When I decided to start my PhD journey, I had only a vague idea of what to do. I emailed my advisor, Dr. Rosy, asking her about projects on bioenergy production or water treatment. She replied telling me I could work on dechlorination and electricity production in microbial fuel cells (MFCs). I was OK with this suggestion and with her help I wrote a dissertation proposal to get funding from my Mexican government. I started my PhD journey on August 2013 with the goal of enhancing acetate production (for dechlorination and MFC systems) in fermentation via carbon monoxide (CO). The idea was to use CO as an inhibitor of methanogenesis, a main electron sink in acetate production.
As many young and full-of-energy students, I began my experimental work during my first week as a PhD student. With the help of my first mentor, Joe Miceli, I added CO to small bioreactors inoculated with sludge and fermenting ethanol. Our first observation was disappointing. CO was so toxic it inhibited not only methanogenesis but also all microbial activity. However, after a couple of days, ethanol fermentation began. Microorganisms were adapting to the harsh conditions!! The result of this first experiment was not as expected, methane production was not inhibited. But the results were even more exciting; microorganisms were converting CO into methane, H2, acetate, propionate, butyrate and ethanol! After this experiment I started enriching microorganisms with CO to create CO-consuming cultures capable of producing biofuels and commodity-chemicals.
My first enrichment was from sludge collected from a wastewater treatment plant, but now we have CO-consuming cultures from the ocean and volcanic sand in Hawaii, the deep ocean in San Diego, high pH-environments in Oman, frozen environments in Alberta, Canada, and of course, hot environments here in the Sonoran desert. With this, I’ve realized that CO-oxidizing microorganisms (named carboxidotrophs) are EVERYWHERE, from water treatment plants to extreme environments all over the world. They have existed since the beginning of life, and are responsible for the stable CO levels in the atmosphere, despite the increasing pollution. Even more, if we keep them happy in engineered systems, carboxidotrophs can help us solve environmental issues: from recalcitrant biomass conversion to bioenergy (such as H2, ethanol, butanol) production.
The engrossing world of anaerobic CO-oxidation has made me forget about dechlorination and MFCs (for now) and focus on the exploration of novel CO-consuming microbes. Besides patience, these slow growers have taught me that life is so miraculous it can even feed on toxic inorganic substances and develop in places we cannot imagine. The process of adaptation is even more fascinating than what Darwin described back in 1859. Microorganisms adapt to everything, from harsh environments to toxic gases capable of depleting oxygen in our blood and stopping respiration in microbes. The need of survival goes beyond resisting winter. Life has no boundaries. Bugs mimic their surroundings, microbes withstand freezing temperatures, and humans develop artificial lungs… what else can life do?
Sofia Esquivel-Elizondo is a 4th year PhD student in Environmental Engineering advised by Dr. Rosa Krajmalnik-Brown. She and her research on Microbial Metabolic Exploration are funded by the Center for Bio-mediated and Bio-inspired Geotechnics. Sofia is originally from Mexico where she studied her undergrad in Chemical Engineering and her Masters in Bioprocess Engineering. Although she is an engineer she is passionate about Microbiology and her goal is connect these two disciplines for the benefit of society.