ORCID Profile
0000-0002-1833-2025
Current Organisation
University of Adelaide
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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.
Publisher: Oxford University Press (OUP)
Date: 20-12-2013
DOI: 10.1111/JAM.12060
Abstract: To clone and characterize two related intracellular esterases from Oenococcus oeni and Lactobacillus hilgardii under wine-like conditions. The published genome sequences for O. oeni and Lact. hilgardii were used to identify, clone and purify putative esterase genes from these species designated EstCOo8 and EstC34, respectively. Both esterases are members of family V of lipolytic enzymes. However, EstC34 contains an SGSLG nucleophilic elbow structural motif instead of the usual GGSLG motif which is conserved in other lactic acid bacteria. Both esterases exhibited greatest specificity for C(2) -C(4) pNP-linked substrates and retained activity under wine-like conditions. EstCOo8 had an optimum temperature, pH, and ethanol concentration of 40°C, 5.5 and 6% (v/v), respectively. Whereas EstC34 had an optimum temperature, pH and ethanol concentration of 50°C, 5.0 and 10% (v/v), respectively. Both esterases were stable and retained activity under conditions that would be encountered in wine. They have the potential to reduce short-chain ethyl esters such as ethyl acetate. This study provides information that might help improve the performance of LAB during malolactic fermentation in wine in the future, either by strain selection, optimization or direct enzyme addition.
Publisher: Frontiers Media SA
Date: 15-01-2021
DOI: 10.3389/FMICB.2020.612118
Abstract: Currently, the main role of Lactic Acid Bacteria (LAB) in wine is to conduct the malolactic fermentation (MLF). This process can increase wine aroma and mouthfeel, improve microbial stability and reduce the acidity of wine. A growing number of studies support the appreciation that LAB can also significantly, positively and negatively, contribute to the sensorial profile of wine through many different enzymatic pathways. This is achieved either through the synthesis of compounds such as diacetyl and esters or by liberating bound aroma compounds such as glycoside-bound primary aromas and volatile thiols which are odorless in their bound form. LAB can also liberate hydroxycinnamic acids from their tartaric esters and have the potential to break down anthocyanin glucosides, thus impacting wine color. LAB can also produce enzymes with the potential to help in the winemaking process and contribute to stabilizing the final product. For ex le, LAB exhibit peptidolytic and proteolytic activity that could break down the proteins causing wine haze, potentially reducing the need for bentonite addition. Other potential contributions include pectinolytic activity, which could aid juice clarification and the ability to break down acetaldehyde, even when bound to SO 2 , reducing the need for SO 2 additions during winemaking. Considering all these findings, this review summarizes the novel enzymatic activities of LAB that positively or negatively affect the quality of wine. Inoculation strategies, LAB improvement strategies, their potential to be used as targeted additions, and technological advances involving their use in wine are highlighted along with suggestions for future research.
Publisher: Elsevier BV
Date: 02-2022
DOI: 10.1016/J.IJFOODMICRO.2021.109496
Abstract: We report the fermentative traits of two Kazachstania species (K. aerobia and K. servazzii) in non-sterile red wine and the resulting chemical and sensory properties. This builds on our previous work which revealed that Kazachstania spp. increased acetate esters in sterilised white wine. In this study Kazachstania spp. were initially evaluated in laboratory-scale fermentations (500 mL) in Merlot must to assess whether similar increases in chemical/volatile compounds would occur. The impact of malolactic fermentation (MLF) by Oenococcus oeni (VP41) on aroma composition was considered and found to reduce ester profiles in Merlot wines. The sensory implications of sequential inoculation with Kazachstania spp., followed by Saccharomyces cerevisiae, were then evaluated in small-lot fermentations (7 kg) of Shiraz must. Fungal ersity was monitored during early fermentation stages and was influenced by the early implantation of Kazachstania spp., followed by the dominance of S. cerevisiae. The effect of MLF in Shiraz wines was inconclusive due to high ethanol levels providing an inhospitable environment for lactic acid bacteria. When compared to S. cerevisiae alone, Kazachstania spp. significantly increased acetate esters, particularly phenylethyl acetate and isoamyl acetate, in both Merlot and Shiraz. The Shiraz wines fermented with Kazachstania spp. had higher jammy and red fruit aroma/flavour compared to S. cerevisiae (monoculture) wines. No influence was observed on colour one-year post-bottling. Results from this study show the contribution of Kazachstania spp. to the aroma profile of red wines and demonstrate their potential as starter cultures for improving the aromatic complexity of wines.
Publisher: Springer Science and Business Media LLC
Date: 25-10-2021
Publisher: Oxford University Press (OUP)
Date: 06-2019
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.
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.
Publisher: Springer Science and Business Media LLC
Date: 21-08-2014
DOI: 10.1007/S00253-014-5976-0
Abstract: The initial conversion of grape must to wine is an alcoholic fermentation (AF) largely carried out by one or more strains of yeast, typically Saccharomyces cerevisiae. After the AF, a secondary or malolactic fermentation (MLF) which is carried out by lactic acid bacteria (LAB) is often undertaken. The MLF involves the bioconversion of malic acid to lactic acid and carbon dioxide. The ability to metabolise L-malic acid is strain specific, and both in idual Oenococcus oeni strains and other LAB strains vary in their ability to efficiently carry out MLF. Aside from impacts on acidity, LAB can also metabolise other precursors present in wine during fermentation and, therefore, alter the chemical composition of the wine resulting in an increased complexity of wine aroma and flavour. Recent research has focused on three main areas: enzymatic changes during MLF, safety of the final product and mechanisms of stress resistance. This review summarises the latest research and technological advances in the rapidly evolving study of MLF and investigates the directions that future research may take.
