Yeast Growth Research Articles

Bee venom: A potential natural alternative to conventional preservatives for prolonging the shelf-life of soft cheese ‘Talaga’

The study aims to explore bee venom (honey-BV) as a potential natural preservative for "Tallaga" soft cheese. Characterization of the active compounds in honey-BV was conducted via chromatographic analyses. Antimicrobial efficacy against pathogenic bacteria and fungi was evaluated, and minimum inhibitory concentration (MIC) was determined. Subsequently, honey-BV was applied to Tallaga cheese at 15 mg/g concentrations. The main active ingredients identified in bee venom were apamin (2%) and melittin (48.7%). Both concentrations of bee venom (100 and 200 mg/mL) exhibited significant antifungal and antibacterial properties against tested organisms, with MIC values varied from 0.2 to 0.5 mg/mL for bacteria to 3–13 mg/mL for fungi. Application of honey-BV in Tallaga cheese resulted in complete elimination of Staphylococcal populations after 2 weeks of cold storage, with no detectable growth of molds or yeasts throughout the storage period. Additionally, a steady decrease in aerobic plate count was observed over time. In summary, honey-BV holds promise as a natural preservative for soft cheese, however, more investigation is required to optimize the concentration for economic viability, taking into account health benefits and safety considerations.

Влияние геотермальной воды в составе твердых сред культивирования на морфологические свойства дрожжей рода Saccharomyces

The influence of geothermal waters located on the territory of the city of Makhachkala (Republic of Dagestan), in the composition of solid cultivation media, on the cultural and morphological features of genus Saccharomyces yeast was studied. Changes in cell properties and the formation of specific parameters of giant yeast colonies S. cerevisiae Y-503, S. cerevisiae DAW-3a, S. oviformis M-12x have been established. For YPD and PD media, as a result of a series of experiments, optimal options were selected containing geothermal and distilled water in a ratio of 1:1 (well No. 36) and 2:1 (well No. 26). It was shown that the YPD medium was optimal for yeast growth, while in the population of the tetraploid Y-503 strain, the average cell size was slightly larger than cell strain M-12x and significantly exceeded the DAW-3a values. Installed that the use of diluted water from well No. 36 in the cultivation medium is most effective and leads to accelerated growth of yeast colonies. In the variant geothermal / distilled water, this indicator exceeded the control by 1.3 (Y-503, M-12x) times; in the variant with geothermal water without dilution - by 1.6 (Y-503) and 1.4 (M-12x) times. The cells of the S. cerevisiae Y-503 strain, regardless of the medium used, are characterized by the presence of various forms, including elongated ones; DAW-3a - exceptionally rounded; S. oviformis M-12x - rounded and oval shapes. A comparative analysis of the parameters of the colonies showed that all variants are characterized by a rounded shape, a radially striated surface; flat, with a convex center profile; light beige color and pasty, spreadable texture. As a result of our research, a modified nutrient medium PD has been developed - an agar for growing yeast, containing geothermal water from well No. 36 of the Makhachkala field as an additional source of mineral and organic compounds. The proposed composition of the medium is of interest for its further use in microbiological studies.

Physicochemical, Antioxidant, and Sensory Characteristics of Sponge Cake Fortified with Quinoa Flour, Oolong, and White Tea Powder

Nowadays, there is a growing demand for healthy foods enriched with various functional bioactive ingredients. Cakes are ready-to-eat baked products consumed worldwide and are suitable for the development of functional food products. In this study, a Box–Behnken design was used to investigate the effect of three independent variables, including oolong tea powder (OT, 0–20%), white tea powder (WT, 0–15%), and quinoa flour (QF, 0–40%), on the quality characteristics of sponge cake during 21 days of storage. Following the evaluation of the model, the optimum levels of ingredients for the preparation of sponge cake were 15% WT, 17.17% OT, and 24.97% QF. Total phenolic content of 52.09 mg gallic acid/100 g, antioxidant activity of 0.068 mg/mL, overall acceptability of 4.89, lightness of 47.94, and peroxide value of 0.68 mEq/kg were obtained under optimized conditions. The growth of molds and yeasts was prevented during storage time. The hardness, gumminess, and chewiness of the optimized sponge cake improved with increasing WT, OT, and QF levels in comparison to the control. Scanning electron micrographs showed a more porous structure in optimized cake samples. In conclusion, the utilization of OT, WT, and QF as phenolic compounds in sponge cake led to an increase in its nutritional value and improved shelf life.

