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Kalmokoff ML, Ingledew WM. Evaluation of Ethanol Tolerance in SelectedSaccharomycesStrains. JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS 2018. [DOI: 10.1094/asbcj-43-0189] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Martin L. Kalmokoff
- Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 0W0
| | - W. M. Ingledew
- Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 0W0
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Moreno-García J, Mauricio JC, Moreno J, García-Martínez T. Stress responsive proteins of a flor yeast strain during the early stages of biofilm formation. Process Biochem 2016. [DOI: 10.1016/j.procbio.2016.02.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Singh S, Sarma S, Agarwal M, Goyal A, Moholkar VS. Ultrasound enhanced ethanol production from Parthenium hysterophorus: A mechanistic investigation. BIORESOURCE TECHNOLOGY 2014; 188:287-94. [PMID: 25555927 DOI: 10.1016/j.biortech.2014.12.038] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 12/10/2014] [Accepted: 12/12/2014] [Indexed: 05/24/2023]
Abstract
This study presents mechanistic investigations in ultrasound-assisted bioethanol fermentation using Parthenium hysterophorus biomass. Ultrasound (35 kHz, 10% duty cycle) has been used for sonication. Experimental results were fitted to mathematical model; the kinetic and physiological parameters in the model were obtained using Genetic Algorithm (GA) based optimization. In control experiments (mechanical shaking), maximum ethanol titer of 10.93 g/L and cell mass concentration of 5.26 g/L was obtained after 18 h. In test experiments (mechanical shaking and intermittent sonication), ethanol titer of 12.14 g/L and cell mass concentration of 5.7 g/L was obtained in 10h. This indicated ∼ 2 × enhanced productivity of ethanol and cell mass with sonication. Trends in model parameters obtained after fitting of model to experimental data essentially revealed that beneficial influence of ultrasound on fermentation is a manifestation of enhanced trans-membrane transportation and dilution of toxic substances due to strong micro-convection induced by ultrasound.
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Affiliation(s)
- Shuchi Singh
- Center for Energy, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India
| | - Shyamali Sarma
- Center for Energy, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India
| | - Mayank Agarwal
- Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India
| | - Arun Goyal
- Center for Energy, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India; Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India
| | - Vijayanand S Moholkar
- Center for Energy, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India; Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India.
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Stewart GG, Russell I. ONE HUNDRED YEARS OF YEAST RESEARCH AND DEVELOPMENT IN THE BREWING INDUSTRY. JOURNAL OF THE INSTITUTE OF BREWING 2013. [DOI: 10.1002/j.2050-0416.1986.tb04453.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Dinsdale MG, Lloyd D, Jarvis B. YEAST VITALITY DURING CIDER FERMENTATION: TWO APPROACHES TO THE MEASUREMENT OF MEMBRANE POTENTIAL. JOURNAL OF THE INSTITUTE OF BREWING 2013. [DOI: 10.1002/j.2050-0416.1995.tb00883.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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D'Amore T. CAMBRIDGE PRIZE LECTURE IMPROVING YEAST FERMENTATION PERFORMANCE. JOURNAL OF THE INSTITUTE OF BREWING 2013. [DOI: 10.1002/j.2050-0416.1992.tb01119.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Peinado JM, Leão C. Nicolau van Uden, a life with yeasts (1921-1991). IUBMB Life 2012; 64:556-60. [DOI: 10.1002/iub.1036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 03/02/2012] [Indexed: 11/10/2022]
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8
