Search

In this study the combinatory effect of several extrinsic factors on reduced (vacuum) pressure fermentations was explored. Specifically, the pressure, temperature, and FAN levels of high gravity Saccharomyces cerevisiae fermentations were manipulated, while yeast morphology was assessed using automated multivariate image analysis. Fermentation attributes including yeast growth, viability, and ethanol production were monitored using standard methods. Across all FAN and temperature levels, reduced pressure (vacuum pressure) fermentations resulted in a greater than or equal number of cells in suspension, higher average viability, and greater ethanol production in comparison to atmospheric pressure fermentations; however, the magnitude of the effect varied with extrinsic factors. The image analysis revealed that while yeast size was extremely variable across all fermentations, the ratio of vacuole to cell area consistently decreased over each fermentation and could be used to predict the point where the yeast experienced a sharp decline in viability ending the fermentation. This study showed that a combination of traditional measurements and novel automated analyses can be used by brewers to anticipate performance and endpoints of their fermentations, and that reduced pressure can have significant effects upon the rate and final ethanol concentration of variable industrial fermentations. [ABSTRACT FROM AUTHOR]

Filamentous growth in Saccharomyces cerevisiae is a stress response commonly induced under nutrient deprivation and by certain alcohols. It is a compound phenotype characterized by pseudohyphal growth, invasion and a shift to more polarized budding. Previous methods have not allowed the time-resolved determination of filamentous growth. Here we present a new method for budding pattern characterization that enables the measurement of filamentous growth and metabolite concentration during yeast cell growth at precise time intervals. By combining chemical cell immobilization and single-cell imaging using an oCelloScope™, this method provides more accurate budding pattern classification compared with previous methods. The applications of the method include, for example, investigation of quorum sensing-controlled yeast filamentous growth and metabolism under stress and identification of toxic metabolites.

In this study the combinatory effect of several extrinsic factors on reduced (vacuum) pressure fermentations was explored. Specifically, the pressure, temperature, and FAN levels of high gravity Saccharomyces cerevisiae fermentations were manipulated, while yeast morphology was assessed using automated multivariate image analysis. Fermentation attributes including yeast growth, viability, and ethanol production were monitored using standard methods. Across all FAN and temperature levels, reduced pressure (vacuum pressure) fermentations resulted in a greater than or equal number of cells in suspension, higher average viability, and greater ethanol production in comparison to atmospheric pressure fermentations; however, the magnitude of the effect varied with extrinsic factors. The image analysis revealed that while yeast size was extremely variable across all fermentations, the ratio of vacuole to cell area consistently decreased over each fermentation and could be used to predict the point where the yeast experienced a sharp decline in viability ending the fermentation. This study showed that a combination of traditional measurements and novel automated analyses can be used by brewers to anticipate performance and endpoints of their fermentations, and that reduced pressure can have significant effects upon the rate and final ethanol concentration of variable industrial fermentations.

The kinetics and success of an industrial fermentation are dependent upon the health of the microorganism(s) responsible. Saccharomyces sp. are the most commonly used organisms in food and beverage production; consequently, many metrics of yeast health and stress have been previously correlated with morphological changes to fermentations kinetics. Many researchers and industries use machine vision to count yeast and assess health through dyes and image analysis. This study assessed known physical differences through automated image analysis taken throughout ongoing high stress fermentations at various temperatures (30 ◦C and 35 ◦C). Measured parameters included sugar consumption rate, number of yeast cells in suspension, yeast cross-sectional area, and vacuole cross-sectional area. The cell morphological properties were analyzed automatically using ImageJ software and validated using manual assessment. It was found that there were significant changes in cell area and ratio of vacuole to cell area over the fermentation. These changes were temperature dependent. The changes in morphology have implications for rates of cellular reactions and efficiency within industrial fermentation processes. The use of automated image analysis to quantify these parameters is possible using currently available systems and will provide additional tools to enhance our understanding of the fermentation process. [ABSTRACT FROM AUTHOR]

