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Chlorella vulgaris, a microalga rich in secondary metabolites and nutrients, offers a promising alternative for promoting microbial growth in food fermentation processes. This study aimed to evaluate the effects of C. vulgaris extracts on fermentation kinetics, sensory characteristics, phytochemical composition, antioxidant activity, and the abundance of volatile organic compounds (VOCs) in treated versus control beers. The bioactive compounds from C. vulgaris were extracted using an ultrasound-assisted method with water as the solvent. A German Pilsner-style lager beer (GPB) was brewed and supplemented with 0.5, 1, and 5 g/L of C. vulgaris extracts prior to primary fermentation. Yeast viability, °Brix, and pH levels were monitored to assess fermentation progress. Phytochemical composition was analyzed by quantifying total polyphenols and flavonoids. The antioxidant activity of the beer was evaluated using both the 2,2-diphenyl-1-picrylhydrazyl (DPPH●) and hydrogen peroxide assays. The addition of C. vulgaris extracts resulted in increased yeast viability and slight variations in gravity during the 7-day fermentation period. Moreover, the beers supplemented with C. vulgaris extracts demonstrated higher levels of total polyphenols, flavonoids, and antioxidant activity compared to the GPB. Specific volatile organic compounds, including 2-methyl-1-propanol, 1-hexanol, isopentyl hexanoate, 2-methylpropyl octanoate, β-myrcene, and geranyl acetate, were significantly more abundant (p < 0.05) in the treated beers than in the control. Sensory evaluations revealed a favorable impact of the treatment on aroma scores compared to the GPB. Overall, the findings indicate that C. vulgaris extracts could be a valuable ingredient for developing functional beers with enhanced health benefits, particularly regarding antioxidant activity. Additionally, the results underscore the importance of exploring innovative approaches that utilize natural sources like Chlorella to enrich the nutritional profile and sensory qualities of fermented products. [ABSTRACT FROM AUTHOR]

Mao wine is produced from mao (Antidesma thwaitesianum) and is a local beverage promoting Sakon Nakhon province, Thailand. Understanding the fermentation process is necessary in order to enhance the quality of mao wine products. This study aims to examine the kinetics of mao wine fermentation using 3 commercial types of Saccharomyces cerevisiae yeasts, namely Lalvin 71B, Lalvin RC212 and Lalvin K1- V1116, with an initial pH of 3.4, a sweetness of 22 % Brix and a yeast concentration of 0.4 g L-1 in controlled conditions at 25 °C for 10 days. The results revealed that the kinetic models, including logistic, Luedeking-Piret and modified Luedeking-Piret equations, are appropriate for analyzing the kinetics of yeast growth, alcohol production and reducing sugar, respectively. Lalvin K1-V1116 yeast yielded the highest capacity for alcohol production (~113 g L-1), sugar-to-alcohol conversion (45 % conversion), and product efficiency (88 %), indicating its suitability for mao wine production. Furthermore, the investigation of the alpha-amylase inhibitory activity revealed that the IC50 values of mao wine samples were 2.88 - 4.78 mg mL-1, which were roughly 410 - 680 times greater than those of acarbose. These findings revealed the low efficacy of mao wine in inhibiting alpha-amylase activity. Nevertheless, a decrease in the level of inhibition may result in a decreased likelihood of side effects or undesirable reactions. This treatment is especially beneficial for people who have medication sensitivities. Additional research is required in order to substantiate its applicability in the management of type 2 diabetes. [ABSTRACT FROM AUTHOR]

Chlorella vulgaris, a microalga rich in secondary metabolites and nutrients, offers a promising alternative for promoting microbial growth in food fermentation processes. This study aimed to evaluate the effects of C. vulgaris extracts on fermentation kinetics, sensory characteristics, phytochemical composition, antioxidant activity, and the abundance of volatile organic compounds (VOCs) in treated versus control beers. The bioactive compounds from C. vulgaris were extracted using an ultrasound-assisted method with water as the solvent. A German Pilsner-style lager beer (GPB) was brewed and supplemented with 0.5, 1, and 5 g/L of C. vulgaris extracts prior to primary fermentation. Yeast viability, °Brix, and pH levels were monitored to assess fermentation progress. Phytochemical composition was analyzed by quantifying total polyphenols and flavonoids. The antioxidant activity of the beer was evaluated using both the 2,2-diphenyl-1-picrylhydrazyl (DPPH●) and hydrogen peroxide assays. The addition of C. vulgaris extracts resulted in increased yeast viability and slight variations in gravity during the 7-day fermentation period. Moreover, the beers supplemented with C. vulgaris extracts demonstrated higher levels of total polyphenols, flavonoids, and antioxidant activity compared to the GPB. Specific volatile organic compounds, including 2-methyl-1-propanol, 1-hexanol, isopentyl hexanoate, 2-methylpropyl octanoate, β-myrcene, and geranyl acetate, were significantly more abundant (p < 0.05) in the treated beers than in the control. Sensory evaluations revealed a favorable impact of the treatment on aroma scores compared to the GPB. Overall, the findings indicate that C. vulgaris extracts could be a valuable ingredient for developing functional beers with enhanced health benefits, particularly regarding antioxidant activity. Additionally, the results underscore the importance of exploring innovative approaches that utilize natural sources like Chlorella to enrich the nutritional profile and sensory qualities of fermented products.

