Endre søk
Begrens søket
1 - 17 of 17
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1. Beatriz Badia, Mariana
    et al.
    Mans, Robert
    Lis, Alicia V.
    Ariel Tronconi, Marcos
    Lucia Arias, Cintia
    Maurino, Veronica Graciela
    Santiago Andreo, Carlos
    Fabiana Drincovich, Maria
    van Maris, Antonius J. A.
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Gerrard Wheeler, Mariel Claudia
    Specific Arabidopsis thaliana malic enzyme isoforms can provide anaplerotic pyruvate carboxylation function in Saccharomyces cerevisiae2017Inngår i: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 284, nr 4, s. 654-665Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    NAD(P)-malic enzyme (NAD(P)-ME) catalyzes the reversible oxidative decarboxylation of malate to pyruvate, CO2, and NAD(P)H and is present as a multigene family in Arabidopsis thaliana. The carboxylation reaction catalyzed by purified recombinant Arabidopsis NADP-ME proteins is faster than those reported for other animal or plant isoforms. In contrast, no carboxylation activity could be detected in vitro for the NAD-dependent counterparts. In order to further investigate their putative carboxylating role in vivo, Arabidopsis NAD(P)-ME isoforms, as well as the NADP-ME2del2 (with a decreased ability to carboxylate pyruvate) and NADP-ME2R115A (lacking fumarate activation) versions, were functionally expressed in the cytosol of pyruvate carboxylase-negative (Pyc(-)) Saccharomyces cerevisiae strains. The heterologous expression of NADP-ME1, NADP-ME2 (and its mutant proteins), and NADP-ME3 restored the growth of Pyc(-) S. cerevisiae on glucose, and this capacity was dependent on the availability of CO2. On the other hand, NADP-ME4, NAD-ME1, and NAD-ME2 could not rescue the Pyc(-) strains from C-4 auxotrophy. NADP-ME carboxylation activity could be measured in leaf crude extracts of knockout and over-expressing Arabidopsis lines with modified levels of NADP-ME, where this activity was correlated with the amount of NADP-ME2 transcript. These results indicate that specific A. thaliana NADP-ME isoforms are able to play an anaplerotic role in vivo and provide a basis for the study on the carboxylating activity of NADP-ME, which may contribute to the synthesis of C-4 compounds and redox shuttling in plant cells.

  • 2. Cueto-Rojas, Hugo F.
    et al.
    Milne, Nicholas
    van Helmond, Ward
    Pieterse, Mervin M.
    van Maris, Antonius J. A.
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Daran, Jean-Marc
    Wahl, S. Aljoscha
    Membrane potential independent transport of NH3 in the absence of ammonium permeases in Saccharomyces cerevisiae2017Inngår i: BMC Systems Biology, ISSN 1752-0509, E-ISSN 1752-0509, Vol. 11, artikkel-id 49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Microbial production of nitrogen containing compounds requires a high uptake flux and assimilation of the N-source (commonly ammonium), which is generally coupled with ATP consumption and negatively influences the product yield. In the industrial workhorse Saccharomyces cerevisiae, ammonium (NH4+) uptake is facilitated by ammonium permeases (Mep1, Mep2 and Mep3), which transport the NH4+ ion, resulting in ATP expenditure to maintain the intracellular charge balance and pH by proton export using the plasma membrane-bound H+ -ATPase. Results: To decrease the ATP costs for nitrogen assimilation, the Mep genes were removed, resulting in a strain unable to uptake the NH4+ ion. Subsequent analysis revealed that growth of this Delta mep strain was dependent on the extracellular NH3 concentrations. Metabolomic analysis revealed a significantly higher intracellular NHX concentration (3.3-fold) in the Delta mep strain than in the reference strain. Further proteomic analysis revealed significant up-regulation of vacuolar proteases and genes involved in various stress responses. Conclusions: Our results suggest that the uncharged species, NH3, is able to diffuse into the cell. The measured intracellular/extracellular NHX ratios under aerobic nitrogen-limiting conditions were consistent with this hypothesis when NHx compartmentalization was considered. On the other hand, proteomic analysis indicated a more pronounced N-starvation stress response in the Delta mep strain than in the reference strain, which suggests that the lower biomass yield of the Delta mep strain was related to higher turnover rates of biomass components.

