Saccharomyces cerevisiae starter cultures are largely used in winemaking to repress the wild microorganisms and achieve more predictable and desired outcomes. Notwithstanding, alternative microbial ...resources received increasing attention for their potential to produce wines with more distinctive and typical features. Our previous survey revealed a great inter- and intra-species diversity in an extensive collection of non-Saccharomyces wine yeasts from multiple regions of Italy. This study aimed to explore the detected biodiversity evaluating the quality of wines obtained by sequential inoculation of specific selected strains of the collection (Lachancea thermotolerans or Metschnikowia spp. or Starmerella bacillaris), and S. cerevisiae EC 1118. Fermentations of natural grape must at laboratory scale were followed by microbiological, chemical and sensorial analysis of the wines. The results indicated that each yeast species and strain exerted a distinctive impact on the wine, giving final products clearly separated with Principal Component Analysis. In particular, L. thermotolerans contributed producing relevant amounts of lactic acid and had the highest potential to reduce ethanol content; the presence of S. bacillaris increased the level of glycerol, and, remarkably, reduced acetaldehyde and total SO2; Metschnikowia spp. promoted the formation of higher alcohols and esters, and reduced volatile phenols. The sensory analysis based on the orthonasal aroma confirmed the separation between the wines obtained with the sequential fermentations and the control with single inoculation of EC 1118, although the three non-Saccharomyces species used could not be clearly distinguishable by the panelists. This study indicates that the use of selected native non-Saccharomyces strains in conjunction with S. cerevisiae positively modulates some relevant chemical parameters, and improves the aromatic intensity of wine, therefore justifying investments in non-conventional yeasts as co-starter cultures.
•Non-Saccharomyces yeasts in sequential fermentations significantly improve wine properties.•Effects of non-Saccharomyces yeasts are highly species- and strain-dependent.•L. thermotolerans/S. cerevisiae reduced ethanol and increased wine natural acidity.•S. bacillaris/S. cerevisiae produced more glycerol and less SO2 and acetaldehyde.•Metschnikowia spp./S. cerevisiae positively modulated wine aroma profile.
Together with acidifying lactic acid bacteria, yeasts play a key role in the production process of sourdough, where they are either naturally present or added as a starter culture. Worldwide, a ...diversity of yeast species is encountered, with Saccharomyces cerevisiae, Candida humilis, Kazachstania exigua, Pichia kudriavzevii, Wickerhamomyces anomalus, and Torulaspora delbrueckii among the most common ones. Sourdough-adapted yeasts are able to withstand the stress conditions encountered during their growth, including nutrient starvation as well as the effects of acidic, oxidative, thermal, and osmotic stresses. From a technological point of view, their metabolism primarily contributes to the leavening and flavour of sourdough products. Besides ethanol and carbon dioxide, yeasts can produce metabolites that specifically affect flavour, such as organic acids, diacetyl, higher alcohols from branched-chain amino acids, and esters derived thereof. Additionally, several yeast strains possess functional properties that can potentially lead to nutritional and safety advantages. These properties encompass the production of vitamins, an improvement of the bioavailability of phenolic compounds, the dephosphorylation of phytic acid, the presence of probiotic potential, and the inhibition of fungi and their mycotoxin production. Strains of diverse species are new candidate functional starter cultures, offering opportunities beyond the conventional use of baker's yeast.
The main challenge of ensiling is conserving the feed through a fermentative process that results in high nutritional and microbiological quality while minimizing fermentative losses. This challenge ...is of growing interest to farmers, industry and research and involves the use of additives to improve the fermentation process and preserve the ensiled material. Most studies involved microbial additives; lactic acid bacteria (LAB) have been the focus of much research and have been widely used. Currently, LABs are used in modern and sustainable agriculture because of their considerable potential for enhancing human and animal health. Although the number of studies evaluating LABs in silages has increased, the potential use of these micro‐organisms in association with silage has not been adequately studied. Fermentation processes using the same strain produce very different results depending on the unique characteristics of the substrate, so the choice of silage inoculant for different starting substrates is of extreme importance to maximize the nutritional quality of the final product. This review describes the current scenario of the bioprospecting and selection process for choosing the best LAB strain as an inoculant for ensiling. In addition, we analyse developments in the fermentation process and strategies and methods that will assist future studies on the selection of new strains of LAB as a starter culture or inoculant.
