Andreas Schmid

Helmholtz-Zentrum für Umweltforschung, Leipzig, Saxony, Germany

Are you Andreas Schmid?

Claim your profile

Publications (167)720.45 Total impact

  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: Metabolic engineering strategies mark a milestone for the fermentative production of bulk and fine chemicals. Yet, toxic products and volatile reaction intermediates with low solubilities remain challenging. Prominent examples are artificial multistep pathways like the production of perillyl acetate (POHAc) from glucose via limonene. For POHAc, these limitations can be overcome by mixed-culture fermentations. A limonene biosynthesis pathway and cytochrome P450 153A6 (CYP153A6) as regioselective hydroxylase are used in two distinct recombinant E. coli. POHAc formation from glucose in one recombinant cell was hindered by ineffective coupling of limonene synthesis and low rates of oxyfunctionalization. The optimization of P450 gene expression led to the formation of 6.20 ± 0.06 mg gcdw (-1) POHAc in a biphasic batch cultivation with glucose as sole carbon and energy source. Increasing the spatial proximity between limonene synthase and CYP153A6 by a genetic fusion of both enzymes changed the molar limonene/POHAc ratio from 3.2 to 1.6. Spatial separation of limonene biosynthesis from its oxyfunctionalization improved POHAc concentration 3.3-fold to 21.7 mg L(-1) as compared to a biphasic fermentation. Mixed-cultures of E. coli BL21 DE3 containing the limonene biosynthesis pathway and E. coli MG1655 harboring either CYP153A6, or alternatively a cymene monooxygenase, showed POHAc formation rates of 0.06 or 0.11 U gcdw (-1) , respectively. This concept provides a novel framework for fermentative syntheses involving toxic, volatile, or barely soluble compounds or pathway intermediates. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Biotechnology and Bioengineering 03/2015; DOI:10.1002/bit.25592 · 4.16 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Microscale cultivation systems are important tools to elucidate cellular dynamics beyond the population average and understand the functional architecture of single cells. However, there is scant knowledge about the bias of different microcultivation technologies itself on cellular functions. We therefore performed a systematic cross-platform comparison of three different microscale cultivation systems commonly harnessed in single-cell analysis: microfluidic non-contact cell traps driven by negative dielectrophoresis, microfluidic monolayer growth chambers, and semi-solid agarose pads. We assessed specific single cell growth rates, division rates and morphological characteristics of single Corynebacterium glutamicum cells and microcolonies as a bacterial model organism with medical and biotechnological relevance under standardized growth conditions. Strikingly, specific single-cell and microcolony growth rates µmax were robust and conserved for several cell generations with all three microcultivation technologies, whereas division rates cells grown on agarose pads deviated by up to 50% from cells cultivated in negative dielectrophoresis traps and monolayer growth chambers. Furthermore, morphological characteristics like cell lengths and division symmetries of individual cells were affected when grown on agarose pads. This indicated a significant impact of solid cultivation supports on cellular traits. The results demonstrate the impact of the microcultivation technology on microbial physiology for the first time and show the need of a careful selection and design of the microcultivation technology in order to allow unbiased analysis of cellular behavior.
    Lab on a Chip 02/2015; DOI:10.1039/C4LC01270D · 5.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The efficient coupling of biotransformation steps to an existing fermentation pathway is an interesting strategy to expand the product portfolio of Corynebacterium glutamicum as whole-cell biocatalyst. This is especially challenging if the biotransformation step comprises a direct link to central metabolism, as in the case of α-ketoglutarate-dependent oxygenase catalysis. Aiming at trans-4-hydroxy-L-proline (Hyp) production from glucose in a minimal medium, the proline-4-hydroxylase gene from Dactylosporangium sp. strain RH1 was introduced into a proline-producing, isoleucine-bradytroph C. glutamicum strain. The production of proline was found to be induced by isoleucine limitation. Proline and Hyp production were found to depend differently on isoleucine limitation. Severe isoleucine limitation was shown to result in proline accumulation and low hydroxylation rates both in batch and continuous cultivation set-ups. The investigation of different steady states with various glucose:isoleucine molar ratios revealed that optimal conditions for Hyp production are met around a molar ratio of 46:1, where isoleucine limitation is sufficient to trigger proline production but the hydroxylation rate is high enough to convert the majority of formed proline to Hyp. A high cell-density fed-batch set-up was designed, capable of producing 7.1 g L−1 of Hyp from glucose in 23 h with 98.5% conversion of proline to Hyp. Reaction engineering, specifically the fine-tuning of the glucose:isoleucine concentration ratio, enabled control of the fermentation profile and thus the accumulation of the desired product Hyp from glucose in minimal and defined media. Biotechnol. Bioeng. © 2014 Wiley Periodicals, Inc.
