HEXOSE FERMENTATION RATES IN SACCHAROMYCES CEREVISIAE: GENETIC CONSTRUCTION OF WINE YEAST STRAINS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1010970
• Project Start Date: Dec 1, 2016
• Project End Date: Oct 26, 2017
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671

Performing Department
Viticulture and Enology

Non Technical Summary
Fermentation of available sugars is the foundation of the production of bread and of beer and wine. These fermentations are all conducted by the baker's yeast Saccharomyces cerevisiae. This yeast shows a preference for use of sugars over all other substrates efficiently converting these sugars to ethanol and other end products, depleting the environment of nutrients and inhibiting potential spoilage organisms or pathogens. If the yeast are negatively impacted by their environment fermentation may slow or arrest. Slow fermentations tie up fermentor space and often lead to a decreased quality of the product and increases susceptibility for spoilage and loss of quality. In such cases wines often need further processing such as filtration to remove all microorganisms present to assure stability post-bottling and can require use of higher concentrations of antimicrobial agents such as sulfur dioxide. In severe cases the product cannot be sold commercially and there is a loss of profitability plus loss of agricultural output for the inputs used. For these reasons it is important to understand the factors that result in a decrease in fermentative capacity in order to prevent these situations from arising. The goal of my research program is to understand the basic biology of fermentation, the key regulatory factors, and the environmental circumstances that lead to a loss of fermentation capacity by yeast strains. We conduct basic biological analysis of the transport and catabolism of sugars and the regulation of these processes. In this current grant we are studying a novel finding, the ability of spoilage bacteria to fundamentally alter the metabolic activity of yeast leading to arrest of fermentation and proliferation of the spoilage bacteria in the wine during production. A small molecule released by these bacteria induces a protein complex to form in the yeast that reduces fermentation ability making the environment more hospitable for the bacteria. The yeast are better able to resist the inhibitory factors being produced by the bacteria and thus can survive in a complex microbial community. This research will not only provide information on how to manage these complex microbial populations in the wine industry but will also help elucidate the mechanisms by which microorganisms communicate chemically in natural ecosystems and modify each other's behavior.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
501	4020	1102	50%
503	4020	1080	50%

Knowledge Area
501 - New and Improved Food Processing Technologies; 503 - Quality Maintenance in Storing and Marketing Food Products;

Subject Of Investigation
4020 - Fungi;

Field Of Science
1102 - Mycology; 1080 - Genetics;