Candida glabrata and Candida albicans, the most frequently isolated candidiasis species in the world, have developed mechanisms of resistance to treatment with azoles. Among the clinically used antifungal drugs are statins and other compounds that inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), resulting in decreased growth and ergosterol levels in yeasts. Ergosterol is a key element for the formation of the yeast cell membrane. However, statins often cause DNA damage to yeast cells, facilitating mutation and drug resistance. The aim of the current contribution was to synthesize seven series of compounds as inhibitors of the HMGR enzyme of Candida ssp., and to evaluate their effect on cellular growth, ergosterol synthesis and generation of petite mutants of C. glabrata and C. albicans. Compared to the reference drugs (fluconazole and simvastatin), some HMGR inhibitors caused lower growth and ergosterol synthesis in the yeast species and generated fewer petite mutants. Moreover, heterologous expression was achieved in Pichia pastoris, and compounds 1a, 1b, 6g and 7a inhibited the activity of recombinant CgHMGR and showed better binding energy values than for α-asarone and simvastatin. Thus, we believe these are good candidates for future antifungal drug development. [ABSTRACT FROM AUTHOR]

This study was aimed to investigate the effect of earthworms after their decomposition on yeast growth. To achieve this objective, in vitro crude soluble extracts were prepared from two earthworms lots: freshly harvested from the field "FHE" and the other previously starved for one week "SE". The dry residues of these two crude extracts were used at different concentrations as a solid media for the growth of two yeast species: one "Candida tropicalis" got from another laboratory and the other was isolated by our team from earthworms' casts "Filobasidium uniguttulatum", and their growth was evaluated by colonies counting. The results obtained, compared with the Sabouraud Dextrose Agar (SDA), showed that the growth of both yeast isolates was significantly higher on mediums prepared using exclusively earthworms' crude extracts and agar. Optimal growth was obtained at a concentration corresponding to 0.375g/100 mL of earthworms' soluble matter of the two types of earthworms' lots. These results affirmed the richness and the diversification of those extracts, in nutrients and growth factors, that comes mainly from the intrinsic composition of earthworm's body biomass. The efficiency of the FHE and SE extracts for cultivation of yeast shows their possible use as a culture media that may be applied to other soil microorganisms and even in vivo as soil amendments or biofertilizers. [ABSTRACT FROM AUTHOR]

Background and Aims: Microoxygenation (MOX) is widely used in winemaking. Its impact, however, on Pinot Noir wines has not been well documented. We investigated the influence of MOX on colour parameters and on the anthocyanin and polymeric pigment concentration of a young Pinot Noir wine. The relationship between MOX, yeast growth and acetaldehyde production was also explored. Methods and Results: Microoxygenation was applied before or after malolactic fermentation (MLF), and at two oxygen doses [10.8 and 52.4 mg/(L ·month)], for 30 days. The end result was reported after dissolved oxygen was depleted and 90 mg/L SO2 was added. Microoxygenation induced a higher yeast growth and acetaldehyde production, where the latter was associated with both yeast metabolism and chemical oxidation. A larger loss in total anthocyanins and malvidin‐3‐glucoside occurred under MOX but absorbance at 520 nm and colour intensity were higher. With the higher oxygen dose, MOX promoted the formation of large polymeric pigments. Conclusions: Acetaldehyde formation was strongly induced by MOX, contributing to reactions between anthocyanins and acetaldehyde forming pigments in the red spectrum. Between MOX treatments, only slight variation was found for each parameter, indicating a less important effect of the timing and dosage of MOX on the young Pinot Noir wine than anticipated from prior work. Significance of the Study: Microoxygenation caused a significant impact on the colour development of light‐coloured Pinot Noir wine, increasing the colour intensity. [ABSTRACT FROM AUTHOR]

Maintenance of the proteome (proteostasis) is essential for cellular homeostasis and prevents cytotoxic stress responses that arise from protein misfolding. However, little is known about how different types of misfolded proteins impact homeostasis, especially when protein degradation pathways are compromised. We examined the effects of misfolded protein expression on yeast growth by characterizing a suite of substrates possessing the same aggregation‐prone domain but engaging different quality control pathways. We discovered that treatment with a proteasome inhibitor was more toxic in yeast expressing misfolded membrane proteins, and this growth defect was mirrored in yeast lacking a proteasome‐specific transcription factor, Rpn4p. These results highlight weaknesses in the proteostasis network's ability to handle the stress arising from an accumulation of misfolded membrane proteins. [ABSTRACT FROM AUTHOR]