  • 3. Gabba, M.
    et al.
    Frallicciardi, J.
    van ’t Klooster, J.
    Henderson, R.
    Syga, Ł.
    Mans, R.
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Poolman, B.
    Weak Acid Permeation in Synthetic Lipid Vesicles and Across the Yeast Plasma Membrane2020Inngår i: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 118, nr 2, s. 422-434Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a fluorescence-based approach for determination of the permeability of small molecules across the membranes of lipid vesicles and living cells. With properly designed experiments, the method allows us to assess the membrane physical properties both in vitro and in vivo. We find that the permeability of weak acids increases in the order of benzoic > acetic > formic > lactic, both in synthetic lipid vesicles and the plasma membrane of Saccharomyces cerevisiae, but the permeability is much lower in yeast (one to two orders of magnitude). We observe a relation between the molecule permeability and the saturation of the lipid acyl chain (i.e., lipid packing) in the synthetic lipid vesicles. By analyzing wild-type yeast and a manifold knockout strain lacking all putative lactic acid transporters, we conclude that the yeast plasma membrane is impermeable to lactic acid on timescales up to ∼2.5 h.

  • 4.
    Guevara-Martínez, Mónica
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. Faculty of Science and Technology, Center of Biotechnology, Universidad Mayor de San Simón, Cochabamba, Bolivia.
    Perez-Zabaleta, Mariel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. Faculty of Science and Technology, Center of Biotechnology, Universidad Mayor de San Simón, Cochabamba, Bolivia.
    Gustavsson, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Quillaguamán, Jorge
    Faculty of Science and Technology, Center of Biotechnology, Universidad Mayor de San Simón, Cochabamba, Bolivia.
    Larsson, Gen
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    The role of the acyl-CoA thioesterase YciA in the production of (R)-3-hydroxybutyrate by recombinant Escherichia coli2019Inngår i: Applied Microbiology and Biotechnology, s. 1-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biotechnologically produced (R)-3-hydroxybutyrate is an interesting pre-cursor for antibiotics, vitamins, and other molecules benefitting from enantioselective production. An often-employed pathway for (R)-3-hydroxybutyrate production in recombinant E. coli consists of three-steps: (1) condensation of two acetyl-CoA molecules to acetoacetyl-CoA, (2) reduction of acetoacetyl-CoA to (R)-3-hydroxybutyrate-CoA, and (3) hydrolysis of (R)-3-hydroxybutyrate-CoA to (R)-3-hydroxybutyrate by thioesterase. Whereas for the first two steps, many proven heterologous candidate genes exist, the role of either endogenous or heterologous thioesterases is less defined. This study investigates the contribution of four native thioesterases (TesA, TesB, YciA, and FadM) to (R)-3-hydroxybutyrate production by engineered E. coli AF1000 containing a thiolase and reductase from Halomonas boliviensis. Deletion of yciA decreased the (R)-3-hydroxybutyrate yield by 43%, whereas deletion of tesB and fadM resulted in only minor decreases. Overexpression of yciA resulted in doubling of (R)-3-hydroxybutyrate titer, productivity, and yield in batch cultures. Together with overexpression of glucose-6-phosphate dehydrogenase, this resulted in a 2.7-fold increase in the final (R)-3-hydroxybutyrate concentration in batch cultivations and in a final (R)-3-hydroxybutyrate titer of 14.3 g L-1 in fed-batch cultures. The positive impact of yciA overexpression in this study, which is opposite to previous results where thioesterase was preceded by enzymes originating from different hosts or where (S)-3-hydroxybutyryl-CoA was the substrate, shows the importance of evaluating thioesterases within a specific pathway and in strains and cultivation conditions able to achieve significant product titers. While directly relevant for (R)-3-hydroxybutyrate production, these findings also contribute to pathway improvement or decreased by-product formation for other acyl-CoA-derived products.