Keywords

saccharomyces

yeast

prion

fermentation

wine hexose transporter

Goals / Objectives
Saccharomyces cerevisiae is a budding yeast central to many food production processes. This organism is responsible for beverage fermentations yielding beer and wine, and for bread production and is also used in the synthesis of biofuels. In addition, it is used directly, or following fractionation, as an adjuvant in numerous foods. In this capacity it serves as a flavoring agent or to boost the nutritional value of the food itself. All of these processes are batch processes, and involve growing the yeast on a sugar substrate. A common problem in these production processes is the arrest of sugar utilization by the yeast population. Problems with substrate utilization result in a lower biomass yield and a less efficient process, and are costly to correct. Arrest of sugar utilization is generally caused by abiotic or biotic stress to the yeast and is manifest by the degradation of sugar transporters. The focus of my research program is to understand transporter regulation, the impact of stress on transporter activity and turnover, and to define more accurate methods of detection of stresses impacting overall fermentation performance. Recently we have discovered that bacteria in the yeast ecosystem can induce a heritable prion state that modifies yeast sugar metabolism [17,18,20,25]. The role of this prion in yeast survival and the mechanisms of prion induction are being investigated.Studies in my laboratory and elsewhere have underscored the importance of yeast stress as a cause of arrest of fermentation in wine production [1,5,6,7,8,19,24,32,35]. A clear picture has emerged of the factors most likely to cause stress: nitrogen limitation, micronutrient limitation, temperature shock, ethanol intolerance, presence of inhibitors, microbial competition [1,5 8, 19, 24, 28, 32,36]. Some of these factors are interacting. For example, strains are more tolerant of high ethanol concentrations at moderate temperatures, but as temperature becomes elevated ethanol tolerance is decreased. The imposition of stress often leads also to the formation of off-characters or negatively perceived food or beverage attributes in addition to the arrest of sugar utilization. Some of these problems can be addressed by the appropriate selection of strains and employment of sound fermentation management practices [8,19].Our early work lead to the discovery of the family of hexose transporters in yeast and of the mechanisms by which these genes are regulated [3,4,9,10,11,12,15,16,21,22,23,26,27,30,31,33, 34,37, 38,39,40,41,42,43]. This information has provided the foundation for understanding why and how fermentations arrest. Since arrest of fermentation is an adaptive response to the presence of stress in the environment, it is difficult to reverse once it has occurred short of restoring the yeast to fully permissive growth conditions. This is often not possible in batch processes. We are therefore focusing on identifying methods for the early detection of yeast stress so that corrective actions may be taken. Our analysis of wine strain diversity indicates there is a variable response to stress among commercial and native yeast isolates. We are using genomics technologies and classical genetic analyses to understand the genetic basis of these strain differences [2,6,7,13,14,17,29]. More recently our work has focused on the "difficult to ferment juices". These are vineyard lots that chronically display difficulties in the fermentation regardless of the yeast strain