Description of the subject. The use of non-Saccharomyces yeast for improving fine cocoa flavor perception has been poorly explored. Objectives. In this study, we investigated the contribution of the ...non-Saccharomyces yeasts producing β-glycosidase isolated from the spontaneous fermentation of cocoa to the quality and production of aromas during the alcoholic fermentation of a medium based on cocoa pulp.Method. The screening for β-glycosidase activity and molecular identification of non-Saccharomyces yeast isolates from Amazonian cocoa bean fermentations were performed on agar plates with esculin as a substrate and by 5.8S ITS rDNA sequence analysis, respectively. The yeasts producing β-glycosidases were used as a starter culture for alcoholic micro-fermentations of a medium based on cocoa pulp, incubated at 30 °C for 48 h. The quantification of organic acids, ethanol, and sugars was obtained by HPLC, and aroma compounds after cocoa pulp fermentation were identified by GC-FID and GC-MS.Results. Twenty-six non-Saccharomyces yeast isolates were selected by β-glycosidase activity, comprising species such as Pichia kudriavzevii (n = 15), Pichia sp. (n = 2), Pichia sporocuriosa (n = 1), Candida orthopsilosis (n = 3), Issatchenkia sp. (n = 1), I. orientalis (n = 1), and P. kudriavzevii/I. orientalis (n = 3). All yeast strains exhibited rapid growth in cocoa pulp medium, low ethanol production, high organic acid production, and higher glucose consume than fructose. These yeasts produced thirty different volatile compounds. The main groups included alcohols (3), esters (19), terpenes (4), phenols (2), organic acids (2), and aldehydes (3), with 67% of these having fruity and floral aromas. Pichia sp., P. kudriavzevii/I. orientalis and Issatchenckia sp. were the largest producers of volatile compounds. Notably, this study identified volatile compounds with fruity aromas previously unassociated with cocoa fermentations for the first time.Conclusions. These data demonstrate the potential of β-glycosidase-producing non-Saccharomyces yeasts to improve floral and fruity aromas, suggesting their promising use as a starter culture for cocoa fermentation.
Activité de β-glycosidase associée à la formation de composés aromatiques parmi les levures natives non-Saccharomyces isolées de la fermentation du cacaoDescription du sujet. L'utilisation de levures non-Saccharomyces pour améliorer la perception des saveurs fines du cacao a été peu explorée.Objectifs. Dans cette étude, nous avons étudié l'apport des levures non-Saccharomyces productrices de β-glycosidase isolées de la fermentation spontanée du cacao à la qualité et à la production d'arômes lors de la fermentation alcoolique d'un milieu à base de pulpe de cacao.Méthode. Le criblage de l'activité β-glycosidase et l'identification moléculaire d'isolats de levures non-Saccharomyces provenant de fermentations de fèves de cacao amazoniennes ont été réalisés sur des plaques de gélose avec de l'esculine comme substrat et par analyse de séquence d'ADNr 5,8S ITS, respectivement. Les levures productrices de β-glycosidases ont été utilisées comme starter pour des micro-fermentations alcooliques d'un milieu à base de pulpe de cacao, incubées à 30 °C pendant 48 h. La quantification des acides organiques, de l'éthanol et des sucres a été obtenue par HPLC et les composés aromatiques après fermentation de la pulpe de cacao ont été identifiés par GC-FID et GC-MS.Résultats. Vingt-six isolats de levures non-Saccharomyces ont été sélectionnés par activité β-glycosidase, comprenant des espèces telles que Pichia kudriavzevii (n = 15), Pichia sp. (n = 2), Pichia sporocuriosa (n = 1), Candida orthopsilosis (n = 3), Issatchenkia sp. (n = 1), I. orientalis (n = 1) et P. kudriavzevii/I. orientalis (n = 3). Toutes les souches de levure ont présenté une croissance rapide dans un milieu de pulpe de cacao, une faible production d'éthanol, une production élevée d'acide organique et une consommation de glucose plus élevée que le fructose. Ces levures produisaient trente composés volatils différents. Les principaux groupes comprenaient les alcools (3), les esters (19), les terpènes (4), les phénols (2), les acides organiques (2) et les aldéhydes (3), dont 67 % avaient des arômes fruités et floraux. Pichia sp., P. kudriavzevii/I. orientalis et Issatchenckia sp. étaient les plus grands producteurs de composés volatils. Notamment, cette étude a identifié pour la première fois des composés volatils aux arômes fruités auparavant non associés aux fermentations du cacao.Conclusions. Ces données démontrent le potentiel des levures non-Saccharomyces productrices de β-glycosidase pour améliorer les arômes floraux et fruités, suggérant leur utilisation prometteuse comme culture de départ pour la fermentation du cacao.
