Hanseniaspora Uvarum Research Articles

Biocontrol of Gray Mold of Cherry Tomatoes with the Volatile Organic Monomer from Hanseniaspora uvarum, Trans-Cinnamaldehyde

Botrytis cinerea is one of the most destructive pathogens of cherry tomatoes during preharvest and postharvest phase. Our previous study demonstrated that volatile organic compounds (VOCs) produced by Hanseniaspora uvarum could markedly suppress the mycelium growth and conidia germination of B. cinerea. However, the main inhibitory VOCs of H. uvarum are not fully clear. In this study, a total of 21 volatile organic monomers (VOMs) of H. uvarum were tested for their antifungal activity against B. cinerea in vitro. It was found that trans-cinnamaldehyde, 2-nonanone, ethyl caprylate, benzyl alcohol, hexanoic acid, hexyl alcohol, isobutyl acetate, ethyl propionate, isoamyl acetate, ethyl 2-methylbutyrate, phenethyl alcohol, ethyl acetate, 4-ethylphenol, 3-phenyl-1-propanol, ethyl cinnamate, 3-methyl-1-butanol, and ethyl 3-hydroxybhexanoate could significantly inhibit mycelium growth within 3 days at higher concentrations, whereas ethyl 3-hydroxybutyrate, ethyl caprate, decanoic acid, and lauric acid exhibited a lower inhibition. Furthermore, the five VOMs, including trans-cinnamaldehyde, 2-nonanone, ethyl caprylate, benzyl alcohol, and hexanoic acid, also had the efficiency on inhibiting conidia germination. In particular, trans-cinnamaldehyde was the best inhibitor of mycelium growth and conidia germination. Hence, trans-cinnamaldehyde was also tested in vivo as postharvest biofumigants. In vivo assay showed that trans-cinnamaldehyde could significantly reduce B. cinerea infection of cherry tomatoes and maintain fruit hardness, color, total soluable solids, and titratable acidity under conditions of artificial and natural infection. Collectively, these results indicated that trans-cinnamaldehyde, the main inhibitory VOMs of H. uvarum, has the potential for effectively controlling postharvest gray mold of cherry tomatoes and maintaining fruit quality in commercial application.

Laboratory and Field Evaluation of Host-Related Foraging Odor-Cue Combinations to Attract Drosophila suzukii (Diptera: Drosophilidae).

The invasive spotted-wing drosophila, Drosophila suzukii (Matsumura), is a major pest of soft-skinned fruits. Since its introduction into North America and Europe, significant progress has been made in understanding the volatile cues used by this fly during food, oviposition site, and mate finding. Despite this progress, commercially available lures are non-selective. Here, we tested two Hanseniaspora uvarum (Niehaus) yeast compounds (isoamyl acetate and isobutyl acetate) and a leaf compound β-cyclocitral alone and in combination with a blend of four fermentation compounds ('Fermentation lure': acetic acid, ethanol, methionol, and acetoin) to improve D. suzukii attraction and selectivity. In laboratory assays, males and females were attracted to all seven individual compounds, although in electrophysiological assays, their antennae exhibited a dose-dependent response to only four of these compounds. In two-choice cage studies, the Fermentation lure was more attractive to D. suzukii than water controls, whereas β-cyclocitral and the mixture of isoamyl acetate and isobutyl acetate were not attractive in this larger-cage study. Moreover, adding the two-component H. uvarum compound blend to the Fermentation lure reduced D. suzukii attraction to the Fermentation blend. When these experiments were repeated in blueberry, raspberry, blackberry, and cherry orchards across several states in the United States over 2 yr, similar outcomes were observed: β-cyclocitral or the mixture of the H. uvarum blend did not improve the attractiveness of the Fermentation lure or its selectivity. This study demonstrates that cues from different sources may interfere with each other and reduce D. suzukii attraction to otherwise attractive odor combinations.

Diversity of yeasts in the soil adjacent to fruit trees of the Rosaceae family.

