| 1. |
- Pereira, Rui, 1986, et al.
(författare)
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Metabolic Engineering of Yeast
- 2021
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Ingår i: Metabolic Engineering: Concepts and Applications: Volume 13a and 13b. - : Wiley. ; 13, s. 689-733
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter focuses on a few examples that can serve as illustrations of how powerful yeast metabolic engineering stands today. Yeast, especially S. cerevisiae, plays an essential role in bioethanol production. Rapid ethanol production by yeast cells makes the fermentation process less susceptible to contamination. Higher alcohols are attractive due to some advantages compared with bioethanol, such as higher energy density, better blending into gasoline, higher octane value, lower hygroscopicity, and less corrosivity. The ethanol production process in the industry is mainly achieved through simultaneous saccharification and fermentation. Production of insulin, by volume the largest pharmaceutical protein produced, has paved the way for a wide use of S. cerevisiae for production of recombinant proteins. Virus like particles are proteins of virus capsid, which are produced by recombinant DNA technology and are important for the development of viral vaccines as they can self-assemble and display similar immunogenic properties as native viruses.
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| 2. |
- LaRue, Jerry, et al.
(författare)
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Symmetry-resolved CO desorption and oxidation dynamics on O/Ru(0001) probed at the C K-edge by ultrafast x-ray spectroscopy
- 2022
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 157:16
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Tidskriftsartikel (refereegranskat)abstract
- We report on carbon monoxide desorption and oxidation induced by 400 nm femtosecond laser excitation on the O/Ru(0001) surface probed by time-resolved x-ray absorption spectroscopy (TR-XAS) at the carbon K-edge. The experiments were performed under constant background pressures of CO (6 × 10−8 Torr) and O2 (3 × 10−8 Torr). Under these conditions, we detect two transient CO species with narrow 2π* peaks, suggesting little 2π* interaction with the surface. Based on polarization measurements, we find that these two species have opposing orientations: (1) CO favoring a more perpendicular orientation and (2) CO favoring a more parallel orientation with respect to the surface. We also directly detect gas-phase CO2 using a mass spectrometer and observe weak signatures of bent adsorbed CO2 at slightly higher x-ray energies than the 2π* region. These results are compared to previously reported TR-XAS results at the O K-edge, where the CO background pressure was three times lower (2 × 10−8 Torr) while maintaining the same O2 pressure. At the lower CO pressure, in the CO 2π* region, we observed adsorbed CO and a distribution of OC–O bond lengths close to the CO oxidation transition state, with little indication of gas-like CO. The shift toward “gas-like” CO species may be explained by the higher CO exposure, which blocks O adsorption, decreasing O coverage and increasing CO coverage. These effects decrease the CO desorption barrier through dipole–dipole interaction while simultaneously increasing the CO oxidation barrier.
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| 3. |
- Liu, Quanli, 1988, et al.
(författare)
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Current state of aromatics production using yeast: achievements and challenges
- 2020
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Ingår i: Current Opinion in Biotechnology. - : Elsevier BV. - 0958-1669 .- 1879-0429. ; 65, s. 65-74
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Forskningsöversikt (refereegranskat)abstract
- Aromatics find a range of applications in the chemical, food, cosmetic and pharmaceutical industries. While production of aromatics on the current market heavily relies on petroleum-derived chemical processes or direct extraction from plants, there is an increasing demand for establishing new renewable and sustainable sources of aromatics. To this end, microbial cell factories-mediated bioproduction using abundant feedstocks comprises a highly promising alternative to aromatics production. In this review, we provide the recent development of de novo biosynthesis of aromatics derived from the shikimate pathway in yeasts, including the model Saccharomyces cerevisiae as well as other non-conventional species. Moreover, we discuss how evolved metabolic engineering tools and strategies contribute to the construction and optimization of aromatics cell factories.
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| 4. |
- Liu, Quanli, 1988, et al.
(författare)
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De novo biosynthesis of bioactive isoflavonoids by engineered yeast cell factories
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Isoflavonoids comprise a class of plant natural products with great nutraceutical, pharmaceutical and agricultural significance. Their low abundance in nature and structural complexity however hampers access to these phytochemicals through traditional crop-based manufacturing or chemical synthesis. Microbial bioproduction therefore represents an attractive alternative. Here, we engineer the metabolism of Saccharomyces cerevisiae to become a platform for efficient production of daidzein, a core chemical scaffold for isoflavonoid biosynthesis, and demonstrate its application towards producing bioactive glucosides from glucose, following the screening-reconstruction-application engineering framework. First, we rebuild daidzein biosynthesis in yeast and its production is then improved by 94-fold through screening biosynthetic enzymes, identifying rate-limiting steps, implementing dynamic control, engineering substrate trafficking and fine-tuning competing metabolic processes. The optimized strain produces up to 85.4 mg L−1 of daidzein and introducing plant glycosyltransferases in this strain results in production of bioactive puerarin (72.8 mg L−1) and daidzin (73.2 mg L−1). Our work provides a promising step towards developing synthetic yeast cell factories for de novo biosynthesis of value-added isoflavonoids and the multi-phased framework may be extended to engineer pathways of complex natural products in other microbial hosts.
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| 5. |
- Liu, Yi, 1986, et al.