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Biryukova EN, Arinbasarova AY, Medentsev AG. Adaptation of the yeast Yarrowia lipolytica to ethanol. Microbiology (Reading) 2009. [DOI: 10.1134/s0026261709020039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Shao X, Lynd L, Wyman C, Bakker A. Kinetic modeling of cellulosic biomass to ethanol via simultaneous saccharification and fermentation: Part I. Accommodation of intermittent feeding and analysis of staged reactors. Biotechnol Bioeng 2009; 102:59-65. [DOI: 10.1002/bit.22048] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Gao C, Fleet GH. The effects of temperature and pH on the ethanol tolerance of the wine yeasts,Saccharomyces cerevisiae, Candida stellataandKloeckera apiculata. ACTA ACUST UNITED AC 2008. [DOI: 10.1111/j.1365-2672.1988.tb01909.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Brandam C, Castro-Martínez C, Délia ML, Ramón-Portugal F, Strehaiano P. Effect of temperature on Brettanomyces bruxellensis: metabolic and kinetic aspects. Can J Microbiol 2008; 54:11-8. [DOI: 10.1139/w07-126] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of temperatures ranging from 15 to 35 °C on a culture of Brettanomyces bruxellensis was investigated in regards to thermodynamics, metabolism, and kinetics. In this temperature range, we observed an increase in growth and production rates. The growth behavior was well represented using the Arrhenius model, and an apparent activation energy of 16.61 kcal/mol was estimated. A stuck fermentation was observed at 35 °C as represented by high cell death. The carbon balance established that temperature had no effect on repartition of the glucose consumption between biomass and products. Hence, the same biomass concentration was obtained for all temperatures, except at 35 °C. Moreover, using logistic and Luedeking–Piret models, we demonstrated that production rates of ethanol and acetic acid were partially growth associated. Parameters associated with growth (αeth and αaa) remained constant with changing temperature, whereas, parameters associated with the population (βeth and βaa) varied. Optimal values were obtained at 32 °C for ethanol and at 25 °C for acetic acid.
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Affiliation(s)
- Cédric Brandam
- Laboratoire de génie chimique, UMR-CNRS 5503, 5 rue Paulin Talabot, 31106 Toulouse CEDEX 1, France
| | - Claudia Castro-Martínez
- Laboratoire de génie chimique, UMR-CNRS 5503, 5 rue Paulin Talabot, 31106 Toulouse CEDEX 1, France
| | - Marie-Line Délia
- Laboratoire de génie chimique, UMR-CNRS 5503, 5 rue Paulin Talabot, 31106 Toulouse CEDEX 1, France
| | - Felipe Ramón-Portugal
- Laboratoire de génie chimique, UMR-CNRS 5503, 5 rue Paulin Talabot, 31106 Toulouse CEDEX 1, France
| | - Pierre Strehaiano
- Laboratoire de génie chimique, UMR-CNRS 5503, 5 rue Paulin Talabot, 31106 Toulouse CEDEX 1, France
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Brosnan MP, Donnelly D, James TC, Bond U. The stress response is repressed during fermentation in brewery strains of yeast. J Appl Microbiol 2000; 88:746-55. [PMID: 10792534 DOI: 10.1046/j.1365-2672.2000.01006.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Yeast cells encounter a variety of environmental stresses during brewing and must respond to ensure cell survival. Cells can respond to stress by inducing a Heat Shock Response in which heat shock proteins (Hsps) are synthesized. In laboratory strains of Saccharomyces cerevisiae, the heat shock protein, Hsp104, plays a major role in the acquisition of tolerance to a variety of stresses such as heat, ethanol and sodium arsenite, and as such acts as an excellent stress indicator. The induction of Hsp104 in bottom-and top-fermenting brewery strains was examined when grown under laboratory and industrial fermentation conditions, and it was found that each brewing strain exhibits its own unique pattern of Hsp104 expression. During industrial fermentations, brewery strains are capable of mounting a stress response at the early stages of fermentation. However, as the fermentation proceeds, the response is repressed. The results suggest that conditions experienced in industrial brewing prevent the activation of the stress response. This study increases our understanding of alterations in gene expression patterns during the brewing process, and yields information that will aid in the definition of best practice in yeast management.