Yeasts are common constituents of different types of soil. Their diversity depends on the season, the type and depth of the soil, the plant species, and the locality. In this study, diversity of yeasts isolated from the soil adjacent to five fruit trees (apple, appricot, peach, pear, and plum) in two localities (in Slovakia) in four sampling periods was examined. Our results demonstrated differences in the species richness and evenness among the yeast populations, which inhabited the soil beneath individual fruit tree species in both localities. Altogether, 32 ascomycetous and 27 basidiomycetous yeast species were discovered. The highest species richness was found in the soil adjacent to the apricot trees. Galactomyces candidum, Metschnikowia pulcherrima, Hanseniaspora uvarum, Schwanniomyces capriottii, and Tausonia pullulans, as well as the genus Apiotrichum, were present in soil samples in all samplings. Two species of the genus Holtermanniella (H.festucosa and H.takashimae) were exclusively isolated during Sampling IV in April. Cyberlindnera spp., Clavispora reshetovae, S.capriottii, and Trichosporon asahii were found only in one of two localities. Ascomycetous yeasts were present more frequently than their basidiomycetous counterparts in the three samplings (one in June and two in October); they formed from 65.6% to 70.8% of the total yeast population, whereas basidiomycetous yeasts prevailed in the April sampling (61.2%).

Yeast Species, Strains, and Growth Media Mediate Attraction of Drosophila suzukii (Diptera: Drosophilidae).

Specific ecological interactions between insects and microbes have potential in the development of targeted pest monitoring or control techniques for the spotted wing drosophilid, Drosophila suzukii (Matsumura), an exotic invasive pest of soft fruit. To evaluate D. suzukii attraction to yeast species from preferred types of fruit, three yeasts were isolated from blackberry fruit and two yeasts from raspberry fruit and used to bait simple plastic bottle traps. Saccharomyces cerevisiae and Hanseniaspora uvarum were identified from blackberries, whereas a different H. uvarum strain was identified from raspberry. Yeast identification was based on sequence analysis of the D1/D2 domain of the large subunit 26S rRNA gene. Commercial baker’s yeast (S. cerevisiae) was similar or more effective for the capture of D. suzukii males and females than yeasts isolated from blackberry or raspberry when grown in sucrose. However, when grown in corn syrup, a strain of S. cerevisiae from blackberry captured the highest number of females and a strain of H. uvarum isolated from raspberry captured high numbers of males and females. Species of Candida, Hanseniaspora, and Pichia from a laboratory yeast collection did not outperform baker’s yeast in pairwise tests when grown in sucrose solution or yeast-peptone-dextrose medium. The raspberry strain of H. uvarum grown in corn syrup outperformed S. cerevisiae grown in sucrose, in terms of captures in baited traps under laboratory conditions. We conclude that yeast species, strain, and growth medium can have a marked influence on D. suzukii attraction to baited traps, a finding that could assist in the development of yeast-related monitoring or control techniques targeted at this pest.

Improved insecticidal control of spotted wing drosophila (Drosophila suzukii) using yeast and fermented strawberry juice baits

The phagostimulant effect of baits on the Drosophila suzukii control efficacy of different insecticides applied at sub-lethal concentrations was tested in bioassays. The baits were fermented strawberry juice (FSJ), a suspension of the yeast Hanseniaspora uvarum, a combination of the two and Combi-protec, a proprietary mixture of plant extract, proteins and sugars. Without insecticides, the baits did not affect D. suzukii mortality. With spinosad, cyantraniliprole or lambda-cyhalothrin, the baits caused higher mortality of D. suzukii summer morphs, under summer conditions, compared with using the insecticides in water. The mortality and reduced reproduction efficacy of insecticides was greater with H. uvarum, FSJ + H. uvarum or Combi-protec treatments compared with FSJ only bait. H. uvarum and FSJ baits also increased the mortality of D. suzukii winter morphs, held under winter conditions, when used with spinosad or cyantraniliprole but not with lambda-cyhalothrin. Cyantraniliprole + H. uvarum also reduced oviposition in winter morphs that were transferred to summer conditions after three days of exposure to treatments under winter conditions. Leaf type did not have an impact on combined bait and insecticide treatments; all were effective when applied to blackberry, blueberry, cherry, raspberry or strawberry leaves. Phagostimulant baits improved the insecticidal control of D. suzukii summer and winter morphs by increasing mortality and reducing oviposition and the lethal dose of insecticides. The relative phagostimulant effect of the baits did not fully correspond with their olfactory attraction to D. suzukii.

Indigenous Yeast Interactions in Dual-Starter Fermentations May Improve the Varietal Expression of Moschofilero Wine.

