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Varriale L, Geib D, Ulber R. Short-term adaptation as a tool to improve bioethanol production using grass press-juice as fermentation medium. Appl Microbiol Biotechnol 2024; 108:393. [PMID: 38916650 PMCID: PMC11199226 DOI: 10.1007/s00253-024-13224-0] [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: 03/20/2024] [Revised: 06/03/2024] [Accepted: 06/04/2024] [Indexed: 06/26/2024]
Abstract
Grass raw materials collected from grasslands cover more than 30% of Europe's agricultural area. They are considered very attractive for the production of different biochemicals and biofuels due to their high availability and renewability. In this study, a perennial ryegrass (Lolium perenne) was exploited for second-generation bioethanol production. Grass press-cake and grass press-juice were separated using mechanical pretreatment, and the obtained juice was used as a fermentation medium. In this work, Saccharomyces cerevisiae was utilized for bioethanol production using the grass press-juice as the sole fermentation medium. The yeast was able to release about 11 g/L of ethanol in 72 h, with a total production yield of 0.38 ± 0.2 gEthanol/gsugars. It was assessed to improve the fermentation ability of Saccharomyces cerevisiae by using the short-term adaptation. For this purpose, the yeast was initially propagated in increasing the concentration of press-juice. Then, the yeast cells were re-cultivated in 100%(v/v) fresh juice to verify if it had improved the fermentation efficiency. The fructose conversion increased from 79 to 90%, and the ethanol titers reached 18 g/L resulting in a final yield of 0.50 ± 0.06 gEthanol/gsugars with a volumetric productivity of 0.44 ± 0.00 g/Lh. The overall results proved that short-term adaptation was successfully used to improve bioethanol production with S. cerevisiae using grass press-juice as fermentation medium. KEY POINTS: • Mechanical pretreatment of grass raw materials • Production of bioethanol using grass press-juice as fermentation medium • Short-term adaptation as a tool to improve the bioethanol production.
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Affiliation(s)
- Ludovica Varriale
- Department of Mechanical and Process Engineering, Division of Bioprocess Engineering, Rhein-Palatinate Technical University Kaiserslautern-Landau, Gottlieb-Daimler-Str. 49, 67663, Kaiserslautern, Germany
| | - Doris Geib
- Department of Mechanical and Process Engineering, Division of Bioprocess Engineering, Rhein-Palatinate Technical University Kaiserslautern-Landau, Gottlieb-Daimler-Str. 49, 67663, Kaiserslautern, Germany
| | - Roland Ulber
- Department of Mechanical and Process Engineering, Division of Bioprocess Engineering, Rhein-Palatinate Technical University Kaiserslautern-Landau, Gottlieb-Daimler-Str. 49, 67663, Kaiserslautern, Germany.
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2
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de Oliveira Pereira I, Dos Santos ÂA, Guimarães NC, Lima CS, Zanella E, Matsushika A, Rabelo SC, Stambuk BU, Ienczak JL. First- and second-generation integrated process for bioethanol production: Fermentation of molasses diluted with hemicellulose hydrolysate by recombinant Saccharomyces cerevisiae. Biotechnol Bioeng 2024; 121:1314-1324. [PMID: 38178588 DOI: 10.1002/bit.28648] [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: 09/02/2023] [Revised: 12/11/2023] [Accepted: 12/19/2023] [Indexed: 01/06/2024]
Abstract
The integration of first- (1G) and second-generation (2G) ethanol production by adding sugarcane juice or molasses to lignocellulosic hydrolysates offers the possibility to overcome the problem of inhibitors (acetic acid, furfural, hydroxymethylfurfural and phenolic compounds), and add nutrients (such as salts, sugars and nitrogen sources) to the fermentation medium, allowing the production of higher ethanol titers. In this work, an 1G2G production process was developed with hemicellulosic hydrolysate (HH) from a diluted sulfuric acid pretreatment of sugarcane bagasse and sugarcane molasses. The industrial Saccharomyces cerevisiae CAT-1 was genetically modified for xylose consumption and used for co-fermentation of sucrose, fructose, glucose, and xylose. The fed-batch fermentation with high cell density that mimics an industrial fermentation was performed at bench scale fermenter, achieved high volumetric ethanol productivity of 1.59 g L-1 h-1, 0.39 g g-1 of ethanol yield, and 44.5 g L-1 ethanol titer, and shown that the yeast was able to consume all the sugars present in must simultaneously. With the results, it was possible to establish a mass balance for the global process: from pretreatment to the co-fermentation of molasses and HH, and it was possible to establish an effective integrated process (1G2G) with sugarcane molasses and HH co-fermentation employing a recombinant yeast.
