Influence of nitrogen status on fermentation performances of non-Saccharomyces yeasts:a review

Nitrogen,one of the most crucial nutrients present in grapes and musts,plays a key role in yeast activities during alcoholic fermentation.Such influences are imposed on yeast growth and fermentation performances including the formation of secondary metabolites.Saccharomyces cerevisiae,the main yeast responsible for fermentation,has been studied extensively regarding nitrogen impacts.On the other hand,a similar study for non-Saccharomyces yeasts,whose contributions to winemaking have gradually been acknowledged,remains to be fully explored,with a few studies being reported.This review starts by discussing nitrogen impacts on non-Saccharomyces yeast growth and fermentation kinetics in different case scenarios,then proceeds to summarize the nitrogen preferences of individual yeast strains with regulation mechanisms elucidated by recent studies.Detailed discussions on the influences on the production of volatile compounds and proposed pathways therein are made,followed by future work suggested as the final section.In summarizing the nitrogen impacts on non-Saccharomyces yeasts throughout alcoholic fermentation,this review will be helpful in obtaining a more comprehensive view on these non-conventional wine yeasts in terms of nutrient requirements and corresponding volatile production.Research gaps will therefore be elucidated for future research.

Evaluation and selection of yeasts as potential aroma enhancers for the production of dry-cured ham

Yeasts play a critical role in the flavor formation of dry-cured ham.In this study,41 yeast isolates from the dry-cured ham at different processing stages were evaluated for their technological properties.Debaryomyces hansenii was the most dominant yeast and has been detected at each phase of dry-cured ham,followed by Candida zeylanoides which was mainly detected in salting phase.Yarrowia bubula and Yarrowia alimentaria were found at the first two-phase of dry-cured ham.All isolates of yeast showed enzymatic activities against milk protein and tributyrin,while only 4 strains displayed proteolytic activity on meat protein.Yeast strains were grown in a meat model medium and volatile compounds were identified.The result showed that inoculated yeast strains could promote the production of volatiles and there were significant differences among strains.D.hansenii S25 showed the highest production of volatile compounds,followed by the strain C.zeylanoides C4.D.hansenii S25 was the highest producer of alcohols showing the highest production of benzeneethanol and 3-(methylthio)-1-propanol.Based on OAV and PLS analysis,D.hansenii S25 was strongly correlated with overall flavor and key volatile compounds of dry-cured ham,which could be selected as potential starter cultures.

Screening of protease-producing marine yeasts for production of the bioactive peptides

Over 400 yeast strains from seawater and sediments were obtained, but only five strains named HN2 -3, N13d, N13C, Mb5 and HN3 - 2 among them could form clear zones around their colonies on the double plates with 2.0% casein. Peptides in the hydrolysate produced by the proteases from strains HN2 -3 and N13d had higher angiotensin I-converting-enzyme （ACE）-inhibitory activity. The two marine yeast strains were identified to be Aureobasidium pullulans according to the results of routine yeast identification and molecular methods. After purification of the proteases from the two marine yeast strains, it was found that the optimal pH for them was both 9.0, both of them were serine alkaline protease. However, the optimal temperature for the protease from the strain HN2 -3 was 52℃ while that from strain N13d was 48℃. ACE-inhibitory activity of the peptides in the hydrolysate of shrimp protein produced by the purified protease from the strain HN2 -3 was the highest while antioxidant activity in the hydrolysate of spirulina protein produced by the purified protease from the strain N13d was the highest.

Sensitivity of Four Yeasts to Fungicides and CO2 Concentrations and Their Antagonistic Ability in Combination with Fungicide to Pathogenic Fungi in vitro

The yeasts Cryptococcus laurentii, Trichosporon pullulans, Rhodotorula glutinis andTrichosporon sp.were used to investigate their sensitivity to four fungicides anddifferent concentrations of CO2, as well as their antagonistic ability to Penicilliumexpansumand Alternariaalternata in vitro when applied with fungicide. There were significantdifferences in sensitivity to the fungicides among the different yeasts(P=0.05). R.glutinis was more sensitive to Deccocil, Iprodione and Stroby as compared to otheryeasts. Combination antagonistic yeasts with fungicide could more significantly enhancebiocontrol ability of the yeasts against the pathogenic fungi in vitro(P = 0.05). C.laurentii was the most effective antagonist among the four yeasts and could completelycontrol spore germination of P.expansum and A.alternata when combined with Stroby at theconcentration of 100 L L-1. The yeasts, except R.glutinis, could grow well on nutrientyeast dextrose agar (NYDA) after 8 d incubation even at 20% CO2 concentration at 25℃.Particularly Trichosporon sp. showeda better adaptability to low temperature as comparedto other antagonists.