    Fulltekst (pdf)
    fulltext
  • 5.
    Hörnström, David
    et al.
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Larsson, Gen
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Gustavsson, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Molecular optimization of autotransporter-based tyrosinase surface display2019Inngår i: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1862, nr 2, s. 486-494Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Display of recombinant enzymes on the cell surface of Gram-negative bacteria is a desirable feature with applications in whole-cell biocatalysis, affinity screening and degradation of environmental pollutants. One common technique for recombinant protein display on the Escherichia colt surface is autotransport. Successful autotransport of an enzyme largely depends on the following: (1) the size, sequence and structure of the displayed protein, (2) the cultivation conditions, and (3) the choice of the autotransporter expression system. Common problems with autotransporter-mediated surface display include low expression levels and truncated fusion proteins, which both limit the cell-specific activity. The present study investigated an autotransporter expression system for improved display of tyrosinase on the surface of E. coli by evaluating different variants of the autotransporter vector including: promoter region, signal peptide, the recombinant passenger, linker regions, and the autotransporter translocation unit itself. The impact of these changes on translocation to the cell surface was monitored by the cell-specific activity as well as antibody-based flow cytometric analysis of full-length and degraded passenger. Applying these strategies, the amount of displayed full-length tyrosinase on the cell surface was increased, resulting in an overall 5-fold increase of activity as compared to the initial autotransport expression system. Surprisingly, heterologous expression using 7 different translocation units all resulted in functional expression and only differed 1.6-fold in activity. This study provides a basis for broadening of the range of proteins that can be surface displayed and the development of new autotransporter-based processes in industrial-scale whole-cell biocatalysis.

  • 6. Juergens, H.
    et al.
    Niemeijer, M.
    Jennings-Antipov, L. D.
    Mans, R.
    Morel, J.
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Pronk, J. T.
    Gardner, T. S.
    Evaluation of a novel cloud-based software platform for structured experiment design and linked data analytics2018Inngår i: Scientific Data, E-ISSN 2052-4463, Vol. 5, artikkel-id 180195Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Open data in science requires precise definition of experimental procedures used in data generation, but traditional practices for sharing protocols and data cannot provide the required data contextualization. Here, we explore implementation, in an academic research setting, of a novel cloud-based software system designed to address this challenge. The software supports systematic definition of experimental procedures as visual processes, acquisition and analysis of primary data, and linking of data and procedures in machine-computable form. The software was tested on a set of quantitative microbial-physiology experiments. Though time-intensive, definition of experimental procedures in the software enabled much more precise, unambiguous definitions of experiments than conventional protocols. Once defined, processes were easily reusable and composable into more complex experimental flows. Automatic coupling of process definitions to experimental data enables immediate identification of correlations between procedural details, intended and unintended experimental perturbations, and experimental outcomes. Software-based experiment descriptions could ultimately replace terse and ambiguous ‘Materials and Methods’ sections in scientific journals, thus promoting reproducibility and reusability of published studies.

  • 7.
    Lindroos, Magnus
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Hörnström, David
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Larsson, Gen
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Gustavsson, Martin
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    van Maris, Antonius J. A.
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Continuous removal of the model pharmaceutical chloroquine from water using melanin-covered Escherichia coli in a membrane bioreactor2019Inngår i: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 365, s. 74-80Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Environmental release and accumulation of pharmaceuticals and personal care products is a global concern in view of increased awareness of ecotoxicological effects. Adsorbent properties make the biopolymer melanin an interesting alternative to remove micropollutants from water. Recently, tyrosinase-surface-displaying Escherichia coli was shown to be an interesting self-replicating production system for melanin-covered cells for batch-wise absorption of the model pharmaceutical chloroquine. This work explores the suitability of these melanin-covered E. coli for the continuous removal of pharmaceuticals from wastewater. A continuous-flow membrane bioreactor containing melanized E. coli cells was used for adsorption of chloroquine from the influent until saturation and subsequent regeneration. At a low loading of cells (10 g/L) and high influent concentration of chloroquine (0.1 mM), chloroquine adsorbed until saturation after 26 +/- 2 treated reactor volumes (39 +/- 3 L). The average effluent concentration during the first 20 h was 0.0018 mM, corresponding to 98.2% removal. Up to 140 +/- 6 mg chloroquine bound per gram of cells following mixed homo- and heterogeneous adsorption kinetics. In situ low pH regeneration released all chloroquine without apparent capacity loss over three consecutive cycles. This shows the potential of melanized cells for treatment of conventional wastewater or highly concentrated upstream sources such as hospitals or manufacturing sites.