Morphology, Development, and Pigment Production of Talaromyces marneffei are Diversely Modulated Under Physiologically Relevant Growth Conditions.

Talaromyces marneffei is an opportunistic pathogenic fungus that mainly affects HIV-positive individuals endemic to Southeast Asia and China. Increasing efforts have been made in the pathogenic mechanism and host interactions understanding of this pathogen in the last two decades; however, there are still no conclusions on how T. marneffei was transmitted from the donor bamboo rats to humans. A perception that the failure of fungus isolation from soil was attributed to the low salt tolerance of T. marneffei. Therefore, the effect of environmental fluctuations in fungal growth and development is fundamental for the characterization of its origin and fungal biology understanding. Herein, we characterized high osmolarity, pH, metal ions, nutrients, and oxidative stress have versatile effects on T. marneffei hyphal or yeast growth, conidia generation, and pigment production. Among these, high pH, low glucose amounts, and the inorganic nitrogen ammonium tartrate stimulated the red pigment production, whereas high osmolarity, high pH, and the inorganic nitrogen sodium nitrate could significantly accelerate the conidia generation. Specifically, zinc starvation repressed conidia generation and prevented the wrinkled yeast colony formation, indicating the function of zinc regulators in pathogenicity regulation. Since conidia are recognized as the infectious propagules, the effects characterization of different environmental factors in T. marneffei morphology in this work will not only expand the growth and pathogenic biology understanding of the fungus but also provide more clues for the T. marneffei infection transmission origin investigation.

Engineering Saccharomyces cerevisiae for targeted hydrolysis and fermentation of glucuronoxylan through CRISPR/Cas9 genome editing

BackgroundThe abundance of glucuronoxylan (GX) in agricultural and forestry residual side streams positions it as a promising feedstock for microbial conversion into valuable compounds. By engineering strains of the widely employed cell factory Saccharomyces cerevisiae with the ability to directly hydrolyze and ferment GX polymers, we can avoid the need for harsh chemical pretreatments and costly enzymatic hydrolysis steps prior to fermentation. However, for an economically viable bioproduction process, the engineered strains must efficiently express and secrete enzymes that act in synergy to hydrolyze the targeted polymers.ResultsThe aim of this study was to equip the xylose-fermenting S. cerevisiae strain CEN.PK XXX with xylanolytic enzymes targeting beechwood GX. Using a targeted enzyme approach, we matched hydrolytic enzyme activities to the chemical features of the GX substrate and determined that besides endo-1,4-β-xylanase and β-xylosidase activities, α-methyl-glucuronidase activity was of great importance for GX hydrolysis and yeast growth. We also created a library of strains expressing different combinations of enzymes, and screened for yeast strains that could express and secrete the enzymes and metabolize the GX hydrolysis products efficiently. While strains engineered with BmXyn11A xylanase and XylA β-xylosidase could grow relatively well in beechwood GX, strains further engineered with Agu115 α-methyl-glucuronidase did not display an additional growth benefit, likely due to inefficient expression and secretion of this enzyme. Co-cultures of strains expressing complementary enzymes as well as external enzyme supplementation boosted yeast growth and ethanol fermentation of GX, and ethanol titers reached a maximum of 1.33 g L− 1 after 48 h under oxygen limited condition in bioreactor fermentations.ConclusionThis work underscored the importance of identifying an optimal enzyme combination for successful engineering of S. cerevisiae strains that can hydrolyze and assimilate GX. The enzymes must exhibit high and balanced activities, be compatible with the yeast’s expression and secretion system, and the nature of the hydrolysis products must be such that they can be taken up and metabolized by the yeast. The engineered strains, particularly when co-cultivated, display robust growth and fermentation of GX, and represent a significant step forward towards a sustainable and cost-effective bioprocessing of GX-rich biomass. They also provide valuable insights for future strain and process development targets.

