Custom-designed bacterium overproduces the amino acid L-arginine at an industrial scale

The synergistic combination of random selection and systems metabolic engineering approaches enables the construction of a high-performance Corynebacterium glutamicum strain for overproducing L-arginine, an important biochemical component in both medical and industrial applications.

Article  |  Spring 2015

L-arginine is an important amino acid that helps in healing wound, promotes muscle mass growth, and plays other crucial roles in our neurological and cardiovascular systems. It helps our body to secrete important biochemical signals including prolactin, glucagon, insulin, growth hormones, and nitric oxide. Due to various health benefits, the consumption of L-arginine as a diet supplement is on the rise and its efficient industrial-level production is an important task for its commercialization.

Like many other amino acids, L-arginine is produced by microbial fermentation, and continuous effort has been made for almost 60 years to improve the microbial production of L-arginine.The traditional method to develop and select for improved microbial strains has been random mutagenesis, which can be very laborious and often leads to unwanted mutations in the microorganisms.

A research team led by Professor Sang Yup Lee at the Korea Advanced Institute of Science and Technology (KAIST) published their findings in Nature Communications (August 5 2014). The newly-developed method utilizes both random mutagenesis and rational designing in a synergistic manner for the biorefinery setting at an industrial level.

Professor Sang Yup Lee and his team applied a systems metabolic engineering approach to rationally design microorganisms for the overproduction of L-arginine. Systems metabolic engineering is a discipline that utilizes various systems and synthetic biology tools to develop industrial microbial strains and ultimately to optimize all aspects of biorefinery processes to produce industrially valuable chemicals including biofuels, biopolymers, engineering plastics, medicinal compounds, silk proteins, and other materials from renewable resources. The team initially used random mutagenesis to Corynebacterium glutamicum to construct a base strain that is tolerant to L-arginine, and subsequently used rational engineering approaches in a step-wise manner. Negative regulation for L-arginine biosynthesis was relieved, and the L-arginine biosynthetic pathway was optimized by reinforcing fluxes toward L-arginine. The pentose phosphate pathway flux was also optimized to increase the intracellular pool of the NADPH, which is a cofactor utilized in the L-arginine biosynthesis. The exporter for L-glutamate, which is the precursor for L-arginine, was also deleted for improved L-arginine production. The performance of the engineered strain was examined at laboratory- and industrial-scale bioreactors (i.e., 5 L and 1,500 L, respectively), and the results showed a successful demonstration with good reproducibility. In the biorefinery process, scale-up of the bioreactor is a critical step towards the industrial-level production of the target chemicals, but often results in poorer performance of the microbial strain because of the differentiated cultivation environments caused by the scaled-up bioreactor. Taken together, systems metabolic engineering was performed to construct Corynebacterium glutamicum overproducing L-arginine at an industrial scale. This will be an important milestone since essentially the same approaches can be used to produce other important biochemicals that share L-arginine biosynthetic pathways such as L-ornithine, putrescine, and cyanophycin.
This paper (entitled “Metabolic engineering of Corynebacterium glutamicum for L-arginine production”) was published on August 5, 2014 in Nature communications.

Reference: Seok Hyun Park, Hyun Uk Kim, Tae Yong Kim, Jun Seok Park, Suok-Su Kim & Sang Yup Lee. Metabolic engineering of Corynebacterium glutamicum for L-arginine production. Nature Communications. 5, Article number: 4618. doi:10.1038/ncomms5618.