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Qiu Y, Liu W, Wu M, Bao H, Sun X, Dou Q, Jia H, Liu W, Shen Y. Construction of an alternative NADPH regeneration pathway improves ethanol production in Saccharomyces cerevisiae with xylose metabolic pathway. Synth Syst Biotechnol 2024; 9:269-276. [PMID: 38469586 PMCID: PMC10926300 DOI: 10.1016/j.synbio.2024.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/05/2024] [Accepted: 02/19/2024] [Indexed: 03/13/2024] Open
Abstract
Full conversion of glucose and xylose from lignocellulosic hydrolysates is required for obtaining a high ethanol yield. However, glucose and xylose share flux in the pentose phosphate pathway (PPP) and glycolysis pathway (EMP), with glucose having a competitive advantage in the shared metabolic pathways. In this work, we knocked down ZWF1 to preclude glucose from entering the PPP. This reduced the [NADPH] level and disturbed growth on both glucose or xylose, confirming that the oxidative PPP, which begins with Zwf1p and ultimately leads to CO2 production, is the primary source of NADPH in both glucose and xylose. Upon glucose depletion, gluconeogenesis is necessary to generate glucose-6-phosphate, the substrate of Zwf1p. We re-established the NADPH regeneration pathway by replacing the endogenous NAD+-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene TDH3 with heterogenous NADP + -GAPDH genes GDH, gapB, and GDP1. Among the resulting strains, the strain BZP1 (zwf1Δ, tdh3::GDP1) exhibited a similar xylose consumption rate before glucose depletion, but a 1.6-fold increased xylose consumption rate following glucose depletion compared to the original strain BSGX001, and the ethanol yield for total consumed sugars of BZP1 was 13.5% higher than BSGX001. This suggested that using the EMP instead of PPP to generate NADPH reduces the wasteful metabolic cycle and excess CO2 release from oxidative PPP. Furthermore, we used a copper-repressing promoter to modulate the expression of ZWF1 and optimize the timing of turning off the ZWF1, therefore, to determine the competitive equilibrium between glucose-xylose co-metabolism. This strategy allowed fast growth in the early stage of fermentation and low waste in the following stages of fermentation.
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Affiliation(s)
- Yali Qiu
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, China
| | - Wei Liu
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, China
| | - Meiling Wu
- Advanced Medical Research Institute, Shandong University, Jinan, 250012, China
| | - Haodong Bao
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, China
| | - Xinhua Sun
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, China
| | - Qin Dou
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, China
| | - Hongying Jia
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, China
| | - Weifeng Liu
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, China
| | - Yu Shen
- State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, China
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Barros KO, Mader M, Krause DJ, Pangilinan J, Andreopoulos B, Lipzen A, Mondo SJ, Grigoriev IV, Rosa CA, Sato TK, Hittinger CT. Oxygenation influences xylose fermentation and gene expression in the yeast genera Spathaspora and Scheffersomyces. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2024; 17:20. [PMID: 38321504 PMCID: PMC10848558 DOI: 10.1186/s13068-024-02467-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 01/28/2024] [Indexed: 02/08/2024]
Abstract
BACKGROUND Cost-effective production of biofuels from lignocellulose requires the fermentation of D-xylose. Many yeast species within and closely related to the genera Spathaspora and Scheffersomyces (both of the order Serinales) natively assimilate and ferment xylose. Other species consume xylose inefficiently, leading to extracellular accumulation of xylitol. Xylitol excretion is thought to be due to the different cofactor requirements of the first two steps of xylose metabolism. Xylose reductase (XR) generally uses NADPH to reduce xylose to xylitol, while xylitol dehydrogenase (XDH) generally uses NAD+ to oxidize xylitol to xylulose, creating an imbalanced redox pathway. This imbalance is thought to be particularly consequential in hypoxic or anoxic environments. RESULTS We screened the growth of xylose-fermenting yeast species in high and moderate aeration and identified both ethanol producers and xylitol producers. Selected species were further characterized for their XR and XDH cofactor preferences by enzyme assays and gene expression patterns by RNA-Seq. Our data revealed that xylose metabolism is more redox balanced in some species, but it is strongly affected by oxygen levels. Under high aeration, most species switched from ethanol production to xylitol accumulation, despite the availability of ample oxygen to accept electrons from NADH. This switch was followed by decreases in enzyme activity and the expression of genes related to xylose metabolism, suggesting that bottlenecks in xylose fermentation are not always due to cofactor preferences. Finally, we expressed XYL genes from multiple Scheffersomyces species in a strain of Saccharomyces cerevisiae. Recombinant S. cerevisiae expressing XYL1 from Scheffersomyces xylosifermentans, which encodes an XR without a cofactor preference, showed improved anaerobic growth on xylose as the primary carbon source compared to S. cerevisiae strain expressing XYL genes from Scheffersomyces stipitis. CONCLUSION Collectively, our data do not support the hypothesis that xylitol accumulation occurs primarily due to differences in cofactor preferences between xylose reductase and xylitol dehydrogenase; instead, gene expression plays a major role in response to oxygen levels. We have also identified the yeast Sc. xylosifermentans as a potential source for genes that can be engineered into S. cerevisiae to improve xylose fermentation and biofuel production.