The dairy fermentation industry relies on the activity of lactic acid bacteria in robust starter cultures to accomplish milk acidification. Maintenance of the composition of these starter cultures, ...whether defined or undefined, is essential to ensure consistent and high-quality fermentation end products. To date, limited information exists regarding the microbial composition of undefined starter culture systems. Here, we describe a culture-based analysis combined with a metagenomics approach to evaluate the composition of two undefined mesophilic starter cultures. In addition, we describe a qPCR-based genotype detection assay, which is capable of discerning nine distinct lactococcal genotypes to characterize these undefined starter cultures, and which can be applied to monitor compositional changes in an undefined starter culture during a fermentation.
This study reports on the development of a combined culture-based analysis and metagenomics approach to evaluate the composition of two undefined mesophilic starter cultures. In addition, a novel qPCR-based genotype detection assay, capable of discerning nine distinct lactococcal genotypes (based on lactococcal cell wall polysaccharide biosynthesis gene clusters), was used to monitor compositional changes in an undefined starter culture following phage attack. These analytical approaches facilitate a multifaceted assessment of starter culture compositional stability during milk fermentation, which has become an important QC aspect due to the increasing demand for consistent and high-quality dairy products.
The important role of Lactiplantibacillus plantarum strains in improving the human mucosal and systemic immunity, preventing non-steroidal anti-provocative drug-induced reduction in T-regulatory ...cells, and as probiotic starter cultures in food processing has motivated in-depth molecular and genomic research of these strains. The current study, building on this research concept, reveals the importance of Lactiplantibacillus plantarum 13-3 as a potential probiotic and bacteriocin-producing strain that helps in improving the condition of the human digestive system and thus enhances the immunity of the living beings via various extracellular proteins and exopolysaccharides. We have assessed the stability and quality of the L. plantarum 13-3 genome through de novo assembly and annotation through FAST-QC and RAST, respectively. The probiotic-producing components, secondary metabolites, phage prediction sites, pathogenicity and carbohydrate-producing enzymes in the genome of L. plantarum 13-3 have also been analyzed computationally. This study reveals that L. plantarum 13-3 is nonpathogenic with 218 subsystems and 32,918 qualities and five classes of sugars with several important functions. Two phage hit sites have been identified in the strain. Cyclic lactone autoinducer, terpenes, T3PKS, and RiPP-like gene clusters have also been identified in the strain evidencing its role in food processing. Combined, the non-pathogenicity and the food-processing ability of this strain have rendered this strain industrially important. The subsystem and qualities characterization provides a starting point to investigate the strain’s healthcare-related applications as well.
Aims
The purpose of this study was to functionalize an ovine stretched cheese belonging to 'Vastedda' typology with red grape pomace powder (GPP) of Nero d’Avola cultivar and to characterize the ...microbiological, physicochemical, phenolic profile and sensory characteristics of the final cheeses.
Methods and Results
Before cheeses production, GPP was characterized for its microbiological profile, antibacterial activity and polyphenolic content. No colonies of bacteria and yeasts were detected in the GPP. GPP showed a large inhibition spectrum against spoilage and pathogenic bacteria. Three classes of polyphenolic compounds belonging to flavan‐3‐ols, flavonol and phenolic acids were identified. Two cheeses 0 and 1% (w w−1) of GPP were produced with pasteurized ewe's milk and commercial starter cultures. Plate counts and randomly amplified polymorphic DNA analysis demonstrated the ability of the starter strains to drive the fermentation process in the presence of GPP. GPP enrichment resulted in an increase of protein, phenolic compounds, sensory traits and reduced fat.
Conclusions
GPP addition to cheese represents an optimal strategy for the valorization of winemaking by‐products and to obtain polyphenol‐enriched cheese.
Significance and Impact of the Study
This study allowed to achieve an ovine cheese with specific physicochemical, nutraceutical and sensorial characteristics able to enlarge the functional dairy product portfolio.
