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Tamayo E, Nada B, Hafermann I, Benz JP. Correlating sugar transporter expression and activities to identify transporters for an orphan sugar substrate. Appl Microbiol Biotechnol 2024; 108:83. [PMID: 38189952 PMCID: PMC10774165 DOI: 10.1007/s00253-023-12907-4] [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: 07/10/2023] [Revised: 11/16/2023] [Accepted: 11/23/2023] [Indexed: 01/09/2024]
Abstract
Filamentous fungi like Neurospora crassa are able to take up and metabolize important sugars present, for example, in agricultural and human food wastes. However, only a fraction of all putative sugar transporters in filamentous fungi has been characterized to date, and for many sugar substrates, the corresponding transporters are unknown. In N. crassa, only 14 out of the 42 putative major facilitator superfamily (MFS)-type sugar transporters have been characterized so far. To uncover this hidden potential for biotechnology, it is therefore necessary to find new strategies. By correlation of the uptake profile of sugars of interest after different induction conditions with the expression profiles of all 44 genes encoding predicted sugar transporters in N. crassa, together with an exhaustive phylogenetic analysis using sequences of characterized fungal sugar transporters, we aimed to identify transporter candidates for the tested sugars. Following this approach, we found a high correlation of uptake rates and expression strengths for many sugars with dedicated transporters, like galacturonic acid and arabinose, while the correlation is loose for sugars that are transported by several transporters due to functional redundancy. Nevertheless, this combinatorial approach allowed us to elucidate the uptake system for the disaccharide lactose, a by-product of the dairy industry, which consists of the two main cellodextrin transporters CDT-1 and CDT-2 with a minor contribution of the related transporter NCU00809. Moreover, a non-MFS transporter involved in glycerol transport was also identified. Deorphanization of sugar transporters or identification of transporters for orphan sugar substrates by correlation of uptake kinetics with transporter expression and phylogenetic information can thus provide a way to optimize the reuse of food industry by-products and agricultural wastes by filamentous fungi in order to create economic value and reduce their environmental impact. KEY POINTS: • The Neurospora crassa genome contains 30 uncharacterized putative sugar transporter genes. • Correlation of transporter expression and sugar uptake profiles can help to identify transporters for orphan sugar substrates. • CDT-1, CDT-2, and NCU00809 are key players in the transport of the dairy by-product lactose in N. crassa.
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Affiliation(s)
- Elisabeth Tamayo
- Fungal Biotechnology in Wood Science, Holzforschung München, TUM School of Life Sciences, Technical University of Munich, Freising, Germany.
| | - Basant Nada
- Fungal Biotechnology in Wood Science, Holzforschung München, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
- Faculty of Science, Suez Canal University, Ismailia, Egypt
| | - Isabell Hafermann
- Fungal Biotechnology in Wood Science, Holzforschung München, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - J Philipp Benz
- Fungal Biotechnology in Wood Science, Holzforschung München, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
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Ma XY, Coleman B, Prabhu P, Wen F. Segmentation and evaluation of pathway module efficiency: Quantitative approach to monitor and overcome evolving bottlenecks in xylose to ethanol pathway. BIORESOURCE TECHNOLOGY 2024; 395:130377. [PMID: 38278451 DOI: 10.1016/j.biortech.2024.130377] [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: 12/05/2023] [Revised: 01/15/2024] [Accepted: 01/22/2024] [Indexed: 01/28/2024]
Abstract
Engineering microbes that can efficiently ferment xylose to ethanol is critical to the development of renewable fuels from lignocellulosic biomass. To accelerate the strain optimization process, a method termed Segmentation and Evaluation of Pathway Module Efficiency (SEPME) was developed to enable rapid and iterative identification and removal of metabolic bottlenecks. Using SEPME, the overall pathway was segmented into two modules: the upstream xylose assimilation pathway and the downstream pentose phosphate pathway, glycolysis, and fermentation. The efficiencies of both modules were then quantified to identify the rate controlling module, followed by analyses of control coefficients, reaction rates, and byproduct concentrations to narrow down targets within the module. SEPME analysis revealed that as the strain was engineered with increasing xylose-to-ethanol yields, the bottlenecks shifted within a module and across the two modules. Guided by SEPME, these bottlenecks were removed one by one, and a strain approaching the theoretical ethanol yield was obtained.
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Affiliation(s)
- Xiao Yin Ma
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, United States; Catalysis Science and Technology Institute, University of Michigan, Ann Arbor, MI 48109, United States
| | - Bryan Coleman
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, United States; Catalysis Science and Technology Institute, University of Michigan, Ann Arbor, MI 48109, United States
| | - Ponnandy Prabhu
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, United States
| | - Fei Wen
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, United States; Catalysis Science and Technology Institute, University of Michigan, Ann Arbor, MI 48109, United States.
