DOCSLIB.ORG

Microbial Stability and Safety of Acid Sauces and Mayonnaise- Based Salads Assessed Through Probabilistic Growth/No Growth Models

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Microbial Stability and Safety of Acid Sauces and Mayonnaise- Based Salads Assessed Through Probabilistic Growth/No Growth Models Microbial stability and safety of acid sauces and mayonnaise- based salads assessed through probabilistic growth/no growth models ir. An Vermeulen Voor Wouter… Promotoren: Prof. dr. ir. Frank Devlieghere Vakgroep voedselveiligheid en voedselkwaliteit Faculteit Bio-Ingenieurswetenschappen, UGent and Prof. dr. ir. Jan Van Impe Departement Chemische Ingenieurstechnieken Faculteit Ingenieurswetenschappen, KULeuven Decaan: Prof. dr. ir. Herman Van Langenhove Rector: Prof. dr. Paul Van Cauwenberge ir. An Vermeulen Microbial stability and safety of acid sauces and mayonnaise- based salads assessed through probabilistic growth/no growth models Thesis submitted in fulfillment of the requirements for the degree of Doctor (Ph.D.) in Applied Biological Sciences Proefschrift voorgedragen tot het bekomen van de graad van Doctor in de Toegepaste Biologische Wetenschappen Titel van het doctoraat in het Nederlands: Microbiële stabiliteit en veiligheid van zure sausen en salades, aan de hand van probabilistische groei/niet-groeimodellen Illustration: Fictitious example of a growth/no growth model plotted in Matlab®7.1 (The Mathworks, Inc, Natick, MA, USA). To refer to this thesis: Vermeulen, A. 2008. Microbial stability and safety of acid sauces and mayonnaise-based salads assessed through probabilistic growth/no growth models Thesis submitted in fulfillment of the requirements for the degree of doctor (Ph.D.) in Applied Biological Sciences. Faculty of Bioscience Engineering, University of Ghent ISBN number: 978-90-5989-215-6 The author and the promoters give the authorization to consult and copy parts of this work for personal use only. Every other use is subject to copyright laws. Permission to reproduce any material contained in this work should be obtained from the author. The research was performed at the: Laboratory of Food Microbiology and Food Preservation, Faculty of Bioscience Engineering, UGent, Ghent, Belgium Chemical and Biochemical Process Technology and Control Section, Faculty of Engineering, KULeuven, Leuven, Belgium Woord vooraf Als net afgestuurde bio-ingenieur begon ik een onderzoek aan het labo voor levensmiddelen-microbiologie en –conservering. Een onderwerp in de predictieve microbiologie leek me van bij het begin een mooie uitdaging. Het wiskundig beschrijven van observaties sprak me enorm aan. Het begon met één micro-organisme, Listeria monocytogenes, en het werd me onmiddellijk duidelijk dat héél veel observaties nodig zijn om een goed groei/niet-groeimodel te ontwikkelen. Zeker toen we het lumineuze idee hadden om ook de celdichtheid als variabele te gaan beschouwen groeide het aantal observaties exponentieel. Later steeg ook de interesse voor de bederforganismen en werden nog extra modellen ontwikkeld voor melkzuur- bacteriën en gisten. Mijn eerste onderzoeksjaren bestonden bijgevolg vooral uit het inoculeren van microtiterplaten, opvolgen van groei, en dataverwerking. Om een idee te geven: in totaal werden ongeveer 60 200 cupjes geïnoculeerd waarvan een groeicurve opgesteld werd. Elke groeicurve werd bepaald aan de hand van