    Biotechnology and Bioengineering 02/2015; 112(2). DOI:10.1002/bit.25442 · 4.16 Impact Factor
  • Source
    Christian Dusny, Andreas Schmid
    Microbial Biotechnology 01/2015; 8(1):23. DOI:10. 1111/1751-7915.12252 · 3.21 Impact Factor
  • Nadine Ladkau, Andreas Schmid, Bruno Bühler
    [Show abstract] [Hide abstract]
    ABSTRACT: Whole-cell biocatalysis has emerged as an important tool for the synthesis of value-added fine and bulk chemicals as well as pharmaceuticals. Especially, the rapid development of recombinant DNA technologies resulted in a shift from the exploitation of natural enzymes and pathways to the design of recombinant cell factories comprising heterologous enzymes and/or synthetic, orthologous pathways for the synthesis of industrially relevant compounds. This review discusses recent developments and concepts applied in the frame of multistep whole-cell biocatalysis along with representative examples.
    Current Opinion in Biotechnology 12/2014; 30:178–189. DOI:10.1016/j.copbio.2014.06.003 · 8.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recent environmental economic developments generate a need for sustainable and cost-effective (microbial) processes for the production of high-volume, low-priced bulk chemicals. As an example, n-Butanol has, as a 2nd generation biofuel, beneficial characteristics compared to ethanol in liquid transportation fuel applications. The industrial revival of the classic n-butanol (ABE) fermentation requires process and strain engineering solutions for overcoming the main process limitations: product toxicity and low space-time yield (STY). Reaction intensification on the biocatalyst, fermentation, and bioprocess level can be based on economic and ecologic evaluations using quantifiable constraints. This review describes the means of process intensification for biotechnological processes. A quantitative approach is then used for the comparison of the massive literature on n-butanol fermentation. A comprehensive literature study – including key fermentation performance parameters – is presented and the results are visualized using the window of operation methodology. The comparison allowed the identification of the key constraints high cell densities, high strain stability, high specific production rate, cheap in situ product removal (ISPR), high n-butanol tolerance to operate ISPR efficiently, and cheap carbon source. It can thus be used as a guideline for the bioengineer during the combined biocatalyst, fermentation, and bioprocess development and intensification.This article is protected by copyright. All rights reserved
    Engineering in Life Sciences 11/2014; DOI:10.1002/elsc.201400041 · 1.89 Impact Factor
  • Christian Dusny, Andreas Schmid
    [Show abstract] [Hide abstract]
    ABSTRACT: Life is based on the cell as the elementary replicative and self-sustaining biological unit. Each single cell constitutes an independent and highly dynamic system with a remarkable individuality in a multitude of physiological traits and responses to environmental fluctuations. However, with traditional population-based cultivation set-ups, it is not possible to decouple inherent stochastic processes and extracellular contributions to phenotypic individuality for two central reasons: the lack of environmental control and the occlusion of single-cell dynamics by the population average. With microfluidic single-cell analysis as a new cell assay format, these issues can now be addressed, enabling cultivation and time-resolved analysis of single cells in precisely manipulable extracellular environments beyond the bulk. In this article, we explore the interplay of cellular physiology and environment at a single-cell level. We review biological basics that govern the functional state of the cell and put them in context with physical fundamentals that shape the extracellular environment. Furthermore, the significance of single-cell growth rates as pivotal descriptors for global cellular physiology is discussed and highlighted by selected studies. These examples illustrate the unique opportunities of microfluidic single-cell cultivation in combination with growth rate analysis, addressing questions of fundamental bio(techno)logical interest.