A yeast based assay establishes the pathogenicity of novel missense ACTA2 variants associated with aortic aneurysms.

The ACTA2 gene codes for alpha-smooth muscle actin, a critical component of the contractile apparatus of the vascular smooth muscle cells. Autosomal dominant variants in the ACTA2 gene have been associated to familial non-syndromic thoracic aortic aneurysm/dissection (TAAD). They are thought to act through a dominant-negative mechanism. These variants display incomplete penetrance and variable expressivity, complicating the validation of ACTA2 variants pathogenicity by family segregation studies. In this study, we developed a yeast based assay to test putative TAAD-associated ACTA2 variants. We identified five new heterozygous ACTA2 missense variants in TAAD patients through next generation sequencing. We decided to test their pathogenicity in Saccharomyces cerevisiae, since yeast actin is very similar to human alpha-smooth muscle actin, and the residues at which the TAAD-associated variants occur in ACTA2 are well conserved. A wild type yeast strain was transformed with a vector expressing the different mutant alleles, to model the heterozygous condition of patients. Then, we evaluated yeast growth by spot test and cytoskeletal and mitochondrial morphology by fluorescence microscopy. We found that mutant yeast strains displayed only mild growth defects but a significant increase in the percentage of cells with abnormal mitochondrial distribution and abnormal organization of the actin cytoskeleton compared to controls. All variants appeared to interfere with the activity of wild type actin in yeast, suggesting a dominant-negative pathogenic mechanism. Our results demonstrate the utility of using the yeast actin model system to validate the pathogenicity of TAAD-associated ACTA2 variants.

Gamma irradiation and ozone application as preservation methods for longer-term storage of bee pollen

Bee pollen is a healthy product with a good nutritional profile and therapeutic properties. Its high moisture content, however, promotes the growth of bacteria, molds, and yeast during storage commonly result in product degradation. Therefore, the aim of this study is to assess the effectiveness of gamma irradiation (GI) and ozone (OZ) as bee pollen preservation methods for longer storage time, as well as whether they are influenced by pollen species. To do that, GI at a dosage of 2.5, 5.0, and 7.5 kGy was applied at a rate of 0.68 kGy/h and OZ application at a concentration of 0.01, 0.02, and 0.03 g/m3 was applied for one time for 6 h, to Egyptian clover and maize bee pollen, then stored at ambient temperature for 6 months. We then determined the total phenolic content (TPC) and antioxidant activity of treated and non-treated pollen samples at 0, 3, and 6 months of storage. Total bacteria, mold, and yeast count were also evaluated at 0, 2, 4, and 6 months. Statistical analyses revealed that, TPC, antioxidant, and microbial load of both clover and maize pollen samples were significantly (p < 0.05) affected by both treatment and storage time and their interaction. Both methods were extremely effective at preserving the antioxidant properties of pollen samples after 6 months of storage at room temperature. Furthermore, the highest concentrations of both GI and OZ applications completely protected pollen samples from mold and yeast while decreasing bacterial contamination. GI at the highest dose (7.5 KGy) was found to be more effective than other GI doses and OZ application in preserving biologically active compounds and lowering the microbial count of pollen samples for 6 months. As a result, we advise beekeepers to use GI at this dose for longer-term storage.

