Selection and Characterization of a Lysine Yielding Mutant of
Corynebacterium glutamicum
- A Soil Isolate from Pakistan
Habib-ur-Rehman§٭,
Abdul Hameed and Safia Ahmed
Department of Microbiology, Quaid-i-Azam
University 5320, Islamabad, §Present address: Poultry Research
Institute, Shamsabad,
Rawalpindi,
Pakistan *Corresponding author: habib.rehman71@hotmail.com
Abstract
L-lysine is the second limiting amino acid for
poultry and supplemented in broiler feed for optimal performance. Lysine can be
produced by inducing mutation in glutamate producing bacteria. The study was
conducted to enhance lysine production from a local strain of Corynebacterium
glutamicum. The bacterium was mutated by exposure to UV. Mutants resistant
to s-2-aminoethyle L-cystein (AEC) and showing auxotrophy for L-homoserine were
screened for lysine production qualitatively and quantitatively. A mutant
showing highest production of lysine (8.2 mg/mL) was selected for optimization
of physical and nutritional parameters for maximum production of lysine in shake
flask. An initial pH 7.6, 30˚C temperature, 300 rpm and 60 h incubation time
were the optimized values of physical requirements. Cane molasses and corn
starch hydrolysate were required at 15% (wt/vol) in the fermentation media which
provided around 9% total sugars to produce maximum lysine (17 to 18 mg/mL). When
amonium sulphate was used at 3.5% (wt/vol) level in molasses or corn starch
hydrolysate based fermentation media, production of lysine slightly increased
above 18 mg/mL. It is concluded that industrial by products like cane molasses,
corn steep liquor, and corn starch hydrolysate can be used as carbon and organic
nitrogen sources in fermentation medium for scale up process of lysine
production and this lysine enriched broth may be used in broiler feed later.
However, more potent lysine producing mutant and additional
in vivo trials would be required to
commercialize this product.