Multi-starter wine fermentations employing non-Saccharomyces (NS) yeasts are becoming an emerging trend in winemaking. It is therefore important to determine the impacts of different NS strains in the wine phenotype and in particular the aroma outputs in different inoculation schemes and fermentation conditions. Here, two native NS yeasts, Lachancea thermotolerans LtMM7 and Hanseniaspora uvarum HuMM19, were assessed for their ability to improve the quality of Moschofilero, a Greek aromatic white wine. The NS strains were initially examined in laboratory scale fermentations in mixed inoculations with ScMM23, a native Saccharomyces cerevisiae strain. LtMM7 was selected to be further evaluated in pilot scale fermentations. Five different inoculation schemes were considered: single inoculation of ScMM23 (IS), simultaneous inoculation of ScMM23 with HuMM19 (SMH) or LtMM7 (SML), and sequential inoculation of HuMM19 (SQH) or LtMM7 (SQL) followed by ScMM23. At laboratory scale fermentations, the chemical profiles were largely affected by both the NS species and the inoculation scheme applied. The sequential inoculation using HuMM19 produced the most divergent wine phenotype. However, HuMM19 caused significant increases in acetic acid and ethyl acetate levels that impeded its use in pilot scale trials. LtMM7 significantly affected the chemical profiles of wines produced at the winery, especially in the sequential inoculation scheme. Importantly, LtMM7 significantly increased the levels of acetate esters or ethyl esters, depending on the inoculation method applied. In particular, acetate esters like isobutyl acetate, hexyl acetate, and 2-phenylethyl acetate, which all impart fruity or floral aromas, were significantly increased in SQL. On the other hand, higher levels of total ethyl esters were associated with SML. The most striking differences were observed in the levels of fruit-impair esters like ethyl decanoate, 3-methylbutyl octanoate, and isoamyl hexanoate. This is the first study to report a significant increase in the ethyl ester fraction by L. thermotolerans. Interestingly, L. thermotolerans in SQL also increased the concentrations of damascenone and geraniol, the major teprenic compound of Moschofilero, which are associated with several typical floral and fruity aromas of the variety. Present results show that L. thermotolerans may enhance the varietal character and increase the chemical complexity of Moschofilero wines.

Yeast diversity investigation of Vitis davidii Föex during spontaneous fermentations using culture-dependent and high-throughput sequencing approaches.

Vitis davidii Föex is widely planted in South China as a potential wine making grape. In this study, yeast communities during the spontaneous fermentations of two varieties of Vitis davidii Föex in Guizhou, China were investigated. Hanseniaspora uvarum, Pichia terricola, Saccharomyces cerevisiae/S. mikatae, and Schizosaccharomyces japonicus were the four main yeast species detected by culture-dependent and high-throughput sequencing approaches. However, the composition of minor yeast species was quite different as revealed by the two approaches. Ten yeast species including Debaryomyces hansenii, Rhodotorula mucilaginosa, Sporidiobolus paraoseus, Starmerella bacillaris, Zygoascus meyerae, etc. were detected by culture-dependent approaches, whereas the other five species were found by high-throughput sequencing analysis. S. japonicus was widely found during spontaneous fermentations and its concentrations were mostly higher than that of S. cerevisiae. The difference in grape varieties and fermentation conditions contributed to yeast diversity. The results of this study provide basic information on indigenous yeast diversity from Vitis davidii Föex in Guizhou, which would help to exploit the potential of non-Saccharomyces yeast species with good oenological attributes.

Impact on Sensory and Aromatic Profile of Low Ethanol Malbec Wines Fermented by Sequential Culture of Hanseniaspora uvarum and Saccharomyces cerevisiae Native Yeasts

It is well known that high ethanol levels in wines adversely affect the perception of new wine consumers. Moreover, numerous issues, such as civil restrictions, health risk and trade barriers, are associated with high ethanol concentrations. Several strategies have been proposed to produce wines with lower alcoholic content, one simple and inexpensive approach being the use of new wine native yeasts with less efficiency in sugar to ethanol conversion. Nevertheless, it is also necessary that these yeasts do not impair the quality of wine. In this work, we tested the effect of sequential culture between Hanseniaspora uvarum BHu9 and Saccharomyces cerevisiae BSc114 on ethanol production. Then, the wines produced were analyzed by GC-MS and tested by a sensorial panel. Co-culture had a positive impact on ethanol reduction and sensory profile when compared to the S. cerevisiae monoculture. Wines with lower alcohol content were related to fruity aroma; moreover, color intensity was associated. The wines obtained with S. cerevisiae BSc114 in pure conditions were described by parameters linked with high ethanol levels, such as hotness and astringency. Moreover, floral profile was related to this treatment. Based on these findings, this work provides a contribution to answer the current consumers’ preferences and addresses the main challenges faced by the enological industry.