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Affiliation(s)
- Katharina O Barros
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, USA
- Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Center for Genomic Science Innovation, University of Wisconsin-Madison, Madison, WI, USA
- Departamento de Microbiologia, ICB, C.P. 486, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Megan Mader
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, USA
| | - David J Krause
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, USA
- Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Center for Genomic Science Innovation, University of Wisconsin-Madison, Madison, WI, USA
| | - Jasmyn Pangilinan
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Bill Andreopoulos
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Computer Science, San Jose State University, One Washington Square, San Jose, CA, USA
| | - Anna Lipzen
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Stephen J Mondo
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Agricultural Biology, Colorado State University, Fort Collins, CO, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Igor V Grigoriev
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Plant and Microbial Department, University of California Berkeley, Berkeley, CA, USA
| | - Carlos A Rosa
- Departamento de Microbiologia, ICB, C.P. 486, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Trey K Sato
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, USA.
| | - Chris Todd Hittinger
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, USA.
- Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Center for Genomic Science Innovation, University of Wisconsin-Madison, Madison, WI, USA.
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Xu B, Zhang W, Zhao E, Hong J, Chen X, Wei Z, Li X. Unveiling malic acid biorefinery: Comprehensive insights into feedstocks, microbial strains, and metabolic pathways. BIORESOURCE TECHNOLOGY 2024; 394:130265. [PMID: 38160850 DOI: 10.1016/j.biortech.2023.130265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 12/24/2023] [Accepted: 12/25/2023] [Indexed: 01/03/2024]
Abstract
The over-reliance on fossil fuels and resultant environmental issues necessitate sustainable alternatives. Microbial fermentation of biomass for malic acid production offers a viable, eco-friendly solution, enhancing resource efficiency and minimizing ecological damage. This review covers three core aspects of malic acid biorefining: feedstocks, microbial strains, and metabolic pathways. It emphasizes the significance of utilizing biomass sugars, including the co-fermentation of different sugar types to improve feedstock efficiency. The review discusses microbial strains for malic acid fermentation, addressing challenges related to by-products from biomass breakdown and strategies for overcoming them. It delves into the crucial pathways and enzymes for malic acid production, outlining methods to optimize its metabolism, focusing on enzyme regulation, energy balance, and yield enhancement. These insights contribute to advancing the field of consolidated bioprocessing in malic acid biorefining.
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Affiliation(s)
- Boyang Xu
- Anhui Fermented Food Engineering Research Center, School of Food and Biological Engineering, Hefei University of Technology, Hefei City 230009, Anhui Province, PR China
| | - Wangwei Zhang
- Anhui Fermented Food Engineering Research Center, School of Food and Biological Engineering, Hefei University of Technology, Hefei City 230009, Anhui Province, PR China
| | - Eryong Zhao
- Anhui Fermented Food Engineering Research Center, School of Food and Biological Engineering, Hefei University of Technology, Hefei City 230009, Anhui Province, PR China
| | - Jiong Hong
- School of Life Sciences, University of Science and Technology of China, Hefei City 230026, Anhui Province, PR China
| | - Xiangsong Chen
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei City 230031, Anhui Province, PR China
| | - Zhaojun Wei
- School of Biological Sciences and Engineering, North Minzu University, Yinchuan City 750030, Ningxia Hui Autonomous Region, PR China.
| | - Xingjiang Li
- Anhui Fermented Food Engineering Research Center, School of Food and Biological Engineering, Hefei University of Technology, Hefei City 230009, Anhui Province, PR China.
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Bolzico BC, Racca S, Khawam JN, Leonardi RJ, Tomassi AH, Benzzo MT, Comelli RN. Exploring xylose metabolism in non-conventional yeasts: kinetic characterization and product accumulation under different aeration conditions. J Ind Microbiol Biotechnol 2024; 51:kuae023. [PMID: 38936832 PMCID: PMC11247345 DOI: 10.1093/jimb/kuae023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 06/26/2024] [Indexed: 06/29/2024]
Abstract
d-Xylose is a metabolizable carbon source for several non-Saccharomyces species, but not for native strains of S. cerevisiae. For the potential application of xylose-assimilating yeasts in biotechnological processes, a deeper understanding of pentose catabolism is needed. This work aimed to investigate the traits behind xylose utilization in diverse yeast species. The performance of 9 selected xylose-metabolizing yeast strains was evaluated and compared across 3 oxygenation conditions. Oxygenation diversely impacted growth, xylose consumption, and product accumulation. Xylose utilization by ethanol-producing species such as Spathaspora passalidarum and Scheffersomyces stipitis was less affected by oxygen restriction compared with other xylitol-accumulating species such as Meyerozyma guilliermondii, Naganishia liquefaciens, and Yamadazyma sp., for which increased aeration stimulated xylose assimilation considerably. Spathaspora passalidarum exhibited superior conversion of xylose to ethanol and showed the fastest growth and xylose consumption in all 3 conditions. By performing assays under identical conditions for all selected yeasts, we minimize bias in comparisons, providing valuable insight into xylose metabolism and facilitating the development of robust bioprocesses. ONE-SENTENCE SUMMARY This work aims to expand the knowledge of xylose utilization in different yeast species, with a focus on how oxygenation impacts xylose assimilation.
