Vladimir Jiranek

Rapid Method for Proline Determination in Grape Juice and Wine

Publisher: American Chemical Society (ACS)

Date: 20-04-2012

DOI: 10.1021/JF300403B

Abstract: Proline is typically the most abundant amino acid present in grape juice and wine. The amount present is influenced by viticultural and winemaking factors and can be of diagnostic importance. A method for rapid routine quantitation of proline would therefore be of benefit for wine researchers and the industry in general. Colorimetric determination utilizing isatin as a derivatizing agent has previously been applied to plant extracts, biological fluids, and protein hydrolysates. In the current study, this method has been successfully adapted to grape juice and wine and proved to be sensitive to milligram per liter amounts of proline. At sugar concentrations above 60 g/L, interference from the isatin-proline reaction was observed, such that proline concentrations were considerably underestimated in grape juice and dessert wine. However, the method was robust for the analysis of fermentation s les and table wines. Results were within ±10% agreement with data generated from typical HPLC-based analyses. The isatin method is therefore considered suitable for the routine analysis required to support research into the utilization or release of proline by yeast during fermentation.

Sulfate transport mutants affect hydrogen sulfide and sulfite production during alcoholic fermentation

Publisher: Wiley

Date: 03-2021

DOI: 10.1002/YEA.3553

Abstract: Hydrogen sulfide is a common wine fault, with a rotten‐egg odour, which is directly related to yeast metabolism in response to nitrogen and sulfur availability. In grape juice, sulfate is the most abundant inorganic sulfur compound, which is taken up by yeast through two high‐affinity sulfate transporters, Sul1p and Sul2p, and a low affinity transporter, Soa1p. Sulfate contributes to H 2 S production under nitrogen limitation, by being reduced via the Sulfur Assimilation Pathway (SAP). Therefore, yeast strains with limited H 2 S are highly desirable. We report on the use of toxic analogues of sulfate following ethyl methane sulfate treatment, to isolate six wine yeast mutants that produce no or reduced H 2 S and SO 2 during fermentation in synthetic and natural juice. Four amino acid substitutions (A99V, G380R, N588K and E856K) in Sul1p were found in all strains except D25‐1 which had heterozygous alleles. Two changes were also identified in Sul2p (L268S and A470T). The Sul1p (G380R) and Sul2p (A470T) mutations were chosen for further investigation as these residues are conserved amongst SLC26 membrane proteins (including sulfate permeases). The mutations were introduced into EC1118 using Crispr cas9 technology and shown to reduce accumulation of H 2 S and do not result in increased SO 2 production during fermentation of model medium (chemically defined grape juice) or Riesling juice. The Sul1p (G380R) and Sul2p (A470T) mutations are newly reported as causal mutations. Our findings contribute to knowledge of the genetic basis of H 2 S production as well as the potential use of these strains for winemaking and in yeast breeding programmes.

Evaluation of the ability of commercial wine yeasts to form biofilms (mats) and adhere to plastic: implications for the microbiota of the winery environment

Publisher: Oxford University Press (OUP)

Date: 31-01-2018

DOI: 10.1093/FEMSEC/FIX188

Abstract: Commercially available active dried wine yeasts are regularly used by winemakers worldwide to achieve reliable fermentations and obtain quality wine. This practice has led to increased evidence of traces of commercial wine yeast in the vineyard, winery and uninoculated musts. The mechanism(s) that enables commercial wine yeast to persist in the winery environment and the influence to native microbial communities on this persistence is poorly understood. This study has investigated the ability of commercial wine yeasts to form biofilms and adhere to plastic. The results indicate that the biofilms formed by commercial yeasts consist of cells with a combination of different lifestyles (replicative and non-replicative) and growth modes including invasive growth, bud elongation, sporulation and a mat sectoring-like phenotype. Invasive growth was greatly enhanced on grape pulp regardless of strain, while adhesion on plastic varied between strains. The findings suggest a possible mechanism that allows commercial yeast to colonise and survive in the winery environment, which may have implications for the indigenous microbiota profile as well as the population profile in uninoculated fermentations if their dissemination is not controlled.

Genome Sequence of Australian Indigenous Wine Yeast Torulaspora delbrueckii COFT1 Using Nanopore Sequencing

Publisher: American Society for Microbiology

Date: 26-04-2018

DOI: 10.1128/GENOMEA.00321-18

Abstract: Here, we report the first sequenced genome of an indigenous Australian wine isolate of Torulaspora delbrueckii using the Oxford Nanopore MinION and Illumina HiSeq sequencing platforms. The genome size is 9.4 Mb and contains 4,831 genes.

Exploring the diversity of bacteriophage specific to Oenococcus oeni and Lactobacillus spp and their role in wine production

Publisher: Springer Science and Business Media LLC

Date: 25-10-2021

DOI: 10.1007/S00253-021-11509-2

Measures to improve wine malolactic fermentation

Publisher: Springer Science and Business Media LLC

Date: 16-01-2019

DOI: 10.1007/S00253-018-09608-8

Abstract: This review focuses on the considerable amount of research that has been directed towards the improvement of efficiency and reliability of malolactic fermentation (MLF), which is important in winemaking. From this large body of work, it is clear that reliable MLF is essential for process efficiency and prevention of spoilage in the final product. Impediments to successful MLF in wine, the impact of grape and wine ecology and how this may affect MLF outcome are discussed. Further focus is given to how MLF success may be enhanced, via alternative inoculation strategies, MLF progress sensing technologies and the use of different bacterial species. An update of how this information may be used to enhance and improve sensory outcomes through metabolite production during MLF and suggestions for future research priorities for the field are also provided.