  • 8. Marques, W. L.
    et al.
    Mans, R.
    Henderson, R. K.
    Marella, E. R.
    Horst, J. T.
    Hulster, E. D.
    Poolman, B.
    Daran, J. -M
    Pronk, J. T.
    Gombert, A. K.
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Combined engineering of disaccharide transport and phosphorolysis for enhanced ATP yield from sucrose fermentation in Saccharomyces cerevisiae2018Inngår i: Metabolic engineering, ISSN 1096-7176, E-ISSN 1096-7184, Vol. 45, s. 121-133Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Anaerobic industrial fermentation processes do not require aeration and intensive mixing and the accompanying cost savings are beneficial for production of chemicals and fuels. However, the free-energy conservation of fermentative pathways is often insufficient for the production and export of the desired compounds and/or for cellular growth and maintenance. To increase free-energy conservation during fermentation of the industrially relevant disaccharide sucrose by Saccharomyces cerevisiae, we first replaced the native yeast α-glucosidases by an intracellular sucrose phosphorylase from Leuconostoc mesenteroides (LmSPase). Subsequently, we replaced the native proton-coupled sucrose uptake system by a putative sucrose facilitator from Phaseolus vulgaris (PvSUF1). The resulting strains grew anaerobically on sucrose at specific growth rates of 0.09 ± 0.02 h−1 (LmSPase) and 0.06 ± 0.01 h−1 (PvSUF1, LmSPase). Overexpression of the yeast PGM2 gene, which encodes phosphoglucomutase, increased anaerobic growth rates on sucrose of these strains to 0.23 ± 0.01 h−1 and 0.08 ± 0.00 h−1, respectively. Determination of the biomass yield in anaerobic sucrose-limited chemostat cultures was used to assess the free-energy conservation of the engineered strains. Replacement of intracellular hydrolase with a phosphorylase increased the biomass yield on sucrose by 31%. Additional replacement of the native proton-coupled sucrose uptake system by PvSUF1 increased the anaerobic biomass yield by a further 8%, resulting in an overall increase of 41%. By experimentally demonstrating an energetic benefit of the combined engineering of disaccharide uptake and cleavage, this study represents a first step towards anaerobic production of compounds whose metabolic pathways currently do not conserve sufficient free-energy.

  • 9. Marques, Wesley Leoricy
    et al.
    Mans, Robert
    Marella, Eko Roy
    Cordeiro, Rosa Lorizolla
    van den Broek, Marcel
    Daran, Jean-Marc G.
    Pronk, Jack T.
    Gombert, Andreas K.
    van Maris, Antonius J. A.
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Elimination of sucrose transport and hydrolysis in Saccharomyces cerevisiae: a platform strain for engineering sucrose metabolism2017Inngår i: FEMS yeast research (Print), ISSN 1567-1356, E-ISSN 1567-1364, Vol. 17, nr 1, artikkel-id fox006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many relevant options to improve efficacy and kinetics of sucrose metabolism in Saccharomyces cerevisiae and, thereby, the economics of sucrose-based processes remain to be investigated. An essential first step is to identify all native sucrose-hydrolysing enzymes and sucrose transporters in this yeast, including those that can be activated by suppressor mutations in sucrose-negative strains. A strain in which all known sucrose-transporter genes (MAL11, MAL21, MAL31, MPH2, MPH3) were deleted did not grow on sucrose after 2 months of incubation. In contrast, a strain with deletions in genes encoding sucrose-hydrolysing enzymes (SUC2, MAL12, MAL22, MAL32) still grew on sucrose. Its specific growth rate increased from 0.08 to 0.25 h(-1) after sequential batch cultivation. This increase was accompanied by a 3-fold increase of in vitro sucrose-hydrolysis and isomaltase activities, as well as by a 3- to 5-fold upregulation of the isomaltase-encoding genes IMA1 and IMA5. One-step Cas9-mediated deletion of all isomaltase-encoding genes (IMA1-5) completely abolished sucrose hydrolysis. Even after 2 months of incubation, the resulting strain did not grow on sucrose. This sucrose-negative strain can be used as a platform to test metabolic engineering strategies and for fundamental studies into sucrose hydrolysis or transport.