Assessment of viable biomass is challenging in bioprocesses involving complex media with distinct biomass and media particle populations. Biomass monitoring in these circumstances usually requires elaborate offline methods or sophisticated inline sensors. Reliable monitoring tools in an at-line capacity represent a promising alternative but are still scarce to date. In this study, a flow cytometry-based method for biomass monitoring in spent sulfite liquor medium as feedstock for second generation bioethanol production with yeast was developed. The method is capable of (i) yeast cell quantification against medium background, (ii) determination of yeast viability, and (iii) assessment of yeast physiology though morphological analysis of the budding division process. Thus, enhanced insight into physiology and morphology is provided which is not accessible through common online and offline biomass monitoring methods. To demonstrate the capabilities of this method, firstly, a continuous ethanol fermentation process of Saccharomyces cerevisiae with filtered and unfiltered spent sulfite liquor media was analyzed. Subsequently, at-line process monitoring of viability in a retentostat cultivation was conducted. The obtained information was used for a simple control based on addition of essential nutrients in relation to viability. Thereby, inter-dependencies between nutrient supply, physiology, and specific ethanol productivity that are essential for process design could be illuminated. [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.

The kinetics and success of an industrial fermentation are dependent upon the health of the microorganism(s) responsible. Saccharomyces sp. are the most commonly used organisms in food and beverage production; consequently, many metrics of yeast health and stress have been previously correlated with morphological changes to fermentations kinetics. Many researchers and industries use machine vision to count yeast and assess health through dyes and image analysis. This study assessed known physical differences through automated image analysis taken throughout ongoing high stress fermentations at various temperatures (30 °C and 35 °C). Measured parameters included sugar consumption rate, number of yeast cells in suspension, yeast cross-sectional area, and vacuole cross-sectional area. The cell morphological properties were analyzed automatically using ImageJ software and validated using manual assessment. It was found that there were significant changes in cell area and ratio of vacuole to cell area over the fermentation. These changes were temperature dependent. The changes in morphology have implications for rates of cellular reactions and efficiency within industrial fermentation processes. The use of automated image analysis to quantify these parameters is possible using currently available systems and will provide additional tools to enhance our understanding of the fermentation process.

The present study describes the isolation of the novel strain Candida intermedia CBS 141442 and investigates the potential of this microorganism for the conversion of lignocellulosic streams. Different C. intermedia clones were isolated during an adaptive laboratory evolution experiment under the selection pressure of lignocellulosic hydrolysate and in strong competition with industrial, xylose-fermenting Saccharomyces cerevisiae cells. Isolates showed different but stable colony and cell morphologies when growing in a solid agar medium (smooth, intermediate and complex morphology) and liquid medium (unicellular, aggregates and pseudohyphal morphology). Clones of the same morphology showed similar fermentation patterns, and the C. intermedia clone I5 (CBS 141442) was selected for further testing due to its superior capacity for xylose consumption (90% of the initial xylose concentration within 72 h) and the highest ethanol yields (0.25 ± 0.02 g ethanol/g sugars consumed). Compared to the well-known yeast Scheffersomyces stipitis, the selected strain showed slightly higher tolerance to the lignocellulosic-derived inhibitors when fermenting a wheat straw hydrolysate. Furthermore, its higher glucose consumption rates (compared to S. stipitis) and its capacity for glucose and xylose co-fermentation makes C. intermedia CBS 141442 an attractive microorganism for the conversion of lignocellulosic substrates, as demonstrated in simultaneous saccharification and fermentation processes.

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]

Acrylic coatings were prepared by UV-induced crosslinking of two different diacrylates monomers having the same molecular weight but containing either a polyethyleneoxide chain or an alkylic chain. The fouling behavior of the UV-cured coatings was assessed by a simple set-up, monitoring the growth of Rhodotorula mucilaginosa and the adhesion of the film formed by the pigmented yeast. The effect of the monomers, the photoinitiator and the polymers on the microorganism growth was studied. The monomers partially inhibited the yeast growth, the coatings showed fouling release activity: yeast could grow on both coatings but with different morphology, they detached easily by washing depending on the type of coating. By examining the physico-chemical and mechanical properties of the polymers, the fouling release behavior was found mostly dependent on the surface tension and the water uptake of the coatings. [ABSTRACT FROM AUTHOR]