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Affiliation(s)
- Bruna C Bolzico
- Grupo de Procesos Biológicos en Ingeniería Ambiental (GPBIA), Facultad de Ingeniería y Ciencias Hídricas (FICH), Universidad Nacional del Litoral (UNL), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
| | - Sofia Racca
- Grupo de Procesos Biológicos en Ingeniería Ambiental (GPBIA), Facultad de Ingeniería y Ciencias Hídricas (FICH), Universidad Nacional del Litoral (UNL), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
| | - Jorge N Khawam
- Grupo de Procesos Biológicos en Ingeniería Ambiental (GPBIA), Facultad de Ingeniería y Ciencias Hídricas (FICH), Universidad Nacional del Litoral (UNL), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
| | - Rodrigo J Leonardi
- Grupo de Procesos Biológicos en Ingeniería Ambiental (GPBIA), Facultad de Ingeniería y Ciencias Hídricas (FICH), Universidad Nacional del Litoral (UNL), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
| | - Ariel H Tomassi
- Grupo de Procesos Biológicos en Ingeniería Ambiental (GPBIA), Facultad de Ingeniería y Ciencias Hídricas (FICH), Universidad Nacional del Litoral (UNL), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
| | - Maria T Benzzo
- Grupo de Procesos Biológicos en Ingeniería Ambiental (GPBIA), Facultad de Ingeniería y Ciencias Hídricas (FICH), Universidad Nacional del Litoral (UNL), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
| | - Raul N Comelli
- Grupo de Procesos Biológicos en Ingeniería Ambiental (GPBIA), Facultad de Ingeniería y Ciencias Hídricas (FICH), Universidad Nacional del Litoral (UNL), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Universitaria, CC 242 Paraje El Pozo, Santa Fe 3000, Argentina
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Persson VC, Perruca Foncillas R, Anderes TR, Ginestet C, Gorwa-Grauslund M. Impact of xylose epimerase on sugar assimilation and sensing in recombinant Saccharomyces cerevisiae carrying different xylose-utilization pathways. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:168. [PMID: 37932829 PMCID: PMC10629123 DOI: 10.1186/s13068-023-02422-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 10/28/2023] [Indexed: 11/08/2023]
Abstract
BACKGROUND Over the last decades, many strategies to procure and improve xylose consumption in Saccharomyces cerevisiae have been reported. This includes the introduction of efficient xylose-assimilating enzymes, the improvement of xylose transport, or the alteration of the sugar signaling response. However, different strain backgrounds are often used, making it difficult to determine if the findings are transferrable both to other xylose-consuming strains and to other xylose-assimilation pathways. For example, the influence of anomerization rates between α- and β-xylopyranose in pathway optimization and sugar sensing is relatively unexplored. RESULTS In this study, we tested the effect of expressing a xylose epimerase in S. cerevisiae strains carrying different xylose-consuming routes. First, XIs originating from three different species in isogenic S. cerevisiae strains were tested and the XI from Lachnoclostridium phytofermentans was found to give the best performance. The benefit of increasing the anomerization rate of xylose by adding a xylose epimerase to the XI strains was confirmed, as higher biomass formation and faster xylose consumption were obtained. However, the impact of xylose epimerase was XI-dependent, indicating that anomer preference may differ from enzyme to enzyme. The addition of the xylose epimerase in xylose reductase/xylitol dehydrogenase (XR/XDH)-carrying strains gave no improvement in xylose assimilation, suggesting that the XR from Spathaspora passalidarum had no anomer preference, in contrast to other reported XRs. The reduction in accumulated xylitol that was observed when the xylose epimerase was added may be associated with the upregulation of genes encoding endogenous aldose reductases which could be affected by the anomerization rate. Finally, xylose epimerase addition did not affect the sugar signaling, whereas the type of xylose pathway (XI vs. XR/XDH) did. CONCLUSIONS Although xylose anomer specificity is often overlooked, the addition of xylose epimerase should be considered as a key engineering step, especially when using the best-performing XI enzyme from L. phytofermentans. Additional research into the binding mechanism of xylose is needed to elucidate the enzyme-specific effect and decrease in xylitol accumulation. Finally, the differences in sugar signaling responses between XI and XR/XDH strains indicate that either the redox balance or the growth rate impacts the SNF1/Mig1p sensing pathway.