used or supplemental nutrition. We have shown that these fermentations fall into two categories those with severe nutrient depletion of the vine and those with the persistence of bacteria. As noted above, we have been exploring the impact of bacteria on modification of yeast metabolic behavior via the induction of a prion state or states. Our ultimate goal is the identification of native strains or genetic modifications of existing commercial strains with enhanced stress tolerance and little to no off-character production that will then be able to be used in high risk production situations.The specific objectives of this proposal for the next grant period are:1. Determination of the role of the [GAR+] prion in arrest of commercial wine fermentations2. Analysis of the spectrum of microorganisms capable of induction the [GAR+] prion3. Identification of the inducer molecules4. Elucidating the role of [GAR+] prion establishment in yeast biology and environmental survivalLiterature Cited:1. Alexandre H. and C Charpentier. 1998. J Ind Micro Biotech 20:20-272. Backhus, LE et al. 2001. FEMS Yeast Re. 1:111-1253. Bisson LF.1988. J Bacteriol 170:2654-26584. Bisson LF. 1988. Bacteriol 170:4838-48455. Bisson LF. 1999. Am J Enol Vitic 50:107-11.6. Bisson LF. 2004. Food Biotech 18:63-967. Bisson LF and DE Block. 2002. Biodiversity and Biotechnology of Wine Yeasts, M. Ciani (ed.), Research Signpost, India8. Bisson LF and CE Butzke. 2000. Am J Enol Vitic 51:168-1779. Bisson, LF et al. 1993. Crit Rev Biochem Molec Biol 28:259-30810. Bisson LF and D G Fraenkel. 1983. Proc Natl Acad Sci USA 80:1730- 173411. Bisson LF and DG Fraenkel. 1983. J Bacteriol 155:995-100012. Bisson LF and DG Fraenkel. 1984. J Bacteriol 159:1013-101713. Bisson LF and JE Karpel. 2010. Ann Rev Food Sci Tech. 1:139-1614. Bisson LF et al. 2007. Adv Food Nutr Res 53:65-12315. Bisson LF and V Kunathigan. 2003. Res Microbiol 154:603-61016. Bisson LF et al. 1987. J Bacteriol 169:1656-166217. Bisson LF and GA Walker 2014 In, Advances in fermented foods and beverages. Chapter 28, Woodhead Publishing (eds)18. Bokulich NA et al. 2015. Am J Enol.Vitic 66:73-7919. Boulton RB et al. 1996. Principles and Practices of Winemaking. 604 Pages, Chapman & Hall, New York20. Brown JC and S Lindquist 2009. Genes Dev 23:2320-3221. Coons DM et al. 1995. J Bacteriol.177:3251-3258 22. Coons DM et al. 1997. Yeast 13:9-2023. Dietzel KL et al. 2012. BMC Genetics 13:10724. Ivorra C et al. 1999. Biotech Bioeng 64:698-70825. Jarosz, DF et al. 2014. Cell 158-1083-109326. Karpel JE et al. 2008. Am J Eno. Vitic 59:265-27527. Kruckeberg AL and LF Bisson. 1990. Molec Cell Biol 10:5903-591328. Kudo M et al.1998. Am J Enol Vitic. 49:295-30129. Kumar GR et al. 2008. Am J Enol Vitic 59:401-41130. Lewis DA and LF Bisson. 1991. Mol Cell Biol 11:3804-381331. Marshall-Carlson L et al. Genetics 128:505-51232. Maurizio JC and JM Salmon. 1992. Biotech Letts 14:577-58233. McClellan CJ and LF Bisson. 1988. J Bacteriol 170:5396-540034. Place WR and L.F Bisson. 2013. Am J Enol Vitic 64:2, doi: 10.5344/ajev.2012.1210135. Salmon JM. 1989. Appl Environ Microbiol 55:953-95836. Stockert MC et al. 2013. Am J Enol Vitic 64:2, doi:10.5344/ajev.2012.1206537. Theodoris G et al. 1994. Genetics 137:957-96638. Theodoris G and L. Bisson. 2001. FEMS Microbiol Letts 97:73-7739. Vagnoli P and LF Bisson. 1998. Yeast 14:359-369 40. Vagnoli P et al. 1998. FEMS Microbiol Letts 160:31-3641. Vallier LG et al. 1994. Genetics 136:1279-128542. Wendell DL and LF Bisson. 1994. J Bacteriol 176:3730-373743. Ye L et al. 1999. J Bacteriol 181:4673-4675