gemiddeld 60 optische densiteitsmetingen wat uiteindelijk ongeveer 3,6 miljoen data opleverde die verwerkt werden tot voorspellende modellen. Op sommige momenten zie je het dan even niet meer zitten en komen eigenschappen als doorzettingsvermogen en volharding naar boven. Wetenschappelijk onderzoek is iets wat je nooit alleen kan doen, maar wel met de hulp van vele anderen, daarom ben ik verschillende mensen een enorme dank verschuldigd. Eerst en vooral wil ik mijn twee promotoren bedanken: Prof. Devlieghere, Frank, voor het aanvaarden van het promotorschap, de belangrijke feedback tijdens het onderzoek en het voorzien van de nodige financiële middelen voor het uitvoeren van het onderzoek. Prof. Van Impe, Jan, voor het aanvaarden van het promotorschap en het ter beschikking stellen van uw medewerksters, Annemie en Kristel, om mij meer wegwijs te maken in de ontwikkeling van predictieve modellen. Eén van de belangrijkste factoren om een doctoraatsonderzoek vol te houden is het plezier om elke dag te gaan werken. Daarvoor wil ik graag al mijn collega’s en ex- collega’s van het LFMFP bedanken. Naast jullie hulp en steun, zorgden jullie elk op jullie eigen manier voor de nodige verstrooiing tijdens de voorbije jaren. Een extra dank u wel gaat uit naar Marie, Weronika, Nada, Trang, Katrijn en Elena die elk een steentje hebben bijgedragen bij het verzamelen van de vele data. Vervolgens wil ik ook graag mijn ouders bedanken. Jullie hebben mij altijd alle kansen gegeven om mijn leven uit te stippelen zoals ik het wil. Papa, de manier waarop jij je ziekte aanvaardde en bleef doorzetten voor ons, is voor mij dikwijls een inspiratiebron geweest, vooral tijdens de moeilijkere momenten van het doctoraatsonderzoek. Ik had zo graag gehad dat jij deze dag nog kon meemaken. Mama, jou wil ik heel graag bedanken voor het altijd klaarstaan met zowel praktische als morele steun op de momenten waarop het echt nodig was. Wouter, jij bent ongetwijfeld het mooiste dat mijn werk aan het labo mij heeft opgeleverd. Ik herinner me nog heel goed de eerste keer dat ik je opmerkte op het labo. Ondertussen zijn we samen sterk geëvolueerd tot man en vrouw en kunnen we samen uitkijken naar een mooie toekomst in ons nieuwe huis met ons eerste kindje, dat we in juli verwelkomen. Dank u wel, An 23 januari 2008 Table of contents Table of contents TABLE OF CONTENTS i INTRODUCTION AND OBJECTIVES v SUMMARY ix SAMENVATTING xiv 1 LITERATURE STUDY 1 1.1 MICROBIAL SAFETY AND STABILITY OF SAUCES AND SALADS 1 1.1.1 Classification and characterisation of emulsified sauces and salads 1 1.1.2 Preservation methods 5 1.1.3 Relevant microorganisms in emulsified sauces 20 1.1.4 Relevant microorganisms in mayonnaise-based salads 36 1.2 PREDICTIVE MICROBIOLOGY 43 1.2.1 Introduction 43 1.2.2 Kinetic models 44 1.2.3 Probability models 44 2 CHAPTER 2: GROWTH/NO GROWTH MODELS DESCRIBING THE INFLUENCE OF pH, LACTIC AND ACETIC ACID ON LACTIC ACID BACTERIA DEVELOPED TO DETERMINE THE STABILITY OF ACIDIFIED SAUCES 58 2.1 INTRODUCTION 59 2.2 MATERIALS AND METHODS 60 2.2.1 Bacterial strains and culture conditions 60 2.2.2 Data generation for growth/no growth modelling 61 2.2.3 Development of growth/no growth models 62 2.2.4 CIMSCEE code 63 2.3 RESULTS 64 2.3.1 Development of growth/no growth models 64 2.3.2 Comparison between the model for L. plantarum and L. fructivorans 73 2.3.3 Comparison with CIMSCEE code 74 Table of contents