Modulation of Wine Flavor using Hanseniaspora uvarum in Combination with Different Saccharomyces cerevisiae, Lactic Acid Bacteria Strains and Malolactic Fermentation Strategies

Hanseniaspora uvarum is one of the predominant non-Saccharomyces yeast species found on grapes and in juice, but its effect on lactic acid bacteria (LAB) growth and wine flavor has not been extensively studied. Therefore, the interaction between H. uvarum, two Saccharomyces cerevisiae yeast strains, two LAB species (Lactobacillus plantarum and Oenococcus oeni) in combination with two malolactic fermentation (MLF) strategies was investigated in Shiraz wine production trials. The evolution of the different microorganisms was monitored, non-volatile and volatile compounds were measured, and the wines were subjected to sensory evaluation. Wines produced with H. uvarum in combination with S. cerevisiae completed MLF in a shorter period than wines produced with only S. cerevisiae. Sequential MLF wines scored higher for fresh vegetative and spicy aroma than wines where MLF was induced as a simultaneous inoculation. Wines produced with H. uvarum had more body than wines produced with only S. cerevisiae. The induction of MLF using L. plantarum also resulted in wines with higher scores for body. H. uvarum can be used to reduce the duration of MLF, enhance fresh vegetative aroma and improve the body of a wine.

Volatile organic compounds of Hanseniaspora uvarum increase strawberry fruit flavor and defense during cold storage.

Volatile organic compounds (VOCs) of antagonistic yeasts are considered as environmental safe fumigants to promote the resistance and quality of strawberry (Fragaria ananassa). By GC‐MS assays, VOCs of Hanseniaspora uvarum (H. uvarum) fumigated strawberry fruit showed increased contents of methyl caproate (5.8%), methyl octanoate (5.1%), and methyl caprylate (10.9%) in postharvest cold storage. Possible mechanisms of H. uvarum VOCs involved in regulations of the defense‐related enzymes and substances in strawberry were investigated during postharvest storage in low temperature and high humidity (2 ± 1°C, RH 90%–95%). Defense‐related enzymes assays indicated H. uvarum VOCs stimulated the accumulation of CAT, SOD, POD, APX, PPO, and PAL and inhibited biosynthesis of MDA in strawberry fruit under storage condition. Moreover, the expression levels of related key enzyme genes, such as CAT, SOD, APX42, PPO, and PAL6, were consistently increased in strawberry fruit after H. uvarum VOCs fumigation.

The combined use of the antagonistic yeast Hanseniaspora uvarum with β-aminobutyric acid for the management of postharvest diseases of kiwifruit

Significant losses in harvested kiwifruit can be directly attributed to decay fungi. In the present study, the use of an antagonistic yeast, Hanseniasporauvarum, combined with β-aminobutyric acid (BABA), a non-proteinogenic amino acid, was evaluated as a treatment for controlling postharvest infections of kiwifruit, artificially-inoculated with either Botrytis cinerea or Alternaria alternata. Natural infection of treated kiwifruits was also assessed. H.uvarum or BABA as stand-alone treatment, significantly reduced gray mold (B. cinerea) and black rot (A. alternata) on kiwifruit, relative to untreated control fruit, and also reduced the level of natural infection. The combination of H.uvarum and BABA, however, provided a superior level of postharvest disease control compared to either treatment alone. The growth of H.uvarum growth in kiwifruit wounds was not affected by BABA. Treatment of kiwifruit with either H.uvarum or BABA individually or in combination induced the gene expression and enzyme activity of chitinase and β-1,3-glucanase in kiwifruit. The ability of BABA to enhance the biocontrol efficacy of H.uvarum may be partially attributed to the elicitation of defense response in kiwifruit. The combined use of H.uvarum and BABA represents a promising alternative approach to the use of synthetic fungicides for the control of postharvest diseases in kiwifruit.

The impact of fungicide treatments on yeast biota of Verdicchio and Montepulciano grape varieties.