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Yang P, Jiang S, Jiang S, Lu S, Zheng Z, Chen J, Wu W, Jiang S. CRISPR-Cas9 Approach Constructed Engineered Saccharomyces cerevisiae with the Deletion of GPD2, FPS1, and ADH2 to Enhance the Production of Ethanol. J Fungi (Basel) 2022; 8:jof8070703. [PMID: 35887459 PMCID: PMC9316504 DOI: 10.3390/jof8070703] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/21/2022] [Accepted: 06/29/2022] [Indexed: 02/05/2023] Open
Abstract
Bioethanol plays an important value in renewable liquid fuel. The excessive accumulation of glycerol and organic acids caused the decrease of ethanol content in the process of industrial ethanol production. In this study, the CRISPR-Cas9 approach was used to construct S. cerevisiae engineering strains by the deletion of GPD2, FPS1, and ADH2 for the improvement of ethanol production. RNA sequencing and transcriptome analysis were used to investigate the effect of gene deletion on gene expression. The results indicated that engineered S. cerevisiae SCGFA by the simultaneous deletion of GPD2, FPS1, and ADH2 produced 23.1 g/L ethanol, which increased by 0.18% in comparison with the wild-type strain with 50 g/L of glucose as substrate. SCGFA strain exhibited the ethanol conversion rate of 0.462 g per g of glucose. In addition, the contents of glycerol, lactic acid, acetic acid, and succinic acid in SCGFA decreased by 22.7, 12.7, 8.1, 19.9, and 20.7% compared with the wild-type strain, respectively. The up-regulated gene enrichment showed glycolysis, fatty acid, and carbon metabolism could affect the ethanol production of SCGFA according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Therefore, the engineering strain SCGFA had great potential in the production of bioethanol.
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Affiliation(s)
- Peizhou Yang
- Anhui Key Laboratory of Intensive Processing of Agricultural Products, College of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China; (S.J.); (S.L.); (Z.Z.); (J.C.); (W.W.); (S.J.)
- Correspondence: ; Tel.: +86-15155197790
| | - Shuying Jiang
- Anhui Key Laboratory of Intensive Processing of Agricultural Products, College of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China; (S.J.); (S.L.); (Z.Z.); (J.C.); (W.W.); (S.J.)
| | - Suwei Jiang
- Department of Biological, Food and Environment Engineering, Hefei University, Hefei 230601, China;
| | - Shuhua Lu
- Anhui Key Laboratory of Intensive Processing of Agricultural Products, College of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China; (S.J.); (S.L.); (Z.Z.); (J.C.); (W.W.); (S.J.)
| | - Zhi Zheng
- Anhui Key Laboratory of Intensive Processing of Agricultural Products, College of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China; (S.J.); (S.L.); (Z.Z.); (J.C.); (W.W.); (S.J.)
| | - Jianchao Chen
- Anhui Key Laboratory of Intensive Processing of Agricultural Products, College of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China; (S.J.); (S.L.); (Z.Z.); (J.C.); (W.W.); (S.J.)
| | - Wenjing Wu
- Anhui Key Laboratory of Intensive Processing of Agricultural Products, College of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China; (S.J.); (S.L.); (Z.Z.); (J.C.); (W.W.); (S.J.)
| | - Shaotong Jiang
- Anhui Key Laboratory of Intensive Processing of Agricultural Products, College of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China; (S.J.); (S.L.); (Z.Z.); (J.C.); (W.W.); (S.J.)
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Kretschmer M, Damoo D, Sun S, Lee CWJ, Croll D, Brumer H, Kronstad J. Organic acids and glucose prime late-stage fungal biotrophy in maize. Science 2022; 376:1187-1191. [PMID: 35679407 DOI: 10.1126/science.abo2401] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Many plant-associated fungi are obligate biotrophs that depend on living hosts to proliferate. However, little is known about the molecular basis of the biotrophic lifestyle, despite the impact of fungi on the environment and food security. In this work, we show that combinations of organic acids and glucose trigger phenotypes that are associated with the late stage of biotrophy for the maize pathogen Ustilago maydis. These phenotypes include the expression of a set of effectors normally observed only during biotrophic development, as well as the formation of melanin associated with sporulation in plant tumors. U. maydis and other hemibiotrophic fungi also respond to a combination of carbon sources with enhanced proliferation. Thus, the response to combinations of nutrients from the host may be a conserved feature of fungal biotrophy.