Biocontrol Efficacy of Two Antagonistic Yeasts Against Postharvest Diseases in Peach Fruits During Storage Periods

Two antagonistic yeasts, Thichosporon pullulans and Cryptococcus laurentii, were investigated for their biocontrol potential to blue mold rot and rhizopus rot on harvested peach fruits(Prunus persica L. Batsch, cv. Okubao), alone or in combination with a low dose of iprodione(50 μg ml-1). The results indicated that T. pullulans and C. laurentii were effective at reducing disease incidence and severity of blue mold rot and rhizopus rot in peach fruits. Biocontrol efficacy of C. laurentii and T. pullulans were significantly enhanced by combination with a low dose of iprodione(50 μg ml-1)against blue mold and rhizopus rot in peach fruits. T. pullulans and C. laurentii combined with a low dose of iprodione(50 μg ml-1)resulted in better disease control than either iprodione or the yeasts used alone. Dipping fruits in suspensions of antagonist cells showed the similar control effect as the treatment with iprodione(500μg ml-1).

Isolation and Identification of Indigenous Yeasts from “<i>Rabil&eacute;</i>”, a Starter Culture Used for Production of Traditional Beer “<i>dolo</i>”, a Condiment in Burkina Faso

Rabilé is a ferment of dolo, a traditional sorghum beer of Burkina Faso and it is harvested at the end of dolo fermentation process. It is a significant source of proteins and it is used like a condiment and food seasoning by some communities. The present study characterized and identified the yeasts isolated from Rabilé. A total of 70 samples were collected from 7 localities of Burkina Faso with dolo sellers according to the ethnic groups. The aerobic mesophilic flora count from Rabilé varied from 8.34 ± 0.72 to 10.07 ± 0.51 log10 CFU·g-1 and yeast varied from 7.24 to 8.28 log10 UFC·g-1. Based on morphological, cultural, sexual and biochemical (carbon and nitrogen assimilation) profiles, 50 yeast strains were identified and found to belong to 4 genera and 7 species. Saccharomyces cerevisiae was found as most predominant yeasts species of yeast in of Rabilé with 64 %, Rhodotorula muciloginosa, (8%), Candida pseudorhangii (6%), Candida heliconiae (12%), Candida utilis (4%), Shizosaccharomyces pombe (4%) and Sporobolomyces odoratus (2%). This activity has been carried out in the Laboratory of Biotechnology for Food and Nutritional Sciences, University Ouaga I Pr Josph KY-ZERBO, Burkina Faso, and it was done from June to October 2018.

Predominant yeasts in Chinese Dong fermented pork(Nanx Wudl)and their aroma-producing properties in fermented sausage condition

Yeasts are one of the predominant microbial groups in fermented meats.In this study,yeast communities of Chinese Dong fermented pork(Nanx Wudl)were investigated and the technological properties of 73 yeast isolates were evaluated.Through culture-dependent and high-throughput sequencing methods,the main yeast species identified included Pichia membranifaciens,Kazachstania bulderi,Millerozyma farinosa,Candida zeylanoides,Kazachstania exigua,Candida parapsilosis and Saccharomyces cerevisiae.Among these yeasts,P.membranifaciens,M.farinosa,K.exigua and K.bulderi were detected in fermented meats for the first time.A total of 73 yeast isolates was investigated for their lipolytic and proteolytic activities.All yeast species showed lipolytic activity,while proteolytic activity against meat protein was only detected in S.cerevisiae.Assay of aroma-producing potential was performed in a model simulating fermented sausage condition.Inoculation of yeast strains increased volatiles production,especially esters and alcohols.The highest ester production was observed in S.cerevisiae Y70 strain,followed by K.exigua Y12 and K.bulderi Y19.C.zeylanoides Y10 and S.cerevisiae Y70 were the highest producers of benzeneethanol and 3-methyl-1-butanol.S.cerevisiae Y70 with its highest production of branched alcohols and esters could be a promising candidate as aroma enhancer in the manufacture of fermented sausages.