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Affiliation(s)
- Isabela de Oliveira Pereira
- Department of Chemical Engineering and Food Engineering (EQA), Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Ângela A Dos Santos
- Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Nick C Guimarães
- Department of Chemical Engineering and Food Engineering (EQA), Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Cleilton S Lima
- Department of Biotechnology, Engineering College of Lorena, University of São Paulo (USP), Lorena, Brazil
| | - Eduardo Zanella
- Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Akinori Matsushika
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology, Higashi-Hiroshima, Japan
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Sarita C Rabelo
- Department of Bioprocess and Biotechnology, College of Agriculture Sciences, São Paulo State University (UNESP), Botucatu, Brazil
| | - Boris U Stambuk
- Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Jaciane L Ienczak
- Department of Chemical Engineering and Food Engineering (EQA), Universidade Federal de Santa Catarina, Florianópolis, Brazil
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3
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Pereira IDO, Dos Santos ÂA, Gonçalves DL, Purificação M, Guimarães NC, Tramontina R, Coutouné N, Zanella E, Matsushika A, Stambuk BU, Ienczak JL. Comparison of Spathaspora passalidarum and recombinant Saccharomyces cerevisiae for integration of first- and second-generation ethanol production. FEMS Yeast Res 2021; 21:6363686. [PMID: 34477865 DOI: 10.1093/femsyr/foab048] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 09/01/2021] [Indexed: 12/23/2022] Open
Abstract
First-generation ethanol (E1G) is based on the fermentation of sugars released from saccharine or starch sources, while second-generation ethanol (E2G) is focused on the fermentation of sugars released from lignocellulosic feedstocks. During the fractionation process to release sugars from hemicelluloses (mainly xylose), some inhibitor compounds are released hindering fermentation. Thus, the biggest challenge of using hemicellulosic hydrolysate is selecting strains and processes able to efficiently ferment xylose and tolerate inhibitors. With the aim of diluting inhibitors, sugarcane molasses (80% of sucrose content) can be mixed to hemicellulosic hydrolysate in an integrated E1G-E2G process. Cofermentations of xylose and sucrose were evaluated for the native xylose consumer Spathaspora passalidarum and a recombinant Saccharomyces cerevisiae strain. The industrial S. cerevisiae strain CAT-1 was modified to overexpress the XYL1, XYL2 and XKS1 genes and a mutant ([4-59Δ]HXT1) version of the low-affinity HXT1 permease, generating strain MP-C5H1. Although S. passalidarum showed better results for xylose fermentation, this yeast showed intracellular sucrose hydrolysis and low sucrose consumption in microaerobic conditions. Recombinant S. cerevisiae showed the best performance for cofermentation, and a batch strategy at high cell density in bioreactor achieved unprecedented results of ethanol yield, titer and volumetric productivity in E1G-E2G production process.
