In silico characterization of microbial electrosynthesis for metabolic engineering of biochemicals

Pandit, Aditya Vikram; Mahadevan, Radhakrishnan

doi:10.1186/1475-2859-10-76

Cited by 50 publications

(34 citation statements)

References 40 publications

(42 reference statements)

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“…Electro-fermentation has shown to be effective at increasing the synthesis of several products including ethanol, n-butanol and succinate with a variety of microorganisms such as Saccharomyces cerevisiae, Clostridium acetobutylicum or Actinobacillus succinogenes [9][10][11][12]. In contrast to all other electron acceptors or donors that can be utilised by microorganisms, electrodes cannot be depleted.…”

Section: Introductionmentioning

confidence: 99%

Anodic respiration of Pseudomonas putida KT2440 in a stirred-tank bioreactor

Hintermayer

Krömer

et al. 2016

Biochemical Engineering Journal

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Section: Introductionmentioning

confidence: 99%

Anodic respiration of Pseudomonas putida KT2440 in a stirred-tank bioreactor

Hintermayer

Krömer

et al. 2016

Biochemical Engineering Journal

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“…The work presented in chapter 4.2 is one of the first modelling studies on MES, as the limited knowledge about the exact metabolic reactions makes it very difficult to design an accurate theoretical network. 97,300,301 Rather than just assuming one reaction of electrode-microbe interaction we propose different options for EET mechanisms and study their effect on production for the first time. The used approach of elementary mode analysis offers the advantageous possibility of calculating every possible solution rather than one, which allows assessing the full metabolic capacities of the studied system.…”

Section: General Discussion Of Research Outcomesmentioning

confidence: 99%

“…34 Even though there is even less information available about cathodic electron transfer there is a general concept proposed that assumes the creation of a proton motive force by intracellular electron consumption, which is available for ATP synthesis. 4,66,97,98 In mediated electrically enhanced fermentations of Actinobacillus succinogenes PARK and ZEIKUS observed an electron flow from the cathode into the product succinate. 74 Simultaneously, the electron transfer via the reduced mediator Neutral Red and the proton-pumping fumarate reductase complex of A. succinogenes induced proton translocation and therefore increased ATP synthesis.…”

Section: Modelling Eetmentioning

confidence: 99%

“…4 But is this the only possibility? Observed is poor growth in very thin biofilms on cathodes, 97 Within their model, it is assumed that cathodic electrons enter the metabolism and directly reduce NAD + to NADH. Analogous to the theory discussed before the authors precariously assume the creation of a proton motive force that drives ATP synthesis even though the fumarate reductase of E. coli is, unlike the one of A. succinogenes, a non-proton-pumping enzyme.…”

Section: Modelling Eetmentioning

confidence: 99%

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Understanding extracellular electron transport of industrial microorganisms and optimization for production application

Kracke¹

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Microbial electrosynthesis (MES) and electro-fermentation are novel approaches to increase microbial production by stimulating the metabolism of the cells electrically. The technique is still in its infancy and while already hyped as promising method to convert CO 2 or cheap carbon sources and electrical energy into valuable chemicals and fuels, little is known about its true potential. This project uses a combination of in silico and in vivo approaches to gather novel information about the benefits and limitations of microbial electrosynthesis as well as its fundamental mechanisms.Understanding microbial electron transport mechanisms is the key to optimization of any bioelectrochemical technology. Therefore, this work analyses the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bioproduction.Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bioelectrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g. cytochromes, ferredoxins, quinones, flavins) are identified and analysed regarding their possible role in electrode-microbe-interactions.Based on these findings a stoichiometric network analysis is performed analysing the effect of electrical stimulation on the microbial metabolism theoretically. Escherichia coli is used as model organism for production with the aim to identify target processes for MES.For the first time, 20 different valuable products were screened for their potential to show increased yields during anaerobic electrically enhanced fermentation. Surprisingly it was found that an increase in product formation by electrical enhancement is not necessarily dependent on the degree of reduction of the product but rather the metabolic pathway it is derived from. Contrary to the usual assumption a reduced product would always require electron supply by a cathode this study shows that a complex metabolic analysis is needed to identify the overall redox state of each process. A variety of beneficial processes is presented with product yield increases of maximal +36% in reductive and +84% in oxidative fermentations and final theoretical product yields up to 100%. This includes compounds that are already produced at industrial scale such as succinic acid, ii lysine and diaminopentane as well as potential novel bio-commodities such as isoprene, para-hydroxybenzoic acid and para-aminobenzoic acid. Furthermore, it is shown that the way of electron transport has major impact on achievable biomass and product yields. The coupling of electron transport to energy conservation could be identified as crucial for most processes.The in vivo approach of this project introduces the development of a standardised reactor platfor...

