Bacterial Protein Expression Service


In the field of bacterial protein expression, KMD Bioscience has continued to evolve and progress as we deliver what we promise. The E. coli expression system is regarded as the most commonly used, and economical expression system for recombinant protein production and large-scale fermentation due to its simple structure, clear genetic background, high yield of target protein, and its short culture period.

Continuous learning and progress enable KMD to provide a high-quality service in bacterial protein expression at all times. With our efficient and cost-effective bacterial expression platform, KMD can offer comprehensive protein expression services in the E. coli system, guaranteeing protein quantities, purities as well as endotoxin levels to meet a variety of research needs. Customers simply provide protein sequence and we will deliver the protein in the quantity and purity that you specified.

To ensure the efficiency and activity of proteins, the following aspects are usually involved:


Host System Selection:


In general, the choice of a host system to express protein depends on different protein requirements. There are many factors to consider, including post-translational modifications, equipment availability, and time constraints. Depending on customer requirements, a variety of hosts can be chosen, including bacteria, yeast, filamentous fungi and unicellular algae. Each type of host has its own merits and drawbacks. Our experts will give you a detailed introduction and explanation, say all you know and say it without reserve.

Escherichia coli and Bacillus subtilis are the most common hosts for the prokaryotic expression system:




Escherichia coli

* Fast propagation

* E. coli cells easily achieve high cell density

* High efficiency of plasmid transfection

Bacillus subtilis

* Express proteins without endotoxins

* Low production cost


Prokaryotic expression of a recombinant protein often uses BL21 (DE3) and K-12-derived strains as expression hosts. BL21 (DE3) has been the gold standard for protein expression since its introduction in 1990. K-12 strains are by far the most commonly used host strains in gene cloning experiments, since they are easily modified by many genetic methods.


Vector Selection:


At present, the most commonly used expression vectors contain a replicon, a promoter, a selection marker, a multiple cloning site (MCS) and a fusion tag removal strategy, as shown below:



Our scientists have developed a bifunctional expression vector (Bi-plasmid vector) by engineering the pET vector, which contains dual MCS sites, T7 promoters, lac operons and ribosome binding sites. Using this plasmid, we can perform a transfection for the client to obtain independent expression of the two proteins.


Affinity Label Selection:


Affinity labels are used in the expression of recombinant proteins to facilitate protein purification and promote the solubility of certain insoluble proteins. Protein labels can be divided into two categories, one is short-peptide labels, and the other is long. The long-peptide label could improve protein solubility, and it is often necessary to add a short-peptide label to help protein purification. The short-peptide label generally contains only a few amino acids with molecular weight of less than 2 kDa, which has little effect on the properties of recombinant protein. The affinity tag can be placed at the C-terminus and N-terminus of the protein. If a secreted protein is desired to be expressed, it is placed at the C-terminus and the signal peptide is placed at the N-terminus. We summarized some of the commonly used properties of protein labels, as shown in Table 1.



Service Process:



Service Highlights:


--Codon optimization: including rare codon analysis, protein hydrophilicity analysis and prediction of transmembrane domains

--High efficiency and short cycle

--A variety of fusion tag vectors and hosts to ensure high soluble protein expression and activity

--High-throughput and large-scale protein expression and production

--Various scale-up capacities ranging from 10 to 500 L

--Low endotoxin level: LAL <0.1EU/ug

--One-stop services, including protein purification, protein sequencing, protein labeling and related services


How to Order?

If you have any questions regarding our services or products, please feel free to contact us by E-mail: or Tel: +86-022-8216-4980;