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Affiliation(s)
- Isabela de Oliveira Pereira
- Department of Chemical Engineering and Food Engineering, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil
| | - Ângela Alves Dos Santos
- Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil
| | - Davi L Gonçalves
- Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil
| | - Marcela Purificação
- Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil
| | - Nick Candiotto Guimarães
- Department of Chemical Engineering and Food Engineering, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil
| | - Robson Tramontina
- Graduate Program in Biosciences and Technology of Bioactive Products, Institute of Biology, State University of Campinas (UNICAMP), Campinas, SP 13083-852, Brazil.,Brazilian Biorenewable Laboratory, National Center for Research in Energy and Materials, Campinas, SP 13083-100, Brazil
| | - Natalia Coutouné
- Brazilian Biorenewable Laboratory, National Center for Research in Energy and Materials, Campinas, SP 13083-100, Brazil.,Graduate Program in Genetics and Molecular Biology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, SP 13083-852, Brazil
| | - Eduardo Zanella
- Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil
| | - Akinori Matsushika
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology, Higashi-Hiroshima, Hiroshima 739-0046, Japan.,Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan
| | - Boris U Stambuk
- Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil
| | - Jaciane Lutz Ienczak
- Department of Chemical Engineering and Food Engineering, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil
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Wang R, Lorantfy B, Fusco S, Olsson L, Franzén CJ. Analysis of methods for quantifying yeast cell concentration in complex lignocellulosic fermentation processes. Sci Rep 2021; 11:11293. [PMID: 34050249 PMCID: PMC8163860 DOI: 10.1038/s41598-021-90703-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 05/10/2021] [Indexed: 11/09/2022] Open
Abstract
Cell mass and viability are tightly linked to the productivity of fermentation processes. In 2nd generation lignocellulose-based media quantitative measurement of cell concentration is challenging because of particles, auto-fluorescence, and intrinsic colour and turbidity of the media. We systematically evaluated several methods for quantifying total and viable yeast cell concentrations to validate their use in lignocellulosic media. Several automated cell counting systems and stain-based viability tests had very limited applicability in such samples. In contrast, manual cell enumeration in a hemocytometer, plating and enumeration of colony forming units, qPCR, and in situ dielectric spectroscopy were further investigated. Parameter optimization to measurements in synthetic lignocellulosic media, which mimicked typical lignocellulosic fermentation conditions, resulted in statistically significant calibration models with good predictive capacity for these four methods. Manual enumeration of cells in a hemocytometer and of CFU were further validated for quantitative assessment of cell numbers in simultaneous saccharification and fermentation experiments on steam-exploded wheat straw. Furthermore, quantitative correlations could be established between these variables and in situ permittivity. In contrast, qPCR quantification suffered from inconsistent DNA extraction from the lignocellulosic slurries. Development of reliable and validated cell quantification methods and understanding their strengths and limitations in lignocellulosic contexts, will enable further development, optimization, and control of lignocellulose-based fermentation processes.
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Affiliation(s)
- Ruifei Wang
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.,Nouryon, Hamnvägen 2, 444 85, Stenungsund, Sweden
| | - Bettina Lorantfy
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.,BioPhero ApS, Lersø Parkallé 42-44, 4. th., 2100, Copenhagen Ø, Denmark
| | - Salvatore Fusco
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.,Department of Biotechnology, University of Verona, Strada le Grazie 15, 37134, Verona, Italy
| | - Lisbeth Olsson
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Carl Johan Franzén
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
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Cámara E, Lenitz I, Nygård Y. A CRISPR activation and interference toolkit for industrial Saccharomyces cerevisiae strain KE6-12. Sci Rep 2020; 10:14605. [PMID: 32884066 PMCID: PMC7471924 DOI: 10.1038/s41598-020-71648-w] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 08/10/2020] [Indexed: 01/17/2023] Open
Abstract
Recent advances in CRISPR/Cas9 based genome editing have considerably advanced genetic engineering of industrial yeast strains. In this study, we report the construction and characterization of a toolkit for CRISPR activation and interference (CRISPRa/i) for a polyploid industrial yeast strain. In the CRISPRa/i plasmids that are available in high and low copy variants, dCas9 is expressed alone, or as a fusion with an activation or repression domain; VP64, VPR or Mxi1. The sgRNA is introduced to the CRISPRa/i plasmids from a double stranded oligonucleotide by in vivo homology-directed repair, allowing rapid transcriptional modulation of new target genes without cloning. The CRISPRa/i toolkit was characterized by alteration of expression of fluorescent protein-encoding genes under two different promoters allowing expression alterations up to ~ 2.5-fold. Furthermore, we demonstrated the usability of the CRISPRa/i toolkit by improving the tolerance towards wheat straw hydrolysate of our industrial production strain. We anticipate that our CRISPRa/i toolkit can be widely used to assess novel targets for strain improvement and thus accelerate the design-build-test cycle for developing various industrial production strains.