The microbial challenge of winemaking: yeast-bacteria compatibility

Publisher: Oxford University Press (OUP)

Date: 06-2019

DOI: 10.1093/FEMSYR/FOZ040

Abstract: The ersity and complexity of wine environments present challenges for predicting success of fermentation. In particular, compatibility between yeast and lactic acid bacteria is affected by chemical and physical parameters that are strain and cultivar specific. This review focuses on the impact of compound production by microbes and physical interactions between microbes that ultimately influence how yeast and bacteria may work together during fermentation. This review also highlights the importance of understanding microbial interactions for yeast-bacteria compatibility in the wine context.

Genomic analysis of Kazachstania aerobia and Kazachstania servazzii reveals duplication of genes related to acetate ester production

Publisher: Microbiology Society

Date: 05-06-2023

DOI: 10.1099/MGEN.0.001029

Abstract: Kazachstania aerobia and Kazachstania servazzii can affect wine aroma by increasing acetate ester concentrations, most remarkably phenylethyl acetate and isoamyl acetate. The genetic basis of this is unknown, there being little to no sequence data available on the genome architecture. We report for the first time the near-complete genome sequence of the two species using long-read (PacBio) sequencing ( K. aerobia 20 contigs, one scaffold and K. servazzii 22 contigs, one scaffold). The annotated genomes of K. aerobia (12.5 Mb) and K. servazzii (12.3 Mb) were compared to Saccharomyces cerevisiae genomes (laboratory strain S288C and wine strain EC1118). Whilst a comparison of the two Kazachstania spp. genomes revealed few differences between them, ergence was evident in relation to the genes involved in ester biosynthesis, for which gene duplications or absences were apparent. The annotations of these genomes are valuable resources for future research into the evolutionary biology of Kazachstania and other yeast species (comparative genomics) as well as understanding the metabolic processes associated with alcoholic fermentation and the production of secondary ‘aromatic’ metabolites (transcriptomics, proteomics and metabolomics).

Isolation and Characterization of High-Ethanol-Tolerance Lactic Acid Bacteria from Australian Wine

Publisher: MDPI AG

Date: 25-04-2022

DOI: 10.3390/FOODS11091231

Abstract: Lactic acid bacteria are very important in winemaking. In this study, 108 lactic acid bacteria isolates were obtained from high-ethanol-content (~17% (v/v)) Grenache wines during uninoculated malolactic fermentation (MLF). The 16S rRNA and species-specific PCR showed that 104 of these were Oenococcusoeni, three were Lactobacillus hilgardii, and one was Staphylococcus pasteuri. AFLP of HindIII and MseI digests of the genomic DNA of the O. oeni strains was developed for the first time to discriminate the strains. The results showed that the method was a suitable technique for discriminating the O. oeni strains. Based on the cluster analysis, nine O. oeni strains were chosen for inclusion in an ethanol tolerance assay involving monitoring of optical density (ABS600nm) and viable plating. Several O. oeni strains (G63, G46, G71, G39) survived and grew well in MRS-AJ with 17% (v/v) ethanol, while the commercial O. oeni reference strain did not. Strain G63 could also survive and grow for 168 h after inoculation in MRS-AJ medium with 19% (v/v) ethanol. These results suggest that O. oeni G63, G46, G71, and G39 could potentially be used as MLF starters for high-ethanol-content wines. All three L. hilgardii strains could survive and grow in MRS-AJ with 19% (v/v) ethanol, perhaps also indicating their suitability as next-generation MLF starter cultures.

Yeast diversity in the vineyard: how it is defined, measured and influenced by fungicides

Publisher: Hindawi Limited

Date: 14-01-2021

DOI: 10.1111/AJGW.12479

Author Correction: Capturing yeast associated with grapes and spontaneous fermentations of the Negro Saurí minority variety from an experimental vineyard near León

Publisher: Springer Science and Business Media LLC

Date: 04-05-2021

DOI: 10.1038/S41598-021-89721-3

Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Use of a wine yeast deletion collection reveals genes that influence fermentation performance under low-nitrogen conditions

Publisher: Oxford University Press (OUP)

Date: 09-02-2018

DOI: 10.1093/FEMSYR/FOY009

Abstract: A deficiency of nitrogenous nutrients in grape juice can cause stuck and sluggish alcoholic fermentation, which has long been a problem in winemaking. Nitrogen requirements vary between wine yeast strains, and the ability of yeast to assimilate nitrogen depends on the nature and concentration of nitrogen present in the medium. In this study, a wine yeast gene deletion collection (1844 deletants in the haploid AWRI1631 background) was screened to identify genes whose deletion resulted in a reduction in the time taken to utilise all sugars when grown in a chemically defined grape juice medium supplemented with limited nitrogen (75 mg L-1 as a free amino acid mixture). Through micro-scale and laboratory-scale fermentations, 15 deletants were identified that completed fermentation in a shorter time than the wildtype (c.a. 15%-59% time reduction). This group of genes was annotated to biological processes including protein modification, transport, metabolism and ubiquitination (UBC13, MMS2, UBP7, UBI4, BRO1, TPK2, EAR1, MRP17, MFA2 and MVB12), signalling (MFA2) and amino acid metabolism (AAT2). Deletion of MFA2, encoding mating factor-a, resulted in a 55% decrease in fermentation duration. Mfa2Δ was chosen for further investigation to understand how this gene deletion conferred fermentation efficiency in limited nitrogen conditions.