Investigation of wine fermentation of three-leaf cayratia (Cayratia trifolia L.) using Saccharomyces cerevisiae 2.1

Background Cayratia trifolia has been extensively studied for its bioactive components and medicinal properties. This study was carried out to evaluate the fermentation ability of Saccharomyces cerevisiae 2.1 yeast to determine suitable fermentation conditions. Methods The initial sugar content for three-leaf cayratia fermentation and fermentation efficiency were calculated. The temperature for three-leaf cayratia fermentation, incubation time, and preliminary 1 liter of three-leaf cayratia wine fermentation were determined. All treatments showed that the total sugar content decreased after 9 days of fermentation compared to the initial level. Temperature during fermentation has a direct effect on yeast activity. Temperature increases the growth of yeast and speed of enzyme activity. The fermentation time changes depending on temperature, initial soluble solid contents, and yeast strains, leading to changes in the ethanol content after the end of fermentation. Results The results showed that the S. cerevisiae 2.1 was able to ferment at room temperature with an initial pH of 4.5, 24 °Brix, and a yeast density of 107 cells/mL. The appropriate fermentation conditions determined for S. cerevisiae 2.1 were 24 °Brix and incubation at room temperature (28-33°C) with a fermentation time of 11 days. Conclusion In 1-L scale fermentation, three-leaf cayratia wine had 9.46% (v/v) and the fermentation efficiency was 90.34%. The wine produced had a unique color, flavor, and aroma that met the sensory evaluation of the Vietnamese national standard TCVN-3217:79.

Optimization of a Chlorella–Saccharomyces co–culture system for enhanced metabolite productivity

Microalgae and yeast co–culture systems are gaining interest as a promising method for higher production of biomass and metabolites. However, because these organisms have particular cultivation requirements, optimization of culture conditions is needed for suitable growth and productivity of the co–culture. This work examines the effects of cultivation media macronutrient composition on the growth and metabolite production of co–cultures of either Chlorella vulgaris or Chlorella sorokiniana with a strain of Saccharomyces cerevisiae. Specifically, the consequence of glucose, yeast extract and peptone supplementation on the physiological responses of the co–culture system was investigated. The co–culture responses were equivalent for both Chlorella species, although C. sorokiniana could maintain a more stable population ratio with yeast. The addition of glucose with peptone significantly enhanced biomass production of the co–culture by approximately 2–fold in comparison to microalgae or yeast monocultures, while the addition of glucose alone or in combination with yeast extract did not exhibit the same effect. An approximately 3–fold increase in lipid content was observed in the co–culture samples under glucose–only supplementation, where yeast growth was restricted. The addition of glucose and yeast extract enhanced the growth of yeast monocultures, but this did not benefit the co–culture. Fourier transform infrared spectroscopy analysis revealed different metabolic fingerprints of the monoculture and the co–culture samples grown in glucose and peptone containing medium, which indicated higher abundance of metabolites including lipids, proteins, carbohydrates in the co–culture samples. Specifically, total protein yields in the co–cultures were increased by 1.6– to 1.7–fold in comparison to microalgae monoculture while total lipid yields were increased by 3.6– to 5.1–fold in the co–cultures. This work highlights the importance of organic carbon and nitrogen availability for microalgae–yeast co–culture growth and their potential for a wide range of valuable applications including nutritional and bioenergy uses.

Restricted glycolysis is a primary cause of the reduced growth rate of zinc-deficient yeast cells

Zinc is required for many critical processes, including intermediary metabolism. In Saccharomyces cerevisiae, the Zap1 activator regulates the transcription of ∼80 genes in response to Zn supply. Some Zap1-regulated genes are Zn transporters that maintain Zn homeostasis, while others mediate adaptive responses that enhance fitness. One adaptive response gene encodes the 2-cysteine peroxiredoxin Tsa1, which is critical to Zn-deficient (ZnD) growth. Depending on its redox state, Tsa1 can function as a peroxidase, a protein chaperone, or a regulatory redox sensor. In a screen for possible Tsa1 regulatory targets, we identified a mutation (cdc19S492A) that partially suppressed the tsa1Δ growth defect. The cdc19S492A mutation reduced activity of its protein product, pyruvate kinase isozyme 1 (Pyk1), implicating Tsa1 in adapting glycolysis to ZnD conditions. Glycolysis requires activity of the Zn-dependent enzyme fructose-bisphosphate aldolase 1, which was substantially decreased in ZnD cells. We hypothesized that in ZnD tsa1Δ cells, the loss of a compensatory Tsa1 regulatory function causes depletion of glycolytic intermediates and restricts dependent amino acid synthesis pathways, and that the decreased activity of Pyk1S492A counteracted this depletion by slowing the irreversible conversion of phosphoenolpyruvate to pyruvate. In support of this model, supplementing ZnD tsa1Δ cells with aromatic amino acids improved their growth. Phosphoenolpyruvate supplementation, in contrast, had a much greater effect on growth rate of WT and tsa1Δ ZnD cells, indicating that inefficient glycolysis is a major factor limiting yeast growth. Surprisingly however, this restriction was not primarily due to low fructose-bisphosphate aldolase 1 activity, but instead occurs earlier in glycolysis.

