RSM-Based Optimization of Fermentation Conditions and Kinetic Studies of Glutamic Acid and Lysine Production by Corynebacterium glutamicum

Abstract

Corynebacterium glutamicum is an authenticated microorganism that supports amino acid production consistent with dietary importance. Fermentation parameters like temperature, agitation speed, and carbon source concentration were optimized using response surface methodology. Surface response model suggested that optimal fermentation parameters including 30°C, 50 g/L glucose concentration, and shaking speed of 120 rpm furnished 14.2 g/L of glutamic acid and 5.1 g/L lysine, comparable with the predicted values. After optimizing fermentation parameters in shake flasks, the fermentation kinetics was studied in a stirred fermenter. The kinetic study revealed that the substrate consumption rate achieved a maximum level of 3.36 g/L/hour between 12 and 18 hours; afterwards, it decreased and fell to 1.9 g/L/hour. Average biomass yield over a period of 48 hours was 0.337 g/L; however, maximum biomass yield of 0.51 g/L was noted between 10 and 20 hours. Overall molar yield coefficient of CO2 ( ${Y^{\text{C}}}_{\text{CO}2/\text{S}}$ ) was found to be 0.234. The molar yield coefficient of biomass ( ${Y^{\text{C}}}_{\text{X}/\text{S}}$ ) was 0.6 in exponential phase which decreased afterwards. This study indicates that the average biomass yield over a time of 48 hours was 0.337 g/L, with a maximum yield within 10 to 20 hours obtained under optimized conditions. The molar yield coefficient of CO2 ( ${Y^{\text{C}}}_{\text{CO}2/\text{S}}$ ) was found to be 0.234. The molar yield coefficient of biomass ( ${Y^{\text{C}}}_{\text{X}/\text{S}}$ ) was 0.6 in exponential phase which decreased and fell to near zero at 48 hrs.