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Affiliation(s)
- Viktor C Persson
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | | | - Tegan R Anderes
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Clément Ginestet
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Marie Gorwa-Grauslund
- Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden.
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Zheng X, Du P, Gao K, Du Y, Cairns TC, Ni X, Chen M, Zhao W, Ma X, Yang H, Zheng P, Sun J. Genome-wide transcription landscape of citric acid producing Aspergillus niger in response to glucose gradient. Front Bioeng Biotechnol 2023; 11:1282314. [PMID: 37941722 PMCID: PMC10628723 DOI: 10.3389/fbioe.2023.1282314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 10/13/2023] [Indexed: 11/10/2023] Open
Abstract
Aspergillus niger is the main industrial workhorse for global citric acid production. This fungus has complex sensing and signaling pathways to respond to environmental nutrient fluctuations. As the preferred primary carbon source, glucose also acts as a critical signal to trigger intracellular bioprocesses. Currently, however, there is still a knowledge gap in systems-level understanding of metabolic and cellular responses to this vital carbon source. In this study, we determined genome-wide transcriptional changes of citric acid-producing Aspergillus niger in response to external glucose gradient. It demonstrated that external glucose fluctuation led to transcriptional reprogramming of many genes encoding proteins involved in fundamental cellular process, including ribosomal biogenesis, carbon transport and catabolism, glucose sensing and signaling. The major glucose catabolism repressor creA maintained a stable expression independent of external glucose, while creB and creD showed significant downregulation and upregulation by the glucose increase. Notably, several high-affinity glucose transporters encoding genes, including mstA, were greatly upregulated when glucose was depleted, while the expression of low-affinity glucose transporter mstC was glucose-independent, which showed clear concordance with their protein levels detected by in situ fluorescence labeling assay. In addition, we also observed that the citric acid exporter cexA was observed to be transcriptionally regulated by glucose availability, which was correlated with extracellular citric acid secretion. These discoveries not only deepen our understanding of the transcriptional regulation of glucose but also shed new light on the adaptive evolutionary mechanism of citric acid production of A. niger.
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Affiliation(s)
- Xiaomei Zheng
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Peng Du
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Kaiyue Gao
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Yimou Du
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Timothy C. Cairns
- Chair of Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Xiaomeng Ni
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
| | - Meiling Chen
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- School of Biotechnology, East China University of Science and Technology, Shanghai, China
| | - Wei Zhao
- Shan Dong Fuyang Biological Technology Co., Ltd., Dezhou, China
| | - Xinrong Ma
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
| | - Hongjiang Yang
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
| | - Ping Zheng
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jibin Sun
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin, China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
- University of Chinese Academy of Sciences, Beijing, China
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7
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Attfield PV. Crucial aspects of metabolism and cell biology relating to industrial production and processing of Saccharomyces biomass. Crit Rev Biotechnol 2023; 43:920-937. [PMID: 35731243 DOI: 10.1080/07388551.2022.2072268] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/27/2022] [Accepted: 04/21/2022] [Indexed: 12/16/2022]
Abstract
The multitude of applications to which Saccharomyces spp. are put makes these yeasts the most prolific of industrial microorganisms. This review considers biological aspects pertaining to the manufacture of industrial yeast biomass. It is proposed that the production of yeast biomass can be considered in two distinct but interdependent phases. Firstly, there is a cell replication phase that involves reproduction of cells by their transitions through multiple budding and metabolic cycles. Secondly, there needs to be a cell conditioning phase that enables the accrued biomass to withstand the physicochemical challenges associated with downstream processing and storage. The production of yeast biomass is not simply a case of providing sugar, nutrients, and other growth conditions to enable multiple budding cycles to occur. In the latter stages of culturing, it is important that all cells are induced to complete their current budding cycle and subsequently enter into a quiescent state engendering robustness. Both the cell replication and conditioning phases need to be optimized and considered in concert to ensure good biomass production economics, and optimum performance of industrial yeasts in food and fermentation applications. Key features of metabolism and cell biology affecting replication and conditioning of industrial Saccharomyces are presented. Alternatives for growth substrates are discussed, along with the challenges and prospects associated with defining the genetic bases of industrially important phenotypes, and the generation of new yeast strains."I must be cruel only to be kind: Thus bad begins, and worse remains behind." William Shakespeare: Hamlet, Act 3, Scene 4.
