CORYNEBACTERIUM GLUTAMICUM: CHARACTERISTICS, MORPHOLOGY, CULTURE - BIOLOGY - 2025

Corynebacterium glutamicum is a gram-positive, facultative anaerobic, rod-shaped bacterium present in soil. It is neither spore-forming nor pathogenic. Along with the rest of the Corynebacteriaceae and the bacteria of the Mycobacteriaceae and Nocardiaceae families, it is part of the group known as the CMN group. This group includes many bacteria of medical and veterinary importance.

The bacterium C. glutamicum is widely used in industry for the production of amino acids. The use of this bacterium for industrial production dates back more than 40 years.

Corynebacterium glutamicum. Photo by AJC1 Flickr. Taken and edited from

The amount of amino acids produced by these bacteria, including monosodium glutamate and L-lysine, currently exceeds 100 tons per year.

General characteristics

These bacteria break down carbohydrates through the fermentation process. Amino acid production is influenced by the given carbon source and by certain supplementation conditions such as biotin limitation.

To obtain the inocula, culture media of tryptone complexes (YT), yeast extract and modified CGXII minimal media have been used.

For cultivation, temperatures of 30 ° C and a pH of 7.4 - 7.5 are recommended. The carbon sources, as well as the substances that are going to be used to enrich the crop, will depend on the results that are to be obtained.

For example, glucose, ammonium sulfate, magnesium sulfate, and dipotassium phosphate have been found to have a significant influence on succinate production.

To obtain a high concentration of L-lysine, the culture medium must have glucose, ammonium sulfate, calcium carbonate, bactocasamino acid, thiamine hydrochloride, D-biotin, potassium dihydrogen phosphate, magnesium sulfate heptahydrate, ferrous sulfate heptahydrate and manganese chloride tetrahydrate.

Corynebacterium glutamicum, Photo by Carlos Barreiro. Taken and edited from

Pathogeny

Although most bacteria belonging to the Corynebacteriaceae family are pathogenic, some of them, including C. glutamicum, are harmless. The latter, known as non-diphtheria corynebacteria (CND), are commensals or saprophytes that can be present in humans, animals and the soil.

Some CNDs, such as C. glutamicum and C. feeiciens, are used in the production of essential amino acids and vitamins.

Uses in biotechnology

The genome of C. glutamicum is relatively stable, grows rapidly, and does not secrete extracellular protease. Furthermore, it is non-pathogenic, does not form spores, and has relatively low growth requirements.

These characteristics, and the fact that it produces enzymes and other useful compounds, have allowed this bacterium to be called a “workhorse” in biotechnology.

Production of amino acids

The first product found that was known to be biosynthesized by C. glutamicum was glutamate. Glutamate is a nonessential amino acid present in about 90% of synapses in the brain.

It is involved in the transmission of information between the neurons of the central nervous system and in the formation and recovery of memory.

Lysine, an essential amino acid for humans and part of the proteins synthesized by living beings, is also produced by C. glutamicum.

Other amino acids obtained from this bacteria include threonine, isoleucine, and serine. Threonine is used mainly to prevent the appearance of herpes.

Serine helps in the production of antibodies and immunoglobulin. Isoleucine, for its part, is involved in protein synthesis and energy production during physical exercise.

Other products and applications

Pantothenate

It is the most active form of vitamin B5 (pantothenic acid), as calcium pantothenate is used as a supplement in diets. Vitamin B5 is essential in the synthesis of carbohydrates, lipids and proteins.

Organic acids

Among others, C. glutamicum produces lactate and succinate. Lactate has multiple applications, such as fabric softener, food acidity regulator, leather tanning, purgative, among others.

Succinate, for its part, is used for the production of lacquers, colorants, perfumes, food additives, medicines and for the manufacture of biodegradable plastics.

Alcohols

Because it ferments sugars, it is capable of producing alcohols, such as ethanol and isobutanol. For this reason, there are trials for the synthesis of ethanol in C. glutamicum crops from sugar cane waste. The objective of these trials is to achieve the industrial production of biofuels.

Xylitol, a polyol, or sugar alcohol, is used as a sweetener for diabetics as it does not raise blood sugar levels.

Bioremediation

C. glutamicum contains two operons in its genome, called ars1 and ars2, which are resistant to arsenic. There are studies in progress with the purpose of eventually using this bacterium to absorb arsenic from the environment.

Biodegradable plastics

In addition to succinate, an organic acid produced naturally by bacteria, useful for the production of biodegradable plastics, there is another possible compound that can be used for these purposes.

This compound is a polyester called poly (3-hydroxybutyrate) (P (3HB)). P (3HB) is not produced naturally by C. glutamicum. However, genetic engineers have carried out studies to create in the bacteria, by genetic manipulation, a biosynthetic route that allows it to be produced.

References

1. S. Abe, K.-I. Takayama, S. Kinoshita (1967). Taxonomical studies on glutamic acid-producing bacteria. The Journal of General and Applied Microbiology.
2. J.-Y. Lee, Y.-A. Na, E. Kim, H.-S. Lee, P. Kim (2016). The actinobacterium Corynebacterium glutamicum, an Industrial workhorse. Journal of Microbiology and Biotechnology.
3. J. Lange, E. Münch, J. Müller, T. Busche, J. Kalinowski, R. Takors, B. Blombach (2018). Deciphering the adaptation of Corynebacterium glutamicum in transition from aerobiosis via microaerobiosis to anaerobiosis. Genes
4. S. Wieschalka, B. Blombach, M. Bott, BJ Eikmanns (2012). Bio-based production of organic acids with Corynebacterium glutamicum. Biotechnology.
5. M. Wachi (2013). Amino acids exporters in Corynebacterium glutamicum. In: H. Yukawa, M. Inui (Eds.) Corynebacterium glutamicum biology and biotechnology.
6. Corynebacterium glutamicum. On Wikipedia. Retrieved on September 25, 2018 from en.wikipedia.org.
7. Corynebacterium glutamicum. On Microbe Wiki. Retrieved on September 25, 2018 from microbewiki.kenyon.edu.