Abstract
L-Lysine is an essential amino acid with high commercial importance, as it has to be available in sufficient quantities in animal and human feeds to meet their nutritional requirement. As there is constant increase in L-lysine demand every year, to meet the increasing demand it is necessary to produce L-lysine in large scale. Generally, L-lysine is produced by batch fermentation. In the present investigation, different fermentation process parameters such as fermentation time, pH, temperature, glucose concentration, airflow rate and aeration rate were studied to optimize the production of L-lysine by Corynebacterium glutamicum MH 20-22 B in a 5 L laboratory-scale stirred tank bioreactor. A comparative study of L-lysine production with free cells and immobilized cells of C. glutamicum MH 20-22 B was also investigated to determine whether free cells or immobilized cells were advantageous for production of L-lysine. In this way, optimized fermentation upstream parameters which produced the maximum yield of L-lysine were developed and it was also concluded from the present study that immobilized cells of C. glutamicum MH 20-22 B were more advantageous for L-lysine production as they yield more L-lysine compared to free cells of C. glutamicum MH 20-22 B. It was observed in the present study that the optimum values of fermentation time, pH, temperature, glucose concentration, airflow rate and aeration rate were 96 h, 7.5, 30 °C, 90 g/l, 1.0 vvm and 200 rpm, respectively, by immobilized cells, whereas in case of free cells the optimum values were 72 h, 7.5, 30 °C, 80 g/l, 1.25 vvm and 300 rpm. Immobilized C. glutamicum MH 20-22 B cells exhibited greater L-lysine production of 31.58 g/l than free cells which produced 26.34 g/l of L-lysine.