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Affiliation(s)
- Matthias Kretschmer
- Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Djihane Damoo
- Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Sherry Sun
- Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Christopher W J Lee
- Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Daniel Croll
- Laboratory of Evolutionary Genetics, Institute of Biology, Université de Neuchâtel, Neuchâtel, Switzerland
| | - Harry Brumer
- Michael Smith Laboratories and Department of Chemistry, University of British Columbia, Vancouver, BC, Canada
| | - James Kronstad
- Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
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How adaptive laboratory evolution can boost yeast tolerance to lignocellulosic hydrolyses. Curr Genet 2022; 68:319-342. [PMID: 35362784 DOI: 10.1007/s00294-022-01237-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 03/01/2022] [Accepted: 03/06/2022] [Indexed: 12/25/2022]
Abstract
The yeast Saccharomyces cerevisiae is an excellent candidate for establishing cell factories to convert lignocellulosic biomass into chemicals and fuels. To enable this technology, yeast robustness must be improved to withstand the fermentation inhibitors (e.g., weak organic acids, phenols, and furan aldehydes) resulting from biomass pretreatment and hydrolysis. Here, we discuss how evolution experiments performed in the lab, a method commonly known as adaptive laboratory evolution (ALE), may contribute to lifting yeast tolerance against the inhibitors of lignocellulosic hydrolysates (LCHs). The key is that, through the combination of whole-genome sequencing and reverse engineering, ALE provides a robust platform for discovering and testing adaptive alleles, allowing to explore the genetic underpinnings of yeast responses to LCHs. We review the insights gained from past evolution experiments with S. cerevisiae in LCH inhibitors and propose experimental designs to optimise the discovery of genetic variants adaptive to biomass toxicity. The knowledge gathered through ALE projects is envisaged as a roadmap to engineer superior yeast strains for biomass-based bioprocesses.
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6
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Brandt BA, García-Aparicio MDP, Görgens JF, van Zyl WH. Rational engineering of Saccharomyces cerevisiae towards improved tolerance to multiple inhibitors in lignocellulose fermentations. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:173. [PMID: 34454598 PMCID: PMC8403374 DOI: 10.1186/s13068-021-02021-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 08/20/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND The fermentation of lignocellulose hydrolysates to ethanol requires robust xylose-capable Saccharomyces cerevisiae strains able to operate in the presence of microbial inhibitory stresses. This study aimed at developing industrial S. cerevisiae strains with enhanced tolerance towards pretreatment-derived microbial inhibitors, by identifying novel gene combinations that confer resistance to multiple inhibitors (thus cumulative inhibitor resistance phenotype) with minimum impact on the xylose fermentation ability. The strategy consisted of multiple sequential delta-integrations of double-gene cassettes containing one gene conferring broad inhibitor tolerance (ARI1, PAD1 or TAL1) coupled with an inhibitor-specific gene (ADH6, FDH1 or ICT1). The performances of the transformants were compared with the parental strain in terms of biomass growth, ethanol yields and productivity, as well as detoxification capacities in a synthetic inhibitor cocktail, sugarcane bagasse hydrolysate as well as hardwood spent sulphite liquor. RESULTS The first and second round of delta-integrated transformants exhibited a trade-off between biomass and ethanol yield. Transformants showed increased inhibitor resistance phenotypes relative to parental controls specifically in fermentations with concentrated spent sulphite liquors at 40% and 80% v/v concentrations in 2% SC media. Unexpectedly, the xylose fermentation capacity of the transformants was reduced compared to the parental control, but certain combinations of genes had a minor impact (e.g. TAL1 + FDH1). The TAL1 + ICT1 combination negatively impacted on both biomass growth and ethanol yield, which could be linked to the ICT1 protein increasing transformant susceptibility to weak acids and temperature due to cell membrane changes. CONCLUSIONS The integration of the selected genes was proven to increase tolerance to pretreatment inhibitors in synthetic or industrial hydrolysates, but they were limited to the fermentation of glucose. However, some gene combination sequences had a reduced impact on xylose conversion.
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Affiliation(s)
- Bianca A Brandt
- Department of Microbiology, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa
| | - Maria D P García-Aparicio
- Department of Process Engineering, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa
| | - Johann F Görgens
- Department of Process Engineering, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa
| | - Willem H van Zyl
- Department of Microbiology, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa.
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7
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Patiño MA, Ortiz JP, Velásquez M, Stambuk BU. d-Xylose consumption by nonrecombinant Saccharomyces cerevisiae: A review. Yeast 2019; 36:541-556. [PMID: 31254359 DOI: 10.1002/yea.3429] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 06/02/2019] [Accepted: 06/21/2019] [Indexed: 01/24/2023] Open
Abstract
Xylose is the second most abundant sugar in nature. Its efficient fermentation has been considered as a critical factor for a feasible conversion of renewable biomass resources into biofuels and other chemicals. The yeast Saccharomyces cerevisiae is of exceptional industrial importance due to its excellent capability to ferment sugars. However, although S. cerevisiae is able to ferment xylulose, it is considered unable to metabolize xylose, and thus, a lot of research has been directed to engineer this yeast with heterologous genes to allow xylose consumption and fermentation. The analysis of the natural genetic diversity of this yeast has also revealed some nonrecombinant S. cerevisiae strains that consume or even grow (modestly) on xylose. The genome of this yeast has all the genes required for xylose transport and metabolism through the xylose reductase, xylitol dehydrogenase, and xylulokinase pathway, but there seems to be problems in their kinetic properties and/or required expression. Self-cloning industrial S. cerevisiae strains overexpressing some of the endogenous genes have shown interesting results, and new strategies and approaches designed to improve these S. cerevisiae strains for ethanol production from xylose will also be presented in this review.
