Understanding the Dynamics of a Methanotroph-Cyanobacterium Coculture through Kinetic Modeling and Experimental Verification

Wang, J., Auburn University
Badr, K., Auburn University
Hilliard, M., Auburn University
Roberts, N., Auburn University
He, Q. P., Auburn University
Kalyuzhnaya, M. G., San Diego State University
Beliaev, A. S., Pacific Northwest National Laboratory
Industrial, municipal, and agricultural waste streams contain stranded organic carbon, which can be converted into biogas through anaerobic digestion. It has been demonstrated that biogas has immense potential as a renewable feedstock for producing high-density fuels and commodity chemicals. However, the utilization of biogas presents a significant challenge due to its low pressure, high proportion of CO2 and presence of contaminants such as H2S, ammonia, and volatile organic carbon compounds. To tap into this immense potential, effective biotechnologies that co-utilize both CO2 and CH4 are needed. Using the basic metabolic coupling principles utilized by many natural consortia, we have demonstrated that photoautotroph- methanotroph co-cultures offers a flexible and highly promising platform for biological CO2/CH4 co-utilization.

From an engineering perspective, coupling methanotrophic metabolism to photosynthesis offers three major advantages for biological biogas conversion. First, exchange of in situ produced O2 and CO2 dramatically reduces mass transfer resistance of the two gas substrates, which can dramatically increases the growth of both strains; Second, in situ O2 consumption removes inhibition on photoautotroph and eliminates risk of explosion; Third, interdependent yet compartmentalized configuration of the coculture offers flexibility and more options for metabolic engineering.

However, development of multi-organism platforms for commercial biogas conversion present significant challenges which center around our ability to control function and composition of species in the coculture. An essential tool for the optimization, design and analysis of the coculture based biogas conversion is the development and validation of kinetics models that can accurately describe and predict the co-culture growth under different conditions. In this work, using Methylomicrobium buryatense - Arthrosipira platensis as the model coculture system, we present the very first effort to quantitatively model the growth dynamics of the coculture. The validated kinetic model can accurate predict the coculture dynamics under different growth conditions.