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Jenkins Sánchez LR, Sips LM, Van Bogaert INA. Just passing through: Deploying aquaporins in microbial cell factories. Biotechnol Prog 2024:e3497. [PMID: 39051848 DOI: 10.1002/btpr.3497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 07/05/2024] [Accepted: 07/10/2024] [Indexed: 07/27/2024]
Abstract
As microbial membranes are naturally impermeable to even the smallest biomolecules, transporter proteins are physiologically essential for normal cell functioning. This makes transporters a key target area for engineering enhanced cell factories. As part of the wider cellular transportome, aquaporins (AQPs) are responsible for transporting small polar solutes, encompassing many compounds which are of great interest for industrial biotechnology, including cell feedstocks, numerous commercially relevant polyols and even weak organic acids. In this review, examples of cell factory engineering by targeting AQPs are presented. These AQP modifications aid in redirecting carbon fluxes and boosting bioconversions either by enhanced feedstock uptake, improved intermediate retention, increasing product export into the media or superior cell viability against stressors with applications in both bacterial and yeast production platforms. Additionally, the future potential for AQP deployment and targeting is discussed, showcasing hurdles and considerations of this strategy as well as recent advances and future directions in the field. By leveraging the natural diversity of AQPs and breakthroughs in channel protein engineering, these transporters are poised to be promising tools capable of enhancing a wide variety of biotechnological processes.
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Affiliation(s)
- Liam Richard Jenkins Sánchez
- BioPort Group, Centre for Synthetic Biology, Department of Biotechnology, Faculty of Bio-science Engineering, Ghent University, Ghent, Belgium
| | - Lobke Maria Sips
- BioPort Group, Centre for Synthetic Biology, Department of Biotechnology, Faculty of Bio-science Engineering, Ghent University, Ghent, Belgium
| | - Inge Noëlle Adriënne Van Bogaert
- BioPort Group, Centre for Synthetic Biology, Department of Biotechnology, Faculty of Bio-science Engineering, Ghent University, Ghent, Belgium
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Yang P, Jiang S, Lu S, Jiang S, Jiang S, Deng Y, Lu J, Wang H, Zhou Y. Ethanol yield improvement in Saccharomyces cerevisiae GPD2 Delta FPS1 Delta ADH2 Delta DLD3 Delta mutant and molecular mechanism exploration based on the metabolic flux and transcriptomics approaches. Microb Cell Fact 2022; 21:160. [PMID: 35964044 PMCID: PMC9375381 DOI: 10.1186/s12934-022-01885-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 08/05/2022] [Indexed: 11/10/2022] Open
Abstract
Background Saccharomyces cerevisiae generally consumes glucose to produce ethanol accompanied by the main by-products of glycerol, acetic acid, and lactic acid. The minimization of the formation of by-products in S. cerevisiae was an effective way to improve the economic viability of the bioethanol industry. In this study, S. cerevisiae GPD2, FPS1, ADH2, and DLD3 genes were knocked out by the Clustered Regularly Interspaced Short Palindromic Repeats Cas9 (CRISPR-Cas9) approach. The mechanism of gene deletion affecting ethanol metabolism was further elucidated based on metabolic flux and transcriptomics approaches. Results The engineered S. cerevisiae with gene deletion of GPD2, FPS1, ADH2, and DLD3 was constructed by the CRISPR-Cas9 approach. The ethanol content of engineered S. cerevisiae GPD2 Delta FPS1 Delta ADH2 Delta DLD3 Delta increased by 18.58% with the decrease of glycerol, acetic acid, and lactic acid contents by 22.32, 8.87, and 16.82%, respectively. The metabolic flux analysis indicated that the carbon flux rethanol in engineered strain increased from 60.969 to 63.379. The sequencing-based RNA-Seq transcriptomics represented 472 differential expression genes (DEGs) were identified in engineered S. cerevisiae, in which 195 and 277 genes were significantly up-regulated and down-regulated, respectively. The enriched pathways of up-regulated genes were mainly involved in the energy metabolism of carbohydrates, while the down-regulated genes were mainly enriched in acid metabolic pathways. Conclusions The yield of ethanol in engineered S. cerevisiae increased with the decrease of the by-products including glycerol, acetic acid, and lactic acid. The deletion of genes GPD2, FPS1, ADH2, and DLD3 resulted in the redirection of carbon flux. Supplementary Information The online version contains supplementary material available at 10.1186/s12934-022-01885-3.
