Oxygen Mass Transfer Coefficient (k sub L a') Consideration for Scale-Up Fermentation Systems at the Biotechnology Laboratory U.S. Army Edgewood Chemical Biological Center

Volumetric oxygen mass transfer coefficients kLa were determined at different agitation speeds, airflow rates, and overhead pressures for a Micros 30, IF 150 and IF 1500 fermentation systems at U.S. Army Edgewood Chemical Biological Centers Biotechnology laboratory. We found agitation speed as the most significant factor resulting in the highest magnitude of kLa values. Three sets of kLa values were further correlated in a power regression form at standard airflow rate of 1.0 volume of air per volume of fermentor per minute vvm for the Micros 30 and IF 150 but 0.5 vvm for IF 1500 with a 1.0 psi overhead pressure for all. The similar kLa value scale-up strategy was tested between the Micros 30 and IF 1500 systems using the gram-positive bacterium Bacillus thuringiensis kurstaki Btk, ATCC 33679 at the kLa value of 0.027 sec-1 for Micros 30 300 rpm and 0.033 sec-1 for IF 1500 175 rpm. Specific accumulated oxygen uptake values were 600 and 509 mg Dissolved OxygenOptical Density, and the Btk spores yields were 4.7 x 108 and 4.4 x 108 Colony-Forming-UnitmL, respectively, for the Micros 30 and IF 1500 systems. This study successfully demonstrated the scale-up fermentation strategy based on the kLa value.