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 (CGNTA) 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. 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 (CGNTA) under

predetermined optimum fermentation conditions (30oC, 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 CGNTA. 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. Acid-treated rice husk hydrolysate was determined to be a better

substrate for L-glutamate production by the CGNTA mutant than the wild type strain of C.

glutamicum. The mutant strain (CGNTA) developed could, therefore, be useful in the

industrial production of glutamic acid using rice husk as substrate pretreated with acid.

This may perhaps form the basis of starting a microbial L-glutamate production industry

from rice husk as substrate in this locality and Nigeria as a whole.

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