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Affiliation(s)
- Elena Cámara
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Ibai Lenitz
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Yvonne Nygård
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden.
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Dornau A, Robson JF, Thomas GH, McQueen-Mason SJ. Robust microorganisms for biofuel and chemical production from municipal solid waste. Microb Cell Fact 2020; 19:68. [PMID: 32178677 PMCID: PMC7077162 DOI: 10.1186/s12934-020-01325-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 03/06/2020] [Indexed: 01/30/2023] Open
Abstract
Background Worldwide 3.4 billion tonnes of municipal solid waste (MSW) will be produced annually by 2050, however, current approaches to MSW management predominantly involve unsustainable practices like landfilling and incineration. The organic fraction of MSW (OMSW) typically comprises ~ 50% lignocellulose-rich material but is underexplored as a biomanufacturing feedstock due to its highly inconsistent and heterogeneous composition. This study sought to overcome the limitations associated with studying MSW-derived feedstocks by using OMSW produced from a realistic and reproducible MSW mixture on a commercial autoclave system. The resulting OMSW fibre was enzymatically hydrolysed and used to screen diverse microorganisms of biotechnological interest to identify robust species capable of fermenting this complex feedstock. Results The autoclave pre-treated OMSW fibre contained a polysaccharide fraction comprising 38% cellulose and 4% hemicellulose. Enzymatic hydrolysate of OMSW fibre was high in d-glucose (5.5% w/v) and d-xylose (1.8%w/v) but deficient in nitrogen and phosphate. Although relatively low levels of levulinic acid (30 mM) and vanillin (2 mM) were detected and furfural and 5-hydroxymethylfurfural were absent, the hydrolysate contained an abundance of potentially toxic metals (0.6% w/v). Hydrolysate supplemented with 1% yeast extract to alleviate nutrient limitation was used in a substrate-oriented shake-flask screen with eight biotechnologically useful microorganisms (Clostridium saccharoperbutylacetonicum, Escherichia coli, Geobacillus thermoglucosidasius, Pseudomonas putida, Rhodococcus opacus, Saccharomyces cerevisiae, Schizosaccharomyces pombe and Zymomonas mobilis). Each species’ growth and productivity were characterised and three species were identified that robustly and efficiently fermented OMSW fibre hydrolysate without significant substrate inhibition: Z. mobilis, S. cerevisiae and R. opacus, respectively produced product to 69%, 70% and 72% of the maximum theoretical fermentation yield and could theoretically produce 136 kg and 139 kg of ethanol and 91 kg of triacylglycerol (TAG) per tonne of OMSW. Conclusions Developing an integrated biorefinery around MSW has the potential to significantly alleviate the environmental burden of current waste management practices. Substrate-oriented screening of a representative and reproducible OMSW-derived fibre identified microorganisms intrinsically suited to growth on OMSW hydrolysates. These species are promising candidates for developing an MSW biorefining platform and provide a foundation for future studies aiming to valorise this underexplored feedstock.
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Affiliation(s)
- Aritha Dornau
- Centre for Novel Agricultural Products (CNAP), Department of Biology, University of York, Heslington, YO10 5DD, York, UK
| | - James F Robson
- Department of Biology, University of York, Heslington, YO10 5DD, York, UK
| | - Gavin H Thomas
- Department of Biology, University of York, Heslington, YO10 5DD, York, UK
| | - Simon J McQueen-Mason
- Centre for Novel Agricultural Products (CNAP), Department of Biology, University of York, Heslington, YO10 5DD, York, UK.