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Nijland JG, Zhang X, Driessen AJM. D-xylose accelerated death of pentose metabolizing Saccharomyces cerevisiae. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:67. [PMID: 37069654 PMCID: PMC10111712 DOI: 10.1186/s13068-023-02320-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 04/10/2023] [Indexed: 04/19/2023]
Abstract
Rapid and effective consumption of D-xylose by Saccharomyces cerevisiae is essential for cost-efficient cellulosic bioethanol production. Hence, heterologous D-xylose metabolic pathways have been introduced into S. cerevisiae. An effective solution is based on a xylose isomerase in combination with the overexpression of the xylulose kinase (Xks1) and all genes of the non-oxidative branch of the pentose phosphate pathway. Although this strain is capable of consuming D-xylose, growth inhibition occurs at higher D-xylose concentrations, even abolishing growth completely at 8% D-xylose. The decreased growth rates are accompanied by significantly decreased ATP levels. A key ATP-utilizing step in D-xylose metabolism is the phosphorylation of D-xylulose by Xks1. Replacement of the constitutive promoter of XKS1 by the galactose tunable promoter Pgal10 allowed the controlled expression of this gene over a broad range. By decreasing the expression levels of XKS1, growth at high D-xylose concentrations could be restored concomitantly with increased ATP levels and high rates of xylose metabolism. These data show that in fermentations with high D-xylose concentrations, too high levels of Xks1 cause a major drain on the cellular ATP levels thereby reducing the growth rate, ultimately causing substrate accelerated death. Hence, expression levels of XKS1 in S. cerevisiae needs to be tailored for the specific growth conditions and robust D-xylose metabolism.
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Affiliation(s)
- Jeroen G Nijland
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology, Nijenborgh 7, 9747AG, Groningen, The Netherlands
| | - Xiaohuan Zhang
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology, Nijenborgh 7, 9747AG, Groningen, The Netherlands
| | - Arnold J M Driessen
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology, Nijenborgh 7, 9747AG, Groningen, The Netherlands.
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Teixeira V. Special Issue: Yeast Cell Signaling Pathways (Volume 1). Int J Mol Sci 2023; 24:ijms24054929. [PMID: 36902357 PMCID: PMC10003619 DOI: 10.3390/ijms24054929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Accepted: 02/28/2023] [Indexed: 03/08/2023] Open
Abstract
This Special Issue was devoted to unravelling novel aspects of yeast biology and signal transduction in numerous yet intricate basic processes [...].
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Affiliation(s)
- Vitor Teixeira
- i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal;
- IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal
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Mierke F, Brink DP, Norbeck J, Siewers V, Andlid T. Functional genome annotation and transcriptome analysis of Pseudozyma hubeiensis BOT-O, an oleaginous yeast that utilizes glucose and xylose at equal rates. Fungal Genet Biol 2023; 166:103783. [PMID: 36870442 DOI: 10.1016/j.fgb.2023.103783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 02/10/2023] [Accepted: 02/27/2023] [Indexed: 03/06/2023]
Abstract
Pseudozyma hubeiensis is a basidiomycete yeast that has the highly desirable traits for lignocellulose valorisation of being equally efficient at utilization of glucose and xylose, and capable of their co-utilization. The species has previously mainly been studied for its capacity to produce secreted biosurfactants in the form of mannosylerythritol lipids, but it is also an oleaginous species capable of accumulating high levels of triacylglycerol storage lipids during nutrient starvation. In this study, we aimed to further characterize the oleaginous nature of P. hubeiensis by evaluating metabolism and gene expression responses during storage lipid formation conditions with glucose or xylose as a carbon source. The genome of the recently isolated P. hubeiensis BOT-O strain was sequenced using MinION long-read sequencing and resulted in the most contiguous P. hubeiensis assembly to date with 18.95 Mb in 31 contigs. Using transcriptome data as experimental support, we generated the first mRNA-supported P. hubeiensis genome annotation and identified 6540 genes. 80% of the predicted genes were assigned functional annotations based on protein homology to other yeasts. Based on the annotation, key metabolic pathways in BOT-O were reconstructed, including pathways for storage lipids, mannosylerythritol lipids and xylose assimilation. BOT-O was confirmed to consume glucose and xylose at equal rates, but during mixed glucose-xylose cultivation glucose was found to be taken up faster. Differential expression analysis revealed that only a total of 122 genes were significantly differentially expressed at a cut-off of |log2 fold change| ≥ 2 when comparing cultivation on xylose with glucose, during exponential growth and during nitrogen-starvation. Of these 122 genes, a core-set of 24 genes was identified that were differentially expressed at all time points. Nitrogen-starvation resulted in a larger transcriptional effect, with a total of 1179 genes with significant expression changes at the designated fold change cut-off compared with exponential growth on either glucose or xylose.