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Affiliation(s)
- M P Brosnan
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, University of Dublin and Guinness R & D, Guinness Brewery, Dublin, Ireland
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Accumulation of trehalose by overexpression of tps1, coding for trehalose-6-phosphate synthase, causes increased resistance to multiple stresses in the fission yeast schizosaccharomyces pombe. Appl Environ Microbiol 1999; 65:2020-4. [PMID: 10223994 PMCID: PMC91291 DOI: 10.1128/aem.65.5.2020-2024.1999] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent studies have shown that heat shock proteins and trehalose synthesis are important factors in the thermotolerance of the fission yeast Schizosaccharomyces pombe. We examined the effects of trehalose-6-phosphate (trehalose-6P) synthase overexpression on resistance to several stresses in cells of S. pombe transformed with a plasmid bearing the tps1 gene, which codes for trehalose-6P synthase, under the control of the strong thiamine-repressible promoter. Upon induction of trehalose-6P synthase, the elevated levels of intracellular trehalose correlated not only with increased tolerance to heat shock but also with resistance to freezing and thawing, dehydration, osmostress, and toxic levels of ethanol, indicating that trehalose may be the stress metabolite underlying the overlap in induced tolerance to these stresses. Among the isogenic strains transformed with this construct, one in which the gene coding for the trehalose-hydrolyzing enzyme, neutral trehalase, was disrupted accumulated trehalose to a greater extent and was more resistant to the above stresses. Increased trehalose concentration is thus a major determinant of the general stress protection response in S. pombe.
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Wang S, Ingledew WM, Thomas KC, Sosulski K, Sosulski FW. Optimization of Fermentation Temperature and Mash Specific Gravity for Fuel Alcohol Production. Cereal Chem 1999. [DOI: 10.1094/cchem.1999.76.1.82] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- S. Wang
- Department of Applied Microbiology and Food Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, Canada S7N 5A8
- Corresponding author. Phone: 306/966-5030. Fax: 306/966-8898. E-mail:
| | - W. M. Ingledew
- Department of Applied Microbiology and Food Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, Canada S7N 5A8
| | - K. C. Thomas
- Department of Applied Microbiology and Food Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, Canada S7N 5A8
| | - K. Sosulski
- Saskatchewan Research Council, 15 Innovation Boulevard, Saskatoon, SK, Canada S7N 2X8
| | - F. W. Sosulski
- Department of Crop Science and Plant Ecology, University of Saskatchewan, SK, Saskatchewan
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Wang S, Thomas KC, Ingledew WM, Sosulski K, Sosulski FW. Production of fuel ethanol from rye and triticale by very-high-gravity (VHG) fermentation. Appl Biochem Biotechnol 1998. [DOI: 10.1007/bf02788811] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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17
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Costa V, Amorim MA, Reis E, Quintanilha A, Moradas-Ferreira P. Mitochondrial superoxide dismutase is essential for ethanol tolerance of Saccharomyces cerevisiae in the post-diauxic phase. MICROBIOLOGY (READING, ENGLAND) 1997; 143 ( Pt 5):1649-1656. [PMID: 9168613 DOI: 10.1099/00221287-143-5-1649] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This work reports the role of both superoxide dismutases-CuZnSOD (encoded by SOD1) and MnSOD (encoded by SOD2)-in the build-up of tolerance to ethanol during growth of Saccharomyces cerevisiae from exponential to post-diauxic phase. Both enzyme activities increase from the exponential phase to the diauxic shift and from the diauxic shift to the post-diauxic phase. The levels of mRNA-SOD1 and mRNA-SOD2 increase from the exponential phase to the diauxic shift; however, during the post-diauxic phase mRNA-SOD1 levels decrease while mRNA-SOD2 levels remain unchanged. These data indicate the existence of two regulatory mechanisms involved in the induction of SOD activity during growth: synthesis de novo of the proteins (until the diauxic shift), and post-transcriptional or post-translational regulation (during the post-diauxic phase). Ethanol does not alter the activities of either enzyme in cells from the diauxic shift or post-diauxic-phases, although the respective mRNA levels decrease in post-diauxic-phase cells treated with ethanol (14% or 20%). Results of experiments with sod1 and sod2 mutants show that MnSOD, but not CuZnSOD, is essential for ethanol tolerance of diauxic-shift and post-diauxic-phase cells. Evidence that ethanol toxicity is correlated with the production of reactive oxygen species in the mitochondria is obtained from results with respiration-deficient mutants. In these cells, the induction of superoxide dismutase activity by ethanol is low; also, the respiratory deficiency restores the capacity of sod2 cells to acquire ethanol tolerance.