Probiotic yeasts: Anti-inflammatory potential of various non-pathogenic strains in experimental colitis in mice

AIM: To evaluate the in vitro immunomodulation capacity of various non-pathogenic yeast strains and to investigate the ability of some of these food grade yeasts to prevent experimental colitis in mice.METHODS: In vitro immunomodulation was assessed by measuring cytokines [interleukin (IL)-12p70,IL-10,tumor necrosis factor and interferon γ] released by human peripheral blood mononuclear cells after 24 h stimulation with 6 live yeast strains (Saccharomyces ssp.) and with bacterial reference strains.A murine model of acute 2-4-6-trinitrobenzene sulfonic acid (TNBS)-colitis was next used to evaluate the distinct prophylactic protective capacities of three yeast strains compared with the performance of prednisolone treatment.RESULTS: The six yeast strains all showed similar non-discriminating anti-inflammatory potential when tested on immunocompetent cells in vitro .However,although they exhibited similar colonization patterns in vivo ,some yeast strains showed significant anti-inflammatory activities in the TNBS-induced colitis model,whereas others had weaker or no preventive effect at all,as evidenced by colitis markers (body-weight loss,macroscopic and histological scores,myeloperoxidase activities and blood inflammatory markers).CONCLUSION: A careful selection of strains is required among the biodiversity of yeasts for specific clinical studies,including applications in inflammatory bowel disease and other therapeutic uses.

Isolation and Identification of Yeasts from Luzhou Flavor Daqu

A yeast strain had been isolated by dilution-plate from the Daqu samples in our study. The strain was identified as a strain of Rhodotorula aurantiaca through observation of its morphological features, micromorphological observation and biolog identification system.

Bioethanol Production from Molasses by Yeasts with Stress-Tolerance Isolated from Aquatic Environments in Japan

Bioethanol is a safe and renewable source of energy that continues to be a research focus, since fossil fuels have been linked to global warming and nuclear energy sources are affected by the increased safety concerns following the 2011 nuclear power plant accident in Japan. In general, bioethanol is converted from a biomass by yeast fermentation. The production efficiency of this bioethanol is not sufficiently high, and its practical use as a substitute for fossil fuels and nuclear energy is thus limited. For the industrial production of bioethanol, the yeast fermentation of biomass cultures containing high concentration sugar, NaCl, and ethanol is necessary, but this might induce phenomena in which the stresses arising in the yeasts weaken their cells during fermentation. As described herein, we isolated 1028 strains of yeasts from natural aquatic environments: Japan’s Tama River and Lake Kasumigaura. Among them, 412 strains were fermentative yeasts and 31 strains showed high fermentation ability under a 30% sorbitol + 10% ethanol condition. These strains were identified as Torulaspola delbrueckii, Wickerhamomyces anomalus, Candida glabrata, Pichia kudriavzevii, Saccharomyces cf. cerevisiae/paradoxus, and Lachancea kluyveri. The strains T. delbrueckii, W. anomalus, and C. glabrata also showed tolerance against 15% NaCl. Most importantly, S. cf. cerevisiae/paradoxus H28 and L. kluyveri F2-67 produced 57.4 g/L and 53.9 g/L ethanol from molasses (sucrose 104.0 g/L, fructose 33.4 g/L, and glucose 24.8 g/L) within 48 hrs at 25°C, respectively.

Molecular Phylogeny and Phenotypic Characterization of Yeasts with a Broad Range of pH Tolerance Isolated from Natural Aquatic Environments