    Environmental Microbiology 10/2014; DOI:10.1111/1462-2920.12667 · 6.24 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Catalytic biofilms minimize reactant toxicity and maximize biocatalyst stability in selective transformations of chemicals to value-added products in continuous processes. The scaling up of such catalytic biofilm processes is challenging, due to fluidic and biological parameters affording a special reactor design affecting process performance. A solid support membrane aerated biofilm reactor was optimized and scaled-up to yield gram amounts of (S)-styrene oxide, a toxic and instable high value chemical synthon. A sintered stainless steel membrane unit was identified as an optimal choice as biofilm substratum and for high oxygen mass transfer. A stable expanded PTFE (ePTFE) membrane was best suited for in situ substrate delivery and product extraction. For the verification of scalability, catalytic biofilms of Pseudomonas sp. strain VLB120ΔC produced (S)-styrene oxide to an average concentration of 390 mM in the organic phase per day (equivalent to 24.4 g Laq (-1) day(-1) ). This productivity was gained by efficiently using the catalyst with an excellent product yield on biomass of 13.6 gproduct gbiomass (-1) . This product yield on biomass is in the order of magnitude reported for other continuous systems based on artificially immobilized biocatalysts and is fulfilling the minimum requirements for industrial biocatalytic processes. Overall, 46 g of (S)-styrene oxide were produced and isolated (purity: 99%; ee: > 99.8%. yield: 30%). The productivity is in a similar range as in comparable small scale biofilm reactors highlighting the large potential of this methodology for continuous bioprocessing of bulk chemicals and biofuels.
    Biotechnology Journal 10/2014; 9(10). DOI:10.1002/biot.201400341 · 3.71 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Biofilm reactors are often mass transfer limited due to excessive biofilm growth, impeding reactor performance. Fluidic conditions play a key role for biofilm structural development and subsequently for overall reactor performance. Continuous interfacial forces generated by aqueous-air segmented flow are controlling biofilm structure and diminish mass transfer limitations in biofilm microreactors. A simple three step method allows the formation of robust biofilms under aqueous-air segmented flow conditions: a first-generation biofilm is developing during single phase flow, followed by the introduction of air segments discarding most of the established biofilm. Finally, a second-generation, mature biofilm is formed in the presence of aqueous-air segments. Confocal laser scanning microscopy experiments revealed that the segmented flow supports the development of a robust biofilm. This mature biofilm is characterized by a three to four fold increase in growth rate, calculated from an increase in thickness, a faster spatial distribution (95% surface coverage in 24h), and a significantly more compact structure (roughness coefficient <1), as compared to biofilms grown under single phase flow conditions. The applicability of the concept in a segmented flow biofilm microreactor was demonstrated using the epoxidation of styrene to (S)-styrene oxide (ee > 99.8%) catalyzed by Pseudomonas sp. strain VLB120▵C cells in the mono-species biofilm. The limiting factor affecting reactor performance was oxygen transfer as the volumetric productivity rose from 11 to 46 g Ltube−1 day−1 after increasing the air flow rate. In summary, different interfacial forces can be applied for separating cell attachment and adaptation resulting in the development of a robust catalytic biofilm in continuous microreactors. Biotechnol. Bioeng. © 2014 Wiley Periodicals, Inc.
    Biotechnology and Bioengineering 09/2014; 111(9). DOI:10.1002/bit.25256 · 4.16 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Microreactors provide higher mass transfer rates than do conventional batch reactors. A tube-in-tube microreactor was used for the NADH-dependent in vitro conversion of 2-hydroxybiphenyl to 3-phenylcatechol that was catalysed by 2-hydroxybiphenyl 3-monooxygenase. A biphasic reaction system allowed high substrate loadings, whereas the microreactor ensured excellent mass transfer rates between the organic and aqueous phases. Oxygen was supplied continuously by membrane aeration across the whole reaction compartment. The productivities achieved in the tube-in-tube microreactor were 38 times higher than those in previously described batch reactors and almost 4 times higher than for the same reaction in a microreactor in which aqueous, organic, and air phases were delivered through consecutive segments. This set-up is a promising concept for oxygen-dependent biocatalytic reactions in microreactors and is developing as a basis for applications in gram-scale organic biosyntheses.
