Comparative Study of Glutamic Acid Production by Wild-Type and Mutant Strains of Corynebacterium Glutamicum

 – Comparative Study of Glutamic Acid Production by Wild-Type and Mutant Strains of Corynebacterium Glutamicum –

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ABSTRACT

Several different lignocellulosic biomass of agricultural origin hold remarkable potential  for conversion into commodity products presenting dual advantage of sustainable resource supply and environmental quality.

There is generally an increasing demand for amino acids especially L-glutamic acid as growth promoting factor, as well as flavour enhancer  in foods.

The present study was an investigation on comparative L-glutamic acid production by wild-type and a mutant strain of Corynebacterium glutamicum (CG^NTA) using rice husk pretreated with 1.0M H₂SO₄ and 1.0M KOH.

The acid-treated and alkali-treated rice husk with high carbohydrate content of 64.25% and 76.37% respectively as determined, were used for the production of glutamic acid by submerged fermentation.

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The acid-treated and alkali-treated rice husk at concentration of 4% gave the highest glutamic acid yield of 27.84g/L and 15.72g/L respectively with the developed mutant strain (CG^NTA) under predetermined optimum fermentation conditions (30^oC, pH 7.0, 4% substrate concentration and 7% inoculum size).

In contrast, lower yields of 10.40g/L and 9.08g/L respectively were obtained with the wild type strain under similar optimum culture conditions.

Out of four parameters optimized, all were found to significantly (p˂ 0.05) influence glutamate production from both the acid and alkali-treated rice husk by the CG^NTA.

Similarly, all parameters except variation in the concentrations of the acid and alkali-treated rice husk  (p˂ 0.05) were found to be significant on the performance of the wild-type strain in glutamate production.

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INTRODUCTION

1.1 Background

Corynebacterium glutamicum is a rod-shaped Gram-positive aerobic bacterium, which can be found in soil, sewages, vegetables, and fruits (Eggeling and Bott, 2005). This bacterium is capable of utilizing various sugars as well as organic acids (Blombach and Seibold, 2010).

Among others, C. glutamicum has the ability to metabolize glucose, fructose, and sucrose as well as lactate, pyruvate, and acetate (Blombach and Seibold, 2010); additionally, C. glutamicum has the ability to grow on mixtures of different carbon sources with a monoauxic growth (Wendisch et al., 2000) as opposed to diauxic growth observed for many other microorganisms such as Escherichia coli and Bacillus subtilis.

Only a few exceptions have been reported as in the case of glucose-ethanol or acetate-ethanol mixtures, where preferential substrate utilization was observed (Zahoor et al., 2012).

Since its discovery, C. glutamicum has become an indispensable microorganism for the biotechnological industry (Wendisch, 2014).

With the development of amino acid market, a new era for the production of these amino acids by many companies and academic associations have enthusiastically arisen with the start of research and development in this field to increase the rate of amino acid production.

This technological race has expedited the expansion of amino acid production by various methods. Thus, almost all the amino acids can be produced by any of the four methods which include; chemical synthesis, protein hydrolysis, enzymatic synthesis and fermentation.

However, industrially, the most advantageous and economical method used for amino acids manufacture is microbial method, that is fermentation (Ikeda, 2003).

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REFERENCES

Hassan, E.G., Alkareem, A.M.A. and Mustafa, A.M.I. (2008). Effect of Fermentation and Particle Size of Wheat Husk on the Antinutritional Factors and Bread Quality. Pakistan Journal of Nutrition, 7(4):521-526

Hawkins, R A. (2009). The Blood-Brain Barrier and Glutamate. American Journal of Clinical Nutrition, 90:867S–74S.

Hermann, T. (2003). Industrial Production of Amino Acids by Coryneform Bacteria. Journal of Biotechnology, 104(1–3):155–172

Houghton, J., Weatherwax, S. and Ferrell, J. (2006). Breaking the Biological Barriers to Cellusosic Ethanol: a Joint Research Agenda. A Research Road Map Resulting from the Biomass to Biofuels Workshop Sponsored by the Office of Science and Office of Energy Efficiency and Renewable Energy, US Dept of Energy. Dec. 7-9, 2005 Rockville, Maryland

Ikeda, M. (2003). Amino Acid Production Processes. Advanced Biochemical Engineering and Biotechnology, 79:1–35Ishikawa,

K., Murakoshi, Y.T., Ohnishi, F., Kondo, K., Osumi, T. and Asano, K. (2008). Medium Composition Suitable for L-lysine Production by Methylophilu smethylotrophus in Fed-Batch Cultivation. Journal of Biosciences and Bioengineering, 106(6):574-579.