The effect of grape juice dilution on oenological fermentation

Publisher: Cold Spring Harbor Laboratory

Date: 30-07-2020

DOI: 10.1101/2020.07.29.226142

Abstract: The impact of water addition to grape juice in winemaking, on both alcoholic and malolactic fermentation duration and outcome has been examined using commercial wine yeasts, Lalvin EC1118™ and Lalvin R2™ and malolactic bacteria Lalvin VP41™. As expected, dilution with water did not impede fermentation, instead resulted in shortened duration, or in the case of malolactic fermentation enabled completion in these conditions. Addition of complex organic nutrient further shortened alcoholic fermentation by Lalvin R2™ and in some conditions also reduced the duration of malolactic fermentation. In general, volatile compounds and some major yeast metabolites were present at lower concentrations at the end of fermentation where juices were diluted and the addition of organic complex nutrient also influenced the concentration of some compounds in wine. These findings are significant to commercial winemaking, highlighting that winemakers should consider potential impacts of juice dilution on processing efficiencies along with wine flavour and aroma. Grape juice dilution shortened both alcoholic and malolactic fermentation In some conditions addition of commercial nutrient decreased fermentation duration In general wine volatiles decrease with grape juice dilution Isoamyl acetate can be decreased in wine by grape juice dilution

Linking gene expression and oenological traits: Comparison between Torulaspora delbrueckii and Saccharomyces cerevisiae strains

Publisher: Elsevier BV

Date: 04-2019

DOI: 10.1016/J.IJFOODMICRO.2019.01.014

Abstract: Wine fermentations typically involve the yeast Saccharomyces cerevisiae. However, many other yeast species participate to the fermentation process, some with interesting oenological traits. In this study the species Torulaspora delbrueckii, used occasionally in mixed or sequential fermentation with S. cerevisiae to improve wine sensory profile, was investigated to understand the physiological differences between the two. Next generation sequencing was used to characterize the transcriptome of T. delbrueckii and highlight the different genomic response of these yeasts during growth under wine-like conditions. Of particular interest were the basic differences in the glucose fermentation pathway and the formation of aromatic and flavour compounds such as glycerol, esters and acetic acid. Paralog genes were missing in glycolysis and glycerol biosynthesis in T. delbrueckii. Results indicate the tendency of T. delbrueckii to produce less acetic acid relied on a higher expression of alcoholic fermentation related genes, whereas acetate esters were influenced by the absence of esterases, ATF1-2. Additionally, in the Δbap2 S. cerevisiae strain, the final concentration of short branched chain ethyl esters (SBCEEs) was related to branched chain amino acid (BCAA) uptake. In conclusion, different adaption strategies are apparent for T. delbrueckii and S. cerevisiae yeasts, an understanding of which will allow winemakers to make better use of such microbial tools to achieve a desired wine sensory outcome.

Fructilactobacillus cliffordii sp. nov., Fructilactobacillus hinvesii sp. nov., Fructilactobacillus myrtifloralis sp. nov., Fructilactobacillus carniphilus sp. nov. and Fructobacillus americanaquae sp

Publisher: Microbiology Society

Date: 16-02-2023

DOI: 10.1099/IJSEM.0.005730

Abstract: Six strains, KI11_D11 T , KI4_B1, KI11_C11 T , KI16_H9 T , KI4_A6 T and KI3_B9 T , were isolated from insects and flowers on Kangaroo Island, South Australia. On the basis of 16S rRNA gene phylogeny, strains KI11_D11 T , KI4_B1, KI11_C11 T , KI16_H9 T , KI4_A6 T were found to be closely related to Fructilactobacillus ixorae Ru20-1 T . Due to the lack of a whole genome sequence for this species, whole genome sequencing of Fructilactobacillus ixorae Ru20-1 T was undertaken. KI3_B9 T was found to be closely related to Fructobacillus tropaeoli F214-1 T . Utilizing core gene phylogenetics and whole genome analyses, such as determination of AAI, ANI and dDDH, we propose that these six isolates represent five novel species with the names Fructilactobacillus cliffordii (KI11_D11 T = LMG 32130 T = NBRC 114988 T ), Fructilactobacillus hinvesii (KI11_C11 T = LMG 32129 T = NBRC 114987 T ), Fructilactobacillus myrtifloralis (KI16_H9 T = LMG 32131 T = NBRC 114989 T ) Fructilactobacillus carniphilus (KI4_A6 T = LMG 32127 T = NBRC 114985 T ) and Fructobacillus americanaquae (KI3_B9 T = LMG 32124 T = NBRC 114983 T ). Chemotaxonomic analyses detected no fructophilic characters for these strains of member of the genus Fructilactobacillus . KI3_B9 T was found to be obligately fructophilic, similarly to its phylogenetic neighbours in the genus Fructobacillus . This study represents the first isolation, to our knowledge, of novel species in the family Lactobacillaceae from the Australian wild.