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Affiliation(s)
- Margareth Andrea Patiño
- Instituto de Biotecnología.,Departamento de Ingeniería Química y Ambiental, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Juan Pablo Ortiz
- Facultad de Ciencias e Ingeniería, Universidad de Boyacá, Tunja, Colombia
| | - Mario Velásquez
- Departamento de Ingeniería Química y Ambiental, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Boris U Stambuk
- Departamento de Bioquímica, Universidad Federal de Santa Catarina, Florianópolis, Brazil
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Overcoming the thermodynamic equilibrium of an isomerization reaction through oxidoreductive reactions for biotransformation. Nat Commun 2019; 10:1356. [PMID: 30902987 PMCID: PMC6430769 DOI: 10.1038/s41467-019-09288-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 02/21/2019] [Indexed: 01/22/2023] Open
Abstract
Isomerases perform biotransformations without cofactors but often cause an undesirable mixture of substrate and product due to unfavorable thermodynamic equilibria. We demonstrate the feasibility of using an engineered yeast strain harboring oxidoreductase reactions to overcome the thermodynamic limit of an isomerization reaction. Specifically, a yeast strain capable of consuming lactose intracellularly is engineered to produce tagatose from lactose through three layers of manipulations. First, GAL1 coding for galactose kinase is deleted to eliminate galactose utilization. Second, heterologous xylose reductase (XR) and galactitol dehydrogenase (GDH) are introduced into the ∆gal1 strain. Third, the expression levels of XR and GDH are adjusted to maximize tagatose production. The resulting engineered yeast produces 37.69 g/L of tagatose from lactose with a tagatose and galactose ratio of 9:1 in the reaction broth. These results suggest that in vivo oxidoreaductase reactions can be employed to replace isomerases in vitro for biotransformation. A desired product cannot be obtained at higher concentration than its equilibrium concentration when isomerases are used for biotransformation. Here, the authors engineer in vivo oxidoreductive reactions in yeast to overcome the equilibrium limitation of in vitro isomerases-based tagatose production.
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9
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Myers KS, Riley NM, MacGilvray ME, Sato TK, McGee M, Heilberger J, Coon JJ, Gasch AP. Rewired cellular signaling coordinates sugar and hypoxic responses for anaerobic xylose fermentation in yeast. PLoS Genet 2019; 15:e1008037. [PMID: 30856163 PMCID: PMC6428351 DOI: 10.1371/journal.pgen.1008037] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 03/21/2019] [Accepted: 02/20/2019] [Indexed: 01/08/2023] Open
Abstract
Microbes can be metabolically engineered to produce biofuels and biochemicals, but rerouting metabolic flux toward products is a major hurdle without a systems-level understanding of how cellular flux is controlled. To understand flux rerouting, we investigated a panel of Saccharomyces cerevisiae strains with progressive improvements in anaerobic fermentation of xylose, a sugar abundant in sustainable plant biomass used for biofuel production. We combined comparative transcriptomics, proteomics, and phosphoproteomics with network analysis to understand the physiology of improved anaerobic xylose fermentation. Our results show that upstream regulatory changes produce a suite of physiological effects that collectively impact the phenotype. Evolved strains show an unusual co-activation of Protein Kinase A (PKA) and Snf1, thus combining responses seen during feast on glucose and famine on non-preferred sugars. Surprisingly, these regulatory changes were required to mount the hypoxic response when cells were grown on xylose, revealing a previously unknown connection between sugar source and anaerobic response. Network analysis identified several downstream transcription factors that play a significant, but on their own minor, role in anaerobic xylose fermentation, consistent with the combinatorial effects of small-impact changes. We also discovered that different routes of PKA activation produce distinct phenotypes: deletion of the RAS/PKA inhibitor IRA2 promotes xylose growth and metabolism, whereas deletion of PKA inhibitor BCY1 decouples growth from metabolism to enable robust fermentation without division. Comparing phosphoproteomic changes across ira2Δ and bcy1Δ strains implicated regulatory changes linked to xylose-dependent growth versus metabolism. Together, our results present a picture of the metabolic logic behind anaerobic xylose flux and suggest that widespread cellular remodeling, rather than individual metabolic changes, is an important goal for metabolic engineering.