  • 10. Papapetridis, Ioannis
    et al.
    Goudriaan, Maaike
    Vitali, María Vázquez
    Keijzer, Nikita A
    Broek, Marcel
    van Maris, Antonius
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. Delft University of Technology, The Netherlands.
    Pronk, Jack T.
    Optimizing anaerobic growth rate and fermentation kinetics in Saccharomyces cerevisiae strains expressing Calvin-cycle enzymes for improved ethanol yield2018Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 11, nr 1, artikkel-id 17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Reduction or elimination of by-product formation is of immediate economic relevance in fermentation processes for industrial bioethanol production with the yeast Saccharomyces cerevisiae. Anaerobic cultures of wildtype S. cerevisiae require formation of glycerol to maintain the intracellular NADH/NAD(+) balance. Previously, functional expression of the Calvin-cycle enzymes ribulose-1,5-bisphosphate carboxylase (RuBisCO) and phosphoribulokinase (PRK) in S. cerevisiae was shown to enable reoxidation of NADH with CO2 as electron acceptor. In slow-growing cultures, this engineering strategy strongly decreased the glycerol yield, while increasing the ethanol yield on sugar. The present study explores engineering strategies to improve rates of growth and alcoholic fermentation in yeast strains that functionally express RuBisCO and PRK, while maximizing the positive impact on the ethanol yield. Results: Multi-copy integration of a bacterial-RuBisCO expression cassette was combined with expression of the Escherichia coli GroEL/GroES chaperones and expression of PRK from the anaerobically inducible DAN1 promoter. In anaerobic, glucose-grown bioreactor batch cultures, the resulting S. cerevisiae strain showed a 31% lower glycerol yield and a 31% lower specific growth rate than a non-engineered reference strain. Growth of the engineered strain in anaerobic, glucose-limited chemostat cultures revealed a negative correlation between its specific growth rate and the contribution of the Calvin-cycle enzymes to redox homeostasis. Additional deletion of GPD2, which encodes an isoenzyme of NAD(+)-dependent glycerol-3-phosphate dehydrogenase, combined with overexpression of the structural genes for enzymes of the non-oxidative pentose-phosphate pathway, yielded a CO2-reducing strain that grew at the same rate as a non-engineered reference strain in anaerobic bioreactor batch cultures, while exhibiting a 86% lower glycerol yield and a 15% higher ethanol yield. Conclusions: The metabolic engineering strategy presented here enables an almost complete elimination of glycerol production in anaerobic, glucose-grown batch cultures of S. cerevisiae, with an associated increase in ethanol yield, while retaining near wild-type growth rates and a capacity for glycerol formation under osmotic stress. Using current genome-editing techniques, the required genetic modifications can be introduced in one or a few transformations. Evaluation of this concept in industrial strains and conditions is therefore a realistic next step towards its implementation for improving the efficiency of first-and second-generation bioethanol production.

  • 11.
    Perez-Zabaleta, Mariel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Guevara-Martínez, Mónica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Gustavsson, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Quillaguamán, Jorge
    Larsson, Gen
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Comparison of engineered Escherichia coli AF1000 and BL21 strains for (R)-3-hydroxybutyrate production in fed-batch cultivation2019Inngår i: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 103, nr 14, s. 5627-5636Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accumulation of acetate is a limiting factor in recombinant production of (R)-3-hydroxybutyrate (3HB) by E. coli in high-cell-density processes. To alleviate this limitation, this study investigated two approaches: (i) Deletion of phosphotransacetylase (pta), pyruvate oxidase (poxB) and/or the isocitrate-lyase regulator (iclR), known to decrease acetate formation, on bioreactor cultivations designed to achieve high 3HB concentrations. (ii) Screening of different E. coli strain backgrounds (B, BL21, W, BW25113, MG1655, W3110 and AF1000) for their potential as low acetate-forming, 3HB-producing platforms. Deletion of pta and pta-poxB in the AF1000 strain background was to some extent successful in decreasing acetate formation, but also dramatically increased excretion of pyruvate and did not result in increased 3HB production in high-cell-density fed-batch cultivations. Screening of the different E. coli strains confirmed BL21 as a low acetate forming background. Despite low 3HB titers in low-cell density screening, 3HB-producing BL21 produced 5 times less acetic acid per mol of 3HB, which translated into a 2.3-fold increase in the final 3HB titer and a 3-fold higher volumetric 3HB productivity over 3HB-producing AF1000 strains in nitrogen-limited fed-batch cultivations. Consequently, the BL21 strain achieved the hitherto highest described volumetric productivity of 3HB (1.52 g L-1 h-1) and the highest 3HB concentration (16.3 g L-1) achieved by recombinant E. coli. Screening solely for 3HB titers in low-cell-density batch cultivations would not have identified the potential of this strain, reaffirming the importance of screening with the final production conditions in mind.