Removal of Volatile Phenols From Wine Using Crosslinked Cyclodextrin Polymers

Publisher: MDPI AG

Date: 18-02-2020

DOI: 10.3390/MOLECULES25040910

Abstract: Volatile phenols have been implicated as contributors to off-odors associated with taints from bushfire smoke and microbial spoilage. Various methods for the amelioration of off-odors have been evaluated, but to date, they have not included cyclodextrin (CD) polymers. In the current study, two CD polymers were prepared from β- and γ-CD, using hexamethylene diisocyanate (HDI) as a crosslinking agent. Adsorption tests were performed with four volatile phenols (guaiacol, 4-methylguaiacol, 4-ethylguaiacol and 4-ethylphenol) at concentrations up to 1 mg/L. The removal of volatile phenols by CD polymers achieved equilibrium almost instantly, with isotherm tests suggesting an adsorption capacity of 20.7 µg of volatile phenol per gram of polymer. Langmuir and Freundlich models were subsequently used to fit the data. In batch adsorption tests, the CD polymers achieved 45 to 77% removal of volatile phenols. Polymer reusability was also evaluated and was found to be excellent. A comparison between volatile phenol adsorption by CDs vs. CD polymers, determined using a novel four-phase headspace solid-phase microextraction (HS-SPME) method for gas chromatography-mass spectrometry (GC-MS), suggests CD polymers offer several advantages for use by the wine industry.

Microvinification-how small can we go?

Publisher: Springer Science and Business Media LLC

Date: 13-11-2011

DOI: 10.1007/S00253-010-2992-6

Abstract: High-throughput methodologies to screen large numbers of microorganisms necessitate the use of small-scale culture vessels. In this context, an increasing number of researchers are turning to microtiter plate (MTP) formats to conduct experiments. MTPs are now widely used as a culturing vessel for phenotypic screening of aerobic laboratory cultures, and their suitability has been assessed for a range of applications. The work presented here extends these previous studies by assessing the metabolic footprint of MTP fermentation. A comparison of Chardonnay grape juice fermentation in MTPs with fermentations performed in air-locked (self-induced anaerobic) and cotton-plugged (aerobic) flasks was made. Maximum growth rates and biomass accumulation of yeast cultures grown in MTPs were indistinguishable from self-induced anaerobic flask cultures. Metabolic profiles measured differed depending on the metabolite. While glycerol and acetate accumulation mirrored that of self-induced anaerobic cultures, ethanol accumulation in MTP ferments was limited by the increased propensity of this volatile metabolite for evaporation in microlitre-scale culture format. The data illustrates that microplate cultures can be used as a replacement for self-induced anaerobic flasks in some instances and provide a useful and economical platform for the screening of industrial strains and culture media.

Chemical and sensory profiling of Shiraz wines co-fermented with commercial non-Saccharomyces inocula

Publisher: Hindawi Limited

Date: 28-12-2018

DOI: 10.1111/AJGW.12320

Evaluation of indigenous non-Saccharomyces yeasts isolated from a South Australian vineyard for their potential as wine starter cultures

Publisher: Elsevier BV

Date: 2020

DOI: 10.1016/J.IJFOODMICRO.2019.108373

Abstract: The use of non-Saccharomyces yeast in conjunction with Saccharomyces cerevisiae in wine fermentation is a growing trend in the wine industry. Non-Saccharomyces, through their distinctive production of secondary metabolites, have the potential to positively contribute to wine sensory profile. To discover new candidate strains for development as starter cultures, indigenous non-Saccharomyces were isolated from un-inoculated fermenting Shiraz musts from a South Australian vineyard (McLaren Vale wine region) and characterised. Among the 77 isolates, 7 species belonging to 5 genera (Kazachstania, Aureobasidium, Meyerozyma, Wickerhamomyces and Torulaspora) were identified by sequencing the internal transcribed spacer regions of the 5.8S rRNA gene (ITS1-5.8S-ITS2 region). The indigenous isolates were evaluated for oenological properties, namely, ethanol tolerance, enzyme activity, and H

Brief temperature extremes during wine fermentation: effect on yeast viability and fermentation progress

Publisher: Hindawi Limited

Date: 27-08-2019

DOI: 10.1111/AJGW.12365

Effect of non‐ Saccharomyces yeast strains on 3‐isobutyl‐2‐methoxypyrazine concentration and aroma properties in Sauvignon Blanc wines during fermentation

Publisher: Hindawi Limited

Date: 08-2022

DOI: 10.1111/AJGW.12563

Practical significance of relative assimilable nitrogen requirements of yeast: a preliminary study of fermentation performance and liberation of H₂S

Publisher: Hindawi Limited

Date: 10-2002

DOI: 10.1111/J.1755-0238.2002.TB00253.X

Biochemical characterisation of the esterase activities of wine lactic acid bacteria

Publisher: Springer Science and Business Media LLC

Date: 09-09-2007

DOI: 10.1007/S00253-007-1173-8

Abstract: Esters are an important group of volatile compounds that can contribute to wine flavour. Wine lactic acid bacteria (LAB) have been shown to produce esterases capable of hydrolysing ester substrates. This study aims to characterise the esterase activities of nine LAB strains under important wine conditions, namely, acidic conditions, low temperature (to 10 degrees C) and in the presence of ethanol (2-18% v/v). Esterase substrate specificity was also examined using seven different ester substrates. The bacteria were generally found to have a broad pH activity range, with the majority of strains showing maximum activity close to pH 6.0. Exceptions included an Oenococcus oeni strain that retained most activity even down to a pH of 4.0. Most strains exhibited highest activity across the range 30-40 degrees C. Increasing ethanol concentration stimulated activity in some of the strains. In particular, O. oeni showed an increase in activity up to a maximum ethanol concentration of around 16%. Generally, strains were found to have greater activity towards short-chained esters (C2-C8) compared to long-chained esters (C10-C18). Even though the optimal physicochemical conditions for enzyme activity differed from those found in wine, these findings are of potential importance to oenology because significant activities remained under wine-like conditions.