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Affiliation(s)
- Friederike Mierke
- Food and Nutrition Science, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden; Systems and Synthetic Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Daniel P Brink
- Systems and Synthetic Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden; Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Joakim Norbeck
- Systems and Synthetic Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Verena Siewers
- Systems and Synthetic Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden.
| | - Thomas Andlid
- Food and Nutrition Science, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
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11
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Chen S, Xu Z, Ding B, Zhang Y, Liu S, Cai C, Li M, Dale BE, Jin M. Big data mining, rational modification, and ancestral sequence reconstruction inferred multiple xylose isomerases for biorefinery. SCIENCE ADVANCES 2023; 9:eadd8835. [PMID: 36724227 PMCID: PMC9891696 DOI: 10.1126/sciadv.add8835] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 12/30/2022] [Indexed: 05/28/2023]
Abstract
The isomerization of xylose to xylulose is considered the most promising approach to initiate xylose bioconversion. Here, phylogeny-guided big data mining, rational modification, and ancestral sequence reconstruction strategies were implemented to explore new active xylose isomerases (XIs) for Saccharomyces cerevisiae. Significantly, 13 new active XIs for S. cerevisiae were mined or artificially created. Moreover, the importance of the amino-terminal fragment for maintaining basic XI activity was demonstrated. With the mined XIs, four efficient xylose-utilizing S. cerevisiae were constructed and evolved, among which the strain S. cerevisiae CRD5HS contributed to ethanol titers as high as 85.95 and 94.76 g/liter from pretreated corn stover and corn cob, respectively, without detoxifying or washing pretreated biomass. Potential genetic targets obtained from adaptive laboratory evolution were further analyzed by sequencing the high-performance strains. The combined XI mining methods described here provide practical references for mining other scarce and valuable enzymes.
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Affiliation(s)
- Sitong Chen
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
- Biorefinery Research Institution, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Zhaoxian Xu
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
- Biorefinery Research Institution, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Boning Ding
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
- Biorefinery Research Institution, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Yuwei Zhang
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
- Biorefinery Research Institution, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Shuangmei Liu
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
- Biorefinery Research Institution, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Chenggu Cai
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
- Biorefinery Research Institution, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Muzi Li
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
- Biorefinery Research Institution, Nanjing University of Science and Technology, Nanjing 210094, China
| | - Bruce E. Dale
- Biomass Conversion Research Laboratory, Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA
- Great Lakes Bioenergy Research Centre (GLBRC), Michigan State University, East Lansing, MI, 48824 USA
| | - Mingjie Jin
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
- Biorefinery Research Institution, Nanjing University of Science and Technology, Nanjing 210094, China
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12
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Borgström C, Persson VC, Rogova O, Osiro KO, Lundberg E, Spégel P, Gorwa-Grauslund M. Using phosphoglucose isomerase-deficient (pgi1Δ) Saccharomyces cerevisiae to map the impact of sugar phosphate levels on D-glucose and D-xylose sensing. Microb Cell Fact 2022; 21:253. [PMID: 36456947 PMCID: PMC9713995 DOI: 10.1186/s12934-022-01978-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 11/21/2022] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Despite decades of engineering efforts, recombinant Saccharomyces cerevisiae are still less efficient at converting D-xylose sugar to ethanol compared to the preferred sugar D-glucose. Using GFP-based biosensors reporting for the three main sugar sensing routes, we recently demonstrated that the sensing response to high concentrations of D-xylose is similar to the response seen on low concentrations of D-glucose. The formation of glycolytic intermediates was hypothesized to be a potential cause of this sensing response. In order to investigate this, glycolysis was disrupted via the deletion of the phosphoglucose isomerase gene (PGI1) while intracellular sugar phosphate levels were monitored using a targeted metabolomic approach. Furthermore, the sugar sensing of the PGI1 deletants was compared to the PGI1-wildtype strains in the presence of various types and combinations of sugars. RESULTS Metabolomic analysis revealed systemic changes in intracellular sugar phosphate levels after deletion of PGI1, with the expected accumulation of intermediates upstream of the Pgi1p reaction on D-glucose and downstream intermediates on D-xylose. Moreover, the analysis revealed a preferential formation of D-fructose-6-phosphate from D-xylose, as opposed to the accumulation of D-fructose-1,6-bisphosphate that is normally observed when PGI1 deletants are incubated on D-fructose. This may indicate a role of PFK27 in D-xylose sensing and utilization. Overall, the sensing response was different for the PGI1 deletants, and responses to sugars that enter the glycolysis upstream of Pgi1p (D-glucose and D-galactose) were more affected than the response to those entering downstream of the reaction (D-fructose and D-xylose). Furthermore, the simultaneous exposure to sugars that entered upstream and downstream of Pgi1p (D-glucose with D-fructose, or D-glucose with D-xylose) resulted in apparent synergetic activation and deactivation of the Snf3p/Rgt2p and cAMP/PKA pathways, respectively. CONCLUSIONS Overall, the sensing assays indicated that the previously observed D-xylose response stems from the formation of downstream metabolic intermediates. Furthermore, our results indicate that the metabolic node around Pgi1p and the level of D-fructose-6-phosphate could represent attractive engineering targets for improved D-xylose utilization.