In this study, yeasts with broad range of pH tolerance were isolated and characterized from natural aquatic environments in Japan. Only a few basic and application studies of alkali-tolerant yeasts have been reported, despite the unmet industrial needs. First, we surveyed alkali-tolerant yeasts from natural aquatic environments at pH 7.6 - 9.4. We isolated 35 yeast strains that grew in pH 9.0 medium, from seven genera and nine species: 25 strains (N1, N2, through N6, N9, K1, K3 through K19) were Rhodotorula mucilaginosa;one (N7) was Rhodosporidium fluvial;one (N8) was Scheffersomyces spartinae;two (N10 and N13) were Wicherhamonyces anomalus;one (N11) was Cyberlindnera saturnus;one (S1) was Candida sp.;two (S2 and S4) were Candida intermedia;one (S3) was Candida quercuum;and one (K2) was Cryptococcus liquefacience. We examined the effects of pH on the growth of representative yeast strains. Strains K12 and S4 showed high growth at pH 3 - 10. Strains N7, N8, N10, N11, and S3 showed high growth at pH 3 - 9. Strains K2 and S1 showed high growth at pH 4 - 8. All nine of these strains had neutralizing activities from acidic media at pH 3 - 5 to pH 6 - 8. We previously isolated acid-tolerant yeasts (Cryptococcus sp. T1 [1] and Candida intermedia CeA16 [2]) from extremely acidified environments;they showed high growth at pH 3 - 9 and neutralizing activities of acidic media by releasing ammonium ions. Thus, alkali-tolerant yeasts and acid-tolerant yeasts were found to be similar species and have both high growth at a broad range of pH and neutralizing activities of acid media. Previously, we also isolated acid-tolerant, acid-neutralizing yeasts from neutral natural environments (26 strains, 12 species) [3]. Next, we constructed the phylogenetic trees of both acid-tolerant yeasts and alkali-tolerant yeasts. All were situated in the same classification position. Similar yeast species with a broad range of pH tolerance were living in natural aquatic environments at pH values from alkali to acid.

Isolation of aromatic yeasts(non-<i>Saccharomyces</i><i>cerevisiae</i>) from Korean traditional <i>nuruks</i>and identification of fermentation characteristics

Ethyl caproate and isoamyl alcohol are important for the quality of Yakju, one of the Korean traditional alcoholic beverages. From Korean traditional fermentation agent, Nuruk, we have isolated 8 yeasts which produced rich aromatic compounds using YEPD agar plates (1% yeast extract, 2% peptone, 2% dextrose, 2% agar) containing 50 uL cerulenin at 30℃. The isolated aromatic yeasts are identified as Pichia anomala (4 strains), Pichia fabianii (2 strains), Pichia farinose (1 strains), Geotrichum candidum (1 strains). We conducted alcohol fermentation with each of the aromatic yeasts and the compounds (ethyl caproate and isoamyl alcohol) producing range were 59.5 - 193.2 ppm and 10.8 - 91.6 ppm respectively. As a control, Fermivin&reg;, famous aromatic wine yeast, was 89.4 ppm and 16.2 ppm respectively. We also find that the isolated Pichia anomala could produce higher level ethanol (4.2% - 5.0%, v/v) than other species (0.4% - 2.2%, v/v). Using the aromatic yeasts in fermentation industries, we expect to improve the quality of traditional alcoholic beverages.

THE PHYLOGENY OF YEASTS--A CLADISTIC ANALYSIS

Cladistic analysis was used to clarify the phylogeny of 16 genera of yeasts whose great morphological differences and inclusion in different classification systems resulted in controversies over the taxonomy of seven genera such as Crypeococcus, etc. Some scholars suggest that they belong to Ascomycetes. but others think they belong to fungi imperfecti. After comprehensive cladistic analysis of many genetic characters, the authors consider that the above-mentioned seven genera of yeasts developed in parallel with Ascomycetes so that they should belong to one and the same developmental system.

Characterization of oral yeasts isolated from healthy individuals attended in different Colombian dental clinics

The aim of this study was to identify the most frequent yeasts in the oral cavity of adult individuals without immune disorders and to associate the presence of these oral yeasts with different characteristics of each individual. Oral rinse samples were obtained from 96 healthy adults and cultured in Sabouraud dextrose agar media and CHROMagar. Yeasts were identified by sequencing the D1/D2 region of the 28 S rRNA gene. Probable association among the socio-demographic characteristics, body mass index, family and personal medical history,oral hygiene, tobacco and/or alcohol consumption habits and presence of oral fungi was analyzed. Contingency tables and logistic regression were employed to evaluate possible relationships between the presence of oral fungi and mixed colonization with these variables. 57.3% of the healthy individuals had oral yeasts and 21.8% had mixed colonization. The most prevalent yeasts were Candida albicans(52%), C. parapsilosis(17.9%), and C.dubliniensis(7.57%). Yeasts with most frequently mixed colonization were C. albicans and C. parapsilosis. No relationships were found among the variables analyzed. However, the presence of mixed colonization was related to the presence of dental prostheses(P<0.006), dental apparatuses(P=0.016) and O’Leary index(P=0.012). This is the first study that characterized oral yeasts in Colombian healthy individuals, determined the most prevalent oral yeasts C. albicans, C. parapsilosis and C. dublinensis and an association of mixed colonization with the use of dental prostheses and aparatology and poor hygiene.