Lower-alcohol wines produced by Metschnikowia pulcherrima and Saccharomyces cerevisiae co-fermentations: The effect of sequential inoculation timing

Publisher: Elsevier BV

Date: 09-2020

DOI: 10.1016/J.IJFOODMICRO.2020.108651

Capturing yeast associated with grapes and spontaneous fermentations of the Negro Saurí minority variety from an experimental vineyard near León

Publisher: Springer Science and Business Media LLC

Date: 12-02-2021

DOI: 10.1038/S41598-021-83123-1

Abstract: ‘Microbial terroir’ relates to the influence of autochthonous yeasts associated with a grape cultivar on the resultant wine. Geographic region, vineyard site and topography, climate and vintage influence the bio ersity of these microbial communities. Current research focus attempts to correlate their ‘microbial fingerprint’ to the sensorial and chemical characteristics of varietal wines from distinct geographical wine regions. This study focuses on the minor red grape variety, Negro Saurí, which has seen a resurgence in the León Appellation of Origin in Spain as a varietal wine. An experimental vineyard at Melgarajo S.A. (42° 15′ 48.68_N 5° 9′ 56.66_W) was s led over four consecutive vintages, with autochthonous yeasts being isolated from grapes, must and pilot-scale un-inoculated fermentations, and identified by ITS sequencing. Forty-nine isolates belonging to Metschnikowia pulcherrima , Lachancea thermotolerans , Hanseniaspora uvarum and Torulaspora delbrueckii were isolated from grapes and must, and early stages of fermentation dependent on seasonal variation. Saccharomyces cerevisiae predominated throughout fermentation, as a heterogeneous and dynamic population, with seven major biotypes identified amongst 110 isolates across four consecutive vintages. Twenty-four S. cerevisiae isolates representing five strains dominated in two or more vintages. Their persistence through fermentation warrants further validation of their oenological properties as starter cultures.

Viability of common wine spoilage organisms after exposure to high power ultrasonics

Publisher: Elsevier BV

Date: 05-2012

DOI: 10.1016/J.ULTSONCH.2011.06.009

Abstract: Microbial spoilage of wine can lead to significant economic loss. At present sulfur dioxide is the main additive to juice/must/wine to prevent and control microbial spoilage. As an alternative, or complement to SO(2), high power ultrasonics (HPU) may be used to control microbes. Several wine spoilage yeasts and bacteria were treated with HPU in saline (0.9% w/v NaCl), juice and red wine to assess their susceptibility to HPU. Significant killing was seen across several yeasts and bacteria commonly associated with winemaking and wine spoilage. In general the viability of yeast was more affected than that of bacteria.

High power ultrasonics as a novel tool offering new opportunities for managing wine microbiology

Publisher: Springer Science and Business Media LLC

Date: 06-09-2007

DOI: 10.1007/S10529-007-9518-Z

Abstract: Industrial scale food and beverage processes that utilize microorganisms are typically faced with issues related to the exclusion, suppression or elimination of spoilage organisms. Yet the use of traditional anti-microbial treatments such as heat, chemical biocides or sterile filtration may themselves be restricted by regulations or else be undesirable due to their adverse sensory impacts on the product. High power ultrasound (HPU) is a technology whose application has been evaluated if not exploited in several food and beverage processes but has yet to be introduced into the wine industry. This review examines the research findings from related industries and highlights possible applications and likely benefits of the use of HPU in winemaking.

Dekkera and Brettanomyces growth and utilisation of hydroxycinnamic acids in synthetic media

Publisher: Springer Science and Business Media LLC

Date: 04-2008

DOI: 10.1007/S00253-007-1328-7

Abstract: Dekkera and Brettanomyces yeast are important spoilage organisms in a number of food and beverage products. Isolates of both genera were cultured in a defined medium and supplemented with hydroxycinnamic acids and vinylphenols to investigate their influence on growth and the formation of ethyl phenol derivatives. The growth rate of Brettanomyces species in the presence of acids was reduced, and no significant conversion to vinyl or ethyl derivatives was observed. The growth rate and substrate utilisation rates of Dekkera anomala and Dekkera bruxellensis yeast differed depending on strain and the acid precursor present. Growth of D. bruxellensis was slowed by the presence of ferulic acid with the addition of 1 mM ferulic acid completely inhibiting growth. This study provides an insight into the spoilage potential of these organisms and possible control strategies involving hydroxycinnamic acids.