i 2.4 DISCUSSION 74 2.5 CONCLUSIONS 77 3 CHAPTER 3: MODELLING THE UNEXPECTED EFFECT OF ACETIC AND LACTIC ACID IN COMBINATION WITH pH ON THE GROWTH/NO GROWTH INTERFACE OF ZYGOSACCHAROMYCES BAILII 78 3.1 INTRODUCTION 80 3.2 MATERIALS AND METHODS 81 3.2.1 Yeast strain and culture condition 81 3.2.2 Data generation for growth/no growth modelling 82 3.2.3 Development of the growth/growth model 83 3.2.4 CIMSCEE code for stability of sauces 84 3.3 RESULTS 85 3.3.1 Description of trends observed in the growth/no growth data 85 3.3.2 Development of the growth/no growth model 87 3.3.3 Comparison with CIMSCEE code 98 3.4 DISCUSSION 99 3.5 CONCLUSIONS 102 4 CHAPTER 4: DEVELOPMENT OF A GROWTH/NO GROWTH MODEL FOR LISTERIA MONOCYTOGENES DESCRIBING THE INFLUENCE OF pH, WATER ACTIVITY AND ACETIC ACID AT 7°C 104 4.1 INTRODUCTION 106 4.2 MATERIALS AND METHODS 107 4.2.1 Media preparation 107 4.2.2 Inoculum preparation 108 4.2.3 Data collection and data processing 109 4.2.4 Development of the logistic regression model 110 4.3 RESULTS 111 4.3.1 Screening of the strains 111 4.3.2 Growth/no growth experiments 113 Table of contents ii 4.3.3 Influence of environmental conditions on the time to detection 123 4.4 DISCUSSION 125 4.5 CONCLUSIONS 127 5 CHAPTER 5: INFLUENCE OF THE INOCULATION LEVEL ON THE GROWTH/NO GROWTH INTERFACE OF LISTERIA MONOCYTOGENES AS A FUNCTION OF pH, aw AND ACETIC ACID 129 5.1 INTRODUCTION 131 5.2 MATERIALS AND METHODS 132 5.2.1 Preparation of different media 132 5.2.2 Inoculum preparation and inoculation procedure 132 5.2.3 Growth assessment 135 5.2.4 Development of growth/no growth models 135 5.3 RESULTS 138 5.3.1 Determination of the number of replicates 138 5.3.2 Data generation 140 5.3.3 Influence of inoculation level on growth probability 142 5.3.4 Model development 143 5.4 DISCUSSION 151 5.5 CONCLUSIONS 153 6 CHAPTER 6: PERFORMANCE OF A GROWTH/NO GROWTH MODEL FOR L. MONOCYTOGENES DEVELOPED FOR MAYONNAISE-BASED SALADS: INFLUENCE OF STRAIN VARIABILITY, FOOD MATRIX, INOCULATION LEVEL AND PRESENCE OF SORBIC AND BENZOIC ACID 155 6.1 INTRODUCTION 157 6.2 MATERIALS AND METHODS 158 6.2.1 Bacterial strains 158 6.2.2 Validation of the model robustness 158 6.2.3 Challenge test in sterile mayonnaise-surimi salad 161 6.2.4 Influence of chemical preservatives on the growth of L. monocytogenes 164 Table of contents iii 6.3 RESULTS 165 6.3.1 Validation of the growth/no growth model for different L. monocytogenes strains 165 6.3.2 Challenge tests in a laboratory-made, sterile mayonnaise-surimi salad 166 6.3.3 Influence of chemical preservatives on the growth of L. monocytogenes 169 6.4 DISCUSSION 171 6.5 CONCLUSIONS 174 7 CHAPTER 7: INCORPORATION OF THE DIFFERENT DEVELOPED GROWTH/NO GROWTH MODELS IN A USER-FRIENDLY SOFTWARE PACKAGE 176 7.1 INTRODUCTION 177 7.2 OVERVIEW OF AVAILABLE TERTIARY MODELS 178 7.3 SAUCE-SALAD MODEL DEVELOPMENT 180 7.3.1 Structure of the software 180 7.3.2 Model equations 185 7.3.3 Interpretation of the results 185 7.4 CONCLUSIONS 187 CONCLUSIONS AND PERSPECTIVES 190 LIST OF ABBREVIATIONS 197 REFERENCES 200 APPENDIX: DETAILED DESCRIPTION ON THE GENERAL ASPECTS OF DATA GENERATION, MODEL DEVELOPMENT AND INTERPRETATION OF THE RESULTS 221 CURRICULUM VITAE I Table of contents iv Introduction and objectives Introduction and objectives Due to modern life-style and modern eating habits, consumers are more and more interested in Ready-To-Eat (RTE) meals.