    ChemCatChem 09/2014; 6(9). DOI:10.1002/cctc.201402354 · 5.18 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The application of whole cells as biocatalysts is often limited by the toxicity of organic solvents, either interesting as substrate or product, or as second phase for in situ product removal and tool to control multistep biocatalysis. Solvent tolerant bacteria, especially Pseudomonas strains are proposed as promising hosts to overcome such limitations due to their inherent solvent tolerance mechanisms. However, potential industrial applications suffer from tedious, unproductive adaptation processes, phenotypic variability, and instable solvent tolerant phenotypes. In this study, genes described to be involved in solvent tolerance were identified in Pseudomonas taiwanensis VLB120 and adaptive solvent tolerance was proven by cultivation in the presence of 1% (v/v) toluene. Deletion of ttgV, coding for the specific transcriptional repressor of solvent efflux pump TtgGHI gene expression, led to constitutively solvent tolerant mutants of P. taiwanensis VLB120 and VLB120ΔC. Interestingly, the increased amount of solvent efflux pumps did not only enhance growth in the presence of toluene and styrene, but also the biocatalytic performance in terms of stereospecific styrene epoxidation, although proton-driven solvent efflux is expected to compete with the styrene monooxygenase for metabolic energy. Maximum specific epoxidation activities of P. taiwanensis VLB120ΔCΔttgV doubled to 67 U/gCDW compared to the parent strain P. taiwanensis VLB120ΔC. This study shows that solvent tolerance mechanisms, e.g., the solvent efflux pump TtgGHI, not only allow for growth in the presence of organic compounds, but can also be used as tools to improve redox biocatalysis involving organic solvents.
    Applied and Environmental Microbiology 08/2014; 80(20). DOI:10.1128/AEM.01940-14 · 3.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The efficiency and productivity of cellular biocatalysts play a key role in the industrial synthesis of fine and bulk chemicals. This study focuses on optimizing the synthesis of (S)-limonene from glycerol and glucose as carbon sources using recombinant E. coli. The cyclic monoterpene limonene is extensively used in the fragrance, food, and cosmetic industries. Recently, limonene also gained interest as alternative jet fuel from biological origin. Key parameters that limit the (S)-limonene yield related to genetics, physiology, and reaction engineering were identified. The growth-dependent production of (S)-limonene was shown for the first time in minimal media. E. coli BL21 (DE3) was chosen as the preferred host strain as it showed low acetate formation, fast growth, and high productivity. A two-liquid phase fed-batch fermentation with glucose as sole carbon and energy source resulted in the formation of 700 mg Lorg (-1) (S)-limonene. Specific activities of 75 mU gcdw (-1) were reached, but decreased relatively quickly. The use of glycerol as carbon source resulted in a prolonged growth and production phase (specific activities of ≥50 mU gcdw (-1) ) leading to a final (S)-limonene concentration of 2,700 mg Lorg (-1) . Although geranyl diphosphate (GPP) synthase had a low solubility, its availability appeared not to limit (S)-limonene formation in vivo under the conditions investigated. GPP rerouting towards endogenous farnesyl diphosphate (FPP) formation did not limit (S)-limonene production either. The two-liquid phase fed-batch setup led to the highest monoterpene concentration obtained with a recombinant microbial biocatalyst to date.
    Biotechnology Journal 08/2014; DOI:10.1002/biot.201400023 · 3.71 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: What defines central carbon metabolism? The classic textbook scheme of central metabolism includes the Embden-Meyerhof-Parnas (EMP) pathway of glycolysis, the pentose phosphate pathway and the citric acid cycle. The prevalence of this definition of central metabolism is however equivocal without an experimental validation. We address this issue using a general experimental approach that combines the monitoring of transcriptional and metabolic flux changes between the steady states on alternative carbon sources. The approach is investigated in the model bacterium Pseudomonas putida with glucose, fructose and benzoate as carbon sources. The catabolic reactions involved in the initial uptake and metabolism of these substrates are expected to show a correlated change in gene expression and metabolic fluxes. However, there was no correlation for the reactions linking the twelve-biomass precursor molecules, indicating a regulation mechanism other than mRNA synthesis for central metabolism. This result substantiates evidence for a (re-) definition of central carbon metabolism including all reactions that are bound to tight regulation and transcriptional invariance. Contrary to expectations, the canonical Entner-Doudoroff and the EMP pathways sensu stricto are not a part of central carbon metabolism in P. putida, as they are not regulated differently to the aromatic degradation pathway. The regulatory analyses presented here provide leads on a qualitative basis to address the use of alternative carbon sources by de-regulation and over expression at the transcriptional level, while rate improvements in central carbon metabolism require careful adjustment of metabolite concentrations, as regulation resides to a large extent on post-translational and/or metabolic regulation.
