AUTHOR=Cestellos-Blanco Stefano , Friedline Skyler , Sander Kyle B. , Abel Anthony J. , Kim Ji Min , Clark Douglas S. , Arkin Adam P. , Yang Peidong 

TITLE=Production of PHB From CO2-Derived Acetate With Minimal Processing Assessed for Space Biomanufacturing

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.700010

DOI=10.3389/fmicb.2021.700010

ISSN=1664-302X

ABSTRACT=<p>Providing life-support materials to crewed space exploration missions is pivotal for mission success. However, as missions become more distant and extensive, obtaining these materials from <italic>in situ</italic> resource utilization is paramount. The combination of microorganisms with electrochemical technologies offers a platform for the production of critical chemicals and materials from CO<sub>2</sub> and H<sub>2</sub>O, two compounds accessible on a target destination like Mars. One such potential commodity is poly(3-hydroxybutyrate) (PHB), a common biopolyester targeted for additive manufacturing of durable goods. Here, we present an integrated two-module process for the production of PHB from CO<sub>2</sub>. An autotrophic <italic>Sporomusa ovata (S. ovata)</italic> process converts CO<sub>2</sub> to acetate which is then directly used as the primary carbon source for aerobic PHB production by <italic>Cupriavidus basilensis (C. basilensis)</italic>. The <italic>S. ovata</italic> uses H<sub>2</sub> as a reducing equivalent to be generated through electrocatalytic solar-driven H<sub>2</sub>O reduction. Conserving and recycling media components is critical, therefore we have designed and optimized our process to require no purification or filtering of the cell culture media between microbial production steps which could result in up to 98% weight savings. By inspecting cell population dynamics during culturing we determined that <italic>C. basilensis</italic> suitably proliferates in the presence of inactive <italic>S. ovata</italic>. During the bioprocess 10.4 mmol acetate L <sup>–1</sup> day<sup>–1</sup> were generated from CO<sub>2</sub> by <italic>S. ovata</italic> in the optimized media. Subsequently, 12.54 mg PHB L<sup>–1</sup> hour<sup>–1</sup> were produced by <italic>C. basilensis</italic> in the unprocessed media with an overall carbon yield of 11.06% from acetate. In order to illustrate a pathway to increase overall productivity and enable scaling of our bench-top process, we developed a model indicating key process parameters to optimize.</p>