Survey of enzyme activity responsible for phenolic off-flavour production by Dekkera and Brettanomyces yeast

Publisher: Springer Science and Business Media LLC

Date: 2009

DOI: 10.1007/S00253-008-1708-7

Abstract: Volatile phenols are produced by Dekkera yeasts and are of organoleptic importance in alcoholic beverages. The key compound in this respect is 4-ethylphenol, responsible for the medicinal and phenolic aromas in spoiled wines. The microbial synthesis of volatile phenols is thought to occur in two steps, beginning with naturally occurring hydroxycinnamic acids (HCAs). The enzyme phenolic acid decarboxylase (PAD) converts HCAs to vinyl derivatives, which are the substrates of a second enzyme, postulated to be a vinylphenol reductase (VPR), whose activity results in the formation of ethylphenols. Here, both steps of the pathway are investigated, using cell extracts from a number of Dekkera and Brettanomyces species. Dekkera species catabolise ferulic, caffeic and p-coumaric acids and possess inducible enzymes with similar pH and temperature optima. Brettanomyces does not decarboxylate HCAs but does metabolise vinylphenols. Dekkera species form ethylphenols but the VPR enzyme appears to be highly unstable in cell extracts. A partial protein sequence for PAD was determined from Dekkera anomala and may indicate the presence of a novel enzyme in this genus.

Quantifying the dominant growth mechanisms of dimorphic yeast using a lattice-based model

Publisher: The Royal Society

Date: 09-2017

DOI: 10.1098/RSIF.2017.0314

Abstract: A mathematical model is presented for the growth of yeast that incorporates both dimorphic behaviour and nutrient diffusion. The budding patterns observed in the standard and pseudohyphal growth modes are represented by a bias in the direction of cell proliferation. A set of spatial indices is developed to quantify the morphology and compare the relative importance of the directional bias to nutrient concentration and diffusivity on colony shape. It is found that there are three different growth modes: uniform growth, diffusion-limited growth (DLG) and an intermediate region in which the bias determines the morphology. The dimorphic transition due to nutrient limitation is investigated by relating the directional bias to the nutrient concentration, and this is shown to replicate the behaviour observed in vivo . Comparisons are made with experimental data, from which it is found that the model captures many of the observed features. Both DLG and pseudohyphal growth are found to be capable of generating observed experimental morphologies.

‘TeeBot’: A High Throughput Robotic Fermentation and Sampling System

Publisher: MDPI AG

Date: 24-09-2021

DOI: 10.3390/FERMENTATION7040205

Abstract: When fermentation research requires the comparison of many strains or conditions, the major bottleneck is a technical one. Microplate approaches are not able to produce representative fermentative performance due to their inability to truly operate anaerobically, whilst more traditional methods do not facilitate s le density sufficient to assess enough candidates to be considered even medium throughput. Two robotic platforms have been developed that address these technological shortfalls. Both are built on commercially available liquid handling platforms fitted with custom labware. Results are presented detailing fermentation performance as compared to current best practice, i.e., shake flasks fitted with airlocks and sideports. The ‘TeeBot’ is capable s ling from 96 or 384 fermentations in 100 mL or 30 mL volumes, respectively, with airlock sealing and minimal headspace. S ling and downstream analysis are facilitated by automated liquid handling, use of 96-well s le plate format and temporary cryo-storage ( °C).

Oenological traits of Lachancea thermotolerans show signs of domestication and allopatric differentiation

Publisher: Springer Science and Business Media LLC

Date: 04-10-2018

DOI: 10.1038/S41598-018-33105-7

Abstract: The yeast Lachancea thermotolerans (previously Kluyveromyces thermotolerans ) is a species of large, yet underexplored, oenological potential. This study delivers comprehensive oenological phenomes of 94 L. thermotolerans strains obtained from erse ecological niches worldwide, classified in nine genetic groups based on their pre-determined microsatellite genotypes. The strains and the genetic groups were compared for their alcoholic fermentation performance, production of primary and secondary metabolites and pH modulation in Chardonnay grape juice fermentations. The common oenological features of L. thermotolerans strains were their glucophilic character, relatively extensive fermentation ability, low production of acetic acid and the formation of lactic acid, which significantly affected the pH of the wines. An untargeted analysis of volatile compounds, used for the first time in a population-scale phenotyping of a non- Saccharomyces yeast, revealed that 58 out of 90 volatiles were affected at an L. thermotolerans strain level. Besides the remarkable extent of intra-specific ersity, our results confirmed the distinct phenotypic performance of L. thermotolerans genetic groups. Together, these observations provide further support for the occurrence of domestication events and allopatric differentiation in L. thermotolerans population.

Diffusion-Limited Growth of Microbial Colonies

Publisher: Springer Science and Business Media LLC

Date: 16-04-2018

DOI: 10.1038/S41598-018-23649-Z

Abstract: The emergence of diffusion-limited growth (DLG) within a microbial colony on a solid substrate is studied using a combination of mathematical modelling and experiments. Using an agent-based model of the interaction between microbial cells and a diffusing nutrient, it is shown that growth directed towards a nutrient source may be used as an indicator that DLG is influencing the colony morphology. A continuous reaction–diffusion model for microbial growth is employed to identify the parameter regime in which DLG is expected to arise. Comparisons between the model and experimental data are used to argue that the bacterium Bacillus subtilis can undergo DLG, while the yeast Saccharomyces cerevisiae cannot, and thus the non-uniform growth exhibited by this yeast must be caused by the pseudohyphal growth mode rather than limited nutrient availability. Experiments testing directly for DLG features in yeast colonies are used to confirm this hypothesis.