• An established respirometer can be expanded with calorimetric functions. • The resulting innovative calorespirometer is suited for the study of microbial growth reactions. • Despite its simple design, it achieves heat losses of 30 % and response times of 6 min. • Yeast experiments highlight the capability to differentiate metabolic pathways. A prototype of an innovative isothermal calorespirometer was developed to measure simultaneously heat production rate (calorimetry) and CO 2 evolution rate (respirometry) in real-time in a static batch vessel system. The relationship between these two variables forms the calorespirometric ratio, which serves as a crucial indicator for metabolic processes and allows for the differentiation of various metabolic pathways in simple (pure culture) and complex (e.g. soil) biological systems. The heat production rate is gauged by a thermoelectric generator situated at the bottom of the measuring channel (calorimetric unit), while the CO 2 evolution rate is monitored through a conductometric cell fixed on the lid of the channel (respirometric unit). The prototype is designed with a twin configuration, featuring both sample and reference channels. The spatial separation of the calorimetric and respirometric measuring units ensures the simultaneous measurement of the two rates from a single sample without the occurrence of crosstalk effects between the signals. The electrical calibration of the calorimetric unit reveals heat losses (approx. 30 %) and response times (approx. 6 min) that are comparable to those of established isothermal calorimeters. In parallel, growth experiments conducted with baker's yeast demonstrate the applicability of the calorespirometer prototype to biological systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Yeast cell death is triggered when essential nutrients such as potassium and lipid are limited but ammonium is in excess. When ammonium and glucose were maintained at 100% of the normal concentration while all the other essential nutrients in yeast nitrogen base (YNB) were reduced to 2%, yeast growth was halted by ammonium toxicity. Yeast started to grow again when either ammonium was also reduced to 2% or gluconate was added, but simultaneously adding gluconate as well as reducing all the nutrients except glucose 50-fold revived yeast growth to a greater extent, i.e. a quarter of the normal growth. Gluconate, as well as formate and alginate, stimulated yeast growth by buffering the drop in pH. Yeast cells were seemingly more susceptible to low pH under the nutrient-limited conditions, entering the stationary phase at pH higher than that of the normal condition. Carboxylate salts may prove a cost-efficient replacement for large proportions of the essential nutrients as yeast cells, in the presence of 2 mg ml−1 gluconate, could still achieve nearly 90% of the normal growth when cultured in only 10% of the normal YNB concentration. [ABSTRACT FROM AUTHOR]

The yeast Dekkera bruxellensis is well-known for its adaptation to industrial ethanol fermentation processes, which can be further improved if nitrate is present in the substrate. To date, the assimilation of nitrate has been considered inefficient because of the apparent energy cost imposed on cell metabolism. Recent research, however, has shown that nitrate promotes growth rate and ethanol yield when oxygen is absent from the environment. Given this, the present work aimed to identify the biological mechanisms behind this physiological behaviour. Proteomic analyses comparing four contrasting growth conditions gave some clues on how nitrate could be used as primary nitrogen source by D. bruxellensis GDB 248 (URM 8346) cells in anaerobiosis. The superior anaerobic growth in nitrate seems to be a consequence of increased cell metabolism (glycolytic pathway, production of ATP and NADPH and anaplerotic reactions providing metabolic intermediates) regulated by balanced activation of TORC1 and NCR de-repression mechanisms. On the other hand, the poor growth observed in aerobiosis is likely due to an oxidative stress triggered by nitrate when oxygen is present. These results represent a milestone regarding the knowledge about nitrate metabolism and might be explored for future use of D. bruxellensis as an industrial yeast. Key points: • Nitrate can be regarded as preferential nitrogen source for D. bruxellensis. • Oxidative stress limits the growth of D. bruxellensis in nitrate in aerobiosis. • Nitrate is a nutrient for novel industrial bioprocesses using D. bruxellensis. [ABSTRACT FROM AUTHOR]

The corn smut fungus Ustilago maydis serves as a model species for studying fungal dimorphism and its role in phytopathogenic development. The pathogen has two growth phases: a saprobic yeast phase and a pathogenic filamentous phase. Dimorphic transition of U. maydis involves complex processes of signal perception, mating, and cellular reprogramming. Recent advances in improvement of reference genomes, high-throughput sequencing and molecular genetics studies have been expanding research in this field. However, the biology of other non-model species is frequently overlooked. This leads to uncertainty regarding how much of what is known in U. maydis is applicable to other dimorphic fungi. In this review, we will discuss dimorphic fungi in the aspects of physiology, reproductive biology, genomics, and molecular genetics. We also perform comparative analyses between U. maydis and other fungi in Ustilaginomycotina, the subphylum to which U. maydis belongs. We find that lipid/hydrophobicity is a potential common cue for dimorphic transition in plant-associated dimorphic fungi. However, genomic profiles alone are not adequate to explain dimorphism across different fungi. [ABSTRACT FROM AUTHOR]

