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

Abstract

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 in situ resource utilization is paramount. The combination of microorganisms with electrochemical technologies offers a platform for the production of critical chemicals and materials from CO2 and H2O, 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 CO2. An autotrophic Sporomusa ovata (S. ovata) process converts CO2 to acetate which is then directly used as the primary carbon source for aerobic PHB production by Cupriavidus basilensis (C. basilensis). The S. ovata uses H2 as a reducing equivalent to be generated through electrocatalytic solar-driven H2O 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 C. basilensis suitably proliferates in the presence of inactive S. ovata. During the bioprocess 10.4 mmol acetate L –1 day–1 were generated from CO2 by S. ovata in the optimized media. Subsequently, 12.54 mg PHB L–1 hour–1 were produced by C. basilensis 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.

A comparative life cycle analysis of electromicrobial production systems

“…18 Two-step systems have also been developed based on bio-acetate as an intermediary molecule, in which CO 2 and H 2 are consumed by the acetogen Sporomusa ovata to produce acetate, which is then converted by a heterotroph such as E. coli to produce various value-added products. 19,20 Other EMP strategies are possible; however, the three EMP systems described here are well-represented in the literature and have been employed for a wide variety of products through genetic engineering.…”

Eliminating Genes for a Two Component System Increases PHB Productivity in Cupriavidus basilensis 4G11 Under PHB Suppressing, Non-Stress Conditions

“…We adapted a PHB production model developed previously 15 which has been utilized to model PHB production dynamics in C. basilensis 4G11 28 . This kinetic model considers cell biomass growth, production of PHB, consumption and cell growth inhibition of key metabolites acetate and nitrogen (in the form of ammonium chloride).…”

Space bioprocess engineering on the horizon

“…Aspirational realizations of SBE would feature prominently in establishment of in-orbit test-facilities, interplanetary waystations, lunar habitats, and a biomanufactory on the surface of Mars 10 . Differentiated from traditional efforts in space systems engineering, these SBE systems would encapsulate elements from in situ resource utilization (ISRU) for the production of biological feedstocks such as fixed carbon and nitrogen for use as inputs for plant, fungal, and microbial production systems 11,12 , fertilizers for downstream use by plants 13 ; in situ (bio)manufacturing (ISM) to produce materials…”