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Affiliation(s)
- Celina Borgström
- grid.4514.40000 0001 0930 2361Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden ,grid.17063.330000 0001 2157 2938Present Address: BioZone Centre for Applied Bioscience and Bioengineering, Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Canada
| | - Viktor C. Persson
- grid.4514.40000 0001 0930 2361Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Oksana Rogova
- grid.4514.40000 0001 0930 2361Centre for Analysis and Synthesis, Department of Chemistry, Lund University, Lund, Sweden
| | - Karen O. Osiro
- grid.4514.40000 0001 0930 2361Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden ,Present Address: Genetics and Biotechnology Laboratory, Embrapa Agroenergy, Brasília, DF 70770-901 Brazil
| | - Ester Lundberg
- grid.4514.40000 0001 0930 2361Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
| | - Peter Spégel
- grid.4514.40000 0001 0930 2361Centre for Analysis and Synthesis, Department of Chemistry, Lund University, Lund, Sweden
| | - Marie Gorwa-Grauslund
- grid.4514.40000 0001 0930 2361Division of Applied Microbiology, Department of Chemistry, Lund University, Lund, Sweden
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13
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Fiamenghi MB, Bueno JGR, Camargo AP, Borelli G, Carazzolle MF, Pereira GAG, dos Santos LV, José J. Machine learning and comparative genomics approaches for the discovery of xylose transporters in yeast. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:57. [PMID: 35596177 PMCID: PMC9123741 DOI: 10.1186/s13068-022-02153-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 05/05/2022] [Indexed: 11/15/2022]
Abstract
Background The need to mitigate and substitute the use of fossil fuels as the main energy matrix has led to the study and development of biofuels as an alternative. Second-generation (2G) ethanol arises as one biofuel with great potential, due to not only maintaining food security, but also as a product from economically interesting crops such as energy-cane. One of the main challenges of 2G ethanol is the inefficient uptake of pentose sugars by industrial yeast Saccharomyces cerevisiae, the main organism used for ethanol production. Understanding the main drivers for xylose assimilation and identify novel and efficient transporters is a key step to make the 2G process economically viable. Results By implementing a strategy of searching for present motifs that may be responsible for xylose transport and past adaptations of sugar transporters in xylose fermenting species, we obtained a classifying model which was successfully used to select four different candidate transporters for evaluation in the S. cerevisiae hxt-null strain, EBY.VW4000, harbouring the xylose consumption pathway. Yeast cells expressing the transporters SpX, SpH and SpG showed a superior uptake performance in xylose compared to traditional literature control Gxf1. Conclusions Modelling xylose transport with the small data available for yeast and bacteria proved a challenge that was overcome through different statistical strategies. Through this strategy, we present four novel xylose transporters which expands the repertoire of candidates targeting yeast genetic engineering for industrial fermentation. The repeated use of the model for characterizing new transporters will be useful both into finding the best candidates for industrial utilization and to increase the model’s predictive capabilities. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13068-022-02153-7.
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14
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Semkiv MV, Ruchala J, Tsaruk AY, Zazulya AZ, Vasylyshyn RV, Dmytruk OV, Zuo M, Kang Y, Dmytruk KV, Sibirny AA. The role of hexose transporter-like sensor hxs1 and transcription activator involved in carbohydrate sensing azf1 in xylose and glucose fermentation in the thermotolerant yeast Ogataea polymorpha. Microb Cell Fact 2022; 21:162. [PMID: 35964033 PMCID: PMC9375311 DOI: 10.1186/s12934-022-01889-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 08/06/2022] [Indexed: 11/24/2022] Open
Abstract
Background Fuel ethanol from lignocellulose could be important source of renewable energy. However, to make the process feasible, more efficient microbial fermentation of pentose sugars, mainly xylose, should be achieved. The native xylose-fermenting thermotolerant yeast Ogataea polymorpha is a promising organism for further development. Efficacy of xylose alcoholic fermentation by O. polymorpha was significantly improved by metabolic engineering. Still, genes involved in regulation of xylose fermentation are insufficiently studied. Results We isolated an insertional mutant of O.polymorpha with impaired ethanol production from xylose. The insertion occurred in the gene HXS1 that encodes hexose transporter-like sensor, a close homolog of Saccharomyces cerevisiae sensors Snf3 and Rgt2. The role of this gene in xylose utilization and fermentation was not previously elucidated. We additionally analyzed O.polymorpha strains with the deletion and overexpression of the corresponding gene. Strains with deletion of the HXS1 gene had slower rate of glucose and xylose consumption and produced 4 times less ethanol than the wild-type strain, whereas overexpression of HXS1 led to 10% increase of ethanol production from glucose and more than 2 times increase of ethanol production from xylose. We also constructed strains of O.polymorpha with overexpression of the gene AZF1 homologous to S. cerevisiae AZF1 gene which encodes transcription activator involved in carbohydrate sensing. Such transformants produced 10% more ethanol in glucose medium and 2.4 times more ethanol in xylose medium. Besides, we deleted the AZF1 gene in O. polymorpha. Ethanol accumulation in xylose and glucose media in such deletion strains dropped 1.5 and 1.8 times respectively. Overexpression of the HXS1 and AZF1 genes was also obtained in the advanced ethanol producer from xylose. The corresponding strains were characterized by 20–40% elevated ethanol accumulation in xylose medium. To understand underlying mechanisms of the observed phenotypes, specific enzymatic activities were evaluated in the isolated recombinant strains. Conclusions This paper shows the important role of hexose sensor Hxs1 and transcription factor Azf1 in xylose and glucose alcoholic fermentation in the native xylose-fermenting yeast O. polymorpha and suggests potential importance of the corresponding genes for construction of the advanced ethanol producers from the major sugars of lignocellulose.