Load more

Recommended publications
  • Heat Resistance of Vegetative Cells and Asci of Two Zygosac- Charomyces Yeasts in Broths at Different Water Activity Values
    835 Journal of Food Protection, Vol. 50, No. 10, Pages 835-841 (October 1987) Copyright1 International Association of Milk, Food and Environmental Sanitarians Heat Resistance of Vegetative Cells and Asci of Two Zygosac- charomyces Yeasts in Broths at Different Water Activity Values MARCO F. G. JERMINI1 and WILHELM SCHMIDT-LORENZ* Food Microbiology Laboratory, Department of Food Science, Swiss Federal Institute of Technology (ETH), CH-8092 Zurich, Switzerland Downloaded from http://meridian.allenpress.com/jfp/article-pdf/50/10/835/1651027/0362-028x-50_10_835.pdf by guest on 01 October 2021 (Received for publication February 2, 1987) ABSTRACT solutions of sucrose or in sucrose-glucose mixtures at re­ duced a (19). Since the influence of lyophilization on The heat resistance of vegetative cells and asci of two os- w motolerant yeasts (Zygosaccharomyces rouxii and Z. bailii) was heat resistance has not yet been investigated, great cau­ tion is needed in evaluating those results. investigated in two different broths of aw 0.963 and 0.858, re­ spectively. The highest heat resistance was observed with asci Corry (12) demonstrated that the heat resistance of of Z. bailii LMZ 108, showing a decimal reduction time CD- Saccharomyces rouxii at 65°C, pH 6.5 and aw 0.95 was value) at 60°C and aw 0.858 of 14.9 min. Asci of Z. rouxii at the highest levels in solutions of sucrose, less in sor­ v LMZ 100 were less heat resistant (D60=c- alue at aw 0.858 = 3.5 bitol and least in solutions of glucose, fructose and min). The heat resistance (D-values) of asci at aw 0.963 proved glycerol.
    [Show full text]
  • Transcriptional Profiling of Zygosaccharomyces Bailii Early
    www.nature.com/scientificreports OPEN Transcriptional profling of Zygosaccharomyces bailii early response to acetic acid or copper Received: 10 May 2018 Accepted: 31 August 2018 stress mediated by ZbHaa1 Published: xx xx xxxx Miguel Antunes, Margarida Palma & Isabel Sá-Correia The non-conventional yeast species Zygosaccharomyces bailii is remarkably tolerant to acetic acid, a highly important microbial inhibitory compound in Food Industry and Biotechnology. ZbHaa1 is the functional homologue of S. cerevisiae Haa1 and a bifunctional transcription factor able to modulate Z. bailii adaptive response to acetic acid and copper stress. In this study, RNA-Seq was used to investigate genomic transcription changes in Z. bailii during early response to sublethal concentrations of acetic acid (140mM, pH 4.0) or copper (0.08 mM) and uncover the regulatory network activated by these stresses under ZbHaa1 control. Diferentially expressed genes in response to acetic acid exposure (297) are mainly related with the tricarboxylic acid cycle, protein folding and stabilization and modulation of plasma membrane composition and cell wall architecture, 17 of which, directly or indirectly, ZbHaa1-dependent. Copper stress induced the diferential expression of 190 genes mainly involved in the response to oxidative stress, 15 ZbHaa1- dependent. This study provides valuable mechanistic insights regarding Z. bailii adaptation to acetic acid or copper stress, as well as useful information on transcription regulatory networks in pre-whole genome duplication (WGD) (Z. bailii) and post-WGD (S. cerevisiae) yeast species, contributing to the understanding of transcriptional networks’ evolution in yeasts. Zygosaccharomyces bailii is described as the most problematic food spoilage yeast due to its remarkable high tolerance to weak acids, namely acetic acid1.
    [Show full text]
  • Search for Genes Responsible for the Remarkably High Acetic Acid Tolerance of a Zygosaccharomyces Bailii-Derived Interspecies Hy
    Palma et al. BMC Genomics (2015) 16:1070 DOI 10.1186/s12864-015-2278-6 RESEARCH ARTICLE Open Access Search for genes responsible for the remarkably high acetic acid tolerance of a Zygosaccharomyces bailii-derived interspecies hybrid strain Margarida Palma†, Filipa de Canaveira Roque†, Joana Fernandes Guerreiro, Nuno Pereira Mira, Lise Queiroz and Isabel Sá-Correia* Abstract Background: Zygosaccharomyces bailii is considered the most problematic acidic food spoilage yeast species due to its exceptional capacity to tolerate high concentrations of weak acids used as fungistatic preservatives at low pH. However, the mechanisms underlying its intrinsic remarkable tolerance to weak acids remain poorly understood. The identification of genes and mechanisms involved in Z. bailii acetic acid tolerance was on the focus of this study. For this, a genomic library from the highly acetic acid tolerant hybrid strain ISA1307, derived from Z. bailii and a closely related species and isolated from a sparkling wine production plant, was screened for acetic acid tolerance genes. This screen was based on the transformation of an acetic acid susceptible Saccharomyces cerevisiae mutant deleted for the gene encoding the acetic acid resistance determinant transcription factor Haa1. Results: The expression of 31 different DNA inserts from ISA1307 strain genome was found to significantly increase the host cell tolerance to acetic acid. The in silico analysis of these inserts was facilitated by the recently available genome sequence of this strain. In total, 65 complete or truncated ORFs were identified as putative determinants of acetic acid tolerance and an S. cerevisiae gene homologous to most of them was found. These include genes involved in cellular transport and transport routes, protein fate, protein synthesis, amino acid metabolism and transcription.