Summary
The quest to develop a performant starter culture mixture to be applied in cocoa fermentation processes started in the 20th century, aiming at achieving high‐quality, reproducible chocolates ...with improved organoleptic properties. Since then, different yeasts have been proposed as candidate starter cultures, as this microbial group plays a key role during fermentation of the cocoa pulp‐bean mass. Yeast starter culture‐initiated fermentation trials have been performed worldwide through the equatorial zone and the effects of yeast inoculation have been analysed as a function of the cocoa variety (Forastero, Trinitario and hybrids) and fermentation method (farm‐, small‐ and micro‐scale) through the application of physicochemical, microbiological and chemical techniques. A thorough screening of candidate yeast starter culture strains is sometimes done to obtain the best performing strains to steer the cocoa fermentation process and/or to enhance specific features, such as pectinolysis, ethanol production, citrate assimilation and flavour production. Besides their effects during cocoa fermentation, a significant influence of the starter culture mixture applied is often found on the cocoa liquors and/or chocolates produced thereof. Thus, starter culture‐initiated cocoa fermentation processes constitute a suitable strategy to elaborate improved flavourful chocolate products.
For quality standardization, the application of functional lactic acid bacteria (LAB) as starter cultures for food fermentation is a well-known method in the fermented food industry. This study ...assessed the effect of adding a non-thermally microbial inactivated starter culture to kimchi, a traditional Korean food, in standardizing its quality. In this study, pretreatment based on sterilization processes, namely, slightly acidic electrolyzed water (SAEW) disinfection and ultraviolet C light-emitting diode (UVC-LED) of raw and subsidiary kimchi materials were used to reduce the initial microorganisms in them, thereby increasing the efficiency and value of the kimchi LAB starter during fermentation. Pretreatment sterilization effectively suppressed microorganisms that threatened the sanitary value and quality of kimchi. In addition, pretreatment based on sterilization effectively reduced the number of initial microbial colonies in kimchi, creating an environment in which kimchi LAB starters could settle or dominate, compared to non-sterilized kimchi. These differences in the initial microbial composition following the sterilization process and the addition of kimchi LAB starters led to differences in the metabolites that positively affect the taste and flavor of kimchi. The combined processing technology used in our study, that is, pre-sterilization and LAB addition, may be a powerful approach for kimchi quality standardization.
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•S. cohnii WX_M8 was salt tolerant and S. saprophyticus MY_A10 was acid tolerant.•Functional genes involved in flavor formation superimpose staphylococcal functions.•The functional ...genes on ester formation showed functional complementarity.•Genes for metabolic function in food-originated staphylococci were speciesstrain-specific.•The mixed fermentation of WX_M8 and MY_A10 featured diverse amino acids metabolism.
Previous studies have demonstrated that Staphylococcus cohnii WX_M8 and S. saprophyticus MY_A10 significantly enhanced the flavor of Chinese bacon in a mixed fermentation. However, due to the complexity of the processing, the contribution of the bacteria is deceptive when investigating only the phenotypic changes at the time of fermentation. In order to clarify the metabolic mechanisms of mixed fermentation, a technological characterization, whole genome and comparative genomics analysis, and metabolites were approached in this study. Results showed that differences in tolerance characteristics existed between WX_M8 and MY_A10. And the genomes of both the two strains consisted of one chromosome and four circular plasmids. Their genome sizes were 2.74 Mp and 2.62 Mp, the GC contents were 32.45% and 33.18%, and the predicted coding genes (CDS) were 2564 and 2541, respectively. Based on the annotation of gene functions and assessment of metabolic pathways in the KEGG database, WX_M8 and MY_A10 strains were found to harbor complete protein degradation and amino acid metabolic pathways, pyruvate and butanol metabolic pathways, and isoleucine metabolic pathways, and their diverse enzyme-encoding genes superimposed the metabolic functions, whereas the alcohol dehydrogenase genes, adh and frmA, achieved complementary functions in the production of esters. Comparative genomics analysis revealed a diversity of encoding genes of aminotransferases and a greater metabolism for sulfur-containing amino acids, aromatic amino acids, and branched-chain amino acids in the mixed fermentation of strains WX_M8 and MY_A10. Metabolites analysis showed that MY_A10 focused on the production of soluble peptides and free amino acids (FAAs), while WX_M8 focused on volatile organic compounds (VOCs), resulting in a significant enhancement of the flavor of Chinese bacon when the two were mixed fermented. This result may provide direction for strains WX_M8 and MY_A10 to be used as starter cultures and targeted to regulate flavor.
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