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.

Improving Semi-Dried Brown Rice Noodle Quality via Mixed Fermentation of Lactobacillus and Yeast

To address the coarse texture and poor cooking quality of brown rice flour,we employed fermentation using lactobacillus and yeast in varying proportions.The fermented flour from early indica rice Pear 13 was then processed into semi-dried brown rice noodles.

Effect of β-Glucan (Angel Yeast) Compared to a Placebo on Cold and Flu Incidence and Symptoms in an Adult Population—A Double Blind, Randomised Controlled Trial

Background: 1-3, 1-6 β-glucan derived from Baker’s yeast (Saccharomyces cerevisiae) has been widely studied for its immune stimulatory capabilities and safety. Previous studies found β-glucan to have efficacy at reducing incidence of URTIs as well as being a low risk for negative side effects. The current study aimed to examine the effects of yeast β-glucan (Angel Yeast) on cold and flu incidences and symptoms in healthy adults. Methods: Two hundred and thirty-one males and females aged 18 to 65 years old supplemented with either β-glucan or a placebo for 3-months. Participants completed a general health questionnaire every 4 weeks and in addition, if participants experienced any cold or flu symptoms, these were recorded daily (along with severity) until resolved or up to 2 weeks. Results: Supplementation with β-glucan reduced the self-reported severity of sore throats and improved sleep quality compared to the placebo group. Conclusions: Yeast β-glucan supplementation appears to be able to help reduce certain symptoms experienced during a cold or flu episode and is safe and well tolerated.

Mathematical Modeling of Cell Polarity Establishment of Budding Yeast

The budding yeast Saccharomyces cerevisiae is a powerful model system for studying the cell polarity establishment.The cell polarization process is regulated by signaling molecules,which are initially distributed in the cytoplasm and then recruited to a proper location on the cell membrane in response to spatial cues or spontaneously.Polarization of these signaling molecules involves complex regulation,so the mathematical models become a useful tool to investigate the mechanism behind the process.In this review,we discuss how mathematical modeling has shed light on different regulations in the cell polarization.We also propose future applications for the mathematical modeling of cell polarization and morphogenesis.

Impact of Storage Temperature on Microbial Diversity and Probiotic Effect of Liquid Brewers’ Yeast

Using probiotics as animal feed additives instead of antibiotics is gaining momentum to avert adverse negative effects on human health. Liquid brewers yeast (LBY) is an industrial by-product containing probiotic microorganisms and is also used as a protein supplement for dairy animals. Nevertheless, value chain actors lack of appropriate handling practices compromises the by-products quality and safety. This study aimed to determine the effect of variation in temperature on microbial diversity and probiotic effects during the storage time of LBY sampled from distributors and farmers from Githunguri sub-county of Kenya. The samples were stored at 20C, 25C and 30C, then tested on 0, 5, 10, 15 and 20 days. The studys parameters involved determining the pH levels, lactic acid bacteria (LAB), total coliform count (TCC), mould, and yeast in LBY. The rate (k) of the reaction kinetics model was used to extrapolate the expected probiotic shelf life. The LAB and yeast populations were reduced in a first-order reaction at all storage temperatures. The rate of reduction in the numbers of LAB reduced with an increase in temperature (k = 0.019 and 0.023) at 20C and 30C, respectively. Yeasts highest rate of growth reduction was 25C (k = 0.009) and least at 30C (k = 0.043). The minimum effective concentration for probiotics of 106 CFU/mL needed to observe the beneficial physiological impact on farm animals was achieved between 34.9 and 35.5 days at the tested storage temperatures. The study provides insight into the unexploited low-cost probiotic potential of LBY in dairy production. Conversely, handling practices and environmental microbial contamination along the value chain can compromise product quality and safety. There is a need to advocate its use in dairy for improved productivity and sensitize farmers to appropriate hygienic measures along the LBY value chain.