Ribosome and protein synthesis lie at the core of cell growth and are major consumers of the cellular budget. Here we review recent progress in the coupling of ribosome synthesis and translational capacity with cell growth in bacteria. We elaborate on the different strategies of bacteria to modulate the protein synthesis rate at fast and slow growth rates. In particular, bacterial cells maintain translational potential at very slow growth as a strategy to keep fitness in fluctuating environments. We further discuss the important role of ribosome synthesis in rapidly proliferating eukaryotic cells such as yeast cells and cancer cells. The tight relation between ribosome and cell growth provides a broad research avenue for researchers from various disciplines. At fast growth rates, cellular ribosome synthesis is tightly coupled with cell growth by guanosine tetra- or pentaphosphate [(p)ppGpp] to attain optimal proteome resource allocation in bacterial cells. Under slow growth conditions, bacterial cells adopt an ingenious strategy to keep translational potential through maintaining both a basal inactive ribosome pool and a moderate translational elongation rate; such a design reflects an adaptive mechanism to fluctuating environments. Ribosome synthesis is also tightly coupled with growth rate in yeast cells, being similar to that in bacterial cells. Excessive ribosome synthesis is crucial for cancer cells to support rapid proliferation and a high protein synthesis rate, and upregulation of ribosome synthesis promotes cancer progression. [ABSTRACT FROM AUTHOR]

Background: Ethanol concentration (PE), ethanol productivity (QP) and sugar consumption (SC) are important values in industrial ethanol production. In this study, initial sugar and nitrogen (urea) concentrations in sweet sorghum stem juice (SSJ) were optimized for high PE (=10%, v/v), QP, (=2.5 g/L·h) and SC (=90%) by Saccharomyces cerevisiae SSJKKU01. Then, repeated-batch fermentations under normal gravity (NG) and high gravity (HG) conditions were studied. Results: The initial sugar at 208 g/L and urea at 2.75 g/Lwere the optimumvalues tomeet the criteria. At the initial yeast cell concentration of ~1 × 108 cells/mL, the PE, QP and SCwere 97.06 g/L, 3.24 g/L·h and 95.43%, respectively. Repeated-batch fermentations showed that the ethanol production efficiency of eight successive cycleswith and without aeration were not significantly different when the initial sugar of cycles 2 to 8 was under NG conditions (~140 g/L). Positive effects of aeration were observed when the initial sugar from cycle 2 was under HG conditions (180-200 g/L). The PE and QP under no aeration were consecutively lower from cycle 1 to cycle 6. Additionally, aeration affected ergosterol formation in yeast cell membrane at high ethanol concentrations, whereas trehalose content under all conditions was not different. Conclusion: Initial sugar, sufficient nitrogen and appropriated aeration are necessary for promoting yeast growth and ethanol fermentation. The SSJ was successfully used as an ethanol production medium for a high level of ethanol production. Aeration was not essential for repeated-batch fermentation under NG conditions, but it was beneficial under HG conditions. [ABSTRACT FROM AUTHOR]

In this paper the effect of aflatoxin B1, ochratoxin A and zearalenon on morphology, growth parameters and metabolic activity of yeasts Saccharomyces cerevisiae, Saccharomyces uvarum, Candida utilis and Kluyveromyces marxianus was determined. The results showed that the three mycotoxins affected the morphology of all these yeasts, primarily the cell diameter, but not their final cell count. Fourier transform infrared spectroscopy showed that the yeast membranes bound the mycotoxins, C. utilis in particular. The cell membranes of most yeasts underwent denaturation, except S. uvarum exposed to ochratoxin A and zearalenone. In the early stage of fermentation, all mycotoxin-exposed yeasts had lower metabolic activity and biomass growth than controls, but fermentation products and biomass concentrations reached the control levels by the end of the fermentation, except for C. utilis exposed to 20 μg/mL of zearalenone. The adaptive response to mycotoxins suggests that certain yeasts could be used to control mycotoxin concentrations in the production of fermented food and beverages.