(författare)
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Engineering yeast phospholipid metabolism for de novo oleoylethanolamide production
- 2020
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Ingår i: Nature Chemical Biology. - : Springer Science and Business Media LLC. - 1552-4450 .- 1552-4469. ; 16:2, s. 197-205
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Tidskriftsartikel (refereegranskat)abstract
- Phospholipids, the most abundant membrane lipid components, are crucial in maintaining membrane structures and homeostasis for biofunctions. As a structurally diverse and tightly regulated system involved in multiple organelles, phospholipid metabolism is complicated to manipulate. Thus, repurposing phospholipids for lipid-derived chemical production remains unexplored. Herein, we develop a Saccharomyces cerevisiae platform for de novo production of oleoylethanolamide, a phospholipid derivative with promising pharmacological applications in ameliorating lipid dysfunction and neurobehavioral symptoms. Through deregulation of phospholipid metabolism, screening of biosynthetic enzymes, engineering of subcellular trafficking and process optimization, we could produce oleoylethanolamide at a titer of 8,115.7 µg l−1 and a yield on glucose of 405.8 µg g−1. Our work provides a proof-of-concept study for systemically repurposing phospholipid metabolism for conversion towards value-added biological chemicals, and this multi-faceted framework may shed light on tailoring phospholipid metabolism in other microbial hosts.
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| 6. |
- Schreck, Simon, et al.
(författare)
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Atom-Specific Probing of Electron Dynamics in an Atomic Adsorbate by Time-Resolved X-Ray Spectroscopy
- 2022
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 129:27
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Tidskriftsartikel (refereegranskat)abstract
- The electronic excitation occurring on adsorbates at ultrafast timescales from optical lasers that initiate surface chemical reactions is still an open question. Here, we report the ultrafast temporal evolution of x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) of a simple well-known adsorbate prototype system, namely carbon (C) atoms adsorbed on a nickel [Ni(100)] surface, following intense laser optical pumping at 400 nm. We observe ultrafast (∼100 fs) changes in both XAS and XES showing clear signatures of the formation of a hot electron-hole pair distribution on the adsorbate. This is followed by slower changes on a few picoseconds timescale, shown to be consistent with thermalization of the complete C/Ni system. Density functional theory spectrum simulations support this interpretation.
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| 7. |
- Li, Yi, 1985, et al.
(författare)
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Bayesian Outlier Detection in Location-aware Wireless Networks
- 2011
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Ingår i: Workshop on Positioning, Navigation and Communication. - 9781457704505 ; , s. 39-44
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Konferensbidrag (refereegranskat)abstract
- Location-aware networks are a rapidly growing area of research witha wide range of applications. The accuracy of localization dependson the reliability of the information exchanged between devices inthe network. In practice, devices may fail or maliciously inject falseposition information into the network. This paper aims to design andtest algorithms to verify the location consistency in wireless networks.We propose a new method based on factor graphs. This method is flexible,easily extendible to cooperative networks, and leads to significantperformance improvements compared to existing techniques that arebased on linear programming.
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| 8. |
- Liu, Yi, 1986, et al.
(författare)
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Recent trends in metabolic engineering of microbial chemical factories
- 2019
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Ingår i: Current Opinion in Biotechnology. - : Elsevier BV. - 0958-1669 .- 1879-0429. ; 60, s. 188-197
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Forskningsöversikt (refereegranskat)abstract
- Microbe-mediated chemical production can replace traditional fossil-dependent production and hereby ensure sustainable production of chemicals that are important for our society. Significant success in economical chemical bioproduction has been accomplished by improving the cellular properties of microbial cells through metabolic engineering. The emergence of new techniques and strategies has led to a significant reduction in the turnaround time in the classic design-build-test-learn (DBTL) cycle in metabolic engineering. Here, we summarize the recent achievements and trends in microbial production of chemicals, with a focus on biofuels and high-value natural compounds. In addition, we offer perspectives on the challenges and opportunities for the successful establishment of future microbial chemical factories.
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| 9. |
- Massel, Felix, 1986-, et al.
(författare)
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The role of anionic processes in Li1−xNi0.44Mn1.56O4 studied by resonant inelastic X-ray scattering
- 2023
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Ingår i: Energy Advances. - : RSC Publishing. - 2753-1457. ; 2:3, s. 375-384
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the first lithiation cycle of the positive electrode material Li1−xNi0.44Mn1.56O4 (LNMO) using soft X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) at the transition metal L- and oxygen K-edges. Our XAS results show that charge compensation in LNMO takes place mostly within the Ni–O bonds, which is consistent with previous similar studies. O K- and Ni L-RIXS reveals how the holes that are created by removal of electrons during delithiation are distributed between the Ni- and O-ions. Non-trivial anionic activity is revealed by O K-RIXS features such as the appearance of low-energy intra-band excitations and re-hybridization with Ni 3d-states forming a new intense band close to the top of the oxygen valence band. At the same time, Ni L-RIXS compares more favorably with covalently than with ionically bonded Ni-oxide based compounds. Thus, a picture emerges where delithiation leads to a gradual transition of the ground state of LNMO from Ni 3d8 to one with non-negligible amounts of ligand holes, i.e. Ni 3d8−x 2−x (0 < x < 2, where stands for a ligand hole) instead of a highly ionic state e.g. Ni 3d6. Our observations highlight the importance of studying the anionic character of redox processes in lithium ion batteries.
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