Sustainable CO2 conversion to value-added products via the union of materials and biology
Climate change is a pressing global dilemma driven by the combustion of hydrocarbon fuels to CO2, a potent greenhouse gas. CO2 conversion to value-added products has been the focus of intensive research with the goal of closing the carbon loop. A promising avenue for the utilization of waste CO2 comprises the materials-biology nexus. Microorganisms evolved over millions of years to fix CO2, H2O and N2 with high selectivity and low substrate activation all while self-regenerating. We have designed semiconductor nanomaterials that pair biocompatibly with these microorganisms to power their biocatalytic activity with light. We firstly demonstrate that by controlling the microenvironment in a silicon nanowire – bacteria ensemble, we can boost the solar-driven rate of CO2 reduction. In addition to optimizing the CO2 conversion rate, we establish synergistic co-cultures with guidable dynamics and outputs. We showcase a consortium involving acetogenic Sporomusa ovata and N2-fixing Rhodopseudomonas palustris for tandem CO2 and N2 reduction to tunable value-added products. Co-culture dynamics and products can be directed by substrate availability and electrochemical inputs. We also present an integrated process to produce a 3D-printable biopolymer from CO2Cupriavidus basilensis directly consumes CO2-derived acetate as the sole carbon source for biopolymer production without any processing of the culture medium between microbial production steps. Furthermore, electrochemically evolved H2 can be used as a redox mediator to supply CO2-fixing bacteria with electrons, but its low solubility in aqueous medium limits the rate of CO2 bioconversion. We therefore designed a platform to culture CO2-fixing bacteria at the gas-liquid interface ensuring ample access to H2, thus boosting the rate of CO2 reduction. Finally, we illustrate an electrochemically catalyzed pathway for the abiotic sugar synthesis from CO2. The sugars sustain Escherichia coli thus establishing a wide biomanufacturing platform from CO2
Stefano Cestellos-Blanco is a graduating Ph.D. candidate in the Department of Materials Science & Engineering at the University of California, Berkeley supervised by Professor Peidong Yang. Stefano earned a B.S. in Chemical Engineering from Stanford University while completing undergraduate research with Professors Richard Zare and Nicholas Melosh. In 2016 he moved across the Bay to study bioelectrocalalytic methods to convert waste CO2 to value-added chemicals, materials, fuels, and feedstocks. Stefano has been recognized as a Philomathia Graduate Fellow in Environmental Sciences and was named a 2020 Global Green Talent by the German Federal Ministry for Research. He also led the winning team of NASA’s Centennial CO2 Challenge demonstrating the abiotic conversion of CO2 to sugars, and he was the MSE department’s 2021 Gareth Thomas Materials Excellence Award recipient. After a stint as a visiting scholar at the Max Planck Institute for Terrestrial Microbiology in Germany, Stefano will return to Stanford as a postdoctoral fellow.