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Affiliation(s)
- V Costa
- Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal
| | - M A Amorim
- Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal
| | - E Reis
- Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal
| | - A Quintanilha
- Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal
| | - P Moradas-Ferreira
- Instituto de Ciências Biomédicas de Abel Salazar, Departamento de Biologia Molecular, e Centro de Citologia Experimental, Universidade do Porto, Portugal
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Sharma SC, Raj D, Forouzandeh M, Bansal MP. Salt-induced changes in lipid composition and ethanol tolerance in Saccharomyces cerevisiae. Appl Biochem Biotechnol 1996; 56:189-95. [PMID: 9045598 DOI: 10.1007/bf02786949] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The effect of salt stress on lipid composition and its relationship with ethanol tolerance in Saccharomyces cerevisiae was studied. Amounts of phospholipids as well as that of sterols decreased, whereas that of protein and glycolipids increased with increasing salt concentration. Relative proportion of amino phospholipids (phosphatidylethanolamine and phosphatidylserine) decreased, whereas that of phosphatidylcholine showed a reverse trend. Cells grown under increasing salt concentration were more resistant to ethanol-induced leakage of UV-absorbing substances, an index of ethanol endurance. Results showed an overlap between osmotolerance and ethanol tolerance in this strain.
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Affiliation(s)
- S C Sharma
- Department of Biochemistry, Panjab University Chandigarh, India
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Piper PW. The heat shock and ethanol stress responses of yeast exhibit extensive similarity and functional overlap. FEMS Microbiol Lett 1995; 134:121-7. [PMID: 8586257 DOI: 10.1111/j.1574-6968.1995.tb07925.x] [Citation(s) in RCA: 287] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Sublethal heat and ethanol exposure induce essentially identical stress responses in yeast. These responses are characterized by the induction of heat shock proteins, proteins requiring a temperature above about 35 degrees C or ethanol levels above a threshold level of 4-6% (v/v) for strong induction. One induced protein, Hsp104, contributes to both thermotolerance and ethanol tolerance, while others are anti-oxidant enzymes. Heat and ethanol stress cause similar changes to plasma membrane protein composition, reducing the levels of plasma membrane H(+)-ATPase protein and inducing the plasma membrane-associated Hsp30. Both stresses also stimulate the activity of the fraction of H(+)-ATPase remaining in the plasma membrane. The resulting enhancement to catalysed proton efflux from the cell represents a considerable energy demand, yet may help to counteract the adverse effects for homeostasis of the increased membrane permeability that results from stress.