    [Show full text]
  • Evaluation of Zygosaccharomyces Bailii to Metabolize Residual Sugar Present in Partially-Fermented Red Wines
    Fermentation 2015, 1, 3-12; doi:10.3390/fermentation1010003 OPEN ACCESS fermentation ISSN 2311-5637 www.mdpi.com/journal/fermentation Article Evaluation of Zygosaccharomyces bailii to Metabolize Residual Sugar Present in Partially-Fermented Red Wines Jesse M. Zuehlke *, Bradford C. Childs and Charles G. Edwards School of Food Science, Washington State University, Pullman, WA 99164-6376, USA; E-Mails: [email protected] (B.C.C.); [email protected] (C.G.E.) * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +1-240-899-4449. Academic Editor: Ronnie G. Willaert Received: 3 February 2015 / Accepted: 17 March 2015 / Published: 26 March 2015 Abstract: An alternative approach to remove residual sugar from red wines using strains of Zygosaccharomyces bailli was studied. Fructose (40 or 60 g/L) and alcohol (13%, 15%, or 17% v/v) were added to a Cabernet Sauvignon wine before inoculation of Z. bailii B2, B6, or W3, or Saccharomyces cerevisiae EC1118. Most yeasts maintained populations ≥106 cfu/mL up to 100 days—the exceptions being W3 and EC1118, which declined to ≤30 cfu/mL in 17% alcohol wines beyond day 75. Wines containing 40 g/L fructose and 13% alcohol achieved dryness (<2 g/L), except those inoculated with B6. At 15% alcohol, B6, W3, and EC1118 consumed large levels of fructose (>80% of the 40 g/L; >50% of the 60 g/L) but limited amounts from wines containing 17% alcohol. Volatile acidities were higher in wines inoculated with strains of Z. bailli compared to S. cerevisiae (0.88 and 0.75 g/L, respectively).
    [Show full text]
  • Identification and Molecular Characterization of the Highly Acetic Acid Tolerant Zygosaccharomyces Bailii Strain IST302
    Identification and molecular characterization of the highly acetic acid tolerant Zygosaccharomyces bailii strain IST302 João Diogo André Peça Thesis to obtain the Master of Science Degree in Microbiology Supervisor: Prof. Dr. Isabel Maria de Sá-Correia Leite de Almeida Co-supervisor: Dr. Margarida Isabel Rosa Bento Palma Examination Committee Chairperson: Prof. Dr. Arsénio do Carmo Sales Mendes Fialho Supervisor: Prof. Dr. Isabel Maria de Sá-Correia Leite de Almeida Member of the committee: Dr. Paulo Jorge Moura Pinto da Costa Dias July 2016 Agradecimentos Apesar de perceber a globalização em que o mundo científico se insere onde o inglês domina como língua de comunicação entre todos, decido escrever apenas este capítulo em português pois entendo que os agradecimentos, sendo uma mensagem mais emocional e especificamente dirigida a pessoas próximas, só pode ser completamente entendida e percebida se for usada a minha língua materna. Gostaria de começar por agradecer a duas pessoas muito importantes durante o processo de trabalho desta tese, quer na parte laboratorial quer na parte de escrita. À Professora Isabel Sá-Correia, primeiro, por me ter dado a oportunidade de trabalhar consigo e fazer parte do Grupo de Investigação para as Ciências Biológicas do IST (BSRG) tendo sempre palavras assertivas mas construtivas que me fizeram acreditar no meu trabalho. Em segundo, à Dr. Margarida Palma, minha coorientadora, que se mostrou incansável em me apoiar sempre que precisei e mesmo quando não pedia, sendo muito importante no processo experimental e de escrita deste documento. Ciente de que a minha desmotivação por vezes prejudicou este trabalho, sem estas duas pessoas e a paciência que mostraram para comigo, este trabalho não seria possível.