Publisher: Microbiology Society
Date: 05-06-2023
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).
Publisher: Hindawi Limited
Date: 14-01-2021
DOI: 10.1111/AJGW.12479
Publisher: American Society for Microbiology
Date: 11-2009
DOI: 10.1128/AEM.01563-09
Abstract: We report the cloning and characterization of EstB28, the first esterase to be so characterized from the wine-associated lactic acid bacterium, Oenococcus oeni . The published sequence for O. oeni strain PSU-1 was used to identify putative esterase genes and design PCR primers in order to lify the corresponding region from strain Ooeni28, an isolate intended for inoculation of wines. In this way a 912-bp open reading frame (ORF) encoding a putative esterase of 34.5 kDa was obtained. The amino acid sequence indicated that EstB28 is a member of family IV of lipolytic enzymes and contains the GDSAG motif common to other lactic acid bacteria. This ORF was cloned into Escherichia coli using an appropriate expression system, and the recombinant esterase was purified. Characterization of EstB28 revealed that the optimum temperature, pH, and ethanol concentration were 40°C, pH 5.0, and 28% (vol/vol), respectively. EstB28 also retained marked activity under conditions relevant to winemaking (10 to 20°C, pH 3.5, 14% [vol/vol] ethanol). Kinetic constants were determined for EstB28 with p -nitrophenyl ( p NP)-linked substrates ranging in chain length from C 2 to C 18 . EstB28 exhibited greatest specificity for C 2 to C 4 p NP-linked substrates.
Publisher: Springer Science and Business Media LLC
Date: 29-09-2012
DOI: 10.1007/S00253-012-4409-1
Abstract: The study of gene expression and accurate quantitation of target genes in any organism depends on correct normalisation. Due to the increase in studies on Oenococcus oeni gene expression, there is a clear need for alternative reference genes in order to reliably measure expression levels. In this manuscript, we propose the approach of using multiple reference genes to provide a more robust basis for establishing a reference gene set. The identification and evaluation of a panel of nine reference genes, including the commonly used ldhD, for real-time PCR normalisation was performed in O. oeni. Expression levels of these reference genes were then measured by real-time qPCR in an independent set of O. oeni s les (n = 30). The nine genes were ranked according to their stability of gene expression measure (M) using geNorm to identify the most consistently expressed reference genes. This approach resulted in the identification of multiple reference genes that may be used for a screening and more robust normalisation of target gene expression measured by real-time RT-qPCR. Expression of esterase genes was then measured in these O. oeni s les in the presence of known esterase substrates. The results give an indication of how these genes may be involved in ester synthesis and hydrolysis in O. oeni.
Publisher: Microbiology Society
Date: 16-02-2023
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.
Publisher: Microbiology Society
Date: 12-09-2022
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.
Publisher: American Society for Microbiology
Date: 12-2004
DOI: 10.1128/JCM.42.12.5549-5557.2004
Abstract: We describe a multiplex PCR assay to identify and discriminate between isolates of C ylobacter coli , C ylobacter jejuni , C ylobacter lari , and C ylobacter upsaliensis . The C. jejuni isolate F38011 lpxA gene, encoding a UDP- N -acetylglucosamine acyltransferase, was identified by sequence analysis of an expression plasmid that restored wild-type lipopolysaccharide levels in Escherichia coli strain SM105 [ lpxA (Ts)]. With oligonucleotide primers developed to the C. jejuni lpxA gene, nearly full-length lpxA licons were lified from an additional 11 isolates of C. jejuni , 20 isolates of C. coli , 16 isolates of C. lari , and five isolates of C. upsaliensis . The nucleotide sequence of each licon was determined, and sequence alignment revealed a high level of species discrimination. Oligonucleotide primers were constructed to exploit species differences, and a multiplex PCR assay was developed to positively identify isolates of C. coli , C. jejuni , C. lari , and C. upsaliensis. We characterized an additional set of 41 thermotolerant isolates by partial nucleotide sequence analysis to further demonstrate the uniqueness of each species-specific region. The multiplex PCR assay was validated with 105 genetically defined isolates of C. coli , C. jejuni , C. lari , and C. upsaliensis , 34 strains representing 12 additional C ylobacter species, and 24 strains representing 19 non- C ylobacter species. Application of the multiplex PCR method to whole-cell lysates obtained from 108 clinical and environmental thermotolerant C ylobacter isolates resulted in 100% correlation with biochemical typing methods.
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.
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
Publisher: Hindawi Limited
Date: 26-08-2019
DOI: 10.1111/AJGW.12410
Publisher: Elsevier BV
Date: 07-2010
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.
Publisher: Elsevier BV
Date: 08-2018
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
Publisher: Springer Science and Business Media LLC
Date: 06-2021
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.FOODCHEM.2013.03.087
Abstract: Previous work has shown that Oenococcus oeni produces esterases that are capable of hydrolysing artificial substrates. Using SPME-GCMS, this study provides evidence that purified O. oeni esterases have the ability to both synthesise and hydrolyse esters. Two purified esterases (EstA2 and EstB28) synthesised ethyl butanoate and ethyl hexanoate to varying degrees. Both purified esterases hydrolysed ethyl butanoate, ethyl hexanoate and ethyl octanoate. Once this dual activity was confirmed, malolactic fermentation (MLF) trials were conducted in wine with O. oeni strains that had been previously observed to have either high or low esterase activity against artificial substrates. Strain specific differences were observed and strains with low esterase hydrolysis activity against artificial substrates had a higher level of total esters measured after MLF. The results demonstrate the impact that O. oeni has on wine aroma and relates this to the ester hydrolysis and synthesis abilities of O. oeni strains.
No related grants have been discovered for Krista Sumby.