Characterization of Yeasts Capable of Neutralizing Acidic Media from Natural Neutral Environments

Acid-tolerant yeasts often inhabit extremely acidic environments: mine drain-ages, hot springs, and even fermented foods. Some of them also possess the ability to neutralize acidic media. However, the examples of these yeasts that are already known were isolated from acidic environments. In this study, the isolation of acid-tolerant yeasts from natural neutral aquatic environments and the identification of yeasts able to neutralize an acidic medium (acid-neutralizing yeast) in Japan were carried out. Various kinds of acid-tolerant and acid-neutralizing yeasts were obtained. In a neutralizing test using an acidic casamino acid solution adjusted to a pH of 4.0 with sulfuric acid, the obtained acid-neutralizing yeasts elevated the pH to approximately 7.0, and their neutralizing abilities were similar to those of previously reported yeasts that had been isolated from acidic environments. These results showed that acid-tolerant yeasts and acid-neutralizing yeasts exist widely in neutral environments, and little difference was found in the neutralizing abilities of yeasts obtained from neutral environments in comparison to those obtained from acidic environments.

Study on Brewing Properties of Three Strong Ale Beer Yeasts

The brewing characteristics of three kinds of beer yeasts commonly used in the market were compared and studied.The results showed that the three kinds of yeasts had different characteristics and slightly different fermentation degrees,but the fermentation speeds all were higher and the diacetyl reduction ability was excellent.The finished beers were golden yellow in appearance,rich and delicate in foam,pleasant in aroma,mellow in body and similar in physicochemical indexes,all in line with domestic beer standards.

High Ethanol Production by Marine-Derived Yeasts-<i>Saccharomyces cerevisiae</i>under Stress Pressures

For practical applications of bioethanol, the uses of both highly concentrated biomass materials and their effective fermentation by yeasts are indispensable in order to produce ethanol at low costs. However, as the saccharified products of those biomass generally contain abundant sugars, the yeasts are affected by the compounds and are inclined to decrease their physiological activities. In the process of fermentation, ethanol is gradually produced by the yeasts in the culture;the concentrated metabolic product also damages itself, and inhibition of the fermentation frequently occurs. The application of yeasts with high fermentative activities under stress pressures such as sugars and ethanol is thus desired for bioethanol production. In this study, various types of high-fermentative yeasts under stress pressures were isolated mainly from coastal waters in Japan and characterized. All yeast strains with high fermentative activities under 20% v/v ethanol were found to be Saccharomyces cerevisiae. The HK21 strain isolated from Tokyo Bay and identified as S. cerevisiae had the highest fermentation activity under 30% w/v sorbitol and under 20% v/v ethanol, and it produced approx. 70 g/l (9% v/v) ethanol from the 15% w/v glucose solution at 25 oC within 5 days.

Ethanol Fermentation by High-Stress-Tolerance Aquatic Yeasts and Their Mutants

Bioethanol is thought to be a renewable source of energy, because the biomasses used to make ethanol, such as sugar cane and its residual substance, molasses, are resources that can be continuously produced. But the practical use of ethanol to replace fossil fuels or atomic energy has been limited, because the production efficiencies of ethanol in relation to its substrates are not so high. Thus, for industrial production of the bioethanol, yeast fermentation would ideally be carried out in biomasses containing more highly concentrated carbohydrates. However, the environmental stresses in highly concentrated cultures might weaken the yeast’s physiological activities. From various kinds of aquatic yeast with stress tolerance, Torulaspora derbrueckii F2-11 and Wicherhamomyces anomalus AN2-64 were selected as candidates for high-sugar-tolerance yeasts as they showed remarkable growth in the YPD + sorbitol (600 g/L) medium at 25°C for 120 hrs. When the amounts and kinds of sugar alcohols in the cells of the two strains were measured in cultures containing 20 g/L or 400 g/L of D-glucose, maltose, or sucrose, the main two sugar alcohols that accumulated as the sugar concentration increased were glycerol and arabitol. Mutation by ethyl methanesulfonate of the parent strains T. derbrueckii F2-11 and W. anomalus AN2-64 induced mutants F2-11M or AN2-64M, which showed higher sugar, heat, and ethanol tolerances than their respective parents. Ethanol productivities and sugar assimilation activities of the mutants were also higher than those of the parents in the 25% (v/v) molasses.