    Applied and Environmental Microbiology 06/2014; 80(17). DOI:10.1128/AEM.01643-14 · 3.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The natural ability of Pseudomonas taiwanensis VLB120 to use xylose as sole carbon and energy source offers a high potential for sustainable industrial biotechnology. In general, three xylose assimilation routes are reported for bacteria. To elaborate the metabolic capacity of P. taiwanensis VLB120 and to identify potential targets for metabolic engineering, an in silico/in vivo experiment was designed, allowing for discrimination between these pathways. Kinetics of glucose and xylose degradation in P. taiwanensis VLB120 were determined and the underlying stoichiometry was investigated by genome-based metabolic modeling and tracer studies using stable isotope labeling. Additionally RT-qPCR experiments have been performed to link physiology to the genomic inventory. Based on in silico experiments a labeling strategy was developed, ensuring a measurable and unique (13) C-labeling distribution in proteinogenic amino acids for every possible distribution between the different xylose metabolization routes. A comparison to in vivo results allows the conclusion that xylose is metabolized by P. taiwanensis VLB120 via the Weimberg pathway. Transcriptomic and physiological studies point to the biotransformation of xylose to xylonate by glucose dehydrogenase. The kinetics of this enzyme are also responsible for the preference of glucose as carbon source by cells growing in the presence of glucose and xylose.
    Environmental Microbiology 06/2014; DOI:10.1111/1462-2920.12537 · 6.24 Impact Factor
  • Journal of Molecular Catalysis B Enzymatic 05/2014; 103:1. DOI:10.1016/j.molcatb.2014.02.011 · 2.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The oxyfunctionalization of unactivated CH bonds can selectively and efficiently be catalyzed by oxygenase-containing whole-cell biocatalysts. Recombinant Escherichia coli W3110 containing the alkane monooxygenase AlkBGT and the outer membrane protein AlkL from Pseudomonas putida GPo1 have been shown to efficiently catalyze the terminal oxyfunctionalization of renewable fatty acid methyl esters yielding bifunctional products of interest for polymer synthesis. In this study, AlkBGTL-containing E. coli W3110 is shown to catalyze the multistep conversion of dodecanoic acid methyl ester (DAME) via terminal alcohol and aldehyde to the acid, exhibiting Michaelis–Menten-type kinetics for each reaction step. In two-liquid phase biotransformations, the product formation pattern was found to be controlled by DAME availability. Supplying DAME as bulk organic phase led to accumulation of the terminal alcohol as the predominant product. Limiting DAME availability via application of bis(2-ethylhexyl)phthalate (BEHP) as organic carrier solvent enabled almost exclusive acid accumulation. Furthermore, utilization of BEHP enhanced catalyst stability by reducing toxic effects of substrate and products. A further shift towards the overoxidized products was achieved by co-expression of the gene encoding the alcohol dehydrogenase AlkJ, which was shown to catalyze efficient and irreversible alcohol to aldehyde oxidation in vivo. With DAME as organic phase, the aldehyde accumulated as main product using resting cells containing AlkBGT, AlkL, as well as AlkJ. This study highlights the versatility of whole-cell biocatalysis for synthesis of industrially relevant bifunctional building blocks and demonstrates how integrated reaction and catalyst engineering can be implemented to control product formation patterns in biocatalytic multistep reactions. Biotechnol. Bioeng. 2014;9999: 1–11. © 2014 Wiley Periodicals, Inc.
    Biotechnology and Bioengineering 05/2014; DOI:10.1002/bit.25248 · 4.16 Impact Factor
  • Reto Ruinatscha, Katja Buehler, Andreas Schmid
    [Show abstract] [Hide abstract]
    ABSTRACT: Technical reactor limitations and low productivities have been shown to limit the implementation of electroenzymatic syntheses beyond lab-scale. One possible solution is a continuous flow-through reactor based on electrochemical plate and 6 frame filter press cells, as proposed in this study. With the aim of maximizing electroenzymatic productivities, the developed reactor set-up allows high electrochemical cofactor regeneration rates using porous, three-dimensional reticulated vitreous carbon electrodes with exceptionally large surface areas up to 19,685 m(2) m(-3). This system provides increased mass transfer rates and flavin adeninedinucleotide (FAD) was reduced at rates up to 93 mM h(-1). The electrochemical FAD reduction was coupled to the styrene monooxygenase (StyA) catalyzed (S)-epoxidation of styrene. Electroenzymatic productivities increased with FAD reduction rates up to 1.3 mM h(-1). This set-up now set the stage for efficient in vitro FAD regeneration and allows a broad electrochemical application of flavin dependent enzymes as biocatalysts.