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Affiliation(s)
- Kevin S. Myers
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Nicholas M. Riley
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Matthew E. MacGilvray
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Trey K. Sato
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Mick McGee
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Justin Heilberger
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Joshua J. Coon
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, United States of America
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, United States of America
- Morgridge Institute for Research, Madison, WI, United States of America
| | - Audrey P. Gasch
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States of America
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI, United States of America
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI, United States of America
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10
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Hara KY, Kobayashi J, Yamada R, Sasaki D, Kuriya Y, Hirono-Hara Y, Ishii J, Araki M, Kondo A. Transporter engineering in biomass utilization by yeast. FEMS Yeast Res 2018; 17:4097189. [PMID: 28934416 DOI: 10.1093/femsyr/fox061] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 08/04/2017] [Indexed: 12/17/2022] Open
Abstract
Biomass resources are attractive carbon sources for bioproduction because of their sustainability. Many studies have been performed using biomass resources to produce sugars as carbon sources for cell factories. Expression of biomass hydrolyzing enzymes in cell factories is an important approach for constructing biomass-utilizing bioprocesses because external addition of these enzymes is expensive. In particular, yeasts have been extensively engineered to be cell factories that directly utilize biomass because of their manageable responses to many genetic engineering tools, such as gene expression, deletion and editing. Biomass utilizing bioprocesses have also been developed using these genetic engineering tools to construct metabolic pathways. However, sugar input and product output from these cells are critical factors for improving bioproduction along with biomass utilization and metabolic pathways. Transporters are key components for efficient input and output activities. In this review, we focus on transporter engineering in yeast to enhance bioproduction from biomass resources.
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Affiliation(s)
- Kiyotaka Y Hara
- Division of Environmental and Life Sciences, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.,School of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Jyumpei Kobayashi
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
| | - Ryosuke Yamada
- Department of Chemical Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Daisuke Sasaki
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
| | - Yuki Kuriya
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
| | - Yoko Hirono-Hara
- School of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Jun Ishii
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
| | - Michihiro Araki
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan.,Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Syogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Akihiko Kondo
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan.,Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
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11
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Cheng C, Tang RQ, Xiong L, Hector RE, Bai FW, Zhao XQ. Association of improved oxidative stress tolerance and alleviation of glucose repression with superior xylose-utilization capability by a natural isolate of Saccharomyces cerevisiae. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:28. [PMID: 29441126 PMCID: PMC5798184 DOI: 10.1186/s13068-018-1018-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 01/11/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Saccharomyces cerevisiae wild strains generally have poor xylose-utilization capability, which is a major barrier for efficient bioconversion of lignocellulosic biomass. Laboratory adaption is commonly used to enhance xylose utilization of recombinant S. cerevisiae. Apparently, yeast cells could remodel the metabolic network for xylose metabolism. However, it still remains unclear why natural isolates of S. cerevisiae poorly utilize xylose. Here, we analyzed a unique S. cerevisiae natural isolate YB-2625 which has superior xylose metabolism capability in the presence of mixed-sugar. Comparative transcriptomic analysis was performed using S. cerevisiae YB-2625 grown in a mixture of glucose and xylose, and the model yeast strain S288C served as a control. Global gene transcription was compared at both the early mixed-sugar utilization stage and the latter xylose-utilization stage. RESULTS Genes involved in endogenous xylose-assimilation (XYL2 and XKS1), gluconeogenesis, and TCA cycle showed higher transcription levels in S. cerevisiae YB-2625 at the xylose-utilization stage, when compared to the reference strain. On the other hand, transcription factor encoding genes involved in regulation of glucose repression (MIG1, MIG2, and MIG3) as well as HXK2 displayed decreased transcriptional levels in YB-2625, suggesting the alleviation of glucose repression of S. cerevisiae YB-2625. Notably, genes encoding antioxidant enzymes (CTT1, CTA1, SOD2, and PRX1) showed higher transcription levels in S. cerevisiae YB-2625 in the xylose-utilization stage than that of the reference strain. Consistently, catalase activity of YB-2625 was 1.9-fold higher than that of S. cerevisiae S288C during the xylose-utilization stage. As a result, intracellular reactive oxygen species levels of S. cerevisiae YB-2625 were 43.3 and 58.6% lower than that of S288C at both sugar utilization stages. Overexpression of CTT1 and PRX1 in the recombinant strain S. cerevisiae YRH396 deriving from S. cerevisiae YB-2625 increased cell growth when xylose was used as the sole carbon source, leading to 13.5 and 18.1%, respectively, more xylose consumption. CONCLUSIONS Enhanced oxidative stress tolerance and relief of glucose repression are proposed to be two major mechanisms for superior xylose utilization by S. cerevisiae YB-2625. The present study provides insights into the innate regulatory mechanisms underlying xylose utilization in wild-type S. cerevisiae, which benefits the rapid development of robust yeast strains for lignocellulosic biorefineries.
