Pakistan Veterinary Journal (Jan 2012)
Selection and Characterization of a Lysine Yielding Mutant of Corynebacterium glutamicum - a Soil Isolate from Pakistan
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% (w/v) 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% (w/v) 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.