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Affiliation(s)
- Peizhou Yang
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agricultural Products, Hefei University of Technology, 420 Feicui Road, Shushan District, Hefei, 230601, Anhui, China.
| | - Shuying Jiang
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agricultural Products, Hefei University of Technology, 420 Feicui Road, Shushan District, Hefei, 230601, Anhui, China
| | - Shuhua Lu
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agricultural Products, Hefei University of Technology, 420 Feicui Road, Shushan District, Hefei, 230601, Anhui, China
| | - Suwei Jiang
- Department of Biological, Food and Environment Engineering, Hefei University, 158 Jinxiu Avenue, Hefei, 230601, China
| | - Shaotong Jiang
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agricultural Products, Hefei University of Technology, 420 Feicui Road, Shushan District, Hefei, 230601, Anhui, China
| | - Yanhong Deng
- Suzhou Cofco Biochemical Co., Ltd., Suzhou, 234001, China
| | - Jiuling Lu
- Suzhou Cofco Biochemical Co., Ltd., Suzhou, 234001, China
| | - Hu Wang
- Suzhou Cofco Biochemical Co., Ltd., Suzhou, 234001, China
| | - Yong Zhou
- Suzhou Cofco Biochemical Co., Ltd., Suzhou, 234001, China
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Hou LH, Meng M, Guo L, He JY. A comparison of whole cell directed evolution approaches in breeding of industrial strain of Saccharomyces cerevisiae. Biotechnol Lett 2015; 37:1393-8. [PMID: 25773199 DOI: 10.1007/s10529-015-1812-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 03/02/2015] [Indexed: 10/23/2022]
Abstract
OBJECTIVE To reduce the fermentation cost in very high gravity fermentations of ethanol using Saccharomyces cerevisiae, whole cell directed evolution approaches were carried out. RESULTS The methods used included cell ploidy manipulation, global transcription machinery engineering and genome shuffling. Ethanol production by the four methods was improved compared with the control. Notably, the ethanol yield of a strain constructed by genome shuffling was enhanced by up to 11 % more than the control reaching 120 g ethanol/l in 35 h using a very high gravity fermentation with 300 g glucose/l. CONCLUSION Genome shuffling can create strains with improved fermentation characteristics in very high gravity fermentations.
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Affiliation(s)
- Li-Hua Hou
- Key Laboratory of Food Nutrition and Safety, Tianjin University of Science & Technology, Ministry of Education, Tianjin, 300457, China,
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Xiong M, Chen G, Barford J. Genetic engineering of yeasts to improve ethanol production from xylose. J Taiwan Inst Chem Eng 2014. [DOI: 10.1016/j.jtice.2013.04.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Increasing ethanol titer and yield in a gpd1Δ gpd2Δ strain by simultaneous overexpression of GLT1 and STL1 in Saccharomyces cerevisiae. Biotechnol Lett 2013; 35:1859-64. [DOI: 10.1007/s10529-013-1271-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 06/07/2013] [Indexed: 10/26/2022]
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Pagliardini J, Hubmann G, Alfenore S, Nevoigt E, Bideaux C, Guillouet SE. The metabolic costs of improving ethanol yield by reducing glycerol formation capacity under anaerobic conditions in Saccharomyces cerevisiae. Microb Cell Fact 2013; 12:29. [PMID: 23537043 PMCID: PMC3639890 DOI: 10.1186/1475-2859-12-29] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 02/24/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Finely regulating the carbon flux through the glycerol pathway by regulating the expression of the rate controlling enzyme, glycerol-3-phosphate dehydrogenase (GPDH), has been a promising approach to redirect carbon from glycerol to ethanol and thereby increasing the ethanol yield in ethanol production. Here, strains engineered in the promoter of GPD1 and deleted in GPD2 were used to investigate the possibility of reducing glycerol production of Saccharomyces cerevisiae without jeopardising its ability to cope with process stress during ethanol production. For this purpose, the mutant strains TEFmut7 and TEFmut2 with different GPD1 residual expression were studied in Very High Ethanol Performance (VHEP) fed-batch process under anaerobic conditions. RESULTS Both strains showed a drastic reduction of the glycerol yield by 44 and 61% while the ethanol yield improved by 2 and 7% respectively. TEFmut2 strain showing the highest ethanol yield was accompanied by a 28% reduction of the biomass yield. The modulation of the glycerol formation led to profound redox and energetic changes resulting in a reduction of the ATP yield (YATP) and a modulation of the production of organic acids (acetate, pyruvate and succinate). Those metabolic rearrangements resulted in a loss of ethanol and stress tolerance of the mutants, contrarily to what was previously observed under aerobiosis. CONCLUSIONS This work demonstrates the potential of fine-tuned pathway engineering, particularly when a compromise has to be found between high product yield on one hand and acceptable growth, productivity and stress resistance on the other hand. Previous study showed that, contrarily to anaerobiosis, the resulting gain in ethanol yield was accompanied with no loss of ethanol tolerance under aerobiosis. Moreover those mutants were still able to produce up to 90 gl-1 ethanol in an anaerobic SSF process. Fine tuning metabolic strategy may then open encouraging possibilities for further developing robust strains with improved ethanol yield.