    [Show full text]
  • Genome Sequence of the Highly Weak-Acid-Tolerant Zygosaccharomyces Bailii IST302, Amenable to Genetic Manipulations and Physiological Studies
    Genome sequence of the highly weak-acid-tolerant Zygosaccharomyces bailii IST302, amenable to genetic manipulations and physiological studies Margarida Palma1, Martin Münsterkötter2, João Peça1, Ulrich Güldener2,3, Isabel Sá-Correia1* 1Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, 1049- 001 Lisbon, Portugal 2Institute of Bioinformatics and Systems Biology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Ingolstädter Landstrasse 1, Neuherberg D-85764, Germany 3Chair of Genome-oriented Bioinformatics, TUM School of Life Sciences Weihenstephan, Technical University of Munich, 85354 Freising, Germany *corresponding author: Prof. Isabel Sá-Correia, Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal ; e: mail: [email protected]; Tel. +351-218417682; Fax +351-218489199 Keywords (6) Zygosaccharomyces bailii, genome sequence, food spoilage yeasts, weak acid tolerance, cellular aggregation Running title Z bailii IST302 genome sequence and annotation Abstract Zygosaccharomyces bailii is one of the most problematic spoilage yeast species found in the food and beverage industry particularly in acidic products, due to its exceptional resistance to weak acid stress. This article describes the annotation of the genome sequence of Z. bailii IST302, a strain recently proven to be amenable to genetic manipulations and physiological studies. The work was based on the annotated genomes of strain ISA1307, an interspecies hybrid between Z. bailii and a closely related species, and the Z. bailii reference strain CLIB 213T. The resulting genome sequence of Z. bailii IST302 is distributed through 105 scaffolds, comprising a total of 5142 genes and a size of 10.8 Mb.
    [Show full text]
  • Document Downloaded From: This Paper Must Be Cited As: the Final Publication Is Available at Copyright Additional Information Ht
    Document downloaded from: http://hdl.handle.net/10251/147624 This paper must be cited as: Ribes-Llop, S.; Fuentes López, A.; Barat Baviera, JM. (2019). Effect of oregano (Origanum vulgare L. ssp. hirtum) and clove (Eugenia spp.) nanoemulsions on Zygosaccharomyces bailii survival in salad dressings. Food Chemistry. 295:630-636. https://doi.org/10.1016/j.foodchem.2019.05.173 The final publication is available at https://doi.org/10.1016/j.foodchem.2019.05.173 Copyright Elsevier Additional Information 1 Effect of oregano (Origanum vulgare L. ssp. hirtum) and clove (Eugenia spp.) 2 nanoemulsions on Zygosaccharomyces bailii survival in salad dressings 3 4 Susana Ribes, Ana Fuentes*, Jose Manuel Barat 5 Departamento Tecnología de Alimentos, Universitat Politècnica de València, Camino de Vera s/n, 6 46022 Valencia, Spain 7 8 9 10 11 12 13 14 15 *Corresponding author: 16 Ana Fuentes: Telephone. +34 96 387 90 00; ext. 73664; fax: +34963787369; 17 Susana RIBES: [email protected] 18 Ana FUENTES*: [email protected] 19 José Manuel BARAT: [email protected] 20 1 21 Abstract 22 This work aimed to evaluate the in vitro effect of encapsulated oregano and clove essential 23 oils on oil-in-water nanoemulsions against Zygosaccharomyces bailii. The antifungal efficacy 24 of these nanoemulsions and their sensory acceptance were tested in salad dressings. Both 25 essential oils were effective inhibitors against the target yeast, with minimal inhibitory and 26 fungicidal concentrations of 1.75 mg/mL. In the in vitro assay done with the nanoemulsions, 27 no yeast growth was observed for any tested essential oil concentration.