Microbiological Quality of “Rabilé”, a Yeast Used for Fermentation of Dolo, a Local Beer in Dédougou, Burkina Faso

Sorghum beer or dolo is part of the eating habits of part of the population of Dédougou because of its low price compared with industrial beers. Its production is an ancestral tradition that uses traditional equipment and gives dolo organoleptic properties that are not found in industrial beers. The production process involves several stages, including fermentation, which itself comprises natural lactic fermentation followed by alcoholic fermentation using traditional yeasts, which are not controlled in any way. The general aim of this study is to assess the microbiological quality of these fermentative yeasts in the town of Dédougou, in order to contribute to the health safety of the population and the promotion of these local beers. Twenty samples of fermenting yeast were analyzed according to ISO standards, to isolate enterobacteria, total and faecal coliforms according to standard procedures for isolating these micro-organisms. The isolated strains were identified using the API20E gallery. Microbiological analyses revealed the presence of 51.17% enterobacteria, 45.38% total coliforms and 3.45% thermotolerant coliforms. We counted 40% Escherichia coli, 20% Enterobacter cloacae, 20% Klebsiella pneumoniae and 20% Klebsiella spp. All the strains detected are capable of surviving in hostile conditions and could harm the quality of the dolo, consumer health and cause real collective food poisoning in the town of Dédougou. This enabled us to assess the microbial quality of these yeasts and to propose more suitable measures for producing and preserving dolo under hygienic conditions to protect consumer health.

Immobilization techniques for beverage production using yeast cell systems: challenges, types, and future perspectives - a mini review

Yeast immobilization is a process of physical entrapment of yeast cells using different techniques while maintaining their biological activity.Continuous fermentation systems have significant advantages over conventional methods.Research highlights that immobilized yeast cell systems have several benefits as compared to free yeast cells.The immobilized yeast cell systems improve fermentation rates,especially when paired with continuous fermentation and appropriate immobilization techniques.Understanding various immobilization techniques,continuous fermentation processes,yeast metabolic activity related to beverage flavor production,and bioreactor designs is vital for optimizing the use of immobilized yeast cells systems on industrial scale.This review provides an overview of recent basic research on immobilized yeast cell systems,with a focus on continuous beverage fermentation.In this study,different reactor configurations and immobilization techniques are explored.The study focus on the impacts of immobilization on the yeast cells,and discuss the recent advancements in these techniques.The review concludes with a discussion on the practical applications of immobilized yeast cells and continuous fermentation in beverage production.

Marine Yeasts and Their Applications in Mariculture

The terrestrial yeasts have been receiving great attention in science and industry for over one hundred years because they can produce many kinds of bioactive substances. However, little is known about the bioactive substances of marine yeasts. In recent years, it has been found that marine yeasts have wide applications in mariculture and other fields. Therefore,marine yeasts, the bioactive substances from them and the applications of marine yeasts themselves and the bioactive substances they produced are reviewed in this paper.

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.

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.

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.

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.

Occurrence and Diversity of Marine Yeasts in Antarctica Environments

A total of 28 yeast strains were obtained from the sea sediment of Antarctica.According to the results of routine identi-fication and molecular characterization,the strains belonged to species of Yarrowia lipolytica,Debaryomyces hansenii,Rhodotorula slooffiae,Rhodotorula mucilaginosa,Sporidiobolus salmonicolor,Aureobasidium pullulans,Mrakia frigida and Guehomyces pullu-lans,respectively.The Antarctica yeasts have wide potential applications in biotechnology,for some of them can produce b-galactosidase and killer toxins.

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.

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.

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.

Alkaline Protease Production by a Strain of Marine Yeasts

Yeast strain 10 with high yield of protease was isolated from sediments of saltern near Qingdao, China. The protease had the highest activity at pH 9.0 and 45 ℃. The optimal medium for the maximum alkaline protease production of strain 10 was 2.5 g soluble starch and 2.0 g NaNO3 in 100 mL seawater with initial pH 6.0. The optimal cultivation conditions for the maximum protease production were temperature 24.5 ℃, aeration rate 8.0 L min -1 and agitation speed 150 r min -1. Under the optimal conditions, 623.1 U mg -1 protein of alkaline protease was reached in the culture within 30 h of fermentation.