Abstract
Corynebacterium glutamicum, a soil-derived gram-positive actinobacterium, has been widely used for the production of biochemical molecules such as amino acids (i.e., L-glutamate and L-lysine), nucleic acids, alcohols, and organic acids. The metabolism of the bacterium has been engineered to increase the production of the target biochemical molecule, which requires a cytosolic enzyme expression. As recent demand for new proteinaceous biologics (such as antibodies, growth factors, and hormones) increase, C. glutamicum is attracting industrial interest as a recombinant protein expression host for therapeutic protein production due to the advantages such as low protease activity without endotoxin activity. In this review, we have summarized the recent studies on the heterologous expression of the recombinant protein in C. glutamicum for metabolic engineering, expansion of substrate availability, and recombinant protein secretion. We have also outlined the advances in genetic components such as promoters, surface anchoring systems, and secretory signal sequences in C. glutamicum for effective recombinant protein expression.
Highlights
Recombinant proteins, including biologics and enzymes, are useful in the biopharmaceutical, food, and chemical industries (Butenas, 2013)
C. glutamicum is favorable for producing high yields of proteins that are difficult to secrete in the host and the proteins that must remain active in a non-pathogenic environment
This review summarizes the recent studies on the heterologous expression of the recombinant protein in C. glutamicum for various applications including metabolic engineering, expansion of substrate availability, and recombinant protein secretion
Summary
Recombinant proteins, including biologics and enzymes, are useful in the biopharmaceutical, food, and chemical industries (Butenas, 2013). The metabolic processes of C. glutamicum may be rationally modified for the production of various biochemicals using three approaches: (1) amplification of biosynthetic pathway enzymes to increase target products, (2) reduction of by-product formation, and (3) introduction of important enzyme feedback controls to optimize target biomaterials All these approaches involve the use of recombinant protein expression in the cytosol to produce beneficial biochemicals. Jensen and Wendisch overexpressed the ornithine cyclodeaminase (OCD) gene from Pseudomonas putida for the production of L-proline, which is a biochemical that is typically used as a commodity chemical or feed additive; this overexpression resulted in an increased product yield of 0.36 g proline/substrate (Jensen and Wendisch, 2013) Another foreign protein (D-lactate dehydrogenase) from Lactobacillus delbrueckii was expressed to address the limitations of using lactic acid bacteria, which require a relatively expensive complex medium for D-lactate production, and Okino et al reported a high level of D-lactate production in C. glutamicum (Okino et al, 2008). Thereafter, various phage display systems have been developed to express heterologous proteins on the surface of phages; the size of exogenous proteins that
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