Unsaturated fatty acids and sterols are essential constituents of the yeast plasma membrane. Recently, their contribution to modulating the production of yeast-derived volatile compounds has received significant attention. The objective of this study was to determine how sterol and lipid supplementation, including ergosterol, plant sterols or oleic acid, differentially influenced yeast growth as well as the production of fermentative aromas when added individually or in combinations. Oleic acid significantly altered the volatile profiles produced and lowered yeast growth. Generally, phytosterol (β-sitosterol) and ergosterol supplementation resulted in similar responses regarding the production of aromas, however, they differed in the magnitude of the response in the case of medium chain fatty acids and acetate esters synthesis. The combinations of sterols with oleic acid resulted in a response more closely associated with the oleic acid control treatment, showing lower levels of acetate ester production. [ABSTRACT FROM AUTHOR]

In this paper the effect of aflatoxin B , ochratoxin A and zearalenon on morphology, growth parameters and metabolic activity of yeasts Saccharomyces cerevisiae, Saccharomyces uvarum, Candida utilis and Kluyveromyces marxianus was determined. The results showed that the three mycotoxins affected the morphology of all these yeasts, primarily the cell diameter, but not their final cell count. Fourier transform infrared spectroscopy showed that the yeast membranes bound the mycotoxins, C. utilis in particular. The cell membranes of most yeasts underwent denaturation, except S. uvarum exposed to ochratoxin A and zearalenone. In the early stage of fermentation, all mycotoxin-exposed yeasts had lower metabolic activity and biomass growth than controls, but fermentation products and biomass concentrations reached the control levels by the end of the fermentation, except for C. utilis exposed to 20 μg/ mL of zearalenone. The adaptive response to mycotoxins suggests that certain yeasts could be used to control mycotoxin concentrations in the production of fermented food and beverages. [ABSTRACT FROM AUTHOR]

Over the last decade, the market of special beers with improved healthy function and/or with new refreshing taste has significantly increased. One of the possible solutions enables grape and mixing beer with bioactive component responsible for well known health promoting action of red wine. The influence of the addition of Prokupac grape on the physicochemical properties and the fermentation kinetics of the grape beer were studied and results were compared with control lager beer. The effect of grape addition on the activity of yeast was also studied. Original extract, alcohol content, degree of fermentation, fermentation rate and yeast growth were significantly higher in beers with grapes as a consequence of higher concentration of simple sugars in grapes compared with pure wort. Based on the CIELab chromatic parameters the color of grape beer samples was yellow with certain proportion of redness, while the control beer was purely yellow. The increase in the concentration of grape mash affects the reduction of lightness and yellowness of beers, while the redness of samples was directly proportional with grape quantity. The phenolic content and antioxidant capacity of grape beers was remarkably higher compared with control beer, which indicates that the grape beer is a better source of natural antioxidants than regular lager beer. [Projekat Ministarstva nauke Republike Srbije, br. 46001]

Microbial pectinolytic strains are targeted as potential starter to control cocoa fermentation. This study analysesthe ability of yeasts pectinolytic strains to grow under stress conditions. After an initial growth, a decline trendwas observed in yeast growth cycle during the cocoa fermentation. The 36 yeasts pectinolytic strains screenedfrom 205 isolates showed tolerance to both alcoholic stress (10-12% alcohol) and thermic stress (up to 40°C)corresponding to surviving population round 75%. However, temperature-alcohol cross stress provokes fullinhibition of strains that failed to grow at only 35°C under 8-10% alcohol. As acid stress, citric acid at 4% hasthe same effect as alcohol. In contrast, acetic acid and lactic acid respectively at 0.5% and 2% exertedindividually, a higher pressure on yeast growth inhibiting up to 60% the fungal population. However, theviability of yeasts strains to a given concentration of lactic (1%) or acetic (0.25%) acid proved to be relativelystable with YS201 at increasing temperature up to 40°C. Cross stress involving temperature and alcohol orsingle acid stress may be the limiting factor for yeasts pectinolytic growth as starter in controlled cocoafermentation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of fungicides on fungal growth, must fermentation and aroma was monitored. [•] Ametoctradin, dimethomorph and mepanipyrim affected sugars-to-ethanol yield. [•] In unfiltered must, the fermentative activity of yeasts was unaffected. [•] In filtered must, a slight decrease of biomass and ethanol productions were observed. [•] A decrease in fruity aroma was then registered with respect to the control wine. [ABSTRACT FROM AUTHOR]

Abstract: Growth and thermal inactivation curves were obtained for Zygosaccharomyces bailii in acidified aqueous systems resembling low sugar products. Growth curves were modeled using Gompertz equation while thermal inactivation curves were fitted with the Baranyi equation. The parameters of the models were estimated and used to establish the effect of aspartame and other additives (sorbate, xylitol and glucose) on the growth and survival of Z. bailii. Aspartame addition produced different effects on growth rate depending on the solute added and the potassium sorbate concentration. The joint use of xylitol and aspartame showed the lowest growth rates in the absence or in the presence of 0.005% w/w sorbate. Regardless of subinhibitory levels of KS, the addition of aspartame increased the population of the stationary phase of the systems containing glucose or xylitol, suggesting that Z. bailii metabolizes aspartame. The use of aspartame increased the thermal inactivation rates of all systems. Glucose or xylitol addition to the system containing aspartame and sorbate increased the heat sensitivity of Z. bailii. In the absence of sorbate, only glucose decreased the heat resistance of the yeast, whereas xylitol did not affect it. The results obtained highlight the importance of considering the effect of system composition when evaluating microbial stability of food systems. [Copyright &y& Elsevier]

