Bacterial Protein Expression Service


KMD Bioscience has been working on recombinant protein expression and antibody development for many years. The E. coli expression system is widely used in research and development phase. and economical expression system for recombinant protein production and large-scale fermentation because of its simple structure, clear genetic background, high yield of target protein, and its short culture period.

KMD Bioscience leverages many years of experience in bacterial expression services to deliver the highest quality recombinant protein. With our efficient and cost-effective bacterial expression platform, we can offer comprehensive protein expression services in E. coli system, which guaranteed 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.

In order 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. We can choose different hosts according to client requirements, such as bacteria, yeast, filamentous fungi and unicellular algae. Each type of host has its own merits and drawbacks.

Escherichia coli and Bacillus subtilis are the common hosts of 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 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 it was first introduced in 1990. K-12 strains are by far the most frequently 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 incorporate a replicon, a promoter, a selection marker, a multiple cloning site (MCS) and a fusion tag removal strategy, as shown below:



Our scientists obtained 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 make the protein purification easier and promote the solubility of certain insoluble proteins. Protein labels can be divided into two categories, one is short-peptide labels, the other is long. The long-peptide label could improve protein solubility, and it is often necessary to add short-peptide label to help protein purification. The short-peptide label generally contains only a few amino acids with molecular weight 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: +86-400-621-6806;