Metabolic shift induced by synthetic co-cultivation promotes high yield of chain elongated acids from syngas

Abstract

Bio-catalytic processes for sustainable production of chemicals and fuels receive increased attention within the concept of circular economy. Strategies to improve these production processes include genetic engineering of bio-catalysts or process technological optimization. Alternatively, synthetic microbial co-cultures can be used to enhance production of chemicals of interest. It remains often unclear however how microbe to microbe interactions affect the overall production process and how this can be further exploited for application. In the present study we explored the microbial interaction in a synthetic co-culture of Clostridium autoethanogenum and Clostridium kluyveri, producing chain elongated products from carbon monoxide. Monocultures of C. autoethanogenum converted CO to acetate and traces of ethanol, while during co-cultivation with C. kluyveri, it shifted its metabolism significantly towards solventogenesis. In C. autoethanogenum, expression of the genes involved in the central carbon- and energy-metabolism remained unchanged during co-cultivation compared to monoculture condition. Therefore the shift in the metabolic flux of C. autoethanogenum appears to be regulated by thermodynamics, and results from the continuous removal of ethanol by C. kluyveri. This trait could be further exploited, driving the metabolism of C. autoethanogenum to solely ethanol formation during co-cultivation, resulting in a high yield of chain elongated products from CO-derived electrons. This research highlights the important role of thermodynamic interactions in (synthetic) mixed microbial communities and shows that this can be exploited to promote desired conversions.

Enrichment of Anaerobic Syngas-Converting Communities and Isolation of a Novel Carboxydotrophic Acetobacterium wieringae Strain JM

“…Such interactions can be relevant for the overall fitness of microbial communities as they influence thermodynamics of the system. Diender et al (2019) have recently shown a similar synergistic relation in synthetic co-cultures of Clostridium autoethanogenum and Clostridium kluyveri. In that study, it was shown that the presence of the ethanol-consuming bacterium C. kluyveri induced a higher degree of solventogenesis by the carboxydotrophic organism (compared with monocultures of C. autoethanogenum).…”

Modeling a co-culture ofClostridium autoethanogenumandClostridium kluyverito increase syngas conversion to medium-chain fatty-acids

“…MCFA are used to produce pharmaceutical and personal care products, animal feed additives and lubricants, among other, and can be converted chemically or enzymatically into valuable biofuel molecules such as methyl esters, methyl ketones, alkenes and alkanes [13,14]. The theoretical maximum yield of hexanoate production in a co-culture of C. autoethanogenum and C. kluyveri is 0.056 mmol of hexanoate per mmol of CO, whereas the yield obtained in the most recent study [11] was 0.009 mmol hexanoate per mmol of CO, so there is substantial room for improvement and new strategies need to be developed.…”

“…Transcriptomic data was obtained from steady-state co-cultures grown in chemostats [11]. The Genomes of C. autoethanogenum: DSM 10061 (GCA 000484505.1) [31] and C. kluyveri : DSM 555 (GCA 000016505.1) [32] were retrieved from the European Nucleotide Archive.…”

“…Co-cultivation of a syngas-fermenting organism with other organisms (that use the primary products of syngas fermentation) can be used to extend the range of possible products. Previously, a co-culture of Clostridium autoethanogenum and Clostridium kluyveri was described to produce medium-chain fatty acids (C4-C6) and their respective alcohols by assimilation of CO or syngas [10,11]. C. autoethanogenum is an acetogenic bacterium able to produce acetate and ethanol when growing on CO or syngas [12].…”

“…In this study, we present a multi-species model built by combining the GEMs of C. autoethanogenum [24] and C. kluyveri [25]. The model accounts for experimental measurements informing on relative species abundances and volumetric production rates of syngas fermentation products obtained in chemostat runs under different conditions [11]. In order to test the model, experimental values were introduced as environmental constraints by employing community flux balance analysis (cFBA) [21,26].…”