Malolactic enzyme from Oenococcus oeni

Publisher: Informa UK Limited

Date: 05-2013

DOI: 10.4161/BIOE.22988

Modern yeast development: finding the balance between tradition and innovation in contemporary winemaking

Publisher: Oxford University Press (OUP)

Date: 18-10-2022

DOI: 10.1093/FEMSYR/FOAC049

Abstract: A key driver of quality in wines is the microbial population that undertakes fermentation of grape must. Winemakers can utilise both indigenous and purposefully inoculated yeasts to undertake alcoholic fermentation, imparting wines with aromas, flavours and palate structure and in many cases contributing to complexity and uniqueness. Importantly, having a toolbox of microbes helps winemakers make best use of the grapes they are presented with, and tackle fermentation difficulties with flexibility and efficiency. Each year the number of strains available commercially expands and more recently, includes strains of non-Saccharomyces, strains that have been improved using both classical and modern yeast technology and mixed cultures. Here we review what is available commercially, and what may be in the future, by exploring recent advances in fermentation relevant strain improvement technologies. We also report on the current use of microbes in the Australian wine industry, as reported by winemakers, as well as regulations around, and sentiment about the potential use of genetically modified organisms in the future.

Impact of Lachancea thermotolerans on Chemical Composition and Sensory Profiles of Viognier Wines

Publisher: MDPI AG

Date: 30-04-2022

DOI: 10.3390/JOF8050474

Abstract: Viognier is a warm climate grape variety prone to loss of acidity and accumulation of excessive sugars. The yeast Lachancea thermotolerans can improve the stability and balance of such wines due to the partial conversion of sugars to lactic acid during alcoholic fermentation. This study compared the performance of five L. thermotolerans strains in co-inoculations and sequential inoculations with Saccharomyces cerevisiae in high sugar H Viognier fermentations. The results highlighted the dichotomy between the non-acidified and the bio-acidified L. thermotolerans treatments, with either comparable or up to 0.5 units lower pH relative to the S. cerevisiae control. Significant differences were detected in a range of flavour-active yeast volatile metabolites. The perceived acidity mirrored the modulations in wine pH/TA, as confirmed via “Rate-All-That-Apply” sensory analysis. Despite major variations in the volatile composition and acidity alike, the varietal aromatic expression (i.e., stone fruit aroma/flavour) remained conserved between the treatments.

Inhibitory effect of hydroxycinnamic acids on Dekkera spp.

Publisher: Springer Science and Business Media LLC

Date: 02-12-2009

DOI: 10.1007/S00253-009-2352-6

Abstract: Simple phenolic components of wine, hydroxycinnamic acids (HCAs) are known to have antimicrobial properties. This study sought to determine the potential of ferulic acid as an antifungal agent for the control of Dekkera. Growth was inhibited by all HCAs examined in this study, with ferulic acid being the most potent at all concentrations. In the presence of ethanol, the inhibitory effects of ferulic acid were lified. Scanning electron microscopy images reveal cellular damage upon exposure to ferulic acid. Thus, manipulation of ferulic acid concentrations could be of industrial significance for control of Dekkera and may be the basis for differences in susceptibility of wines to Dekkera spoilage.

Apilactobacillus apisilvae sp. nov., Nicolia spurrieriana gen. nov. sp. nov., Bombilactobacillus folatiphilus sp. nov. and Bombilactobacillus thymidiniphilus sp. nov., four new lactic acid bacterial i

Publisher: Microbiology Society

Date: 12-09-2022

DOI: 10.1099/IJSEM.0.005588

Abstract: Four strains, SG5_A10 T , SGEP1_A5 T , SG4_D2 T , and SG4_A1 T , were isolated from the honey or homogenate of Australian stingless bee species Tetragonula carbonaria and Austroplebeia australis . Based on 16S rRNA gene phylogeny, core gene phylogenetics, whole genome analyses such as determination of amino acid identity (AAI), cAAI of conserved genes, average nucleotide identity (ANI), and digital DNA–DNA hybridization (dDDH), chemotaxonomic analyses, and the novel isolation sources and unique geography, we propose three new species and one genus with the names Apilactobacillus apisilvae sp. nov. (SG5_A10 T = LMG 32133 T = NBRC 114991 T ), Bombilactobacillus thymidiniphilus sp. nov. (SG4_A1 T = LMG 32125 T = NBRC 114984 T ), Bombilactobacillus folatiphilus sp. nov. (SG4_D2 T = LMG 32126 T = NBRC 115004 T ) and Nicolia spurrieriana sp. nov. (SGEP1_A5 T = LMG 32134 T = NBRC 114992 T ). Three out of the four strains were found to be fructophilic, where SG5_A10 T and SGEP1_A5 T belong to obligately fructophilic lactic acid bacteria, and SG4_D2 T representing a new type denoted here as kinetically fructophilic. This study represents the first published lactic acid bacterial species associated with the unique niche of Australian stingless bees.

A survey of lactic acid bacteria for enzymes of interest to oenology

Publisher: Hindawi Limited

Date: 10-2006

DOI: 10.1111/J.1755-0238.2006.TB00063.X

Yeast bioprospecting versus synthetic biology—which is better for innovative beverage fermentation?