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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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Enhanced ethanol production from industrial lignocellulose hydrolysates by a hydrolysate-cofermenting Saccharomyces cerevisiae strain. Bioprocess Biosyst Eng 2019; 42:883-896. [PMID: 30820665 DOI: 10.1007/s00449-019-02090-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/11/2019] [Indexed: 10/27/2022]
Abstract
Industrial production of lignocellulosic ethanol requires a microorganism utilizing both hexose and pentose, and tolerating inhibitors. In this study, a hydrolysate-cofermenting Saccharomyces cerevisiae strain was obtained through one step in vivo DNA assembly of pentose-metabolizing pathway genes, followed by consecutive adaptive evolution in pentose media containing acetic acid, and direct screening in biomass hydrolysate media. The strain was able to coferment glucose and xylose in synthetic media with the respective maximal specific rates of glucose and xylose consumption, and ethanol production of 3.47, 0.38 and 1.62 g/g DW/h, with an ethanol titre of 41.07 g/L and yield of 0.42 g/g. Industrial wheat straw hydrolysate fermentation resulted in maximal specific rates of glucose and xylose consumption, and ethanol production of 2.61, 0.54 and 1.38 g/g DW/h, respectively, with an ethanol titre of 54.11 g/L and yield of 0.44 g/g. These are among the best for wheat straw hydrolysate fermentation through separate hydrolysis and cofermentation.
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9
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Westman JO, Nyman J, Manara RMA, Mapelli V, Franzén CJ. A novel chimaeric flocculation protein enhances flocculation in Saccharomyces cerevisiae. Metab Eng Commun 2018; 6:49-55. [PMID: 29896447 PMCID: PMC5994806 DOI: 10.1016/j.meteno.2018.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 04/06/2018] [Accepted: 04/07/2018] [Indexed: 01/29/2023] Open
Abstract
Yeast flocculation is the reversible formation of multicellular complexes mediated by lectin-like cell wall proteins binding to neighbouring cells. Strong flocculation can improve the inhibitor tolerance and fermentation performance of yeast cells in second generation bioethanol production. The strength of flocculation increases with the size of the flocculation protein and is strain dependent. However, the large number of internal repeats in the sequence of FLO1 from Saccharomyces cerevisiae S288c makes it difficult to recombinantly express the gene to its full length. In the search for novel flocculation genes resulting in strong flocculation, we discovered a DNA sequence, FLONF, that gives NewFlo phenotype flocculation in S. cerevisiae CEN.PK 113-7D. The nucleotide sequence of the internal repeats of FLONF differed from those of FLO1. We hypothesized that a chimaeric flocculation gene made up of a FLO1 variant derived from S. cerevisiae S288c and additional repeats from FLONF from S. cerevisiae CCUG 53310 would be more stable and easier to amplify by PCR. The constructed gene, FLOw, had 22 internal repeats compared to 18 in FLO1. Expression of FLOw in otherwise non-flocculating strains led to strong flocculation. Despite the length of the gene, the cassette containing FLOw could be easily amplified and transformed into yeast strains of different genetic background, leading to strong flocculation in all cases tested. The developed gene can be used as a self-immobilization technique or to obtain rapidly sedimenting cells for application in e.g. sequential batches without need for centrifugation. A novel gene sequence conferring NewFlo phenotype flocculation was isolated. The chimaeric gene FLOw was constructed from parts of FLO1 and FLONF. Overexpression of FLOw gave strong flocculation in several S. cerevisiae strains.
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Affiliation(s)
- Johan O Westman
- Chalmers University of Technology, Department of Biology and Biological Engineering, Division of Industrial Biotechnology, 412 96 Göteborg, Sweden
| | - Jonas Nyman
- University of Southampton, Chemistry, University Road, Southampton SO17 1BJ, UK
| | - Richard M A Manara
- University of Southampton, Chemistry, University Road, Southampton SO17 1BJ, UK
| | - Valeria Mapelli
- Chalmers University of Technology, Department of Biology and Biological Engineering, Division of Industrial Biotechnology, 412 96 Göteborg, Sweden
| | - Carl Johan Franzén
- Chalmers University of Technology, Department of Biology and Biological Engineering, Division of Industrial Biotechnology, 412 96 Göteborg, Sweden
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