    [Show full text]
  • Fructophilic Yeast Zygosaccharomyces Rouxii
    ZrFsy1, a High-Affinity Fructose/H+ Symporter from Fructophilic Yeast Zygosaccharomyces rouxii Maria Jose´ Leandro1,2*, Hana Sychrova´ 2, Catarina Prista1, Maria C. Loureiro-Dias1 1 CBAA, Instituto Superior de Agronomia, Universidade Te´cnica de Lisboa, Lisbon, Portugal, 2 Department of Membrane Transport, Institute of Physiology AS CR, v.v.i., Prague, Czech Republic Abstract Zygosaccharomyces rouxii is a fructophilic yeast than can grow at very high sugar concentrations. We have identified an ORF encoding a putative fructose/H+ symporter in the Z. rouxii CBS 732 genome database. Heterologous expression of this ORF in a S. cerevisiae strain lacking its own hexose transporters (hxt-null) and subsequent kinetic characterization of its sugar + transport activity showed it is a high-affinity low-capacity fructose/H symporter, with Km 0.4560.07 mM and Vmax 0.5760.02 mmol h21 (gdw) 21. We named it ZrFsy1. This protein also weakly transports xylitol and sorbose, but not glucose or other hexoses. The expression of ZrFSY1 in Z. rouxii is higher when the cells are cultivated at extremely low fructose concentrations (,0.2%) and on non-fermentable carbon sources such as mannitol and xylitol, where the cells have a prolonged lag phase, longer duplication times and change their microscopic morphology. A clear phenotype was determined for the first time for the deletion of a fructose/H+ symporter in the genome where it occurs naturally. The effect of the deletion of ZrFSY1 in Z. rouxii cells is only evident when the cells are cultivated at very low fructose concentrations, when the ZrFsy1 fructose symporter is the main active fructose transporter system.
    [Show full text]
  • EVALUATION of COMMON and NOVEL SANITIZERS AGAINST SPOILAGE YEASTS FOUND in WINE ENVIRONMENTS a Dissertation Presented to The
    EVALUATION OF COMMON AND NOVEL SANITIZERS AGAINST SPOILAGE YEASTS FOUND IN WINE ENVIRONMENTS A Dissertation Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Maria de Lourdes Alejandra Aguilar Solis January 2014 © 2014 Maria de Lourdes Alejandra Aguilar Solis EVALUATION OF COMMON AND NOVEL SANITIZERS AGAINST SPOILAGE YEASTS FOUND IN WINE ENVIRONMENTS Maria de Lourdes Alejandra Aguilar Solis, Ph. D. Cornell University 2014 Wine is subjected to many sources of microbial contamination throughout the wine making process, including but not limited to fermentation, barrel maturation, bottling, etc. In wineries, sanitation protocols should consider not only the type of microorganisms that need to be challenged, but also the type of surface that is going to be sanitized, since contact surfaces need to be treated differently according to physical and chemical properties. In the past, chlorinated compounds were used as sanitizers in wine industry, however we now know that they can be involved in the formation of trichloroanisoles (TCA), resulting in wine defects. Chlorine dioxide unlike other chlorinated compounds does not form TCA, or at least at very low levels. However, this research concluded its poor efficacy to sanitize wine barrels, likely due to the organic nature of the barrels. Alternative sanitizers in wine industry also include: sulfur dioxide, peroxyacetic acid, hot water, steam, ozone, etc. On the other hand, Velcorin ® (Dimethyl dicarbonate or DMDC) is currently used as a wine sterilant, however, due to its high disinfection effectiveness against yeast, we investigated its potential as a sanitizer for wine contact surfaces.