Abstract: We demonstrate a new strategy for the label-free monitoring of yeast cell growth and its interaction with drugs using simple bending-mode of polymer microcantilever biosensors. Saccharomyces cerevisiae strains YN94-1 and YN94-19 were deposited onto microcantilever sensor surfaces and the growth curves corresponding to the bending were investigated under different culture conditions. The real-time polymer microcantilever bending signal revealed distinct growth characteristics of cells cultured in Synthetic Complete (SC) medium with and without the addition of uracil and 5′-fluororotic acid, which are indiscernible using conventional screening methods. In addition, cantilever deflection signals of up to ∼7μm were observed, which can only be explained through surface stress interactions between yeast cells and the polymer cantilevers due to the enhanced sensitivity of the viscoelastic polymer cantilevers. This new method of enhanced sensitivity in static mode microcantilever monitoring of cell growth opens opportunities for highly sensitive applications in the fields of disease diagnosis and drug discovery and testing. [Copyright &y& Elsevier]

Abstract: Mead is a traditional drink that contains 8%–18% (v/v) of ethanol, resulting from the alcoholic fermentation of diluted honey by yeasts. Mead fermentation is a time-consuming process and the quality of the final product is highly variable. Therefore, the present investigation had two main objectives: first, to determine the adequate inoculum size of two commercial wine-making strains of Saccharomyces cerevisiae for the optimisation of mead fermentation; and second, to determine if an increase in yeast pitching rates in batch fermentations altered the resulting aroma profiles. Minor differences were detected in the growth kinetics between the two strains at the lowest pitching rate. With increasing pitching rates net growth of the strain ICV D47 progressively decreased, whereas for the QA23 the increasing inoculum size had no influence on its net growth. The time required to reach the same stage of fermentation ranged from 24 to 96 h depending on the inoculum size. The final aroma composition was dependent on the yeast strain and inoculum size. Fourteen of the twenty-seven volatile compounds quantified could contribute to mead aroma and flavour because their concentrations rose above their respective thresholds. The formation of these compounds was particularly pronounced at low pitching rates, except in mead fermented by strain ICV D47, at 106 CFUs/mL. The esters isoamyl acetate, ethyl octanoate and ethyl hexanoate were the major powerful odourants found in the meads. The results obtained in this study demonstrate that yeast strain and inoculum size can favourably impact mead''s flavour and aroma profiles. [Copyright &y& Elsevier]

Abstract: Recently, carbohydrates biomass from microalgae is considered as a promising and inexpensive feedstock for biofeuls production by microorganism fermentation. The main obstacle of the process is microalgae pretreatment and carbohydrates extraction from algal cell. In this study, comparison of three pretreatment methods was performed and the results showed that ultrasonic assisted extraction (UAE) was very effective. The effects of four parameters (ultrasonic power, extraction time, flow rate and algal cell concentration, respectively) on extraction efficiency were also investigated. Additionally, in order to identify significant factors for glucose yield, combination of these four parameters was examined by using fractional factorial design (FFD) and the regression model was obtained. Meanwhile, the refined model was confirmed as a good fitting model via analysis of variance (ANOVA). After extraction, glucose obtained from microalgae was used as substrate for Rhodosporidium toruloides fermentation and yeast biomass was much higher than that of control culture. [Copyright &y& Elsevier]

The influence of different concentrations of two new fungicides (metiram and pyraclostrobin) on the fermentative activity of Saccharomyces cerevisiae yeast during winemaking process has been evaluated through in vitro assays. These fungicides were assayed as pure active compounds (single and in combination) and as a commercial formulation which contains both fungicides (55% metiram + 5% pyraclostrobin). The presence of pyraclostrobin pure standard in the culture medium, at the highest concentration evaluated (10 mg/L), increased the biomass and ethanol production rate. No effect on the alcoholic fermentation was observed for metiram pure standard due to its low solubility in the synthetic medium. However, a total inhibition of yeast growth was observed in presence of ≥40 mg/L of the commercial formulation. Se analizó, mediante ensayos in vitro, la influencia de diferentes concentraciones de dos nuevos fungicidas - metiram y piraclostrobín - sobre la actividad fermentativa de la levadura Saccharomyces cerevisiae en la elaboración de vino. Estos fungicidas fueron evaluados como materias activas puras, tanto de forma individual como combinada, y como producto fitosanitario comercial formulado con ambas materias activas (55% metiram + 5% piraclostrobín). La presencia de piraclostrobín en el medio de cultivo a la concentración más alta evaluada (10 mg/L) provocó una mayor producción de biomasa y etanol. El metiram, debido a su baja solubilidad en el medio sintético, no mostró ningún efecto sobre la fermentación alcohólica. Por otro lado, concentraciones ≥40 mg/L de la formulación comercial provocaron una inhibición total del crecimiento de la levadura. [ABSTRACT FROM AUTHOR]