Project Methods
Objective 1. Determination of the role of the [GAR+] prion in arrest of commercial fermentations. The plasma membrane ATPase (PMA1) is largely responsible for maintenance of ethanol tolerance. Pma1 pumps protons out of the cell in order to maintain pH homeostasis. If the cytoplasm becomes acidic cells lose viability. Ethanol increases the flux of protons from the medium into the cell and protons also arise from sugar catabolism. The proton-pumping capacity of the PMA1 pump is saturable and a role of this proton pump in down-regulation of metabolism under stressful cytoplasmic pH conditions assures continued cell viability albeit at the expense of continued metabolism. Under certain metabolic conditions Pma1 binds to the regulator of glucose utilization, Std1. This binding reduces glucose consumption and enables use of alternative carbon sources and this complex is heritable. Proteins that can exist in heritable complexes are termed prions. The Pma1/Std1 prion has been named "GAR" for glucose associated repression resistance. Strains that have induced the [GAR+] prion display reduced fermentation rates during wine production and are less effective at dominating the microbiota present. Fermentations conducted with the [GAR+] strains of UCD932 or EC1118 display elevated populations of bacteria throughout the fermentation and will more likely arrest fermentation depending upon the bacteria present. In some cases even in the absence of bacteria fermentation will slow or stop, but this phenomenon is highly strain dependent. All of this work was conducted under laboratory or pilot winery scale conditions. Can the [GAR+] prion be induced under commercial winemaking conditions? To test this we obtained commercial samples of arrested wines from the 2013, 2014 and 2015 vintages in California. These wines were analyzed for the presence of yeast and bacteria. [GAR+] yeast strains were isolated from approximately 25% of the wines and from 33% of the wineries who submitted samples. Thus prion induction indeed occurs under commercial conditions of problematic fermentations. In this coming grant period we will continue to isolate both yeast and bacteria from these arrested commercial fermentations and to characterize the ability of the bacterial isolates to induce the prion, inhibit yeast growth, or play a neutral role in impacting fermentation capacity.Objective 2. Analysis of the spectrum of microorganisms capable of inducing the [GAR+] prion. We have obtained isolates from several genera of bacteria from arrested wine fermentations and problematic juices. To date over 200 arrested wines have been examined, plated and analyzed. From these wines 17 species of bacteria have been identified multiple times. The most dominant class are the acetic acid bacteria with five species of Acetobacter and five of Gluconobacter present. Of the Acetobacter species four are inhibitory against yeast growth and fermentation an one shows strains with a mixed phenotype with 4 independent isolates displaying inhibition, 4 displaying no impact (neutral) and two inducing of the [GAR+] prion. Of the Gluconobacter species, all isolates of one species are inducing, two species show a mixed response of, inducing or inhibitory or neutral and two species are neutral. Five species of lactic acid bacteria have also been identified. Of these four species are inducing and one is inhibitory. In addition two species of Staphylococcus have also been isolated from arrested wines and both are inducing. Thus common wine bacteria can also induce the prion in wine yeast strains. This coming grant period we will expand this analysis to assess the ability of grape biota to induce the prion as prion induction can occur early in juice but then as ethanol accumulates the inducing organism may be lost. The majority of wines that we obtained had no viable microbes by the time we received them so it is not possible in those cases to assess the impact of prion induction on fermentation arrest.Objective 3 Identification of the inducer molecules. Metabolite profiling will be used to characterize the spent medium of bacteria capable of inducing the [GAR+] prion with the goal of identifying possible inducer candidates. The metabolomic analysis will be conducted by the Core Facility on campus. We are in the process of identifying groups of species that display prion-inducing, non-inducing and inhibitory behaviors against standard wine yeast (UCD932, EC1118) and laboratory strain W303. The ability of each isolate to impact yeast has been evaluated on the GGM (glucosamine glycerol medium) enabling detection [GAR+] prion as well as inhibition of growth. Comparison to control organisms will identify those strains having no effect. Bacteria are grown in liquid culture, GGM or other bacterial media, the bacteria are removed via sterile filtration and the resulting sterile supernatant used as incubation medium directly or following dilution in fresh media for yeast from 4 to 24 hours with yeast then plated on GGM to assess the presence of the [GAR+] state. For example of the 10 independent isolates of Acetobacter pasteurianus from arrested wines 4 isolates showed no impact on yeast growth on solid GGM media, 4 were inhibitory and 2 showed induction of the [GAR+] prion. It is possible that the strains showing inhibition can also be inducing but induction is obscured by the inhibition. To test this dilutions of the supernatant from these strains will be evaluated for inhibition as well as for induction of the prion at lower concentrations. The other sets of bacteria showing variable phenotypes will be evaluated similarly. The metabolomics of the inducing, inhibitory and neutral supernatants will be evaluated to determine the identity of compounds varying in concentrations in ways consistent with their [GAR+] induction phenotype. The compounds identified will be individually tested in purified form to assess ability of the compound to induce prion formation.Objective 4. Elucidating the role of [GAR+] prion establishment in yeast biology and environmental survival. To further elucidate the nature of the [GAR+] prion, we have been comparatively evaluating the lipid and polysaccharide compositions and exo and endo metabolomes of pairs of [GAR+] prion induced and gar- or non-induced strains. Preliminary data suggests dramatic differences in overall surface composition (polysaccharide and lipid), impacts on amino acid utilization and oxygen depletion, and changes in the aromatic profiles of the strains as a function of induction of the prion. These effects are not modulated by transporter activity so the prion must have other impacts on cell biology. The endometabolome did indicate a difference in fermentative capacity and the accumulation of intermediates of glycolysis in the [GAR+] state. In the coming grant period these studies will be replicated and published.