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Affiliation(s)
- Cheng Cheng
- School of Life Science and Biotechnology, Dalian University of Technology, Dalian, 116024 China
| | - Rui-Qi Tang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240 China
| | - Liang Xiong
- School of Life Science and Biotechnology, Dalian University of Technology, Dalian, 116024 China
| | - Ronald E. Hector
- Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA-ARS, Peoria, IL USA
| | - Feng-Wu Bai
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240 China
| | - Xin-Qing Zhao
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240 China
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12
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Tani T, Taguchi H, Akamatsu T. Analysis of metabolisms and transports of xylitol using xylose- and xylitol-assimilating Saccharomyces cerevisiae. J Biosci Bioeng 2017; 123:613-620. [PMID: 28126230 DOI: 10.1016/j.jbiosc.2016.12.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 12/13/2016] [Accepted: 12/20/2016] [Indexed: 01/16/2023]
Abstract
To clarify the relationship between NAD(P)+/NAD(P)H redox balances and the metabolisms of xylose or xylitol as carbon sources, we analyzed aerobic and anaerobic batch cultures of recombinant Saccharomyces cerevisiae in a complex medium containing 20 g/L xylose or 20 g/L xylitol at pH 5.0 and 30°C. The TDH3p-GAL2 or gal80Δ strain completely consumed the xylose within 24 h and aerobically consumed 92-100% of the xylitol within 96 h, but anaerobically consumed only 20% of the xylitol within 96 h. Cells of both strains grew well in aerobic culture. The addition of acetaldehyde (an effective oxidizer of NADH) increased the xylitol consumption by the anaerobically cultured strain. These results indicate that in anaerobic culture, NAD+ generated in the NAD(P)H-dependent xylose reductase reaction was likely needed in the NAD+-dependent xylitol dehydrogenase reaction, whereas in aerobic culture, the NAD+ generated by oxidation of NADH in the mitochondria is required in the xylitol dehydrogenase reaction. The role of Gal2 and Fps1 in importing xylitol into the cytosol and exporting it from the cells was analyzed by examining the xylitol consumption in aerobic culture and the export of xylitol metabolized from xylose in anaerobic culture, respectively. The xylitol consumptions of gal80Δ gal2Δ and gal80Δ gal2Δ fps1Δ strains were reduced by 81% and 88% respectively, relative to the gal80Δ strain. The maximum xylitol concentration accumulated by the gal80Δ, gal80Δ gal2Δ, and gal80Δ gal2Δ fps1Δ strains was 7.25 g/L, 5.30 g/L, and 4.27 g/L respectively, indicating that Gal2 and Fps1 transport xylitol both inward and outward.
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Affiliation(s)
- Tatsunori Tani
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Nishi-ku, Kumamoto 860-0082, Japan
| | - Hisataka Taguchi
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Nishi-ku, Kumamoto 860-0082, Japan
| | - Takashi Akamatsu
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Nishi-ku, Kumamoto 860-0082, Japan.
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13
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Development of Synthetic Microbial Platforms to Convert Lignocellulosic Biomass to Biofuels. ADVANCES IN BIOENERGY 2017. [DOI: 10.1016/bs.aibe.2016.12.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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14
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Isolation and characterization of xylitol-assimilating mutants of recombinant Saccharomyces cerevisiae. J Biosci Bioeng 2016; 122:446-55. [DOI: 10.1016/j.jbiosc.2016.03.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 02/22/2016] [Accepted: 03/12/2016] [Indexed: 11/22/2022]
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15
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Zhang B, Zhang J, Wang D, Han R, Ding R, Gao X, Sun L, Hong J. Simultaneous fermentation of glucose and xylose at elevated temperatures co-produces ethanol and xylitol through overexpression of a xylose-specific transporter in engineered Kluyveromyces marxianus. BIORESOURCE TECHNOLOGY 2016; 216:227-37. [PMID: 27240239 DOI: 10.1016/j.biortech.2016.05.068] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 05/17/2016] [Accepted: 05/19/2016] [Indexed: 05/08/2023]
Abstract
Engineered Kluyveromyces marxianus strains were constructed through over-expression of various transporters for simultaneous co-fermentation of glucose and xylose. The glucose was converted into ethanol, whereas xylose was converted into xylitol which has higher value than ethanol. Over-expressing xylose-specific transporter ScGAL2-N376F mutant enabled yeast to co-ferment glucose and xylose and the co-fermentation ability was obviously improved through increasing ScGAL2-N376F expression. The production of glycerol was blocked and acetate production was reduced by disrupting gene KmGPD1. The obtained K. marxianus YZJ119 utilized 120g/L glucose and 60g/L xylose simultaneously and produced 50.10g/L ethanol and 55.88g/L xylitol at 42°C. The yield of xylitol from consumed xylose was over 98% (0.99g/g). Through simultaneous saccharification and co-fermentation at 42°C, YZJ119 produced a maximal concentration of 44.58g/L ethanol and 32.03g/L xylitol or 29.82g/L ethanol and 31.72g/L xylitol, respectively, from detoxified or non-detoxified diluted acid pretreated corncob.