Study of the effect of calcium signal participating in the antioxidant mechanism of yeast under high-sugar environment.

Saccharomyces cerevisiae is susceptible to high-sugar stress in the production of bioethanol, wine and bread. Calcium signal is widely involved in various physiological and metabolic activities of cells. The present study aimed to explore the effects of Ca2+ signal on the antioxidant mechanism of yeast during high-sugar fermentation. Compared to yeast without available Ca2+, yeast in the high glucose with Ca2+ group had higher dry weight, higher ethanol output at 12 and 24 h and higher glycerol output at 24 and 36 h. During the whole growth process, the trehalose synthesis capacity of yeast in the high glucose with Ca2+ group was lower and intracellular reactive oxygen species content was higher compared to yeast without available Ca2+. Intracellular malondialdehyde content of yeast under high glucose with Ca2+ was significantly lower than yeast under high glucose without available Ca2+ except for 6 h. The superoxide dismutase and catalase activities of yeast and glutathione content were higher in the high glucose with Ca2+ group compared to yeast in high glucose without available Ca2+. The expression levels of SOD1, GSH1, GPX2 genes were higher for high glucose without available Ca2+ at 6 h, while yeast in the high glucose with Ca2+ group had a higher expression of antioxidant-related genes except SOD1 and CTT1 at 12 h. The expression levels of antioxidant-related genes of yeast for high glucose with Ca2+ were higher at 24 h, and those of genes except SOD1 of yeast in the high glucose with Ca2+ group were higher at 36 h. High-glucose stress limited the growth of yeast, while a moderate extracellular Ca2+ signal could improve the antioxidant capacity of yeast in a high-glucose environment by regulating protectant metabolism and enhancing the antioxidant enzyme activity and expression of antioxidant genes in a high-sugar environment. © 2024 Society of Chemical Industry.

CALMODULIN-LIKE16 and PIN-LIKES7a cooperatively regulate rice seedling primary root elongation under chilling.

Low-temperature sensitivity at the germination stage is a challenge for direct seeding of rice in Asian countries. How Ca2+ and auxin (IAA) signaling regulate primary root growth under chilling remains unexplored. Here, we showed that OsCML16 interacted specifically with OsPILS7a to improve primary root elongation of early rice seedlings under chilling. OsCML16, a subgroup 6c member of the OsCML family, interacted with multiple cytosolic loop regions of OsPILS7a in a Ca2+-dependent manner. OsPILS7a localized to the endoplasmic reticulum membranes and functioned as an auxin efflux carrier in a yeast growth assay. Transgenics showed that presence of OsCML16 enhanced primary root elongation under chilling, whereas the ospils7a knockout mutant lines showed the opposite phenotype. Moreover, under chilling conditions, OsCML16 and OsPILS7a-mediated Ca2+ and IAA signaling and regulated the transcription of IAA signaling-associated genes (OsIAA11, OsIAA23, and OsARF16) and cell division marker genes (OsRAN1, OsRAN2, and OsLTG1) in primary roots. These results show that OsCML16 and OsPILS7a cooperatively regulate primary root elongation of early rice seedlings under chilling. These findings enhance our understanding of the crosstalk between Ca2+ and IAA signaling and reveal insights into the mechanisms underlying cold-stress response during rice germination.

A Matlab-based application for quantification of yeast cell growth on solid media.

