoring. Overall, the expression of recombinant proteins in E. coli is a complex process that requires careful consideration of various factors. Recent advances in the field have improved the efficiency and solubility of recombinant proteins, but challenges remain in the expression of certain proteins and the optimization of growth conditions. The use of advanced techniques and strategies can help overcome these challenges and improve the production of recombinant proteins.Recombinant protein expression in Escherichia coli has become a widely used method for producing heterologous proteins due to the organism's fast growth, ease of manipulation, and availability of molecular tools. This review discusses recent advances and challenges in the field, focusing on the selection of host organisms, plasmids, promoters, and strategies for protein expression and purification. The choice of host organism is crucial, as it determines the technology and reagents needed for the project. While various microorganisms are available, E. coli is the most commonly used due to its fast growth, high cell density, and ability to produce large quantities of recombinant proteins. However, the expression of some proteins can be problematic due to inclusion body formation, protein inactivity, or failure to produce the protein. The selection of an appropriate plasmid is also important, as it determines the expression level and solubility of the recombinant protein. Commonly used plasmids include the pET series, which uses the T7 promoter for high-level expression, and the pMAL series, which uses the tac promoter for controlled expression. The choice of promoter is also critical, as it affects the level of expression and the solubility of the protein. Promoters such as the lac promoter and its derivatives, the tac promoter, and the araP_BAD promoter are commonly used, each with its own advantages and limitations. Affinity tags are often used to facilitate the purification of recombinant proteins. These tags can be added to the protein to allow for easy purification using chromatography techniques. However, the use of affinity tags can sometimes interfere with the structure or activity of the protein, so care must be taken in their selection and use. The choice of host strain is also important, as different strains have different abilities to express recombinant proteins. Strains such as BL21(DE3) and Origami are commonly used, each with its own advantages and limitations. The use of plasmid addiction systems can also be beneficial in large-scale production, as they allow for the selection of cells that carry the plasmid. In addition to the selection of host, plasmid, and promoter, the optimization of growth conditions is also important for successful expression. Factors such as medium composition, aeration, and temperature can all affect the expression and solubility of the recombinant protein. Autoinduction media have been developed to simplify the process of induction, allowing for the timely addition of inducer without the need for manual monitoring. Overall, the expression of recombinant proteins in E. coli is a complex process that requires careful consideration of various factors. Recent advances in the field have improved the efficiency and solubility of recombinant proteins, but challenges remain in the expression of certain proteins and the optimization of growth conditions. The use of advanced techniques and strategies can help overcome these challenges and improve the production of recombinant proteins.