The yeast Candida parapsilosis has emerged as a major human pathogen. The fungus is found in diverse environments as well as in different mammalian hosts, indicative of a successful adaptation to various niches. Fatty acids are the building blocks of cell membranes. Thus, the yeast must have evolved efficient ways to assimilate fatty acids from different sources, such as glucose via de novo fatty acid synthesis or lipids via lipolysis. We have recently shown that blocking the fatty acid synthesis pathway or interfering with the production of secreted lipases impeded yeast growth in glucose and lipid-containing media, respectively. However, in a more complex media (e.g., presence of glucose and lipids), blockage of either pathway individually resulted in growth similar to wild-type yeast. Here, we demonstrate that dual inhibition of these pathways significantly decreased yeast growth in complex media. Therefore, we propose that simultaneously targeting secreted lipases and fatty acid pathways might be ideal to combat C. parapsilosis disease, and perhaps other pathogenic fungi. [ABSTRACT FROM AUTHOR]

Gravitational field-flow fractionation (GrFFF) was applied for the study of the growth of Saccharomyces cerevisiae yeast strain, in the presence or the absence of corn and wheat starch granules as immobilization carriers. Fermentations were conducted at different values of pH (3.0, 4.0, 5.0, and 6.0) and initial glucose concentration (177 g/L, 205 g/L, 247 g/L and 300 g/L) in order to find the most favorable situation for the growth and proliferation of Saccharomyces cerevisiae cells. The distinction of the phases of the yeast cell cycle was also succeeded by the same technique. The results indicate that the growth of yeast cells was enhanced at pH 5.0 and glucose concentrations of 177 g/L and 205 g/L. Higher glucose concentrations (247 g/L and 300 g/L) acted as an inhibitor to cell proliferation. Immobilization on wheat starch provided wider peak profiles, suggesting a broad size of cells and lower concentrations of haploid cells comparing to cells immobilized on corn starch granules. The determination of Michaelis-Menten constants for free and immobilized cells proved the higher affinity of immobilized cells towards the substrate. The values found were in good agreement with those reported in literature. [ABSTRACT FROM AUTHOR]

Abstract: Yeast propagation is an old and well established process in breweries. Yet, development is constantly going on and some questions still remain unanswered. The demand for good brewers yeast can be summarized in the following words: A non-stressed, highly vital and viable yeast that is free from infecting organisms. The road to this goes over a carefully designed sanitary propagation plant with an aeration aggregate that is able to supply a sufficient and adequate amount of oxygen to all cells in the propagator without causing mechanical stress to the yeast cells, and an appropriate propagation wort with the right nutrient composition. No matter how much these parameters are optimized it is, however, still only possible to obtain relatively low cell numbers of around 100–200million cells per millilitre equivalent to approximately 2.5–5g dry matter per litre. This cell number can be obtained by consuming only a few degrees Plato. In the case of propagation yeast for re-fermentation not only the cell number is essential, but also the fact that the fermentable sugar in the wort is consumed so that an overpressure is not created in the bottle. In order to avoid loosing time while waiting for the yeast to consume all the sugar another process must be used. The only way to do this, is by learning from the baking yeast industry and perform the propagation in a fed batch reactor whereby the sugar concentration is kept constantly low – though not too low in order to avoid that the yeast grows purely aerobic and therefore may loose some of its fermentation characteristics – during propagation. Therefore, a kind of hybrid process between the traditional brewery propagation and a purely aerobic yeast propagation process seems to be the right solution. The feasibility of this process is discussed. [Copyright &y& Elsevier]

Purpose: To investigate whether extremely-low frequency magnetic field (MF) exposure produce alterations in the growth, cell cycle, survival and DNA damage of wild type (wt) and mutant yeast strains. Materials and methods: wt and high affinity DNA binding factor 1 ( hdf1), radiation sensitive 52 ( rad52), rad52 hdf1 mutant Saccharomyces cerevisiae strains were exposed to 2.45 mT, sinusoidal 50 Hz MF for 96 h. MF was generated by a pair of Helmholtz coils. During this time the growth was monitored by measuring the optical density at 600 nm and cell cycle evolution were analysed by microscopic morphological analysis. Then, yeast survival was assayed by the drop test and DNA was extracted and electrophoresed. Results: A significant increase in the growth was observed for rad52 strain ( P = 0.005, Analysis of Variance [ANOVA]) and close to significance for rad52 hdf1 strain ( P = 0.069, ANOVA). In addition, the surviving fraction values obtained for MF-exposed samples were in all cases less than for the controls, being the P value obtained for the whole set of MF-treated strains close to significance ( P = 0.066, Student's t-test). In contrast, the cell cycle evolution and the DNA pattern obtained for wt and the mutant strains were not altered after exposure to MF. Conclusions: The data presented in the current report show that the applied MF (2.45 mT, sinusoidal 50 Hz, 96 h) induces alterations in the growth and survival of S. cerevisiae strains deficient in DNA strand breaks repair. In contrast, the MF treatment does not induce alterations in the cell cycle and does not cause DNA damage. [ABSTRACT FROM AUTHOR]