Yeast species that colonize the surface of grape berries at harvest time play an important role during the winemaking process. In this study, the use of culturable microbial techniques permitted a quantitative and qualitative inventory of the different yeast species present on the grape berry surfaces of Montepulciano and Verdicchio varieties when treated with conventional and organic fungicides. The results show that the most widespread yeast species at harvest time were Aureobasidium pullulans and Hanseniaspora uvarum, which are considered normal resident species and independent of the grape varieties and treatments applied. Specific differences when comparing the grape varieties were observed in species and were detected at a lower frequency; Pichia spp. were prevalent in Verdicchio, whereas Lachancea thermotolerans and Zygoascus meyerae were found in Montepulciano. In both vineyards, the farming treatments improved the competitiveness of A. pullulans, which was probably due to its reduced susceptibility to treatments that improved the competition toward other fungi. In contrast, the fermenting yeast H. uvarum was negatively affected by fungicide treatments and showed a reduced presence if compared with untreated grapes. Organic treatments directly impacted the occurrence of Issachenkia terricola in Montepulciano grapes and Debaryomyces hansenii and Pichia membranifaciens in Verdicchio. Conversely, a negative effect of organic treatments was found toward Metschnikowia pulcherrima and Starmerella bacillaris. Overall, the data suggest that the yeast community colonizing the grape berry surface was influenced by both grape variety and farming treatments, which characterized the yeast biota of spontaneous must fermentation.

Live yeast in juvenile diet induces species-specific effects on Drosophila adult behaviour and fitness

The presence and the amount of specific yeasts in the diet of saprophagous insects such as Drosophila can affect their development and fitness. However, the impact of different yeast species in the juvenile diet has rarely been investigated. Here, we measured the behavioural and fitness effects of three live yeasts (Saccharomyces cerevisiae = SC; Hanseniaspora uvarum = HU; Metschnikowia pulcherrima = MP) added to the diet of Drosophila melanogaster larvae. Beside these live yeast species naturally found in natural Drosophila populations or in their food sources, we tested the inactivated “drySC” yeast widely used in Drosophila research laboratories. All flies were transferred to drySC medium immediately after adult emergence, and several life traits and behaviours were measured. These four yeast diets had different effects on pre-imaginal development: HU-rich diet tended to shorten the “egg-to-pupa” period of development while MP-rich diet induced higher larval lethality compared to other diets. Pre- and postzygotic reproduction-related characters (copulatory ability, fecundity, cuticular pheromones) varied according to juvenile diet and sex. Juvenile diet also changed adult food choice preference and longevity. These results indicate that specific yeast species present in natural food sources and ingested by larvae can affect their adult characters crucial for fitness.

The Shared and Specific Genes and a Comparative Genomics Analysis within Three Hanseniaspora Strains.

Kloeckera apiculata plays an important role in the inhibition of citrus postharvest blue and green mould diseases. This study was based on the previous genome sequencing of K. apiculata strain 34-9. After homologous comparison, scaffold 27 was defined as the mitochondrial (mt) sequence of K. apiculata 34-9. The comparison showed a high level of sequence identity between scaffold 27 and the known mtDNA of Hanseniaspora uvarum. The genome sequence of H. vineae T02/19AF showed several short and discontinuous fragments homologous to the mtDNA of H. uvarum. The shared and specific genes of K. apiculata, H. uvarum, and H. vineae were analysed by family using the TreeFam methodology. GO analysis was used to classify the shared and specific genes. Most of the gene families were classified into the functional categories of cellular component and metabolic processes. The whole-genome phylogram and genome synteny analysis showed that K. apiculata was more closely related to H. uvarum than to H. vineae. The genomic comparisons clearly displayed the locations of the homologous regions in each genome. This analysis could contribute to discovering the genomic similarities and differences within the genus Hanseniaspora. In addition, some regions were not collinearity-matched in the genome of K. apiculata compared with that of H. uvarum or H. vineae, and these sequences might have resulted from evolutionary variations.

Bio-efficacy of different biological control agents for the management of chilli fruit rot/anthracnose disease

Chilli (Capsicum annum L.) an important economic crop worldwide is severely infected by fruit rot disease which may cause yield losses of up to 100%. Although different chemical fungicides are being recommended and used for the management of the disease, biocontrol-based strategy attracts considerable attention and offers great potential of novel biocontrol agents. Further, biological control methods for chilli fruit rot/anthracnose disease have not received much attention. Therefore, an investigation was carried out to assess the efficacy of different biological control agents against chilli fruit rot/anthracnose disease. Antagonistic yeast isolates Pichia guillermondii (Y-12), Hanseniaspora uvarum (Y-73) and Trichoderma asperellum (Th-3), Pseudomonas fluorescens (Pf-1) were tested through seed treatment, seedling dip and foliar spray at concentration of 2 í— 108 cfu/g. The pathogens viz., Colletotrichum capsici, Alternaria alternata and Periconia byssoides were found associated with fruit rot during the study. Lowest mean disease intensity (MDI), highest disease control (DC) over untreated control was recorded in the treatment <i>P. guillermondii</i> (Y-12) (5.39% MDI, 64.72% DC) and this was found at par with the treatment <i>P. fluorescens</i> (Pf-1) (5.92% MDI, 65.52% DC). However, <i>T. asperellum</i> (Th-3) showed satisfactory results. The present study highlights the efficacy of antagonistic yeast species against chilli fruit rot pathogens and these findings serve as base for further exploration and exploitation of yeast species for eco-friendly management of crop diseases.

Bio-efficacy of different biological control agents for the management of chilli fruit rot/anthracnose disease

Chilli ( Capsicum annu m L.) an important economic crop worldwide is severely infected by fruit rot disease which may cause yield losses of up to 100%. Although different chemical fungicides are being recommended and used for the management of the disease, biocontrol-based strategy attracts considerable attention and offers great potential of novel biocontrol agents. Further, biological control methods for chilli fruit rot/anthracnose disease have not received much attention. Therefore, an investigation was carried out to assess the efficacy of different biological control agents against chilli fruit rot/anthracnose disease. Antagonistic yeast isolates Pichia guillermondii (Y-12), Hanseniaspora uvarum (Y-73) and Trichoderma asperellum (Th-3), Pseudomonas fluorescens (Pf-1) were tested through seed treatment, seedling dip and foliar spray at concentration of 2 A— 10 8 cfu/g. The pathogens viz., Colletotrichum capsici , Alternaria alternata and Periconia byssoides were found associated with fruit rot during the study. Lowest mean disease intensity (MDI), highest disease control (DC) over untreated control was recorded in the treatment P. guillermondii (Y-12) (5.39% MDI, 64.72% DC) and this was found at par with the treatment P. fluorescens (Pf-1) (5.92% MDI, 65.52% DC). However, T. asperellum (Th-3) showed satisfactory results. The present study highlights the efficacy of antagonistic yeast species against chilli fruit rot pathogens and these findings serve as base for further exploration and exploitation of yeast species for eco-friendly management of crop diseases.

Enhancing wine ester biosynthesis in mixed Hanseniaspora uvarum/Saccharomyces cerevisiae fermentation by nitrogen nutrient addition.

The dynamic changes of wine ester production during mixed fermentation with Hanseniaspora uvarum Yun268 and Saccharomyces cerevisiae F5 was investigated at different levels and timings of nitrogen nutrient addition. Nitrogen additions were performed by supplementing yeast assimilable nitrogen (YAN) into a synthetic grape must with defined composition. Ester precursors and extracellular metabolites involved in ester synthesis were analyzed throughout the fermentation. Results showed that nitrogen additions covering 50-200 mg/L YAN at the point of yeast inoculation slightly affected yeast competition and ester profiles. Interestingly, when YAN was supplemented in the mid-stage, the survival of H. uvarum Yun268 was enhanced, resulting in more than a 2-fold increase in the levels of higher alcohol acetates compared to that at the initial stage. Furthermore, carbon fluxes may be redistributed in the central pathway, which contributed to the production of medium-chain fatty acids and eventually triggered a 1.2-fold elevation in corresponding ethyl ester levels.

Impact of co-inoculation of Saccharomyces cerevisiae, Hanseniaspora uvarum and Oenococcus oeni autochthonous strains in controlled multi starter grape must fermentations

The use of multi-species starter cultures is an approach of increasing significance for winemakers in order to improve the general quality and safety of the final product. As first step of the present study, we isolated and characterize two Saccharomyces cerevisiae yeast starter strains, denoted as ITEM 167292 and ITEM 17293, from natural must fermentations of “Negroamaro” grapes. As second step, we studied the interactions during grape must fermentation between these two strains, the Hanseniaspora uvarum strain ITEM 8785 and five autochthonous Oenococcus oeni strains, by microbial counts and by quantifying l-malic acid and ethanol concentrations. The best performing O. oeni strain, namely OT4, was used to create, with the H. uvarum strain ITEM 8785, two mixed starter formulations with the strains ITEM 167292 and ITEM 17293. The three microbial species showed to be compatible and to complete the fermentative processes producing wines denoted by reduced acetic acid concentrations. The performance of the mixed starter formulations were then validated by carrying pilot-scale vinifications. At the best of our knowledge, this report is the first study regarding the utilization of selected H. uvarum/S. cerevisiae/O. oeni autochthonous strains in a simultaneous multi-starter inoculation for the industrial production of regional typical wines.

Killer Activity of Hanseniaspora uvarum Isolated from Dates Vinegar: Partially Purification and Characterization of Killer Toxin

This study was conducted to isolate and identify killer yeast Hanseniaspora uvarum from dates vinegar and measurement the ability of this yeast to produce killer toxin. The antimicrobial activity of the concentrated supernatant containing partially purified concentrated killer toxin was also detected against several pathogenic bacteria and yeast species, which includes two types of yeast Rhodotorula mucilaginosa and Candida tropicalis and four human pathogenic bacteria Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeurginosa. In addition, the antagonistic activity of examined yeast have been studied toward four types of fungi, where two are pathogenic for human Trichophyton mentagrophytes and Trichophyton rubrum and two are plant pathogens Fusarium solani and Sclerotinia sclerotiorum. The results of killer toxin production experiments revealed the ability of yeast to produce killer toxin with molecular weight at 18 kDa by 12 % SDS electrophoresis. The optimal conditions for killer toxin production were studied, and their antimicrobial activity was determined. The results revealed that killer toxin production was increased at 4 % NaCl, the highest inhibtion zone was 20 mm for S. aureus, while the lowest inhibition zone was 7 mm for E. coli. Killer activity was increased at pH 4 and the best inhibtion zone obtained was about 16 mm for K. pneumoniae, while 8 mm for E. coli and C. tropicalis. The temperature was also affect the production of killer toxin, where 25 °C is the best temperature for toxin production of examined yeast, The best killer activity was 21 mm for C. tropicalis. The antagonistic activity of killer yeast H. uvarum toward pathogenic fungal growth was determined and showed killer activity about 61.11, 44.44, 33.33 and 24.44 % against T. mentagrophytes, T. rubrum, F. solani and S. sclerotiorum in comparison to the control.

Killer Activity of Hanseniaspora uvarum Isolated from Dates Vinegar: Partially Purification and Characterization of Killer Toxin

This study was conducted to isolate and identify killer yeast Hanseniaspora uvarum from dates vinegar and measurement the ability of this yeast to produce killer toxin. The antimicrobial activity of the concentrated supernatant containing partially purified concentrated killer toxin was also detected against several pathogenic bacteria and yeast species, which includes two types of yeast Rhodotorula mucilaginosa and Candida tropicalis and four human pathogenic bacteria Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeurginosa. In addition, the antagonistic activity of examined yeast have been studied toward four types of fungi, where two are pathogenic for human Trichophyton mentagrophytes and Trichophyton rubrum and two are plant pathogens Fusarium solani and Sclerotinia sclerotiorum. The results of killer toxin production experiments revealed the ability of yeast to produce killer toxin with molecular weight at 18 kDa by 12 % SDS electrophoresis. The optimal conditions for killer toxin production were studied, and their antimicrobial activity was determined. The results revealed that killer toxin production was increased at 4 % NaCl, the highest inhibtion zone was 20 mm for S. aureus, while the lowest inhibition zone was 7 mm for E. coli. Killer activity was increased at pH 4 and the best inhibtion zone obtained was about 16 mm for K. pneumoniae, while 8 mm for E. coli and C. tropicalis. The temperature was also affect the production of killer toxin, where 25 °C is the best temperature for toxin production of examined yeast, The best killer activity was 21 mm for C. tropicalis. The antagonistic activity of killer yeast H. uvarum toward pathogenic fungal growth was determined and showed killer activity about 61.11, 44.44, 33.33 and 24.44 % against T. mentagrophytes, T. rubrum, F. solani and S. sclerotiorum in comparison to the control.