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Affiliation(s)
- Julien Pagliardini
- Université de Toulouse, INSA, UPS, INP, LISBP, 135 Av. de Rangueil, F-31077 Toulouse, France INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, Toulouse F-31400, France
| | - Georg Hubmann
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Katholieke Universiteit Leuven, Kasteelpark Arenberg 31 - bus 2438, Heverlee, Flanders B-3001, Belgium
- Department of Molecular Microbiology, VIB, Kasteelpark Arenberg 31 - bus 2438, Heverlee, Flanders B-3001, Belgium
| | - Sandrine Alfenore
- Université de Toulouse, INSA, UPS, INP, LISBP, 135 Av. de Rangueil, F-31077 Toulouse, France INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, Toulouse F-31400, France
| | - Elke Nevoigt
- School of Engineering and Science, Jacobs University gGmbH, Campus Ring 1, Bremen 28759, Germany
| | - Carine Bideaux
- Université de Toulouse, INSA, UPS, INP, LISBP, 135 Av. de Rangueil, F-31077 Toulouse, France INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, Toulouse F-31400, France
| | - Stephane E Guillouet
- Université de Toulouse, INSA, UPS, INP, LISBP, 135 Av. de Rangueil, F-31077 Toulouse, France INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, Toulouse F-31400, France
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Hubmann G, Foulquié-Moreno MR, Nevoigt E, Duitama J, Meurens N, Pais TM, Mathé L, Saerens S, Nguyen HTT, Swinnen S, Verstrepen KJ, Concilio L, de Troostembergh JC, Thevelein JM. Quantitative trait analysis of yeast biodiversity yields novel gene tools for metabolic engineering. Metab Eng 2013; 17:68-81. [PMID: 23518242 DOI: 10.1016/j.ymben.2013.02.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 12/25/2012] [Accepted: 02/20/2013] [Indexed: 01/17/2023]
Abstract
Engineering of metabolic pathways by genetic modification has been restricted largely to enzyme-encoding structural genes. The product yield of such pathways is a quantitative genetic trait. Out of 52 Saccharomyces cerevisiae strains phenotyped in small-scale fermentations, we identified strain CBS6412 as having unusually low glycerol production and higher ethanol yield as compared to an industrial reference strain. We mapped the QTLs underlying this quantitative trait with pooled-segregant whole-genome sequencing using 20 superior segregants selected from a total of 257. Plots of SNP variant frequency against SNP chromosomal position revealed one major and one minor locus. Downscaling of the major locus and reciprocal hemizygosity analysis identified an allele of SSK1, ssk1(E330N…K356N), expressing a truncated and partially mistranslated protein, as causative gene. The diploid CBS6412 parent was homozygous for ssk1(E330N…K356N). This allele affected growth and volumetric productivity less than the gene deletion. Introduction of the ssk1(E330N…K356N) allele in the industrial reference strain resulted in stronger reduction of the glycerol/ethanol ratio compared to SSK1 deletion and also compromised volumetric productivity and osmotolerance less. Our results show that polygenic analysis of yeast biodiversity can provide superior novel gene tools for metabolic engineering.