A novel ascosporogenous yeast species,Zygosaccharomyces siamensis,and the sugar tolerant yeasts associated with raw honey collected in Thailand

Diversity of yeasts in association with bees and their food sources has been explored during the last decade.In Thailand,there has been no study of yeast identification in honey and bees.Hence,a total of 186 yeast strains were isolated from 37 honey samples of 12 different bee species.On the basis of morphological and physiological characteristics,55 representative strains were chosen and identified by sequence analysis of the 26S rDNA D1/D2 domain and the ITS region.The data were compared with the published sequences and the results showed the occurrence of 19 ascomycetous and 1 basidiomycetous yeast species.Six strains of the new species were isolated.Phylogenetic analysis of the 26S rDNA D1/D2 sequence revealed that they were conspecific and most closely related to Zygosaccharomyces mellis.Based on the ITS sequence,the new species was clustered with the type"and clearly distinguished from the type!.Sequence analysis of combined ITS-26S rDNA D1/D2 showed similar results.The occurrence of these two types,with a divergence of more than 1%in their sequences,and low DNA relatedness among them suggested that members of the typeβcan be regarded as separate species.An analysis of the morphological and physiological characteristics was performed.Ascospore formation was observed on acetate agar and Gorodkowa agar.The new Zygosaccharomyces species differed physiologically from Z.mellis in 4 assimilation tests.This data supports the hypothesis that the new species,Zygosaccharomyces siamensis,is a novel ascosporogenous yeast.The type strain is JCM 16825T(=CBS 12273T)and a description is given here.

Debaryomyces hansenii supplementation in low fish meal diets promotes growth,modulates microbiota and enhances intestinal condition in juvenile marine fish

Background The development of a sustainable business model with social acceptance,makes necessary to develop new strategies to guarantee the growth,health,and well-being of farmed animals.Debaryomyces hansenii is a yeast species that can be used as a probiotic in aquaculture due to its capacity to i)promote cell proliferation and differen-tiation,ii)have immunostimulatory effects,iii)modulate gut microbiota,and/or iv)enhance the digestive function.To provide inside into the effects of D.hansenii on juveniles of gilthead seabream(Sparus aurata)condition,we inte-grated the evaluation of the main key performance indicators coupled with the integrative analysis of the intestine condition,through histological and microbiota state,and its transcriptomic profiling.Results After 70 days of a nutritional trial in which a diet with low levels of fishmeal(7%)was supplemented with 1.1%of D.hansenii(17.2×10^(5) CFU),an increase of ca.12%in somatic growth was observed together with an improve-ment in feed conversion in fish fed a yeast-supplemented diet.In terms of intestinal condition,this probiotic modu-lated gut microbiota without affecting the intestine cell organization,whereas an increase in the staining intensity of mucins rich in carboxylated and weakly sulphated glycoconjugates coupled with changes in the affinity for certain lectins were noted in goblet cells.Changes in microbiota were characterized by the reduction in abundance of several groups of Proteobacteria,especially those characterized as opportunistic groups.The microarrays-based transcrip-tomic analysis found 232 differential expressed genes in the anterior-mid intestine of S.aurata,that were mostly related to metabolic,antioxidant,immune,and symbiotic processes.Conclusions Dietary administration of D.hansenii enhanced somatic growth and improved feed efficiency param-eters,results that were coupled to an improvement of intestinal condition as histochemical and transcriptomic tools indicated.This probiotic yeast stimulated host-microbiota interactions without altering the intestinal cell organization nor generating dysbiosis,which demonstrated its safety as a feed additive.At the transcriptomic level,D.hansenii pro-moted metabolic pathways,mainly protein-related,sphingolipid,and thymidylate pathways,in addition to enhance antioxidant-related intestinal mechanisms,and to regulate sentinel immune processes,potentiating the defensive capacity meanwhile maintaining the homeostatic status of the intestine.