Progress 12/01/16 to 10/26/17

Outputs
Target Audience:The goal of this project was to develop a broader understanding of yeast fermentation biology and to design more judicious fermentation management strategies. The target audiences for this work are the food, beverage, fuel and biotechnology fermentation industries. Much of this work has focused on the wine industry given the greater fiscal impact of premature fermentation arrest and the challenges in restarting arrested fermentations destined for human consumption. This work has been presented at national wine industry meetings, at local (California and west coast) technical meetings, and has been published in both scientific and trade journals and reported on websites of industry funding agencies and picked up by the popular technical press. In addition numerous phone calls and emails on this topic have been received and answered, on the order of 100 or more per year. Finally, I developed an issues extension program to cover these and other related fermentation management practices which includes a website that contains a diagnostic guide for problematic fermentations. I also lead the development of a new journal for the American Society of Enology and Viticulture called "Catalyst: Discovery Into Practice" specifically to provide an outlet for publication of extension of fundamental research to industry practice. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Although not a direct component of this program, the Pl has conducted workshops on fermentation management on campus and elsewhere and in multiple states. Several graduate students, PhD (2), MS (3), and visiting PhD scholars (2) have received training in this laboratory over the last fifteen month period. All 4 PhD scholars have completed their degrees within the last four months. One of the MS students has completed and the remaining 2 have drafts of their theses submitted to their committee members and should file their dissertations by the end of 2017. In addition three undergraduate students have conducted research in the lab associated with this project during the fifteen months. All of these individuals made poster or platform presentations of their research at local and/or national meetings. All students participated in writing articles for peer-reviewed journals in reviewing drafts and writing materials and methods sections. How have the results been disseminated to communities of interest?This research program is central to understanding and avoiding arrested or sluggish fermentations. This work has been presented at industry and regional meetings and on campus programs specifically targeted at extension of information (the Wine Flavor 101 program that I launched as a vehicle for dissemination of research). A fermentation management guide has been posted to our departmental website. Users of the site can find a guide to prevention of arrested wine fermentations and a diagnostic key that serves to translate the findings of this program into usable outputs for professionals and amateurs in the wine and grape industries. This website is used not only by wineries but also by those engaged in wine education, distribution and sales. It is also used by members of the baking, brewing and biofuels industries. I am currently writing a book "Wine Microbiology and Fermentation Management" that will summarize my over 30 years of research in this field. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Saccharomyces cerevisiae is a budding yeast central to many food production processes. This organism is responsible for beverage fermentations yielding beer and wine, and for bread production and is also used in the synthesis of biofuels. In addition, it is used directly, or following fractionation, as an adjuvant in numerous foods. In this capacity it serves as a flavoring agent or to boost the nutritional value of the food itself. All of these processes are batch processes, and involve growing the yeast on a sugar substrate. A common problem in these production processes is the arrest of sugar utilization by the yeast population. Problems with substrate utilization result in a lower biomass yield and a less efficient process, and are costly to correct. Arrest of sugar utilization is generally caused by abiotic or biotic stress to the yeast and is manifest by the degradation of sugar transporters. The focus of my research program is to understand transporter regulation, the impact of stress on transporter activity and turnover, and to define more accurate methods of detection of stresses impacting overall fermentation performance. Recently we have discovered that bacteria in the yeast ecosystem can induce a heritable prion state that modifies yeast sugar metabolism. The role of this prion in yeast survival and the mechanisms of prion induction are being investigated. Studies in my laboratory and elsewhere have underscored the importance of yeast stress as a cause of arrest of fermentation in wine production. A clear picture has emerged of the factors most likely to cause stress: nitrogen limitation, micronutrient limitation, temperature shock, ethanol intolerance, presence of inhibitors, microbial competition. Some of these factors are interacting. For example, strains are more tolerant of high ethanol concentrations at moderate temperatures, but as temperature becomes elevated ethanol tolerance is decreased. The imposition of stress often leads also to the formation of off-characters or negatively perceived food or beverage attributes in addition to the arrest of sugar utilization. Some of these problems can be addressed by the appropriate selection of strains and employment of sound fermentation management practices. Our early work lead to the discovery of the family of hexose transporters in yeast and of the mechanisms by which these genes are regulated. This information has provided the foundation for understanding why and how fermentations arrest. Since arrest of fermentation is an adaptive response to the presence of stress in the environment, it is difficult to reverse once it has occurred short of restoring the yeast to fully permissive growth conditions. More recently our work has focused on the "difficult to ferment juices". These are vineyard lots that chronically display difficulties in the fermentation regardless of the yeast strain used or supplemental nutrition. We have shown that these fermentations fall into two categories those with severe nutrient depletion of the vine and those with the persistence of bacteria. As noted above, we have been exploring the impact of bacteria on modification of yeast metabolic behavior via the induction of a prion state or states. Our ultimate goal is the identification of native strains or genetic modifications of existing commercial strains with enhanced stress tolerance and little to no off-character production that will then be able to be used in high risk production situations. The specific objectives for the current terminating grant period were: 1. Determination of the role of the [GAR+] prion in arrest of commercial wine fermentations 2. Analysis of the spectrum of microorganisms capable of induction the [GAR+] prion 3. Identification of the inducer molecules 4. Elucidating the role of [GAR+] prion establishment in yeast biology and environmental survival This grant is being terminated early due to my retirement and loss of laboratory space. However in the 15 months of this current grant objectives 1-3 have been completed and significant progress made on objective 4. We have confirmed the role of the prion in fermentation arrest in actual fermentations in several ways, First by identifying microbes from arrested commercial fermentations that could induce the prion and , second, simultaneously demonstrating that yeast isolated from these fermentations were in the prion state. Third, we reconstructed these arrested fermentations by placing the bacteria in juice in the presence of non-prion induced yeast and were able to both arrest the fermentation and show that the yeast had induced the prion. This confirms the role of the prion in slow and arrested commercial fermentations. We have expanded the list of inducing organisms focusing on L. kunkeei, a bee probiotic. We have shown that many but not all native bee isolates of this organism can induce the prion and arrest fermentation and have shown the accidental crushing of honey bees during grape processing can be a source of this microbe. We have also shown that this microbe alone cannot arrest fermentation due to sulfur dioxide sensitivity and the removal of this compound by grape acetic acid bacteria enables arrest of yeast metabolism. Finally, we have confirmed that an inducer of the prion is acetic acid. Further we have shown that the proton stress due to medium acidity is likely the inducer of the restructuring of yeast metabolism to prevent acidification of the cytoplasm. The fact that this restructuring is inherited by the progeny cells and not recreated de novo each generation defines a new paradigm in yeast physiology.