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Affiliation(s)
- P W Piper
- Department of Biochemistry and Molecular Biology, University College London, UK
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Srinivasan N, Kasthurikrishnan N, Cooks R, Krishnan M, Tsao G. On-line monitoring with feedback control of bioreactors using a high ethanol tolerance yeast by membrane introduction mass spectrometry. Anal Chim Acta 1995. [DOI: 10.1016/0003-2670(95)00362-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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South C, Hogsett D, Lynd L. Modeling simultaneous saccharification and fermentation of lignocellulose to ethanol in batch and continuous reactors. Enzyme Microb Technol 1995. [DOI: 10.1016/0141-0229(94)00016-k] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
Although they were used historically as antimicrobial agents, there is a modern requirement to devise organic solvent systems for exploitation in the biotransformation by intact cells of substrates that are poorly soluble in water. Water-immiscible solvents are normally less cytotoxic than are water-miscible ones. While a unitary mechanism is excluded, damage to the membrane remains the likeliest major mechanism of cytotoxicity, and may be conveniently assessed using an electronic biomass probe. Studies designed to account for the mechanisms of action of general anesthetics and of uncouplers parallel those designed to account for the cytotoxicity of organic solvents. Although there are hundreds of potential physical descriptors of solvent properties, many are broadly similar to each other, such that the intrinsic dimensionality of solvent space is relatively small (< 10). This opens up the possibility of providing a rational biophysical basis for the optimization of the solvents used for biotransformations. The widely used descriptor of solvent behavior, log P (the octanol:water partition coefficient), is a composite of more fundamental molecular descriptors; this explains why there are rarely good correlations between cytotoxicity and log P when a wide variety of solvents is studied. Although the intrinsic dimensionality of solvent space is relatively small, pure solvents still populate it rather sparsely. Thus, mixtures of solvents can and do provide the opportunity of obtaining a solvent optimal for a biotransformation of interest.
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Affiliation(s)
- G J Salter
- Institute of Biological Sciences, University of Wales, Aberystwyth, Dyfed, U.K
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Jones AM, Ingledew WM. Fuel Alcohol Production: Optimization of Temperature for Efficient Very-High-Gravity Fermentation. Appl Environ Microbiol 1994; 60:1048-51. [PMID: 16349211 PMCID: PMC201434 DOI: 10.1128/aem.60.3.1048-1051.1994] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The time required to end ferment wheat mash decreased as the temperature was increased from 17 to 33°C, but it increased as the concentration of dissolved solids was raised from 14.0 to 36.5 g/100 ml. Ethanol yield was not appreciably affected. Over the range of fermentation temperatures tested, the addition of urea accelerated the rate of fermentation, decreased the time required to complete fermentation at all dissolved-solid concentrations, and stimulated the production of slightly more ethanol than was produced by the corresponding unsupplemented control mashes. The optimum temperature for maximum ethanol production in urea-supplemented very-high-gravity wheat mash was 27°C. These data are important for the industrial assessment of very-high-gravity fermentation technology.
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Affiliation(s)
- A M Jones
- Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 0W0
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Thomas KC, Hynes SH, Jones AM, Ingledew WM. Production of fuel alcohol from wheat by VHG technology. Appl Biochem Biotechnol 1993. [DOI: 10.1007/bf02916454] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Lloyd D, Morrell S, Carlsen HN, Degn H, James PE, Rowlands CC. Effects of growth with ethanol on fermentation and membrane fluidity of Saccharomyces cerevisiae. Yeast 1993; 9:825-33. [PMID: 8212890 DOI: 10.1002/yea.320090803] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Saccharomyces cerevisiae HSc was grown with ethanol at concentrations up to 10% (v/v). The immediate effects of additions of externally added ethanol on CO2 production and O2 consumption of washed organisms were studied by stopped-flow membrane inlet quadrupole mass spectrometry. Fermentative activities of organisms grown with ethanol (0-5% v/v) showed similar sensitivities to inhibition by ethanol, whereas those grown with 10% (v/v) ethanol had become protected and were markedly less sensitive. The fluidity of subcellular membrane fractions was measured by determination of the temperature dependence of the rotational order parameter of the spin label 5-doxyl stearic acid (free radical) by electron spin resonance. Mitochondria prepared from yeasts grown with 0, 7, and 9% (v/v) ethanol showed similar overall fluidity, although differences in temperature-dependent behaviour indicate altered lipid composition or lateral phase separations. On the other hand the microsomal fraction from organisms grown with 9% ethanol showed a remarkable increase in fluidity. These data suggest that the protective effects of growth with ethanol near the limit of tolerance on fermentative activities may arise from altered plasma membrane fluidity properties.
