Yeast Research Papers - Academia.edu (original) (raw)

Lignocellulosic ethanol has been considered as an alternative transportation fuel. Utilization of hemicellulosic fraction in lignocelluloses is crucial in economical production of lignocellulosic ethanol. However, this fraction has not... more

Lignocellulosic ethanol has been considered as an alternative transportation fuel. Utilization of hemicellulosic fraction in lignocelluloses is crucial in economical production of lignocellulosic ethanol. However, this fraction has not efficiently been utilized by traditional yeast Saccharomyces cerevisiae. Genetically modified S. cerevisiae, which can utilize xylose, has several limitations including low ethanol yield, redox imbalance, and undesired metabolite formation similar to native xylose utilizing yeasts. Besides, xylose uptake is a major issue, where sugar transport system plays an important role. These genetically modified and wild-type yeast strains have further been engineered for improved xylose uptake. Various techniques have been employed to facilitate the xylose transportation in these strains. The present review is focused on the sugar transport machineries, mechanisms of xylose transport, limitations and how to deal with xylose transport for xylose assimilation in ...

We report on the identification and characterization of a mutated alcohol dehydrogenase 1 from the industrial Saccharomyces cerevisiae strain TMB3000 that mediates the NADH-dependent reduction of 5-hydroxymethylfurfural (HMF) to... more

We report on the identification and characterization of a mutated alcohol dehydrogenase 1 from the industrial Saccharomyces cerevisiae strain TMB3000 that mediates the NADH-dependent reduction of 5-hydroxymethylfurfural (HMF) to 2,5-bis-hydroxymethylfuran. The co-factor preference distinguished this alcohol dehydrogenase from the previously reported NADPH-dependent S. cerevisiae HMF alcohol dehydrogenase Adh6. The amino acid sequence revealed three novel mutations (S109P, L116S and Y294C) that were all predicted at the vicinity of the substrate binding site, which could explain the unusual substrate specificity. Increased biomass production and HMF conversion rate were achieved in a CEN.PK S. cerevisiae strain overexpressing the mutated ADH1 gene. Copyright © 2008 John Wiley & Sons, Ltd.

The use of macroalgae (seaweed) as a potential source of biofuels has attracted considerable worldwide interest. Since brown algae, especially the giant kelp, grow very rapidly and contain considerable amounts of polysaccharides, coupled... more

The use of macroalgae (seaweed) as a potential source of biofuels has attracted considerable worldwide interest. Since brown algae, especially the giant kelp, grow very rapidly and contain considerable amounts of polysaccharides, coupled with low lignin content, they represent attractive candidates for bioconversion to ethanol through yeast fermentation processes. In the current study, powdered dried seaweeds (Ascophylum nodosum and Laminaria digitata) were pre-treated with dilute sulphuric acid and hydrolysed with commercially available enzymes to liberate fermentable sugars. Higher sugar concentrations were obtained from L. digitata compared with A. nodosum with glucose and rhamnose being the predominant sugars, respectively, liberated from these seaweeds. Fermentation of the resultant seaweed sugars was performed using two non-conventional yeast strains: Scheffersomyces (Pichia) stipitis and Kluyveromyces marxianus based on their abilities to utilise a wide range of sugars. Altho...

In winemaking, nutrient supplementation is a common practice for optimising fermentation and producing quality wine. Nutritionally suboptimal grape juices are often enriched with nutrients in order to manipulate the production of yeast... more

