An Experimentally Evaluated Thermodynamic Approach to Estimate Growth of Photoheterotrophic Purple Non-sulfur Bacteria

Abstract

Distribution of energy during the growth and formation of useful chemicals by microorganisms can define the overall performance of a biotechnological system. However, to date, this distribution has not been used to reliably predict growth characteristics of phototrophic microorganisms. The presented research addresses this application by estimating the photon-associated Gibbs energy delivered for the photoheterotrophic growth of purple non-sulfur bacteria and production of dihydrogen. The approach is successfully evaluated with the data from a fed-batch growth of Rhodopseudomonas palustris nifA * fixing N 2 gas in phototrophic conditions and a reliable prediction of growth characteristics is demonstrated. Additionally, literatureavailable experimental data is collected and used for evaluation of the presented thermodynamic approach to predict photoheterotrophic growth yields. A proposed thermodynamic framework with modification to account for the phototrophic growth can be used to predict growth rates in broader environmental niches and to assess the possibility for the development of novel biotechnological applications in light-induced biological systems.

Towards a Biomanufactory on Mars

“…Biological N 2 -fixation offers power-and resource-efficient ammonium production. Although photoautotrophic N 2 fixation with, for example, purple non-sulfur bacteria, is possible, slow growth rates due to the high energetic demand of nitrogenase limit throughput (Doloman and Seefeldt, 2020). Therefore, heterotrophic production with similar bacteria using acetate or sucrose as a feedstock sourced from electromicrobial CO 2 -fixation represents the most promising production scheme, and additionally benefits from a high degree of process redundancy with heterotrophic bioplastic production.…”

“…The inputs to the nitrogen fixation submodule (Figure 5B) include fixed carbon feedstocks, N 2 , and light. The diazotrophic purple-non sulfur bacterium Rhodopseudomonas palustris is the proposed biocatalyst, as this bacterium is capable of anaerobic, light-driven N 2 fixation utilizing acetate as the carbon source, and has a robust genetic system allowing for rapid manipulation (Doloman and Seefeldt, 2020;. The output product is fixed nitrogen in the form of ammonium, which is used as a feedstock for the carbon-fixation submodule of ISRU along with the FPS and ISM modules.…”