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Affiliation(s)
- D Lloyd
- Microbiology Group (PABIO), University of Wales College of Cardiff
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Effects of heat shock and ethanol stress on the viability of aSaccharomyces uvarum (carlsbergensis) brewing yeast strain during fermentation of high gravity wort. ACTA ACUST UNITED AC 1992. [DOI: 10.1007/bf01583843] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Dale MC, Chen C, Okos MR. Cell growth and death rates as factors in the long-term performance, modeling, and design of immobilized cell reactors. Biotechnol Bioeng 1990; 36:983-92. [DOI: 10.1002/bit.260361003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
The ethanol tolerance of yeast and other microorganisms has remained a controversial area despite the many years of study. The complex inhibition mechanism of ethanol and the lack of a universally accepted definition and method to measure ethanol tolerance have been prime reasons for the controversy. A number of factors such as plasma membrane composition, media composition, mode of substrate feeding, osmotic pressure, temperature, intracellular ethanol accumulation, and byproduct formation have been shown to influence the ethanol tolerance of yeast. Media composition was found to have a profound effect upon the ability of a yeast strain to ferment concentrated substrates (high osmotic pressure) and to ferment at higher temperatures. Supplementation with peptone-yeast extract, magnesium, or potassium salts has a significant and positive effect upon overall fermentation rates. An intracellular accumulation of ethanol was observed during the early stages of fermentation. As fermentation proceeds, the intracellular and extracellular ethanol concentrations become similar. In addition, increases in osmotic pressure are associated with increased intracellular accumulation of ethanol. However, it was observed that nutrient limitation, not increased intracellular accumulation of ethanol, is responsible to some extent for the decreases in growth and fermentation activity of yeast cells at higher osmotic pressure and temperature.
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Affiliation(s)
- T D'Amore
- Research Department, Labatt Brewing Company Ltd., London, Ontario, Canada
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Abstract
It is now certain that the inherent ethanol tolerance of the Saccharomyces strain used is not the prime factor regulating the level of ethanol that can be produced in a high sugar brewing, wine, sake, or distillery fermentation. In fact, in terms of the maximum concentration that these yeasts can produce under batch (16 to 17% [v/v]) or fed-batch conditions, there is clearly no difference in ethanol tolerance. This is not to say, however, that under defined conditions there is no difference in ethanol tolerance among different Saccharomyces yeasts. This property, although a genetic determinant, is clearly influenced by many factors (carbohydrate level, wort nutrition, temperature, osmotic pressure/water activity, and substrate concentration), and each yeast strain reacts to each factor differently. This will indeed lead to differences in measured tolerance. Thus, it is extremely important that each of these be taken into consideration when determining "tolerance" for a particular set of fermentation conditions. The manner in which each alcohol-related industry has evolved is now known to have played a major role in determining traditional thinking on ethanol tolerance in Saccharomyces yeasts. It is interesting to speculate on how different our thinking on ethanol tolerance would be today if sake fermentations had not evolved with successive mashing and simultaneous saccharification and fermentation of rice carbohydrate, if distillers' worts were clarified prior to fermentation but brewers' wort were not, and if grape skins with their associated unsaturated lipids had not been an integral part of red wine musts. The time is now ripe for ethanol-related industries to take advantage of these findings to improve the economies of production. In the authors' opinion, breweries could produce higher alcohol beers if oxygenation (leading to unsaturated lipids) and "usable" nitrogen source levels were increased in high gravity worts. White wine fermentations could also, if desired, match the higher ethanol levels in red wines if oxygenation (to provide the unsaturated lipids deleted in part by the removal of the grape skins) were practiced and if care were given to assimilable nitrogen concentrations. This would hold true even at 10 to 14 degrees C, and the more rapid fermentations would maximize utilization of winery tankage.(ABSTRACT TRUNCATED AT 400 WORDS)
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