Publications

• Type: Journal Articles Status: Published Year Published: 2016 Citation: Walker, G. A., Hjelmeland, A, Bokulich, N. A., Mills D. A., Ebeler, S. E. and Bisson, L. F. 2016. Impact of the [GAR+] prion on fermentation and bacterial community composition with Saccharomyces cerevisiae UCD932. Am. J. Enol. Vitic. 67:296-307
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Bisson, L. F. 2016. Yeast hybrids in winemaking. Catalyst Disc. Pract. doi: 10.5344/catalyst.2016.16001.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Bisson, L. F. Walker, G., Ramakrishnan, V., Luo, Y., Fan, Q., Wiemer, E., Luong, P., Ogawa, M. and Joseph L. 2016. The two faces of Lactobacillus kunkeei: wine spoilage agent and bee probiotic. Catalyst Disc. Pract., doi: 10.5344/catalyst.2016.16002.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Ramakrishnan, V., Walker, G. A., Fan, Q., Ogawa. M., Luo, Y., Luong, P., Joseph, C. M. L. and Bisson, L. F. 2016. Inter-Kingdom Modification of Metabolic Behavior: [GAR+] Prion induction in Saccharomyces cerevisiae mediated by wine ecosystem bacteria. Front. Ecol. Evol. doi: 10.3389/fevo.2016.00137.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Joseph, C. M. L., Albino, E. and Bisson, L. F. 2016. Creation and use of a Brettanomyces aroma wheel.Catalyst Disc. Pract. doi: 10.5344/catalyst.2016.16003.
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Sun, Y., Qin, Y., Pei, Y. , Wang, G. Joseph, C. M. K., Linda F. Bisson, L.F. and Liu, Y. 2017. Evaluation of Chinese Saccharomyces cerevisiae wine strains from different geographical origins. Am. J. Enol. Vitic. 68:73-80
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Domizio, P., House, J. F., Jospeh, C. M. L., Bisson, L. and Bamforth, C. W. 2016. Lachancea thermotolerans as an alternative yeast for the production of beer. J. Inst. Brew. DOI 10.1002/jib.362
• Type: Journal Articles Status: Published Year Published: 2017 Citation: P. Domizio, P., Liu, Y., Bisson, L.F. and. Barile, D. 2017. Cell wall polysaccharides released during the alcoholic fermentation by Schizosaccharomyces pombe and S. japonicus: quantification and characterization. Food Microbiol. 61:136-149.
• Type: Book Chapters Status: Published Year Published: 2016 Citation: Bisson, L. F., Fan,,Q., and Walker, G. A. 2016. Sugar and glycerol transport in Saccharomyces cerevisiae. Chapter 6 In, Yeast Membrane Transport, Ramos, J., Sychrov�, H and Kschischo, M. (eds). Adv Exper Med Biol 892 doi: 10.1007/978-3-319-25304-6_6.
• Type: Book Chapters Status: Published Year Published: 2017 Citation: Bisson, L. F., Joseph, C. M. L. and Domizio, P. 2017. Part 1: Diversity of Microbes. Yeasts Chapter 3, in H, Konig, G. Unden, J. Frohlich (eds) Biology of Microorganisms on Grapes, in Must and in Wine, 2nd Edition, Springer, Cham, Switzerland
• Type: Journal Articles Status: Submitted Year Published: 2017 Citation: Walker, G. A., Henderson, C. M., Domizio P., Luong, P., Block, D. E., and Bisson, L. F. 2017. Downshifting yeast dominance: Cell physiology and phospholipid composition are fundamentally altered with establishment of the [GAR+] prion in Saccharomyces cerevisiae, submitted
• Type: Journal Articles Status: Submitted Year Published: 2017 Citation: Moreno-Garc�a, J., Garc�a-Martinez, T., Moreno, J., Mauricio, J. C., Ogawa, M., Luong, P. and Bisson, L. F. 2017. Impact of yeast flocculation and biofilm formation on yeast-fungus co-adhesion in a novel immobilization system, submitted