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Affiliation(s)
- Georg Hubmann
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Belgium
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3' Truncation of the GPD1 promoter in Saccharomyces cerevisiae for improved ethanol yield and productivity. Appl Environ Microbiol 2013; 79:3273-81. [PMID: 23503313 DOI: 10.1128/aem.03319-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glycerol is a major by-product in bioethanol fermentation by the yeast Saccharomyces cerevisiae, and decreasing glycerol formation for increased ethanol yield has been a major research effort in the bioethanol field. A new strategy has been used in the present study for reduced glycerol formation and improved ethanol fermentation performance by finely modulating the expression of GPD1 in the KAM15 strain (fps1Δ pPGK1-GLT1 gpd2Δ). The GPD1 promoter was serially truncated from the 3' end by 20 bp to result in a different expression strength of GPD1. The two engineered promoters carrying 60- and 80-bp truncations exhibited reduced promoter strength but unaffected osmostress response. These two promoters were integrated into the KAM15 strain, generating strains LE34U and LE35U, respectively. The transcription levels of LE34U and LE35U were 37.77 to 45.12% and 21.34 to 24.15% of that of KAM15U, respectively, depending on osmotic stress imposed by various glucose concentrations. In very high gravity (VHG) fermentation, the levels of glycerol for LE34U and LE35U were reduced by 15.81% and 30.66%, respectively, compared to KAM15U. The yield and final concentration of ethanol for LE35U were 3.46% and 0.33% higher, respectively, than those of KAM15U. However, fermentation rate and ethanol productivity for LE35U were reduced. On the other hand, the ethanol yield and final concentration for LE34U were enhanced by 2.28% and 2.32%, respectively, compared to those of KAM15U. In addition, a 2.31% increase in ethanol productivity was observed for LE34U compared to KAM15U. These results verified the feasibility of our strategy for yeast strain development.
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Xiong M, Chen G, Barford J. Alteration of xylose reductase coenzyme preference to improve ethanol production by Saccharomyces cerevisiae from high xylose concentrations. BIORESOURCE TECHNOLOGY 2011; 102:9206-15. [PMID: 21831633 DOI: 10.1016/j.biortech.2011.06.058] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 06/12/2011] [Accepted: 06/14/2011] [Indexed: 05/26/2023]
Abstract
A K270R mutation of xylose reductase (XR) was constructed by site-direct mutagenesis. Fermentation results of the F106X and F106KR strains, which carried wild type XR and K270R respectively, were compared using different substrate concentrations (from 55 to 220 g/L). After 72 h, F106X produced less ethanol than xylitol, while F106KR produced ethanol at a constant yield of 0.36 g/g for all xylose concentrations. The xylose consumption rate and ethanol productivity increased with increasing xylose concentrations in F106KR strain. In particular, F106KR produced 77.6g/L ethanol from 220 g/L xylose and converted 100 g/L glucose and 100g/L xylose into 89.0 g/L ethanol in 72h, but the corresponding values of F106X strain are 7.5 and 65.8 g/L. The ethanol yield of F106KR from glucose and xylose was 0.42 g/g, which was 82.3% of the theoretical yield. These results suggest that the F106KR strain is an excellent producer of ethanol from xylose.
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Affiliation(s)
- Mingyong Xiong
- Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
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Gpd1 and Gpd2 fine-tuning for sustainable reduction of glycerol formation in Saccharomyces cerevisiae. Appl Environ Microbiol 2011; 77:5857-67. [PMID: 21724879 DOI: 10.1128/aem.05338-11] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Gpd1 and Gpd2 are the two isoforms of glycerol 3-phosphate dehydrogenase (GPDH), which is the rate-controlling enzyme of glycerol formation in Saccharomyces cerevisiae. The two isoenzymes play crucial roles in osmoregulation and redox balancing. Past approaches to increase ethanol yield at the cost of reduced glycerol yield have most often been based on deletion of either one or two isogenes (GPD1 and GPD2). While single deletions of GPD1 or GPD2 reduced glycerol formation only slightly, the gpd1Δ gpd2Δ double deletion strain produced zero glycerol but showed an osmosensitive phenotype and abolished anaerobic growth. Our current approach has sought to generate "intermediate" phenotypes by reducing both isoenzyme activities without abolishing them. To this end, the GPD1 promoter was replaced in a gpd2Δ background by two lower-strength TEF1 promoter mutants. In the same manner, the activity of the GPD2 promoter was reduced in a gpd1Δ background. The resulting strains were crossed to obtain different combinations of residual GPD1 and GPD2 expression levels. Among our engineered strains we identified four candidates showing improved ethanol yields compared to the wild type. In contrast to a gpd1Δ gpd2Δ double-deletion strain, these strains were able to completely ferment the sugars under quasi-anaerobic conditions in both minimal medium and during simultaneous saccharification and fermentation (SSF) of liquefied wheat mash (wheat liquefact). This result implies that our strains can tolerate the ethanol concentration at the end of the wheat liquefact SSF (up to 90 g liter(-1)). Moreover, a few of these strains showed no significant reduction in osmotic stress tolerance compared to the wild type.