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“…Electroactive microorganism can gain electrons from cathodes for reductive production processes, and microbes may also benefit from anodic oxidation reactions to achieve redox balance during the fermentation via discharge of excessive electrons (Pandit, 2012;Rosenbaum and Henrich, 2014).…”

Section: A Brief Introduction Of the Mes Technologymentioning

confidence: 99%

Metabolic engineering and bio-electrochemical synthesis in Pseudomonas putida KT2440 for the production of p-hydroxybenzoate and 2-ketogluconate

Yu¹

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Bio-based chemicals have drawn research interests due to the need for sustainable development. Aromatics and the derived compounds are an important class of chemicals that are mostly derived from fossil resources. Microbial bio-production can produce many compounds from renewable feedstocks to reduce the current heavy dependency on fossil resources. The aromatic compound para-hydroxybenzoate (PHBA) is used to make parabens and high-value polymers (liquid crystal polymer). Biologically, this chemical can be derived from the shikimate pathway, the central pathway for the biosynthesis of aromatic amino acids in bacteria, plants and fungi and some protozoa. In recent years, the gram-negative soil bacterium Pseudomonas putida is becoming an interesting chassis for industrial biotechnology. The production of PHBA in recombinant P. putida KT2440 was engineered by overexpressing the chorismate lyase Ubic from Escherichia coli and a feedback resistant 3-Deoxy-D-arabinoheptulosonate 7-phosphate synthase (AroG D146N).Additionally, the pathways competing for the substrate chorismate (trpE and pheA) and the PHBA degradation pathway (pobA) were eliminated. Finally, deletion of the glucose metabolism repressor hexR led to an increase in erythrose-4-phosphate and NADPH supply. This resulted in a maximum titre of 1.73 g L -1 and a carbon yield of 18.1 % (C-mol) in a non-optimized fed-batch fermentation. This is to date the highest PHBA concentration produced by P. putida using a chorismate lyase route.Large-scale aerobic fermentations are more expensive due to the limiting gas transfer and lead to substrate loss in the form of CO2, whereas anaerobic processes are easier to scale up and achieve high carbon yield. In the case of aromatics, anaerobic production could be beneficial. Microbial electrosynthesis is an emerging technology for biosynthesis of chemicals and fuels by microorganisms in an anaerobic bio-electrochemical system (BES).These systems can provide electrons to electroactive microbes for reductive production processes in the cathode or drain excessive electrons in oxidative production processes in the anode. P. putida was tested for the first time for its ability to perform anoxic metabolism in BES with ferricyanide as the mediator and anode as the electron sink. A dual-phase fermentation was employed, where the cells grew aerobically in the first phase and then performed an anaerobic oxidation process in the second phase. In this way, P. putida ) with a 9 % lower productivity than that in TB-grown cells. The proteomics analysis suggested the GADH enzyme complex (PP_3382, PP_3383, and PP_3384) overexpression was limited by the subunit PP_3382 biosynthesis. The slight upregulation of PP_3382 in glycerol-grown cells may contribute to its better performance in this condition, suggesting that the aerobic growth condition can be optimized for a better performance in bio-electrochemical production.In summary, using a chorismate lyase route in P. putida is a suitable strategy to produce aromatics. The use of a bio-...

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In silico characterization of microbial electrosynthesis for metabolic engineering of biochemicals

Cited by 50 publications

References 40 publications

Anodic respiration of Pseudomonas putida KT2440 in a stirred-tank bioreactor

Anodic respiration of Pseudomonas putida KT2440 in a stirred-tank bioreactor

Understanding extracellular electron transport of industrial microorganisms and optimization for production application

Metabolic engineering and bio-electrochemical synthesis in Pseudomonas putida KT2440 for the production of p-hydroxybenzoate and 2-ketogluconate

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