    Fulltekst (pdf)
    fulltext
  • 12.
    Sjöberg, Gustav
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Guevara-Martínez, Mónica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Gustavsson, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Metabolic engineering applications of the Escherichia coli bacterial artificial chromosomeManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In metabolic engineering and synthetic biology, the number of genes expressed to achieve better production and pathway regulation in each strain is steadily increasing. The method of choice for expression in Escherichia coli is usually one or several multi-copy plasmids. Meanwhile, the industry standard for long-term, robust production is chromosomal integration of the desired genes. Despite recent advances, genetic manipulation of the bacterial chromosome remains more time consuming than plasmid construction. To allow screening of different metabolic engineering strategies at a level closer to industry while maintaining the molecular-biology advantages of plasmid-based expression, we have investigated the single-copy bacterial artificial chromosome (BAC) as a development tool for metabolic engineering. Using (R)-3 hydroxybutyrate as a model product, we show that BAC can outperform multi-copy plasmids in terms of yield, productivity and specific growth rate, with respective increases of 12%, 18%, and 5%. We both show that gene expression by the BAC simplifies pathway optimization and that the phenotype of pathway expression from BAC is very close to that of chromosomal expression. From these results, we conclude that the BAC can provide a simple platform for performing pathway design and optimization. 

  • 13.
    Sjöberg, Gustav
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Guevara-Martínez, Mónica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. Univ Mayor San Simon, Ctr Biotechnol, Fac Sci & Technol, Cochabamba, Bolivia..
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Gustavsson, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Metabolic engineering applications of the Escherichia coli bacterial artificial chromosome2019Inngår i: Journal of Biotechnology, ISSN 0168-1656, E-ISSN 1873-4863, Vol. 305, s. 43-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In metabolic engineering and synthetic biology, the number of genes expressed to achieve better production and pathway regulation in each strain is steadily increasing. The method of choice for expression in Escherichia coli is usually one or several multi-copy plasmids. Meanwhile, the industry standard for long-term, robust production is chromosomal integration of the desired genes. Despite recent advances, genetic manipulation of the bacterial chromosome remains more time consuming than plasmid construction. To allow screening of different metabolic engineering strategies at a level closer to industry while maintaining the molecular-biology advantages of plasmid-based expression, we have investigated the single-copy bacterial artificial chromosome (BAC) as a development tool for metabolic engineering. Using (R)-3-hydroxybutyrate as a model product, we show that BAC can outperform multi-copy plasmids in terms of yield, productivity and specific growth rate, with respective increases of 12%, 18%, and 5%. We both show that gene expression by the BAC simplifies pathway optimization and that the phenotype of pathway expression from BAC is very close to that of chromosomal expression. From these results, we conclude that the BAC can provide a simple platform for performing pathway design and optimization.

  • 14.
    Sjöberg, Gustav
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Gustavsson, Martin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Characterization of volatile fatty acid utilization in Escherichia coli aiming for robust valorisation of food residuesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Valorisation of food residues would greatly benefit from development of robust processes that create added value compared to current feed- and biogas applications. Recent advances in membrane-bioreactor-based open mixed microbial cultures, enable robust conversion of fluctuating streams of food residues to a mixture of volatile fatty acids (VFAs). In this study, such a mixed stream of VFAs was investigated as a substrate for Escherichia coli, a well studied organism suitable for application in further conversion of the acids into compounds of higher value, and/or that are easier to separate from the aqueous medium. E. coli was cultured in batch on a VFA-rich anaerobic digest of food residues, tolerating up to 40 mM of total VFAs without any reduction in growth rate. In carbon-limited chemostats of E. coli W3110 ΔFadR on a simulated VFA mixture, the straight chain VFAs (C2-C6) in the mixture were readily consumed simultaneously. At the dilution rate 0.1 h-1, mainly acetic-, propionic- and caproic acid were consumed, while consumption of all the provided acids were observed at 0.05 h-1. Interestingly, also the branched isovaleric acid was consumed through a hitherto unknown mechanism. In total, up to 80% of the carbon supplied from VFAs was consumed by the cells, and approximately 2.7% was excreted as nucleotide precursors in the medium. These results suggest that VFAs derived from food residues are a promising substrate for E. coli.