Progress in laboratory automation depends not only on automating the physical aspects of scientific experimentation, but also on the intellectual aspects. We present the conceptual design, implementation, and our user-experience of “Adam,” which uses machine intelligence to autonomously investigate the function of genes in the yeast Saccharomyces cerevisiae. These investigations involve cycles of hypothesis formation, design of experiments to test these hypotheses, physical execution of the experiments using laboratory automation, and the analysis of the results. The physical execution of the experiments involves growing specific yeast strains in specific media and measuring growth curves. Hundreds of such experiments can be executed daily without human intervention. We believe Adam to be the first machine to have autonomously discovered novel scientific knowledge. [Copyright &y& Elsevier]

Cytoplasmic male sterility (CMS) has often been associated with abnormal mitochondrial open reading frames (ORF), orfH79 is a mitochondria chimeric gene being responsible for the CMS trait in Honglian (HL) rice. Weakly expressed ORFH79 strongly inhibits the growth of yeast cells. In addition, the content of reactive oxygen species (ROS) in the transformants that expressed ORFH79 was increased by 31%, and ATP was decreased by 41% compared with the control. These results showed ORFH79 peptide is toxic to yeast cells. [ABSTRACT FROM AUTHOR]

We have developed a simple method using a magnetic bar array to anchor nonmagnetic biomolecules for time-lapse analysis and identification. Biomolecules of interest are attached, using linker molecules, to the superparamagnetic beads which are in turn captured at gaps of the magnetic bar array. This micro-array system can be used for various studies and applications such as yeast growth studies, as illustrated in this work, and pyrosequencing. The technology is applicable to a wide variety of biomolecules using the suitable linker molecules, with the merits of low lost and reusability. [ABSTRACT FROM AUTHOR]

Abstract: The evolutionary relationship of indoleamine 2,3-dioxygenase (IDO) to some gastropod myoglobins suggests that IDO may undergo autoxidation in vivo such that one or more currently unidentified electron donors are required to maintain IDO heme iron in the active, ferrous state. To evaluate this hypothesis we have used yeast knockout mutants in combination with a recently developed yeast growth assay for IDO activity in vivo to demonstrate a role for cytochrome b 5 and cytochrome b 5 reductase in maintaining IDO activity in vivo. [Copyright &y& Elsevier]

Abstract: The effects of temperature, NaCl concentration and pH on the growth and lag phase time of Pichia anomala was studied by means of a central composite design. From the response surface obtained, using log2 transformations of maximum specific growth rates (μ) and lag times (λ) as responses, it was deduced that μ depended on the temperature (linear and quadratic effects); while λ was affected (linear effects) by the three variables. The relative effects of variables were studied by means of the generalized z-value. The results for μ were: Z temp, μ (harmonic average of z temp, μ )=6.90, z NaCl, μ =−5.61. The values for λ were: z temp, λ =−4.87, z NaCl, λ =3.36, and z pH, λ =−1.08. The product of the specific growth rate and the lag, h 0 (the “work to be done” during the lag phase) depended (p <0.05) on pH. The effects of NaCl and temperature on h 0 were not significant though they produced a 1.32- and 1.23-fold increase on it. [Copyright &y& Elsevier]

Abstract: This study characterizes the effects of oxygen transfer on the growth and carotenoid (astaxanthin) production of the red yeast Phaffia rhodozyma in liquid cultures. The yeast culture on a liquid medium at 20°C had a critical dissolved oxygen (DO) concentration of 10% air-saturation (0.8mg/L) and a maximum specific oxygen uptake rate of 60mg O2/gcellh. In 250-mL shake-flasks with 50ml liquid medium, poor oxygen transfer resulted in constantly lower DO level than the critical DO in the culture. Both the biomass and carotenoid yields increased with the decrease in liquid volume in flasks and the increase in shaker speed, e.g., 8.0g dw/L biomass and 7.4mg/L carotenoid with 50mL liquid at 200rpm versus 10.7g dw/L biomass and 15.5mg/L carotenoid with 20mL liquid at 250rpm. The oxygen transfer coefficient (K L a) was correlated to shaker speed (N) and liquid volume (V L) by K L a= 0.141 N 0.88 (V L /V o)−0.80 based on linear regression of experimental data (R 2 =0.997, V o =flask volume). The carotenoid yield showed a strong linear correlation with the oxygen transfer rate (R 2 =0.989). These results show that oxygen supply is crucial for carotenoid production in P. rhodozyma liquid cultures. [Copyright &y& Elsevier]