    [Show full text]
  • Journal of Microbiological Methods Zygosaccharomyces Bailii and Z. Rouxii Induced Ethanol Formation in Apple Juice Supplemented
    Journal of Microbiological Methods 163 (2019) 105659 Contents lists available at ScienceDirect Journal of Microbiological Methods journal homepage: www.elsevier.com/locate/jmicmeth Zygosaccharomyces bailii and Z. rouxii induced ethanol formation in apple T juice supplemented with different natural preservatives: A response surface methodology approach ⁎ Kevser Karamana, , Osman Sagdicb a Department of Agricultural Biotechnology, Agricultural Faculty, Erciyes University, Kayseri 38039, Turkey b Chemical and Metallurgical Engineering Faculty, Department of Food Engineering, Yıldız Technical University, Istanbul 34210, Turkey ARTICLE INFO ABSTRACT Keywords: In this study, ethanol produced by osmophilic yeasts, Zygosaccharomyces bailii and Z. rouxii, in apple juice Zygosaccharomyces preserved with mint essential oil (MEO), carvacrol and natamycin instead of synthetic preservatives was mod- Modeling eled. Some processing parameters such as sodium benzoate (SB, 0–0.1%) used as a positive control, storage Mint essential oil temperature (4–20 °C) and storage time (1–41 days) were selected in the study. Box-Behnken design in response Carvacrol surface methodology was used to evaluate the effects of processing parameters on ethanol levels of apple juice Natamycin and three models were created for three preservatives for each yeast. Preservative type affected the ethanol Ethanol formation in apple juice for both yeasts studied. Increase of preservative concentration decreased the ethanol formation during the storage period. The best effective preservative was determined as MEO and Z. bailii was found to be quite resistant yeast against to the preserving agents for three models as compared to Z. rouxii. Ethanol level increased with the increase of both storage temperature and time for both yeasts. The results showed that apple juice could be preserved by these three preservatives, but the MEO was the most effective agent for apple juice during the storage.
    [Show full text]
  • Searching for Telomerase Rnas in Saccharomycetes
    bioRxiv preprint doi: https://doi.org/10.1101/323675; this version posted May 16, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Article TERribly Difficult: Searching for Telomerase RNAs in Saccharomycetes Maria Waldl 1,†, Bernhard C. Thiel 1,†, Roman Ochsenreiter 1, Alexander Holzenleiter 2,3, João Victor de Araujo Oliveira 4, Maria Emília M. T. Walter 4, Michael T. Wolfinger 1,5* ID , Peter F. Stadler 6,7,1,8* ID 1 Institute for Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Wien, Austria; {maria,thiel,romanoch}@tbi.univie.ac.at, michael.wolfi[email protected] 2 BioInformatics Group, Fakultät CB Hochschule Mittweida, Technikumplatz 17, D-09648 Mittweida, Germany; [email protected] 3 Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany 4 Departamento de Ciência da Computação, Instituto de Ciências Exatas, Universidade de Brasília; [email protected], [email protected] 5 Center for Anatomy and Cell Biology, Medical University of Vienna, Währingerstraße 13, 1090 Vienna, Austria 6 German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Competence Center for Scalable Data Services and Solutions, and Leipzig Research Center for Civilization Diseases, University Leipzig, Germany 7 Max Planck Institute for Mathematics in the Sciences, Inselstraße 22, D-04103 Leipzig, Germany 8 Santa Fe Institute, 1399 Hyde Park Rd., Santa Fe, NM 87501 * Correspondence: MTW michael.wolfi[email protected]; PFS [email protected] † These authors contributed equally to this work.
    [Show full text]
  • Preservative Resistant Yeast Agar Base (PRY) M1914
    Preservative Resistant Yeast Agar Base (PRY) M1914 For cultivation of Yeasts Composition** Ingredients Gms / Litre Yeast extract 10.000 Mannitol 10.000 Agar 15.000 **Formula adjusted, standardized to suit performance parameters Directions Suspend 35 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely.Sterilize by autoclaving at 121°C for 15 minutes. Cool to 45-50°C and add 10ml glacial acetic acid and immediately dispense as desired,because the medium cannot be reheated. Principle And Interpretation Preservative Resistant Yeast Medium is used to selectively isolate and enumerate Zygosaccharomyces species .It is used for the detection of preservative resistant yeast in water and beverages. The medium prevents growth of other yeasts such as Saccharomyces cerevisiae that are tolerant to lower levels of commonly used food preservatives. Spoilage resulting from growth of the yeast Zygosaccharomyces is widespread, which has caused significant economic losses to the food industry. Within this genus, Z. bailii is one of the most troublesome species due to its exceptional tolerance to various stressful conditions (1).Also Z. lentus is a significant new osmophilic, preservative-resistant spoilage yeast,capable of growth at low temperature(2) . Yeast extract in the medium provides the essential nutrients, while mannitol acts as source of fermentable carbohydrate. Quality Control Appearance Cream to yellow homogeneous free flowing powder Gelling Firm, comparable with 1.5% Agar gel Colour and clarity of prepared medium Light amber coloured clear to slightly opalescent gel forms in Petri plates Cultural Response Cultural Response was observed at 20-25°C for 2-7 day's.
    [Show full text]