  • 15.
    Valk, Laura C.
    et al.
    Delft Univ Technol, Dept Biotechnol, Delft, Netherlands..
    Frank, Jeroen
    Radboud Univ Nijmegen, Soehngen Inst Anaerob Microbiol, Nijmegen, Netherlands..
    de la Torre-Cortes, Pilar
    Delft Univ Technol, Dept Biotechnol, Delft, Netherlands..
    van 't Hof, Max
    Delft Univ Technol, Dept Biotechnol, Delft, Netherlands..
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. Delft Univ Technol, Dept Biotechnol, Delft, Netherlands..
    Pronk, Jack T.
    Delft Univ Technol, Dept Biotechnol, Delft, Netherlands..
    van Loosdrecht, Mark C. M.
    Delft Univ Technol, Dept Biotechnol, Delft, Netherlands..
    Galacturonate Metabolism in Anaerobic Chemostat Enrichment Cultures: Combined Fermentation and Acetogenesis by the Dominant sp nov "Candidatus Galacturonibacter soehngenii"2018Inngår i: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 84, nr 18, artikkel-id UNSP e01370-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Agricultural residues such as sugar beet pulp and citrus peel are rich in pectin, which contains galacturonic acid as a main monomer. Pectin-rich residues are underexploited as feedstocks for production of bulk chemicals or biofuels. The anaerobic, fermentative conversion of D-galacturonate in anaerobic chemostat enrichment cultures provides valuable information toward valorization of these pectin-rich feedstocks. Replicate anaerobic chemostat enrichments, with D-galacturonate as the sole limiting carbon source and inoculum from cow rumen content and rotting orange peels, yielded stable microbial communities, which were dominated by a novel Lachnospiraceae species, for which the name "Candidatus Galacturonibacter soehngenii" was proposed. Acetate was the dominant catabolic product, with formate and H-2 as coproducts. The observed molar ratio of acetate and the combined amounts of H-2 and formate deviated significantly from 1, which suggested that some of the hydrogen and CO2 formed during D-galacturonate fermentation was converted into acetate via the Wood-Ljungdahl acetogenesis pathway. Indeed, metagenomic analysis of the enrichment cultures indicated that the genome of "Candidatus G. soehngenii" encoded enzymes of the adapted Entner-Doudoroff pathway for D-galacturonate metabolism as well as enzymes of the Wood-Ljungdahl pathway. The simultaneous operation of these pathways may provide a selective advantage under D-galacturonate-limited conditions by enabling a higher specific ATP production rate and lower residual D-galacturonate concentration than would be possible with a strictly fermentative metabolism of this carbon and energy source. IMPORTANCE This study on D-galacturonate metabolism by open, mixed-culture enrichments under anaerobic, D-galacturonate-limited chemostat conditions shows a stable and efficient fermentation of D-galacturonate into acetate as the dominant organic fermentation product. This fermentation stoichiometry and population analyses provide a valuable baseline for interpretation of the conversion of pectin-rich agricultural feedstocks by mixed microbial cultures. Moreover, the results of this study provide a reference for studies on the microbial metabolism of D-galacturonate under different cultivation regimes.