In winemaking, nutrient supplementation is a common practice for optimising fermentation and producing quality
wine. Nutritionally suboptimal grape juices are often enriched with nutrients in order to manipulate the production
of yeast aroma compounds. Nutrients are also added to active dry yeast (ADY) rehydration media to enhance
subsequent fermentation performance. In this study we demonstrate that nutrient supplementation at rehydration
also has a significant effect on the formation of volatile sulfur compounds during wine fermentations. The
concentration of the ‘fruity’ aroma compounds, the polyfunctional thiols 3-mercaptohexan-1-ol (3MH) and 3-
mercaptohexyl acetate (3MHA), was increased while the concentration of the ‘rotten egg’ aroma compound,
hydrogen sulfide (H2S), was decreased. Nutrient supplementation of the rehydration media also changed the
kinetics of H2S production during fermentation by advancing onset of H2S production. Microarray analysis revealed
that this was not due to expression changes within the sulfate assimilation pathway, which is known to be a major
contributor to H2S production. To gain insight into possible mechanisms responsible for this effect, a component
of the rehydration nutrient mix, the tri-peptide glutathione (GSH) was added at rehydration and studied for its
subsequent effects on H2S formation. GSH was found to be taken up during rehydration and to act as a source for
H2S during the following fermentation. These findings represent a potential approach for managing sulfur aroma
production through the use of rehydration nutrients.

Probiotics are living microorganisms that have an important role in prevention and treatment of diseases. The aim of this study was isolate yeast with probiotic properties due to the importance of probiotic yeasts. Sampling was performed... more

Probiotics are living microorganisms that have an important role in prevention and treatment of diseases. The aim of this study was isolate yeast with probiotic properties due to the importance of probiotic yeasts. Sampling was performed from different parts of human skin. Growth ability of isolated yeast at concentrations of 0.3, 0.5 and 1% oxgall, 2, 4 and 6% NaCl, pHs of 2, 4, 5.8, 9 and 11 and temperature 37, 40 and 42°C were investigated. The activity of amylase, protease, pectinase, cellulase, lipase, urease, catalase, citratase and hemolysin was investigated. The yeast was able to grow in 0.3% oxgall, concentrations of 2, 4 and 6% NaCl, pHs of 2, 4, 5.8, 9 and 11 and also at a temperature of 37°C. The isolated yeast has the primary properties of probiotics and can be used in future studies.

Two ethanol fermenting Saccharomyces cerevisiae were isolated from date juice and grapes and grown in YEPD medium. They were characterized for alcoholic fermentation using sugarcane molasses and their growth conditions were optimized with... more

Two ethanol fermenting Saccharomyces cerevisiae were isolated from date juice and grapes and grown in YEPD medium. They were characterized for alcoholic fermentation using sugarcane molasses and their growth conditions were optimized with respect to pH and sugar concentration. Results revealed a temperature of 30ºC, pH 6.0 and 6.5% sugar concentration as optimum for fermentation. Stress tolerance tests showed that date juice isolate was highly tolerant to temperature, pH and high ethanol concentration in the medium. Under optimized conditions, S. cerevisiaeisolated from date-juice produced 7.75% of ethanol in molasses as estimated by Conway method.

Immobilized cell technology has shown a significant promotional effect on the fermentation of alcoholic beverages such as beer, wine and cider. However, genetic, morphological and physiological alterations occurring in immobilized yeast... more

Immobilized cell technology has shown a significant promotional effect on the fermentation of alcoholic beverages such as beer, wine and cider. However, genetic, morphological and physiological alterations occurring in immobilized yeast cells impact on aroma formation during fermentation processes. The focus of this review is exploitation of existing knowledge on the biochemistry and the biological role of flavour production in yeast for the biotechnological production of aroma compounds of industrial importance, by means of immobilized yeast. Various types of carrier materials and immobilization methods proposed for application in beer, wine, fruit wine, cider and mead production are presented. Engineering aspects with special emphasis on immobilized cell bioreactor design, operation and scale-up potential are also discussed. Ultimately, examples of products with improved quality properties within the alcoholic beverages are addressed, together with identification and description o...