Quantitative assessment of growth and survival is a suitable technique in studying biochemical, genetic and physiological processes in the cells. The budding yeast Saccharomyces cerevisiae is one of the most widely used eukaryotic model organisms for studying cellular mechanisms and processes in evolutionarily distant species, including humans. Yeast growth can be evaluated on both liquid and solid media by measuring cell suspension turbidity and colony forming units, respectively. Several software tools utilizing different parameters have been proposed to quantify yeast growth on solid media. Here, we developed a Matlab-based application which provides a rapid and robust quantitative yeast growth analysis from spot plating assay. Spot plating assay is a typical procedure to evaluate yeast growth in low-throughput laboratory settings, including growth on different nutrient sources or treatment with specific stressors. The app has a one-step installation process, a self-explanatory interface and shorter analysis steps compared with previous established methods, providing a useful tool for both expert and non-expert yeast researchers.

Hurdles Techniques (Combined Effects): A Novel Approach for Enhanced Broccoli Florets Stability, Quality, and Safety

This study demonstrates the changes in broccoli heads samples sensory, physicochemical, chemias blanching at 100 °C for 90 seconds, then dipping for 10 minutes in a coating solution concal, and microbial load after harvest. The samples were preserved using hurdles techniques such taining 0.15% potassium metabisulfite, 4% sodium chloride, 1% citric, 0.2% sodium benzoate and 1% chitosan. After coating samples were divided into two groups, one packaged using the aerobic method (A.P), and the other by vacuum method (V.P). Coated broccoli was stored at two conditions (ambient at 25 ± 3 °C and refrigeration at 4 ± 1 °C) for different period intervals. The control sample was blanched and packaged aerobically (uncoated). The combined treatments delayed the development loss of weight, titratable acid (TA), chlorophyll, and carotenoids, and prevented the growth of aerobic, anaerobic, psychrotrophic, coli form, mold, and yeast in the stored samples. Coated plus V.P. treatment demonstrated the highest weight, pigments, and TA values during storage. Further-more, it achieved the highest score in sensory evaluation after 50 and 240 days of both ambient and cold storage. Moreover, it inhibited the growth of tested microorganisms. So best treatment for the preservation of broccoli between 50 and 240 days of storage period was coated plus V.P. The combined technology application will lead to a safe product with optical shelf-life, improve microbial stability, and sensory quality. Thus, this technology is a technology that aims to improve the overall quality of food.

Dominant NARS1 mutations causing axonal Charcot-Marie-Tooth disease expand NARS1-associated diseases.

Pathogenic variants in six aminoacyl-tRNA synthetase (ARS) genes are implicated in neurological disorders, most notably inherited peripheral neuropathies. ARSs are enzymes that charge tRNA molecules with cognate amino acids. Pathogenic variants in asparaginyl-tRNA synthetase (NARS1) cause a neurological phenotype combining developmental delay, ataxia and demyelinating peripheral neuropathy. NARS1 has not yet been linked to axonal Charcot-Marie-Tooth disease. Exome sequencing of patients with inherited peripheral neuropathies revealed three previously unreported heterozygous NARS1 variants in three families. Clinical and electrophysiological details were assessed. We further characterized all three variants in a yeast complementation model and used a knock-in mouse model to study variant p.Ser461Phe. All three variants (p.Met236del, p.Cys342Tyr and p.Ser461Phe) co-segregate with the sensorimotor axonal neuropathy phenotype. Yeast complementation assays show that none of the three NARS1 variants support wild-type yeast growth when tested in isolation (i.e. in the absence of a wild-type copy of NARS1), consistent with a loss-of-function effect. Similarly, the homozygous knock-in mouse model (p.Ser461Phe/Ser472Phe in mouse) also demonstrated loss-of-function characteristics. We present three previously unreported NARS1 variants segregating with a sensorimotor neuropathy phenotype in three families. Functional studies in yeast and mouse support variant pathogenicity. Thus, NARS1 is the seventh ARS implicated in dominant axonal Charcot-Marie-Tooth disease, further stressing that all dimeric ARSs should be evaluated for Charcot-Marie-Tooth disease.

