Monday, July 25, 2011
Grand Ballroom, 5th fl (Sheraton New Orleans)
For many bioprocesses which generate an organic acid using E. coli, a base such as NaOH must be added into the bioreactor to maintain the pH at an optimal level for continued growth and product formation. The primary goal of this research is to enhance the NaCl tolerance of E. coli in order to prolong the fermentation time and improve organic acid production. Adaptive evolution was employed to generate NaCl-tolerant random mutants. Four E. coli mutants, designated ALS1184–ALS1187, were isolated after seventy three days of transfer. Comparing to wildtype E. coli MG1655, we observed faster growth rate and enhanced ability of NaCl tolerance with the mutant strains. Several physiological parameters of MG1655 and ALS1187 were calculated and compared using glucose-limited chemostats. Strains ALS1317 (MG1655 pflB) and ALS1318 (ALS1187 pflB) were constructed for lactate accumulation. ALS1318 generated 76.2 g/L lactate compared to 56.3 g/L lactate produced by ALS1317.