Project Details
Projekt
CO2-based production of caproic acid by engineered Acetobacterium woodii and Clostridium drakei applying a synthetic co-culture (CaproSyn)
Subject Area
Biological Process Engineering
Term
since 2019
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 427864786
CaproSyn brings together well complementary expertise of two academic groups from microbiology and molecular biology - Frank Bengelsdorf, Ulm University (UUlm) - and bioprocess engineering - Dirk Weuster-Botz, Technical University of Munich (TUM). Objective of CaproSyn is the knowledge-based realization of an optimized synthetic co-culture consisting of an engineered Acetobacterium woodii strain capable of lactate production from carbon dioxide (CO2) and hydrogen (H2) combined with the lactate consuming and chain elongating Clostridium drakei wild type strain for the efficient production of caproate in a scalable gas fermentation process. The already available lactate producing A. woodii, successfully engineered to overexpress the D-lactate dehydrogenase originating from Leuconostoc mesenteroides within the CaproMix project of the first funding period, will be improved by additional overexpression of a pyruvate formate lyase (PFL) and a PFL-activating enzyme, originating from Clostridium pasteurianum or Clostridium butyricum, to enable a carbon flux shortcut for lactate production from formate, the first intermediate in the Wood-Ljungdahl pathway, in A. woodii. Improved formate provisioning in A. woodii for this shortcut will be achieved by bioprocess engineering, e.g. controlling appropriate H2 partial pressures in fully controlled stirred-tank reactors. Compensation for the reduced growth of A. woodii mutant strains due to the pressure induced formate drain and the improved lactate production will be ensured by controlling the CO partial pressure in the bioreactor carefully. A fully controlled, batch operated stirred-tank bioreactor with continuous gassing will be used to study the synthetic co-culture of engineered A. woodii and C. drakei for the conversion of syngas (CO2+H2+CO) to caproate as the main product. Fluorescence in-situ hybridization (FISH) labelling and flow cytometry will be applied to monitor the growth of both strains individually in co-culture. Engineering of A. woodii will be supported by constrained based metabolic flux modelling built on extracellular rates measured in the co-cultivating processes. The overall objective is to maximize the carbon flux from CO2 to caproate with this engineered synthetic co-culture by applying metabolic engineering (UUlm) and bioprocess engineering (TUM) in an interdisciplinary and synergistic research approach. In summary, this project deals with a number of key scientific questions for establishing efficient co-culture technology for the production of value-added products from CO2, CO and H2. It bears several methodological and technological innovations which not only help to realize the special goal of this project but could be also applied to related co-cultivation approaches.
DFG Programme
Priority Programmes