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Affiliation(s)
- Marta V Semkiv
- Institute of Cell Biology, NAS of Ukraine, Drahomanov St, 14/16, 79005, Lviv, Ukraine
| | - Justyna Ruchala
- University of Rzeszow, Zelwerowicza 4, 35-601, Rzeszow, Poland
| | - Aksynia Y Tsaruk
- Institute of Cell Biology, NAS of Ukraine, Drahomanov St, 14/16, 79005, Lviv, Ukraine
| | - Anastasiya Z Zazulya
- Institute of Cell Biology, NAS of Ukraine, Drahomanov St, 14/16, 79005, Lviv, Ukraine
| | | | - Olena V Dmytruk
- Institute of Cell Biology, NAS of Ukraine, Drahomanov St, 14/16, 79005, Lviv, Ukraine.,University of Rzeszow, Zelwerowicza 4, 35-601, Rzeszow, Poland
| | - MingXing Zuo
- State Key Laboratory of Functions and Applications of Medicinal Plants, Guizhou Medical University, Guizhou, 550014, Guiyang, China
| | - Yingqian Kang
- Department of Microbiology, School of Basic Medical Sciences, Guizhou Medical University, Guizhou, 550014, Guiyang, China
| | - Kostyantyn V Dmytruk
- Institute of Cell Biology, NAS of Ukraine, Drahomanov St, 14/16, 79005, Lviv, Ukraine.,University of Rzeszow, Zelwerowicza 4, 35-601, Rzeszow, Poland
| | - Andriy A Sibirny
- Institute of Cell Biology, NAS of Ukraine, Drahomanov St, 14/16, 79005, Lviv, Ukraine. .,University of Rzeszow, Zelwerowicza 4, 35-601, Rzeszow, Poland.
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15
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Rojas SAT, Boles E, Oreb M. A yeast-based in vivo assay system for analyzing efflux of sugars mediated by glucose and xylose transporters. FEMS Yeast Res 2022; 21:6653521. [PMID: 35918180 DOI: 10.1093/femsyr/foac038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 07/14/2022] [Accepted: 07/29/2022] [Indexed: 11/13/2022] Open
Abstract
Sugar transporter research focuses on the sugar uptake into cells. Under certain physiological conditions, however, the intracellular accumulation and secretion of carbohydrates (efflux) are relevant processes in many cell types. Currently, no cell-based system is available for specifically investigating glucose efflux. Therefore, we designed a system based on a hexose transporter-deficient Saccharomyces cerevisiae strain, in which the disaccharide maltose is provided as a donor of intracellular glucose. By deleting the hexokinase genes, we prevented the metabolization of glucose and thereby achieved the accumulation of growth-inhibitory glucose levels inside the cells. When a permease mediating glucose efflux is expressed in this system, the inhibitory effect is relieved proportionally to the capacity of the introduced transporter. The assay is thereby suitable for screening of transporters and quantitative analyses of their glucose efflux capacities. Moreover, by simultaneous provision of intracellular glucose and extracellular xylose, we investigated how each sugar influences the transport of the other one from the opposite side of the membrane. Thereby, we could show that the xylose transporter variant Gal2N376F is insensitive not only to extracellular but also to intracellular glucose. Considering the importance of sugar transporters in biotechnology, the assay could facilitate new developments in a variety of applications.
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Affiliation(s)
- Sebastian A Tamayo Rojas
- Institute of Molecular Biosciences, Faculty of Biological Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Eckhard Boles
- Institute of Molecular Biosciences, Faculty of Biological Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Mislav Oreb
- Institute of Molecular Biosciences, Faculty of Biological Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
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