(535h) Two Experimental Protocols for Accurate Measurement of Gas Component Uptake and Production Rates in Bioconversion Processes

Authors: 
Wang, J., Auburn University
Stone, K., Auburn University
He, Q. P., Auburn University
Bioconversion processes offer many economic, environmental, and societal advantages for production of fuels and chemicals. Successful commercialization of any biotechnology usually requires accurate characterization of cell growth dynamics, substrate conversion and production excretion rates. Despite recent advancements in analytical equipment, obtaining accurate measurement of gas component uptake or production rates remains challenging due to their high sensitivity to system pressure or volume changes. Specifically, the consumption and production of various gases will result in changes in system pressure (for batch operations) or off-gas flow rate (for continuous operations). These changes would cause significant errors in the estimated gas component uptake and production rates if they were not accounted for. In this work, we propose two easy-to-implement experimental protocols and associated calculation procedures to obtain accurate measurements of gas component consumption and production rates; one is for batch operation and one is for continuous operation.

One protocol is for depressurized (i.e., system pressure below 1 atm) batch systems, where N2 is used to repressurize the system to 1 atm before sampling; the other is for continuous operations, where He is used as tracer or internal standard to obtain accurate measurement of the off-gas flow rate. Both abiotic systems and biotic systems with an aerobic methanotroph were used to demonstrate the effectiveness of the proposed protocols and calculation procedures in ensuring accurate consumption and production rate measurements of gas components. The accuracies of the gas component measurements based on both protocols were assessed through percentage error when the true values are known, or through total carbon balance when the true values are unknown. The proposed protocols and associated calculation procedures are easy-to-implement, do not require specialized equipment, and are generally applicable to various bioconversion processes where gas components are involved.