Publisher: Springer Science and Business Media LLC

Date: 18-01-2020

DOI: 10.1007/S00253-020-10364-X

Abstract: Producers often utilise some of the many available yeast species and strains in the making of fermented alcoholic beverages in order to augment flavours, aromas, acids and textural properties. But still, the demand remains for more yeasts with novel phenotypes that not only impact sensory characteristics but also offer process and engineering advantages. Two strategies for finding such yeasts are (i) bioprospecting for novel strains and species and (ii) genetic modification of known yeasts. The latter enjoys the promise of the emerging field of synthetic biology, which, in principle, would enable scientists to create yeasts with the exact phenotype desired for a given fermentation. In this mini review, we compare and contrast advances in bioprospecting and in synthetic biology as they relate to alcoholic fermentation in brewing and wine making. We explore recent advances in fermentation-relevant recombinant technologies and synthetic biology including the Yeast 2.0 Consortium, use of environmental yeasts, challenges, constraints of law and consumer acceptance.

Microbial modulation of aromatic esters in wine: Current knowledge and future prospects

Publisher: Elsevier BV

Date: 07-2010

DOI: 10.1016/J.FOODCHEM.2009.12.004

Ethanol-tolerant lactic acid bacteria strains as a basis for efficient malolactic fermentation in wine: evaluation of experimentally evolved lactic acid bacteria and winery isolates

Publisher: Hindawi Limited

Date: 26-08-2019

DOI: 10.1111/AJGW.12410

QTL mapping: an innovative method for investigating the genetic determinism of yeast-bacteria interactions in wine

Publisher: Cold Spring Harbor Laboratory

Date: 22-01-2021

DOI: 10.1101/2021.01.21.427107

Abstract: The two most commonly used wine microorganisms, Saccharomyces cerevisiae yeast and Oenococcus oeni bacteria, are responsible for completion of alcoholic and malolactic fermentation (MLF), respectively. For successful co-inoculation, S. cerevisiae and O. oeni must be able to complete fermentation, however, this relies on compatibility between yeast and bacterial strains. For the first time, Quantitative Trait Loci (QTL) analysis was used to elucidate whether S. cerevisiae genetic makeup can play a role in the ability of O. oeni to complete MLF. Assessment of 67 progeny of an S. cerevisiae SBxGN cross, co-inoculated with a single O. oeni strain, SB3, revealed a major QTL linked to MLF completion by O. oeni . This QTL encompassed a well-known translocation, XV-t-XVI, that results in increased SSU1 expression and is functionally linked with numerous phenotypes including lag phase duration and sulfite export and production. A reciprocal hemizygosity assay was performed to elucidate the effect of the gene SSU1 in the SBxGN background. Our results instead revealed a strong effect of SSU1 haploinsufficiency on O. oeni ’s ability to complete malolactic fermentation during co-inoculation, and paves the way for the implementation of QTL mapping projects for deciphering the genetic bases of microbial interactions. For the first time QTL analysis has been used to study yeast-bacteria interactions. A QTL encompassing a translocation, XV-t-XVI, was linked to MLF outcomes. S. cerevisiae SSU1 haploinsufficiency positively impacted MLF by O. oeni.

Directed evolution of Oenococcus oeni strains for more efficient malolactic fermentation in a multi-stressor wine environment

Publisher: Elsevier BV

Date: 08-2018

DOI: 10.1016/J.FM.2018.01.005

Abstract: High concentrations of ethanol, low pH, the presence of sulfur dioxide and some polyphenols have been reported to inhibit Oenococcus oeni growth, thereby negatively affecting malolactic fermentation (MLF) of wine. In order to generate superior O. oeni strains that can conduct more efficient MLF, despite these multiple stressors, a continuous culture approach was designed to directly evolve an existing ethanol tolerant O. oeni strain, A90. The strain was grown for ∼350 generations in a red wine-like environment with increasing levels of stressors. Three strains were selected from screening experiments based on their completion of fermentation in a synthetic wine/wine blend with 15.1% (v/v) ethanol, 26 mg/L SO

QTL mapping: an innovative method for investigating the genetic determinism of yeast-bacteria interactions in wine

Publisher: Springer Science and Business Media LLC

Date: 06-2021

DOI: 10.1007/S00253-021-11376-X

Linkage Projects - Grant ID: LP0347441

Start Date: 2003

End Date: 12-2005

Amount: $69,099.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP130103547

Start Date: 2013

End Date: 12-2018

Amount: $477,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0453935

Start Date: 03-2004

End Date: 12-2007

Amount: $220,106.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP230100406

Start Date: 2023

End Date: 12-2025

Amount: $441,000.00

Funder: Australian Research Council

Industrial Transformation Training Centres - Grant ID: IC130100005

Start Date: 04-2014

End Date: 12-2017

Amount: $2,405,204.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE110100119

Start Date: 07-2011

End Date: 12-2012

Amount: $370,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0776588

Start Date: 04-2008

End Date: 12-2012

Amount: $510,000.00

Funder: Australian Research Council

Industrial Transformation Training Centres - Grant ID: IC170100008

Start Date: 02-2018

End Date: 12-2024

Amount: $4,459,672.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0669816

Start Date: 03-2007

End Date: 03-2009

Amount: $80,000.00

Funder: Australian Research Council