    Journal of Molecular Catalysis B Enzymatic 05/2014; 103:100–105. DOI:10.1016/j.molcatb.2013.07.003 · 2.75 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Over the recent years the production of Ehrlich pathway derived chemicals was shown in a variety of hosts such as Escherichia coli, Corynebacterium glutamicum, and yeast. Exemplarily the production of isobutyric acid was demonstrated in Escherichia coli with remarkable titers and yields. However, these examples suffer from byproduct formation due to the fermentative growth mode of the respective organism. We aim at establishing a new aerobic, chassis for the synthesis of isobutyric acid and other interesting metabolites using Pseudomonas sp. strain VLB120, an obligate aerobe organism, as host strain. The overexpression of kivd, coding for a 2-ketoacid decarboxylase from Lactococcus lactis in Ps. sp. strain VLB120 enabled for the production of isobutyric acid and isobutanol via the valine synthesis route (Ehrlich pathway). This indicates the existence of chromosomally encoded alcohol and aldehyde dehydrogenases catalyzing the reduction and oxidation of isobutyraldehyde. In addition we showed that the strain possesses a complete pathway for isobutyric acid metabolization, channeling the compound via isobutyryl-CoA into valine degradation. Three key issues were addressed to allow and optimize isobutyric acid synthesis: i) minimizing isobutyric acid degradation by host intrinsic enzymes, ii) construction of suitable expression systems and iii) streamlining of central carbon metabolism finally leading to production of up to 26.8 +/- 1.5 mM isobutyric acid with a carbon yield of 0.12 +/- 0.01 g gglc-1. The combination of an increased flux towards isobutyric acid using a tailor-made expression system and the prevention of precursor and product degradation allowed efficient production of isobutyric acid in Ps. sp. strain VLB120. This will be the basis for the development of a continuous reaction process for this bulk chemicals.
    Microbial Cell Factories 01/2014; 13(1):2. DOI:10.1186/1475-2859-13-2 · 4.25 Impact Factor
  • Andreas Schmid
    Journal of Molecular Catalysis B Enzymatic 01/2014; · 2.75 Impact Factor

Publication Stats

5k Citations
720.45 Total Impact Points

Institutions

  • 2014–2015
    • Helmholtz-Zentrum für Umweltforschung
      Leipzig, Saxony, Germany
  • 2005–2014
    • Technische Universität Dortmund
      • • Laboratory of Chemical Biotechnology (BT)
      • • Chair of Chemical Biology
      Dortmund, North Rhine-Westphalia, Germany
  • 1998–2014
    • Universität Stuttgart
      • • Institute for Biochemical Engineering
      • • Institute for Sanitary Engineering, Water Quality and Solid Waste Management
      Stuttgart, Baden-Württemberg, Germany
  • 2010–2012
    • Leibniz-Institut für Analytische Wissenschaften
      Dortmund, North Rhine-Westphalia, Germany
  • 2008
    • Delft University Of Technology
      • Department of Biotechnology
      Delft, South Holland, Netherlands
    • Ewha Womans University
      Sŏul, Seoul, South Korea
    • Max Planck Institute of Molecular Physiology
      Dortmund, North Rhine-Westphalia, Germany
  • 1999–2006
    • Eawag: Das Wasserforschungs-Institut des ETH-Bereichs
      Duebendorf, Zurich, Switzerland
  • 1998–2006
    • ETH Zurich
      • Institute of Energy Technology
      Zürich, ZH, Switzerland
  • 2004
    • University of California, Berkeley
      Berkeley, California, United States
    • Hochschule für Technik Zürich
      Zürich, Zurich, Switzerland
  • 2002
    • Wageningen University
      • Laboratory of Biochemistry
      Wageningen, Gelderland, Netherlands