• Fusion of Pc4CL1 and VvSTS facilitated the accumulation of resveratrol. • Redirecting metabolic flux of the precursor increased resveratrol production. • Multi-copy integration of key genes and knockout of DGA1 facilitated the process. • Y. lipolytica performed best for resveratrol production in the yeast morphology. • The highest titer for microbially produced resveratrol (22.5 g/L) reported to date. Resveratrol is a polyphenol with numerous applications in food, pharma, and cosmetics. Lack of precursors and low titer are the main problems hindering industrial scale resveratrol production. Based on previous prescreening, expressing the combination of FjTAL , Pc4CL1 and VvSTS achieved the best resveratrol titer. This was further improved to 235.1 mg/L through engineering the shikimic acid pathway, applying a modular enzyme assembly of Pc4CL1 and VvSTS , enhancing p -coumaric acid supply and diverting glycolytic flux toward erythrose-4-phosphate. The titer was increased to 819.1 mg/L following two rounds of multicopy integration of resveratrol biosynthesis and malonyl-CoA supply, respectively. The titer reached 22.5 g/L with a yield on glucose of 65.5 mg/g using an optimum fed-batch strategy in a 5 L bioreactor with morphology control. This research is the highest report on the de novo production of resveratrol in Yarrowia lipolytica and the findings lay a solid foundation for other producing polyphenols. [ABSTRACT FROM AUTHOR]

Baker's yeasts have long been known to be one of the oldest microbiological starter of food. The objective of study was to evaluate the potentials of Torulaspora delbrueckii JK08 and Pichia anomala JK04 as baker's yeasts. The cells are noticeably smaller and the growth was slower than that of S. cerevisiae, the conventional baker's yeast. These strains showed a lower leavening ability at an equal cells concentration. However, it tremendously increased when the cells concentration were raised, notably for P. anomala JK04. Interestingly, the strains showed remarkable tolerance to hyperosmotic and cation stresses. It was evident that the strains produced smaller bread loaf and consequently lower specific volume. This affected the textural characteristics of bread, as it had harder texture and greater chewiness. In contrast, the strains produced better springiness, brighter crust and crumb colour. The shelf-life of bread was comparable among the strains, except for P. anomala JK04, for which it was slightly shorter. According to the consumer evaluation, T. delbrueckii JK08 exhibited superior flavour, while P. anomala JK04 showed superior mouth feel. Despite of that, T. delbrueckii JK08 and P. anomala JK04 did not perform better in every aspect, employing its superiority in particular manner are greatly promising in bread making. [ABSTRACT FROM AUTHOR]

Filamentous growth in Saccharomyces cerevisiae is a stress response commonly induced under nutrient deprivation and by certain alcohols. It is a compound phenotype characterized by pseudohyphal growth, invasion and a shift to more polarized budding. Previous methods have not allowed the time-resolved determination of filamentous growth. Here we present a new method for budding pattern characterization that enables the measurement of filamentous growth and metabolite concentration during yeast cell growth at precise time intervals. By combining chemical cell immobilization and single-cell imaging using an oCelloScope™, this method provides more accurate budding pattern classification compared with previous methods. The applications of the method include, for example, investigation of quorum sensing-controlled yeast filamentous growth and metabolism under stress and identification of toxic metabolites.

The present study describes the isolation of the novel strain Candida intermedia CBS 141442 and investigates the potential of this microorganism for the conversion of lignocellulosic streams. Different C. intermedia clones were isolated during an adaptive laboratory evolution experiment under the selection pressure of lignocellulosic hydrolysate and in strong competition with industrial, xylose-fermenting Saccharomyces cerevisiae cells. Isolates showed different but stable colony and cell morphologies when growing in a solid agar medium (smooth, intermediate and complex morphology) and liquid medium (unicellular, aggregates and pseudohyphal morphology). Clones of the same morphology showed similar fermentation patterns, and the C. intermedia clone I5 (CBS 141442) was selected for further testing due to its superior capacity for xylose consumption (90% of the initial xylose concentration within 72 h) and the highest ethanol yields (0.25 ± 0.02 g ethanol/g sugars consumed). Compared to the well-known yeast Scheffersomyces stipitis, the selected strain showed slightly higher tolerance to the lignocellulosic-derived inhibitors when fermenting a wheat straw hydrolysate. Furthermore, its higher glucose consumption rates (compared to S. stipitis) and its capacity for glucose and xylose co-fermentation makes C. intermedia CBS 141442 an attractive microorganism for the conversion of lignocellulosic substrates, as demonstrated in simultaneous saccharification and fermentation processes. [ABSTRACT FROM AUTHOR]

In this paper the effect of aflatoxin B 1 , 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.