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Affiliation(s)
- Biao Zhang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China
| | - Jia Zhang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China
| | - Dongmei Wang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China
| | - Ruixiang Han
- Institutes of Life Sciences, Anhui Medical University, Hefei, Anhui 230032, PR China
| | - Rui Ding
- Institutes of Life Sciences, Anhui Medical University, Hefei, Anhui 230032, PR China
| | - Xiaolian Gao
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Department of Biology and Biochemistry, University of Houston, Houston, TX 77004-5001, USA
| | - Lianhong Sun
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China
| | - Jiong Hong
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China.
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16
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Pérez-Torrado R, Oliveira BM, Zemančíková J, Sychrová H, Querol A. Alternative Glycerol Balance Strategies among Saccharomyces Species in Response to Winemaking Stress. Front Microbiol 2016; 7:435. [PMID: 27064588 PMCID: PMC4814467 DOI: 10.3389/fmicb.2016.00435] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 03/17/2016] [Indexed: 01/15/2023] Open
Abstract
Production and balance of glycerol is essential for the survival of yeast cells in certain stressful conditions as hyperosmotic or cold shock that occur during industrial processes as winemaking. These stress responses are well-known in S. cerevisiae, however, little is known in other phylogenetically close related Saccharomyces species associated with natural or fermentation environments such as S. uvarum, S. paradoxus or S. kudriavzevii. In this work we have investigated the expression of four genes (GPD1, GPD2, STL1, and FPS1) crucial in the glycerol pool balance in the four species with a biotechnological potential (S. cerevisiae; S. paradoxus; S. uvarum; and S. kudriavzevii), and the ability of strains to grow under osmotic and cold stresses. The results show different pattern and level of expression among the different species, especially for STL1. We also studied the function of Stl1 glycerol symporter in the survival to osmotic changes and cell growth capacity in winemaking environments. These experiments also revealed a different functionality of the glycerol transporters among the different species studied. All these data point to different strategies to handle glycerol accumulation in response to winemaking stresses as hyperosmotic or cold-hyperosmotic stress in the different species, with variable emphasis in the production, influx, or efflux of glycerol.
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Affiliation(s)
- Roberto Pérez-Torrado
- Food Biotechnology Department, Systems Biology in Yeast of Biotechnological Interest, Instituto de Agroquímica y Tecnología de los Alimentos, IATA-CSIC Valencia, Spain
| | - Bruno M Oliveira
- Food Biotechnology Department, Systems Biology in Yeast of Biotechnological Interest, Instituto de Agroquímica y Tecnología de los Alimentos, IATA-CSIC Valencia, Spain
| | - Jana Zemančíková
- Department of Membrane Transport, Institute of Physiology CAS, Prague, Czech Republic
| | - Hana Sychrová
- Department of Membrane Transport, Institute of Physiology CAS, Prague, Czech Republic
| | - Amparo Querol
- Food Biotechnology Department, Systems Biology in Yeast of Biotechnological Interest, Instituto de Agroquímica y Tecnología de los Alimentos, IATA-CSIC Valencia, Spain
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17
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Zhang J, Zhang B, Wang D, Gao X, Sun L, Hong J. Rapid ethanol production at elevated temperatures by engineered thermotolerant Kluyveromyces marxianus via the NADP(H)-preferring xylose reductase-xylitol dehydrogenase pathway. Metab Eng 2015; 31:140-52. [PMID: 26253204 DOI: 10.1016/j.ymben.2015.07.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 06/22/2015] [Accepted: 07/27/2015] [Indexed: 11/17/2022]
Abstract
Conversion of xylose to ethanol by yeasts is a challenge because of the redox imbalances under oxygen-limited conditions. The thermotolerant yeast Kluyveromyces marxianus grows well with xylose as a carbon source at elevated temperatures, but its xylose fermentation ability is weak. In this study, a combination of the NADPH-preferring xylose reductase (XR) from Neurospora crassa and the NADP(+)-preferring xylitol dehydrogenase (XDH) mutant from Scheffersomyces stipitis (Pichia stipitis) was constructed. The xylose fermentation ability and redox balance of the recombinant strains were improved significantly by over-expression of several downstream genes. The intracellular concentrations of coenzymes and the reduced coenzyme/oxidized coenzyme ratio increased significantly in these metabolic strains. The byproducts, such as glycerol and acetic acid, were significantly reduced by the disruption of glycerol-3-phosphate dehydrogenase (GPD1). The resulting engineered K. marxianus YZJ088 strain produced 44.95 g/L ethanol from 118.39 g/L xylose with a productivity of 2.49 g/L/h at 42 °C. Additionally, YZJ088 realized glucose and xylose co-fermentation and produced 51.43 g/L ethanol from a mixture of 103.97 g/L xylose and 40.96 g/L glucose with a productivity of 2.14 g/L/h at 42 °C. These promising results validate the YZJ088 strain as an excellent producer of ethanol from xylose through the synthetic xylose assimilation pathway.
