Engineering of Microbioreactors and Microbiomes for the Biodegradation of Volatile Organic Compounds

Abstract

Some of the worst air quality is found in enclosed indoor spaces that do not have the capability for sufficient ventilation. Despite the major health risk of indoor air pollutants, such as volatile organic compounds (VOCs), current technologies to treat indoor VOC pollution could be improved. There is a critical need for a new technology that can effectively control VOCs in enclosed indoor environments. Biofiltration can potentially be adapted for indoor air treatment by intensifying the process with miniaturization. Microbioreactors have maximized surface-to-volume ratios, which allows for increased mass transfer of pollutants and oxygen to bacteria in the aqueous phase, resulting in superior biodegradation of VOCs. Accurate measurements of mass transfer coefficients are critical for reliable characterization of bioreactors. While standardized methods to measure mass transfer coefficients have been established for simple stirred tank reactors, existing methods to characterize MTCs have not yet been standardized for alternative reactor types such as miniaturized and biofiltration reactors, leading to inconsistencies in implementation and confusion about the validity of comparisons across different methodologies, volume scales, or reactor types. The accuracy of two commonly used lab-scale methods were critically evaluated for the measurement of mass transfer coefficients in a miniature plug-flow reactor. A detailed mathematical model was developed and applied to each experimental method, which enabled accurate calculation of the mass transfer coefficients. Building upon promising preliminary microbioreactor prototypes, a systematic study of major reactor design parameters was carried out with the aim of improving reactor performance. A design-build-test-learn pipeline was developed that enabled new reactor design prototypes to be rapidly designed using CAD software, manufactured with 3D printing, and inserted interchangeably in an experimental testing system. Several microbioreactors were manufactured with varying microchannels sizes and configurations. The mass transfer coefficients were characterized and a selection of microbioreactor prototypes were evaluated in a study of toluene biodegradation in continuously operated microbioreactors. The results of the microbioreactor evaluation studies indicate good performance for biological treatment of toluene and methanol as single model VOC substrates. Realistic treatment environments will have mixtures of pollutants, with several to potentially hundreds of separate volatile pollutants. The biological treatment of pollutant mixtures has been shown be more difficult for many microorganisms to treat effectively. Recently, several tools have emerged to enable a rational approach to design of microbial communities. Community metabolic network modeling was evaluated for use in engineering a microbial consortium to effectively and resiliently biodegrade VOCs. Model-predicted microbial communities were experimentally assessed alongside pure strains and conventionally enriched cultures for biodegradation of toluene and styrene as a model VOC mixture. Altogether, the aim of this dissertation was to engineer a high-performing microbioreactor-microbiome system for biological VOC removal. An experimental and mathematical modeling method was developed to accurately characterize the oxygen mass transfer coefficients of microbioreactors. The impact of key design parameters on the mass transfer of microbioreactors and the biodegradation of VOCs was evaluated. Finally, the potential to employ metabolic network modeling for the rational design of synthetic VOC-degradation consortia was explored.