  • 16.
    Verhoeven, Maarten D.
    et al.
    Delft Univ Technol, Dept Biotechnol, Van der Maasweg 9, NL-2629 HZ Delft, Netherlands..
    Bracher, Jasmine M.
    Delft Univ Technol, Dept Biotechnol, Van der Maasweg 9, NL-2629 HZ Delft, Netherlands..
    Nijland, Jeroen G.
    Univ Groningen, Groningen Biomol Sci & Biotechnol Inst GBB, Dept Mol Microbiol, Nijenborgh 7, NL-9747 AG Groningen, Netherlands..
    Bouwknegt, Jonna
    Delft Univ Technol, Dept Biotechnol, Van der Maasweg 9, NL-2629 HZ Delft, Netherlands..
    Daran, Jean-Marc G.
    Delft Univ Technol, Dept Biotechnol, Van der Maasweg 9, NL-2629 HZ Delft, Netherlands..
    Driessen, Arnold J. M.
    Univ Groningen, Groningen Biomol Sci & Biotechnol Inst GBB, Dept Mol Microbiol, Nijenborgh 7, NL-9747 AG Groningen, Netherlands..
    van Maris, Antonius J. A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. Delft Univ Technol, Dept Biotechnol, Van der Maasweg 9, NL-2629 HZ Delft, Netherland.
    Pronk, Jack T.
    Delft Univ Technol, Dept Biotechnol, Van der Maasweg 9, NL-2629 HZ Delft, Netherlands..
    Laboratory evolution of a glucose-phosphorylation-deficient, arabinose-fermenting S. cerevisiae strain reveals mutations in GAL2 that enable glucose-insensitive L-arabinose uptake2018Inngår i: FEMS yeast research (Print), ISSN 1567-1356, E-ISSN 1567-1364, Vol. 18, nr 6, artikkel-id foy062Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cas9-assisted genome editing was used to construct an engineered glucose-phosphorylation-negative S. cerevisiae strain, expressing the Lactobacillus plantarum L-arabinose pathway and the Penicillium chrysogenum transporter PcAraT. This strain, which showed a growth rate of 0.26 h(-1) on L-arabinose in aerobic batch cultures, was subsequently evolved for anaerobic growth on L-arabinose in the presence of D-glucose and D-xylose. In four strains isolated from two independent evolution experiments the galactose-transporter gene GAL2 had been duplicated, with all alleles encoding Gal2(N376T) or Gal(2N376I) substitutions. In one strain, a single GAL2 allele additionally encoded a Gal2(T89I) substitution, which was subsequently also detected in the independently evolved strain IMS0010. In C-14-sugar-transport assays, Gal2(N376S), Gal2(N376T) and Gal(2N376I) substitutions showed a much lower glucose sensitivity of L-arabinose transport and a much higher Km for D-glucose transport than wild-type Gal2. Introduction of the Gal2(N376I) substitution in a non-evolved strain enabled growth on L-arabinose in the presence of D-glucose. Gal2(N376T), T89I and Gal2(T89I) variants showed a lower K-m for L-arabinose and a higher K-m for D-glucose than wild-type Gal2, while reverting Gal2(N376T), T89I to Gal2(N376) in an evolved strain negatively affected anaerobic growth on L-arabinose. This study indicates that optimal conversion of mixed-sugar feedstocks may require complex 'transporter landscapes', consisting of sugar transporters with complementary kinetic and regulatory properties.

  • 17. Verhoeven, Maarten D.
    et al.
    Lee, Misun
    Kamoen, Lycka
    van den Broek, Marcel
    Janssen, Dick B.
    Daran, Jean-Marc G.
    van Maris, Antonius J. A.
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi. Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands; .
    Pronk, Jack T.
    Mutations in PMR1 stimulate xylose isomerase activity and anaerobic growth on xylose of engineered Saccharomyces cerevisiae by influencing manganese homeostasis2017Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 46155Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Combined overexpression of xylulokinase, pentose-phosphate-pathway enzymes and a heterologous xylose isomerase (XI) is required but insufficient for anaerobic growth of Saccharomyces cerevisiae on d-xylose. Single-step Cas9-assisted implementation of these modifications yielded a yeast strain expressing Piromyces XI that showed fast aerobic growth on d-xylose. However, anaerobic growth required a 12-day adaptation period. Xylose-adapted cultures carried mutations in PMR1, encoding a Golgi Ca2+/Mn2+ ATPase. Deleting PMR1 in the parental XI-expressing strain enabled instantaneous anaerobic growth on d-xylose. In pmr1 strains, intracellular Mn2+ concentrations were much higher than in the parental strain. XI activity assays in cell extracts and reconstitution experiments with purified XI apoenzyme showed superior enzyme kinetics with Mn2+ relative to other divalent metal ions. This study indicates engineering of metal homeostasis as a relevant approach for optimization of metabolic pathways involving metal-dependent enzymes. Specifically, it identifies metal interactions of heterologous XIs as an underexplored aspect of engineering xylose metabolism in yeast.

1 - 17 of 17
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf