Occurrence and enological properties of two new non-conventional yeasts (Nakazawaea ishiwadae and Lodderomyces elongisporus) in wine fermentations

Nakazawaea atacamensis f.a., sp. nov. a novel nonconventional fermentative ascomycetous yeast species from the Atacama Desert

In this study, we describe Nakazawaea atacamensis f. a., sp. nov., a novel species obtained from Neltuma chilensis plant samples in Chile's hyperarid Atacama Desert. In total, three strains of N. atacamensis were obtained from independent N. chilensis samples (synonym Prosopis chilensis, Algarrobo). Two strains were obtained from bark samples, while the third strain was obtained from bark-exuded gum from another tree. The novel species was defined using molecular characteristics and subsequently characterized with respect to morphological, physiological, and biochemical properties. A neighbor-joining analysis using the sequences of the D1/D2 domains of the large subunit ribosomal RNA gene revealed that N. atacamensis clustered with Nakazawaea pomicola. The sequence of N. atacamensis differed from closely related species by 1.3%-5.2% in the D1/D2 domains. A phylogenomic analysis based on single-nucleotide polymorphism's data confirms that the novel species belongs to the genus Nakazawaea, where N. atacamensis clustered with N. peltata. Phenotypic comparisons demonstrated that N. atacamensis exhibited distinct carbon assimilation patterns compared to its related species. Genome sequencing of the strain ATA-11A-BT revealed a genome size of approximately 12.4 Mbp, similar to other Nakazawaea species, with 5116 protein-coding genes annotated using InterProScan. In addition, N. atacamensis exhibited the capacity to ferment synthetic wine must, representing a potential new yeast for mono or co-culture wine fermentations. This comprehensive study expands our understanding of the genus Nakazawaea and highlights the ecological and industrial potential of N. atacamensis in fermentation processes. The holotype of N. atacamensis sp. nov. is CBS 18375T . The Mycobank number is MB 849680.

Three Successfully Treated Cases of Lodderomyces elongisporus Fungemia: Case Reports and a Review of the Literature

Fungemia is a fatal systemic infection that can occur in immunocompromised patients. Despite that, antifungal stewardship is spreading widely, but the mortality rate is extremely high, showing 40-60%. Loderomyces elongiporus is a newly morphologically detected pathogen, first described in 1994, followed by isolation in humans in 2008. It has been misrecognized as Candida parapsilosis. Recently, fever attributable to L. elongisporus fungemia cases has been reported, and the etiology and clinical features are still unknown. Here, we present three successfully treated L. elongisporus fungemia cases by echinocandin. In total, 11 cases were reviewed, including ours. Six of the eleven cases (55%) had external devices. All cases had some immunocompromised conditions or underlying diseases, such as diabetes mellitus, lung cancer, etc. Six patients survived, and the remaining five died. Seven patients who had received echinocandin initially survived. Risk factors for L. elongiporus fungemia overlap with those of candidemia. Even though there is no breakpoint for L. elongiporus, echinocandin can be a helpful treatment regimen for L. elongiporus fungemia.

Investigation of non-Saccharomyces yeasts with intracellular β-glycosidase activity for wine aroma modification

Since high proportions of aroma-relevant molecules in plant-derived juices are present in glycosylated forms, the introduction of glycosidase activity during processing is an important tool to modify the aroma composition of the product. During winemaking, the addition of β-glycosidase enzyme or microorganisms with β-glycosidase activity is an established technology. However, low stability under acidic conditions and low selectivity for hydrolysis of different glycosides are still drawbacks, which limit application possibilities. Here, we report the identification and characterization of non-Saccharomyces yeast strains with relatively high β-glycosidase activity in their cultures. We found strong indications for intracellular localization of the enzymes, which is in line with the pH robustness found in experiments with whole cells. Furthermore, we compared the selectivity of aroma compound release from glycoside mixtures using whole cells or cell extracts. The results showed strong differences for the released aroma patterns, which indicates the transport of glycosides and intracellular hydrolysis. Our work demonstrates the application potential of yeasts with intracellular β-glycosidase activities as catalysts with high pH robustness and selective aroma release properties. PRACTICAL APPLICATION: The yeast strains identified and characterized within this work can be applied in wine processing but also in other processes to release aroma molecules from their glycosylated precursors provided by the plants. The strains show relatively high activity of the relevant enzyme, β-glycosidase, also at low pH, which is essential in many processes. In contrast to most other approaches, the enzyme is inside the cells, which can lead to a specific release of certain aroma compounds.

Expectable diversity patterns in wine yeast communities

Wine fermentations are dominated by Saccharomyces yeast. However, dozens of non-Saccharomyces yeast genera can be found in grape musts and in the early and intermediate stages of wine fermentation, where they co-exist with S. cerevisiae. The diversity of non-Saccharomyces species is determinant for the sensorial attributes of the resulting wines, both directly (by producing aroma impact compounds) and indirectly (modulating the performance of Saccharomyces). Many research groups worldwide are exploring the great diversity of wine yeasts to exploit their metabolic potential to improve wine flavor or to prevent wine spoilage. In this work, we share a new dataset from a wide ITS amplicon survey of 272 wine samples, and we perform a preliminary exploration to build a catalogue of 242 fungal and yeast genera detectable in wine samples, estimating global figures of their prevalence and relative abundance patterns across wine samples. Thus, our mycobiome survey provides a broad measure of the yeast diversity potentially found in wine fermentations; we hope that the wine yeast research community finds it useful, and we also want to encourage further discussion on the advantages and limitations that meta-taxonomic studies may have in wine research and industry.

The Flo Adhesin Family

The first step in the infection of fungal pathogens in humans is the adhesion of the pathogen to host tissue cells or abiotic surfaces such as catheters and implants. One of the main players involved in this are the expressed cell wall adhesins. Here, we review the Flo adhesin family and their involvement in the adhesion of these yeasts during human infections. Firstly, we redefined the Flo adhesin family based on the domain architectures that are present in the Flo adhesins and their functions, and set up a new classification of Flo adhesins. Next, the structure, function, and adhesion mechanisms of the Flo adhesins whose structure has been solved are discussed in detail. Finally, we identified from Pfam database datamining yeasts that could express Flo adhesins and are encountered in human infections and their adhesin architectures. These yeasts are discussed in relation to their adhesion characteristics and involvement in infections.

Effects of Simultaneous Co-Fermentation of Five Indigenous Non-Saccharomyces Strains with S. cerevisiae on Vidal Icewine Aroma Quality

In this study, Vidal grape must was fermented using commercial Saccharomyces cerevisiae F33 in pure culture as a control and in mixed culture with five indigenous non-Saccharomyces yeast strains (Hanseniaspora uvarum QTX22, Saccharomycopsis crataegensis YC30, Pichia kluyveri HSP14, Metschnikowia pulcherrima YC12, and Rhodosporidiobolus lusitaniae QTX15) through simultaneous fermentation in a 1:1 ratio. Simultaneous fermentation inhibited the growth of S. cerevisiae F33 and delayed the time to reach the maximum biomass. Compared with pure fermentation, the contents of polyphenols, acetic esters, ethyl esters, other esters, and terpenes were increased by R. lusitaniae QTX15, S. crataegensis YC30, and P. kluyveri HSP14 through simultaneous fermentation. S. crataegensis YC30 produced the highest total aroma activity and the most abundant aroma substances of all the wine samples. The odor activity values of 1 C13-norisoprenoid, 3 terpenes, 6 acetic esters, and 10 ethyl esters improved significantly, and three lactones (δ-decalactone, γ-nonalactone, and γ-decalactone) related to coconut and creamy flavor were only found in this wine. Moreover, this sample showed obvious “floral” and “fruity” note odor due to having the highest amount of ethyl ester aromatic substances and cinnamene, linalool, citronellol, β-damascenone, isoamyl ethanoate, benzylcarbinyl acetate, isobutyl acetate, etc. We suggest that simultaneous fermentation of S. crataegensis YC30 with S. cerevisiae might represent a novel strategy for the future production of Vidal icewine.

The Use of Yeast Mixed Cultures for Deacidification and Improvement of the Composition of Cold Climate Grape Wines

Interest in the use of non-Saccharomyces yeast in mixed cultures is increasing due to the perceived improvement in the quality and complexity of the resulting wines. The aim of the study was to determine the ability of monocultures and mixed yeast cultures for deacidification and improvement of the composition of cold climate grape wines. Fermentation of grape musts with increased total acidity was carried out with the use of monocultures of Saccharomyces cerevisiae MH020215 (Sc), Zygosaccharomyces bailii 749 (Zb) and Metschnikowia pulcherrima MG970690 (Mp), and their mixed cultures, inoculated simultaneously and sequentially. Oenological parameters, organic acids and volatile compounds profiles of obtained wines were characterized. The fermentation kinetics and analytical profiles of the obtained wines showed that the use of mixed yeast cultures contributed to the reduction of volatile acidity and acetic acid content in the wines, as well as obtaining a favorable aromatic profile of the wines. The dominant higher alcohols in all wines were 2-methyl-1-propanol, 3-methyl-1-butanol and 2-methyl-1-butanol. Significantly higher amounts of the first two compounds were found in wines obtained with M. pulcherrima MG070690, both in monoculture and in mixed cultures. The monocultures of M. pulcherrima MG070690 (Mp) compared with Z. bailli 749 (Zb) synthesized higher levels of esters in wines, including ethyl acetate, ethyl propionate, isobutyl acetate, ethyl pyroracemate and isoamyl acetate.

Revealing the yeast modulation potential on amino acid composition and volatile profile of Arinto white wines by a combined chromatographic-based approach

The importance of yeasts in aroma production during wine fermentation is a significant concern for obtaining a wine that appraises a broad number of consumers. For wine producers, wine aroma modulation is an essential issue where the yeasts used during the winemaking process represents a feasible way to improve the complexity and enhance wines specific characteristics. During the fermentation process of wines, yeasts convert grapes sugars into alcohol, carbon dioxide and a large number of secondary metabolites, depending on yeast metabolism, affecting the wine composition, namely its aroma and amino acids (AAs) composition. So, the present work aims to study the effect of different Saccharomyces-type yeasts on the AAs composition and volatile profile of Arinto white wines. To pursue this goal, four white wines from Arinto grapes were fermented with three different commercial yeasts (Saccharomyces bayanus EC1118, Saccharomyces cerevisiae CY3079, Saccharomyces bayanus QA23) and one Native yeast. Arinto wines AAs composition was quantified by HPLC-DAD, after a derivatization step to obtain the aminoenone derivatives. The volatile content of Arinto wines was determined by GC/MS, after an HS-SPME extraction. Results showed significant differences among the AAs content and volatile profile in the Arinto wines. The higher AAs content was found in the Arinto wines fermented with the CY3079 yeast (470.74 mg•L^-1), and the lowest content of AAs in the Arinto wines fermented with EC1118 yeast (343.06 mg•L^-1). Native yeast results in wines with a volatile profile richer in esters compared to the other sample wines. Principal component analysis (PCA) obtained with combined data of AAs and volatile compounds, after normalization, for each Arinto wine samples, shows a clear separation of wines fermented with Native and CY3079 yeasts in relation to QA23 and EC1118 fermented wines . The first and second principal components are responsible for 44.40% and 32.20%, respectively, of the system's variance, which clearly showed a differentiation among wines.

Effects of simultaneous and sequential cofermentation of Wickerhamomyces anomalus and Saccharomyces cerevisiae on physicochemical and flavor properties of rice wine

Microorganism species and inoculation fermentation methods have great influence on physicochemical and flavor properties of rice wine. Thus, this work investigated microbial interactions and physicochemical and aroma changes of rice wine through different inoculation strategies of Wickerhamomyces anomalus (W. anomalus) and Saccharomyces cerevisiae (S. cerevisiae). The results underlined that inoculation strategies and non-Saccharomyces yeasts all affected the volatile acidity, total acidity, and alcohol content of rice wine. The sequential cofermentation consumed relatively more sugar and resulted in the higher ethanol content, causing reduced thiols and increased alcohols, esters, phenylethyls, and terpenes, which was more conducive to improve rice wine flavor than simultaneous cofermentation. Moreover, simultaneous cofermentation increased fatty aroma of rice wine, while sequential cofermentation increased mellow and cereal-like flavor. These results confirmed that sequential cofermentation of S. cerevisiae and W. anomalus was a choice for the future production of rice wine with good flavor and quality.