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Pagliardini J, Hubmann G, Bideaux C, Alfenore S, Nevoigt E, Guillouet SE. Quantitative evaluation of yeast's requirement for glycerol formation in very high ethanol performance fed-batch process. Microb Cell Fact 2010; 9:36. [PMID: 20492645 PMCID: PMC2887396 DOI: 10.1186/1475-2859-9-36] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 05/21/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Glycerol is the major by-product accounting for up to 5% of the carbon in Saccharomyces cerevisiae ethanolic fermentation. Decreasing glycerol formation may redirect part of the carbon toward ethanol production. However, abolishment of glycerol formation strongly affects yeast's robustness towards different types of stress occurring in an industrial process. In order to assess whether glycerol production can be reduced to a certain extent without jeopardizing growth and stress tolerance, the yeast's capacity to synthesize glycerol was adjusted by fine-tuning the activity of the rate-controlling enzyme glycerol 3-phosphate dehydrogenase (GPDH). Two engineered strains whose specific GPDH activity was significantly reduced by two different degrees were comprehensively characterized in a previously developed Very High Ethanol Performance (VHEP) fed-batch process. RESULTS The prototrophic strain CEN.PK113-7D was chosen for decreasing glycerol formation capacity. The fine-tuned reduction of specific GPDH activity was achieved by replacing the native GPD1 promoter in the yeast genome by previously generated well-characterized TEF promoter mutant versions in a gpd2Delta background. Two TEF promoter mutant versions were selected for this study, resulting in a residual GPDH activity of 55 and 6%, respectively. The corresponding strains were referred to here as TEFmut7 and TEFmut2. The genetic modifications were accompanied to a strong reduction in glycerol yield on glucose; the level of reduction compared to the wild-type was 61% in TEFmut7 and 88% in TEFmut2. The overall ethanol production yield on glucose was improved from 0.43 g g(-1) in the wild type to 0.44 g g(-1) measured in TEFmut7 and 0.45 g g(-1) in TEFmut2. Although maximal growth rate in the engineered strains was reduced by 20 and 30%, for TEFmut7 and TEFmut2 respectively, strains' ethanol stress robustness was hardly affected; i.e. values for final ethanol concentration (117 +/- 4 g L(-1)), growth-inhibiting ethanol concentration (87 +/- 3 g L(-1)) and volumetric ethanol productivity (2.1 +/- 0.15 g l(-1) h(-1)) measured in wild-type remained virtually unchanged in the engineered strains. CONCLUSIONS This work demonstrates the power of fine-tuned pathway engineering, particularly when a compromise has to be found between high product yield on one hand and acceptable growth, productivity and stress resistance on the other hand. Under the conditions used in this study (VHEP fed-batch), the two strains with "fine-tuned" GPD1 expression in a gpd2Delta background showed slightly better ethanol yield improvement than previously achieved with the single deletion strains gpd1Delta or gpd2Delta. Although glycerol reduction is known to be even higher in a gpd1Delta gpd2Delta double deletion strain, our strains could much better cope with process stress as reflected by better growth and viability.
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Affiliation(s)
- Julien Pagliardini
- Université de Toulouse, INSA, UPS, INP, LISBP, 135 Av de Rangueil, F-31077 Toulouse, France
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Abstract
The traditional use of the yeast Saccharomyces cerevisiae in alcoholic fermentation has, over time, resulted in substantial accumulated knowledge concerning genetics, physiology, and biochemistry as well as genetic engineering and fermentation technologies. S. cerevisiae has become a platform organism for developing metabolic engineering strategies, methods, and tools. The current review discusses the relevance of several engineering strategies, such as rational and inverse metabolic engineering, evolutionary engineering, and global transcription machinery engineering, in yeast strain improvement. It also summarizes existing tools for fine-tuning and regulating enzyme activities and thus metabolic pathways. Recent examples of yeast metabolic engineering for food, beverage, and industrial biotechnology (bioethanol and bulk and fine chemicals) follow. S. cerevisiae currently enjoys increasing popularity as a production organism in industrial ("white") biotechnology due to its inherent tolerance of low pH values and high ethanol and inhibitor concentrations and its ability to grow anaerobically. Attention is paid to utilizing lignocellulosic biomass as a potential substrate.
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