Enhanced production of recombinant proteins in Corynebacterium glutamicum by construction a bicistronic gene expression system
Abstract Background: Corynebacterium glutamicum is a traditional food-grade industrial microorganism, in which an efficient endotoxin-free recombinant protein expression factory is under developing in recent years. However, the intrinsic disadvantages of low recombinant protein expression levels need to be solved. Here, according to the bacteria-specific polycistronic feature, trials have been made of inserting a leading peptide upstream of target genes as an expression enhancer, and we found it improving the expression level of proteins under the control of inducible tac promoter in C. glutamicum CGMCC1.15647 . Results: In this research, the Escherichia coli ( E. coli ) tac promoter combined with 24 different fore-cistron sequences were constructed in a bicistronic manner in C. glutamicum. Three strong bicistronic vectors were isolated and exhibited higher strength under different culture conditions. The compatibility of these bicistronic vectors was further validated using six model proteins- aldehyde dehydrogenase (ALDH), alcohol dehydrogenase (ADH), RamA (regulator of acetate metabolism), Bovine interferon-a (BoIFN-a), glycoprotein D protein (gD) of infectious bovine rhinotracheitis virus (IBRV) and procollagen type I N-terminal peptide (PINP). All examined proteins were highly expressed compared with the original vector of tac promoter. Large-scale production of PINP was also performed in fed-batch cultivation, and the highest PINP production level was 1.2 g/L. Conclusions: In this study, we improved the strength of the inducible promoter tac promoter for C. glutamicum by screening and inserting fore-cistron in front of the target genes. Those vectors with bicistronic expression pattern have strong compatibility for expressing various heterogeneous proteins in high level. This new strategy could be used to further improve the performance of inducible promoters, achieving double competence of inducible control and high yield.