Physicochemical characterization of wines produced using indigenous yeasts from cold climate grapes

The aim of the study was the physicochemical characterization of wines produced using indigenous yeasts isolated from spontaneously fermented grape musts, obtained from cold climate grapes. Saccharomyces cerevisiae MH020215 and Nakawazaea ishiwadae MG971259 yeast strains were used in this study. The musts obtained from white and red grapes of Johanniter and regent varieties were used as a fermentation raw material. In the produced wines, content of ethyl alcohol, total extract, sugars, free amino nitrogen was analyzed, along with determination of total and volatile acidity and volatile compounds profile. Additionally, organoleptic evaluation was performed. Wines obtained with native S. cerevisiae MH020215 strains were characterized with more favorable enological properties. Synthesis of desirable volatile compounds, especially esters, contributed to the creation of desirable aromatic profile of those wines. Moreover, those beverages contained higher levels of carbonyl compounds (especially acetaldehyde) and lower methanol content. Wines obtained using N. ishiwadae MG971259 cultures were represented by high total acidity level and substantial fusel alcohol content (mainly butanol, propanol), which resulted in an unfavorable sensory profile of the product.

Comparative Study of the Proteins Involved in the Fermentation-Derived Compounds in Two Strains of Saccharomyces cerevisiae during Sparkling Wine Second Fermentation

Sparkling wine is a distinctive wine. Saccharomyces cerevisiae flor yeasts is innovative and ideal for the sparkling wine industry due to the yeasts’ resistance to high ethanol concentrations, surface adhesion properties that ease wine clarification, and the ability to provide a characteristic volatilome and odorant profile. The objective of this work is to study the proteins in a flor yeast and a conventional yeast that are responsible for the production of the volatile compounds released during sparkling wine elaboration. The proteins were identified using the OFFGEL fractionator and LTQ Orbitrap. We identified 50 and 43 proteins in the flor yeast and the conventional yeast, respectively. Proteomic profiles did not show remarkable differences between strains except for Adh1p, Fba1p, Tdh1p, Tdh2p, Tdh3p, and Pgk1p, which showed higher concentrations in the flor yeast versus the conventional yeast. The higher concentration of these proteins could explain the fuller body in less alcoholic wines obtained when using flor yeasts. The data presented here can be thought of as a proteomic map for either flor or conventional yeasts which can be useful to understand how these strains metabolize the sugars and release pleasant volatiles under sparkling wine elaboration conditions.

Assessing the Oenological Potential of Nakazawaea ishiwadae, Candida railenensis and Debaryomyces hansenii Strains in Mixed-Culture Grape Must Fermentation with Saccharomyces cerevisiae

Recently, there has been a growing interest in the role of non-Saccharomyces yeast (NSY) as a coculturing partner with Saccharomyces cerevisiae during grape must fermentation. We investigated three new strains, namely Nakazawaea ishiwadae, Candida railenensis and Debaryomyces hansenii, for their oenological potential in mixed-culture micro-vinifications with S. cerevisiae Vin13 using Muscaris grape must. None of the NSY strains impeded the fermentation performance as all the mixed-culture experiments finished at the same time. Coculturing with N. ishiwadae yielded significantly higher concentrations of ethyl and acetate esters in the final wine product. Apart from higher acetic acid levels, wines produced with C. railenensis and D. hansenii yielded much lower esters concentrations. The concentrations of certain terpenes and norisoprenoids were also significantly modulated in the mixed-culture fermentations. This study reveals the rarely reported species of N. ishiwadae as a promising coculturing partner for increasing aroma-active compounds in a wine.

The impact of hybrid yeasts on the aroma profile of cool climate Riesling wines

•

For the first time a study reports about hybrids yeast influence on Riesling wine.

•

For the first time a study compares different commercial hybrids yeast.

•

For the first time several specific aroma compounds are studied for hybrids yeast.

•

Some non volatile compounds are studied for hybrids yeast.

The current study highlights the effects of intra- and interspecific hybrid yeasts of the genus Saccharomyces (S.) on the alcoholic fermentation and formation of aroma compounds in cool climate Riesling wines. Three different hybrid yeasts: S. cerevisiae × S. paradoxus (SC × SP), S. cerevisiae × S. kudriavzevii (SC × SK) and S. cerevisiae var. cerevisiae × S. cerevisiae var. bayanus (SC × SB) were investigated. The species S. cerevisiae var. bayanus (SB) was chosen as control variant. It has been demonstrated that the hybrid yeasts have the ability to preserve positive properties while, suppressing undesired properties from the parental yeast species. The hybrid SC × SK showed an increase of desired acetate esters and monoterpenes. The concentrations of higher alcohols were higher in wines fermented by SC × SP, compared to the other variants. SC × SP fermentations resulted in decreased concentrations of l-malate and sulphites.