Wine is an undistilled alcoholic beverage made from fermented fruit juice. Meanwhile, fermentation refers to the catabolic and anaerobic process of transforming sugar into carbon dioxide and ethanol with the help of bacteria, preferably... more

Wine is an undistilled alcoholic beverage made from fermented fruit juice. Meanwhile, fermentation refers to the catabolic and anaerobic process of transforming sugar into carbon dioxide and ethanol with the help of bacteria, preferably in the dark. For this experiment, it aims to create wine in a laboratory by learning the process on how to produce and by appreciating the role of each material in the product. The experiment started with the preparation of each ingredient, specifically, fruit juice, active yeast, and refined sugar, and the measurement of their required weights. Next, 50 mL of fruit juice was warmed on a hot plate and then refined sugar was dissolved into the heated juice. After that, the juice heated again to a temperature of 70°C. Active yeast was added and mixed with the hot juice. The mixture was then combined with the remaining fruit juice and its density was determined using a hydrometer or pycnometer. Then, the mixture was transferred in a bottle with a cotton wad or balloon as a cover and was left to ferment in a dark room for a week. After a week, the wine was decanted and filter before being placed in a packaging bottle. The same process was repeated for the remaining wine formulations. The results showed that the wine made from the W1 formulation was much paler than from W2 and W3. It was also observed that the specific gravity of all the wines was greater before fermentation occurred. From the ingredients, yeast acted as the fermenting agent which converted the sugar compounds from the fruit juice and from the refined sugar into alcohol. Also, sugar was used to balance sweetness and to produce more alcohol in the wine since the sugars in the fruit juice is not sufficient to reach the desired ethanol content for wines.

Flavours are biologically active molecules of large commercial interest in the food, cosmetics, detergent and pharmaceutical industry. The production of flavours can take place by either extraction from plant materials, chemical... more

Flavours are biologically active molecules of large commercial interest in the food, cosmetics, detergent and pharmaceutical industry. The production of flavours can take place by either extraction from plant materials, chemical synthesis, through biological conversion of precursor molecules or through de novo biosynthesis. The latter alternatives are gaining importance through the rapidly growing fields of systems biology and metabolic engineering giving efficient production hosts for the so-called “bioflavours”, which are natural flavour and/or fragrance compounds obtained with cell factories or enzymatic systems. One potential production host for bioflavour is yeast. In this mini-review, we give an overview of bioflavour production in yeast from the process engineering perspective. Two specific examples – production of 2-phenylethanol and vanillin - are used to illustrate process challenges and strategies used. Copyright © 2014 John Wiley & Sons, Ltd.

In the present work 65 yeasts were used, 24 were characterized as killer, these yeasts were qualitatively evaluated against ten strains of Penicillium, this to determine the antagonism on the filamentous in question, for that was striae... more

In the present work 65 yeasts were used, 24 were characterized as killer, these yeasts were qualitatively evaluated against ten strains of Penicillium, this to determine the antagonism on the filamentous in question, for that was striae of each levaduriform were placed on plates with medium PDA that had previously been inoculated with conidias of Penicillium. Only 10 yeasts exhibited antagonism against five or more strains of the fungus. These yeasts were tested to evaluate their ability to reduce the radial growth of the filamentous; strains 1268 and 1144 showed the highest reduction percentage on fungus growth; the ten strains of yeasts had been previously characterized and these were RT3 and 1250 (Pichia membranifaciens), 1268 (Cryptococcus weringae), 1123 and 1144 (Metschnikowia pulcherrima), 1025, 1026 and 1027 (Wickerhamomyces anomala), 1153 (Pichia kluyveri) and LALVIN (Saccharomyces cerevisiae).
When analyzed by ANOVA the percentages of radial reduction as well as the inhibition by antagonistic gases presented by the best yeasts showed that they were not significantly superior presented by the rest of the yeasts, however, these levaduriforms can be considered as a possible strategy of biocontrol against Penicillium in addition to being used for further experiments.

A B S T R A C T Microalgae are able to convert nutrients (nitrogen and phosphorus) from wastewater into biomass and bio-products, thus improving the sustainability of wastewater treatment. In High Rate Algal Ponds (HRAP), biomass... more

A B S T R A C T Microalgae are able to convert nutrients (nitrogen and phosphorus) from wastewater into biomass and bio-products, thus improving the sustainability of wastewater treatment. In High Rate Algal Ponds (HRAP), biomass productivity and water treatment efficiency are highly dependent on environmental parameters such as temperature, light intensity and photoperiod. The influence of temperature and photoperiod on biomass productivity and the removal of dissolved nitrogen and phosphorus from municipal wastewater by a native microalgae-bacteria consortium was assessed in batch cultures in view of the development of an HRAP at a larger scale. Temperature affected the growth rate and microalgae biomass production as well as ammonium and phosphate removal rates. At the temperatures 15 and 25 C, the average total nitrogen and phosphorus removal extents ranged from 72 to 83% and 100% respectively. Additionally 33.0 AE 0.1% of the total nitrogen was eliminated by stripping at 25 C, and 50 AE 2% was assimilated by the microorganisms under all conditions tested.