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Affiliation(s)
- Jia Zhang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China
| | - Biao Zhang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China
| | - Dongmei Wang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China
| | - Xiaolian Gao
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Department of Biology and Biochemistry, University of Houston, Houston, TX 77004-5001, USA; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China
| | - Lianhong Sun
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China
| | - Jiong Hong
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China.
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18
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Zhang J, Zhang B, Wang D, Gao X, Hong J. Improving xylitol production at elevated temperature with engineered Kluyveromyces marxianus through over-expressing transporters. BIORESOURCE TECHNOLOGY 2015; 175:642-645. [PMID: 25465792 DOI: 10.1016/j.biortech.2014.10.150] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 10/27/2014] [Accepted: 10/29/2014] [Indexed: 06/04/2023]
Abstract
Three transporter genes including Kluyveromyces marxianus aquaglyceroporin gene (KmFPS1), Candida intermedia glucose/xylose facilitator gene (CiGXF1) or glucose/xylose symporter gene (CiGXS1) were over-expressed in K. marxianus YZJ017 to improve xylitol production at elevated temperatures. The xylitol production of YZJ074 that harbored CiGXF1 was improved to 147.62g/L in Erlenmeyer flask at 42°C. In fermenter, 99.29 and 149.60g/L xylitol were produced from 99.55 and 151.91g/L xylose with productivity of 4.14 and 3.40g/L/h respectively at 42°C. Even at 45°C, YZJ074 could produce 101.30g/L xylitol from 101.41g/L xylose with productivity of 2.81g/L/h. Using fed-batch fermentation through repeatedly adding non-sterilized substrate directly, YZJ074 could produce 312.05g/L xylitol which is the highest yield reported to date. The engineered strains YZJ074 which can produce xylitol at elevated temperatures is an excellent foundation for xylitol bioconversion.
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Affiliation(s)
- Jia Zhang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China
| | - Biao Zhang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China
| | - Dongmei Wang
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China
| | - Xiaolian Gao
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Department of Biology and Biochemistry, University of Houston, Houston, TX 77004-5001, USA; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China
| | - Jiong Hong
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China; Hefei National Laboratory for Physical Science at the Microscale, Hefei, Anhui 230026, PR China.
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19
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Sànchez Nogué V, Karhumaa K. Xylose fermentation as a challenge for commercialization of lignocellulosic fuels and chemicals. Biotechnol Lett 2014; 37:761-72. [DOI: 10.1007/s10529-014-1756-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022]
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20
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Wang BL, Ghaderi A, Zhou H, Agresti J, Weitz DA, Fink GR, Stephanopoulos G. Microfluidic high-throughput culturing of single cells for selection based on extracellular metabolite production or consumption. Nat Biotechnol 2014; 32:473-8. [PMID: 24705516 PMCID: PMC4412259 DOI: 10.1038/nbt.2857] [Citation(s) in RCA: 234] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 02/21/2014] [Indexed: 11/09/2022]
Abstract
Phenotyping single cells based on the products they secrete or consume is a key bottleneck in many biotechnology applications, such as combinatorial metabolic engineering for the overproduction of secreted metabolites. Here we present a flexible high-throughput approach that uses microfluidics to compartmentalize individual cells for growth and analysis in monodisperse nanoliter aqueous droplets surrounded by an immiscible fluorinated oil phase. We use this system to identify xylose-overconsuming Saccharomyces cerevisiae cells from a population containing one such cell per 10(4) cells and to screen a genomic library to identify multiple copies of the xylose isomerase gene as a genomic change contributing to high xylose consumption, a trait important for lignocellulosic feedstock utilization. We also enriched L-lactate-producing Escherichia coli clones 5,800× from a population containing one L-lactate producer per 10(4) D-lactate producers. Our approach has broad applications for single-cell analyses, such as in strain selection for the overproduction of fuels, chemicals and pharmaceuticals.
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Affiliation(s)
- Benjamin L Wang
- 1] Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. [2]
| | - Adel Ghaderi
- 1] Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. [2]
| | - Hang Zhou
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Jeremy Agresti
- Department of Physics and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
| | - David A Weitz
- Department of Physics and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
| | - Gerald R Fink
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA
| | - Gregory Stephanopoulos
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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21
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Su B, Wu M, Lin J, Yang L. Metabolic engineering strategies for improving xylitol production from hemicellulosic sugars. Biotechnol Lett 2013; 35:1781-9. [DOI: 10.1007/s10529-013-1279-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 06/21/2013] [Indexed: 12/25/2022]
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