Reconciling the sustainable manufacturing of commodity chemicals with feasible technoeconomic outcomes assessing the investment case for heat integrated aerobic gas fermentation

The manufacturing industry must diverge from a ‘take, make and waste’ linear production paradigm towards more circular economies. Truly sustainable, circular economies are intrinsically tied to renewable resource flows, where vast quantities need to be available at a central point of consumption. Abundant, renewable carbon feedstocks are often structurally complex and recalcitrant, requiring costly pretreatment to harness their potential fully. As such, the heat integration of supercritical water gasification (SCWG) and aerobic gas fermentation unlocks the promise of renewable feedstocks such as lignin. This study models the technoeconomics and life cycle assessment (LCA) for the sustainable production of the commodity chemicals, isopropanol and acetone, from gasified Kraft black liquor. The investment case is underpinned by rigorous process modelling informed by published continuous gas fermentation experimental data. Time series analyses support the price forecasts for the solvent products. Furthermore, a Monte Carlo simulation frames an uncertain boundary for the technoeconomic model. The technoeconomic assessment (TEA) demonstrates that production of commodity chemicals priced at ~US$1000 per tonne is within reach of aerobic gas fermentation. In addition, owing to the sequestration of biogenic carbon into the solvent products, negative greenhouse gas (GHG) emissions are achieved within a cradle-to-gate LCA framework. As such, the heat integrated aerobic gas fermentation platform has promise as a best-in-class technology for the production of a broad spectrum of renewable commodity chemicals.</jats:p

Engineering improved ethylene production: Leveraging systems Biology and adaptive laboratory evolution

Ethylene is a small hydrocarbon gas widely used in the chemical industry. Annual worldwide production currently exceeds 150 million tons, producing considerable amounts of CO2 contributing to climate change. The need for a sustainable alternative is therefore imperative. Ethylene is natively produced by several different microorganisms, including Pseudomonas syringae pv. phaseolicola via a process catalyzed by the ethylene forming enzyme (EFE), subsequent heterologous expression of EFE has led to ethylene production in non-native bacterial hosts including E. coli and cyanobacteria. However, solubility of EFE and substrate availability remain rate limiting steps in biological ethylene production. We employed a combination of genome scale metabolic modelling, continuous fermentation, and protein evolution to enable the accelerated development of a high efficiency ethylene producing E. coli strain, yielding a 49-fold increase in production, the most significant improvement reported to date. Furthermore, we have clearly demonstrated that this increased yield resulted from metabolic adaptations that were uniquely linked to the EFE enzyme (WT vs mutant). Our findings provide a novel solution to deregulate metabolic bottlenecks in key pathways, which can be readily applied to address other engineering challenges

Metabolism-dependent bioaccumulation of uranium by Rhodosporidium toruloides isolated from the flooding water of a former uranium mine

Remediation of former uranium mining sites represents one of the biggest challenges worldwide that have to be solved in this century. During the last years, the search of alternative strategies involving environmentally sustainable treatments has started. Bioremediation, the use of microorganisms to clean up polluted sites in the environment, is considered one the best alternative. By means of culture-dependent methods, we isolated an indigenous yeast strain, KS5 (Rhodosporidium toruloides), directly from the flooding water of a former uranium mining site and investigated its interactions with uranium. Our results highlight distinct adaptive mechanisms towards high uranium concentrations on the one hand, and complex interaction mechanisms on the other. The cells of the strain KS5 exhibit high a uranium tolerance, being able to grow at 6 mM, and also a high ability to accumulate this radionuclide (350 mg uranium/g dry biomass, 48 h). The removal of uranium by KS5 displays a temperature- and cell viability-dependent process, indicating that metabolic activity could be involved. By STEM (scanning transmission electron microscopy) investigations, we observed that uranium was removed by two mechanisms, active bioaccumulation and inactive biosorption. This study highlights the potential of KS5 as a representative of indigenous species within the flooding water of a former uranium mine, which may play a key role in bioremediation of uranium contaminated sites.This work was supported by the Bundesministerium für Bildung und Forschung grand nº 02NUK030F (TransAqua). Further support took place by the ERDF-co-financed Grants CGL2012-36505 and 315 CGL2014-59616R, Ministerio de Ciencia e Innovación, Spain