Studies were carried out to establish the optimum temperature and time for sterilization of palm wine to enhance its shelf life.In the studies, the temperature and time of sterilization of the beverage were varied within the... more

Studies were carried out to establish the optimum temperature and time for
sterilization of palm wine to enhance its shelf life.In the studies, the temperature and time of sterilization of the beverage were varied within the range of 40-75oC and 10/20 minutes in order to establish the optimum time and temperature for its sterilization without affecting the beverage’s quality in terms of the taste and aroma profile.Each 500ml of palm wine sample was respectively heat-treated at the respective temperatures for 10 and 20 minutes. The result of the studies showed that bacteria and yeast load decreased with the increase in temperature and time of sterilization. The taste and aroma profile diminished with the increase in temperature and time of sterilization. The temperature and the time at which
there was complete destruction of organism with retention in taste and aroma of the beverage was 650C and 10 minutes respectively. A Plot of the number of surviving cells against the temperature of sterilization at a given time follows a log linear kinetics. The statistical evaluation of the sample sterilized at 650C for 10 minutes when compared with the fresh untreated sample (control) showed no significant different between the samples at 95% confidence level.

The key to the keys to immortality and eternal youth lies in the correct answer to the main question: How to naively discover new essential – but still hidden – features required for properly training novel adaptive supervised machine... more

The key to the keys to immortality and eternal youth lies in the correct answer to the main question: How to naively discover new essential – but still hidden – features required for properly training novel adaptive supervised machine learning algorithms (SMLA)

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with... more

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

Candida species are known to cause serious infections in immunocompromised patients but uncommon cases have been reported in immunocompetent individuals regardless of the harmless coexistence of the fungi with the host. Recently, the... more

Candida species are known to cause serious infections in immunocompromised patients but uncommon cases have been reported in immunocompetent individuals regardless of the harmless coexistence of the fungi with the host. Recently, the incidence rate of candidiasis has increased dramatically alongside the emergence of antifungal resistance. Although conventional methods to ensure prompt diagnosis of candidiasis for effective therapy have been established, the scientific world is witnessing progress in the development of more accurate, timely and cost-effective methods that is coinciding with the molecular revolution and advanced DNA analysis. Moreover, the challenges of resistance of Candida to available antifungal agents are being met with the deployment of molecular techniques to investigate the mechanisms of resistance. This review is an attempt to provide up-to-date information on the persistent problems of Candida with highlights on the clinical importance, molecular diagnosis, and resistance to candidate antifungal drugs; azoles and echinocandins. Abstrait: Les espèces de Candida sont connues pour causer des infections graves chez les patients immunodéprimés, mais des cas peu communs ont été rapportés chez des individus immunocompétents, indépendamment de la coexistence inoffensive des champignons avec l'hôte. Récemment, le taux d'incidence de la candidose a considérablement augmenté parallèlement à l'émergence d'une résistance antifongique. Bien que les méthodes conventionnelles permettant d'assurer un diagnostic rapide de la candidose en vue d'un traitement efficace aient été établies, le monde scientifique constate des progrès dans la mise au point de méthodes plus précises, plus rapides et plus rentables qui coïncident avec la révolution moléculaire et l'analyse avancée de l'ADN. De plus, les défis posés par la résistance de Candida aux agents antifongiques disponibles sont résolus par le déploiement de techniques moléculaires pour étudier les mécanismes de résistance. Cette revue tente de fournir des informations à jour sur les problèmes persistants de Candida en soulignant l'importance clinique, le diagnostic moléculaire et la résistance aux antifongiques candidats; les azoles et les echinocandins.