Effects of storage time and different sugar types on color characteristics, bioactive compounds, and antioxidant capacity of jaboticaba jellies

The objective of this study was to evaluate the effects of storage time and the use of different sugar types (crystal, refined, demerara, brown) on color characteristics, bioactive compounds, and antioxidant capacity of jaboticaba jellies. All analyses (microbiological, color, anthocyanins, vitamin C, total phenolic compounds, and antioxidant capacity by ABTS, DPPH, and β-carotene/linoleic acid systems) were performed for 120 days. The results were evaluated by means test and Pearson correlation. It was found that the sugars used in preparation and storage influenced the characteristics of jaboticaba jellies, and mold and yeast growth remained within the standards allowed by Brazilian legislation. All jellies were darkened during storage. Bioactive compound degradation was observed, and antioxidant capacity was reduced. Positive correlations were observed. Thus, demerara sugar, even though it does not provide bright colors in jellies, is the most beneficial for the production of jaboticaba jellies, due to the presence of nutritional compounds.

Effect of laser bioprinting on growth characteristics of yeasts

Laser-induced forward transfer (LIFT) can be helpful for bioprinting of microbial cells, but data on its impact on the microbial physiology are scarce. The aim of study was to investigate the LIFT effect on eukaryotic microorganisms (yeasts) growth characteristics. Candida albicans, Lipomyces lipofer and Saitozyma podzolica yeasts were printed on solid and liquid nutrient media and compared with traditional methods of inoculation. The laser bioprinting affects growth patterns of yeasts, leading to formation of subpopulations with different growth characteristics. The data obtained highlight necessity of studies of the LIFT effect on microorganisms’ physiology.

Production of iron enriched Saccharomyces boulardii: impact of process variables

About half of the 1.62 billion cases of anemia are because of poor diet and iron deficiency. Currently, the use of iron-enriched yeasts can be used as the most effective and possible way to prevent and treat anemia due to the ability of biotransformation of mineral compounds into the organic form. In this research, for the first time, Saccharomyces (S.) boulardii was used for iron enrichment with the aim that the probiotic properties of yeast provide a potential iron supplement besides improving the bioavailability of iron. Also, due to its higher resistance than other Saccharomyces strains against stresses, it can protect iron against processing temperatures and stomach acidic-enzymatic conditions. So, the effect of three important variables, including concentration of iron, molasses and KH2PO4 on the growth and biotransformation of yeast was investigated by the Box-Behnken design (BBD). The best conditions occurred in 3 g/l KH2PO4, 20 g/l molasses and 12 mg/l FeSO4 with the highest biotransformation 27 mg Fe/g dry cell weight (DCW) and 6 g/l biomass weight. Such yeast can improve fermented products, provide potential supplement, and restore the lost iron of bread, which is a useful iron source, even for vegetarians-vegans and play an important role in manage with anemia. It is recommended that in future researches, attention should be paid to increasing the iron enrichment of yeast through permeabilizing the membrane and overcoming the structural barrier of the cell wall.

Competition for Nitrogen Resources: An Explanation of the Effects of a Bioprotective Strain Metschnikowia pulcherrima on the Growth of Hanseniaspora Genus in Oenology.

As a biological alternative to the antimicrobial action of SO2, bioprotection has been proposed to winemakers as a means to limit or prevent grape musts microbial alteration. Competition for nitrogenous nutrients and for oxygen are often cited as potential explanations for the effectiveness of bioprotection. This study analyses the effect of a bioprotective M. pulcherrima strain on the growth of one H. valbyensis strain and one H. uvarum strain. Bioprotection efficiency was observed only against H. valbyensis inoculated at the two lowest concentrations. These results indicate a potential species-dependent efficiency of the bioprotective strain and a strong impact of the initial ratio between bioprotective and apiculate yeasts. The analysis of the consumption of nitrogen compounds revealed that leucine, isoleucine, lysine and tryptophan were consumed preferentially by all three strains. The weaker assimilation percentages of these amino acids observed in H. valbyensis at 24 h growth suggest competition with M. pulcherrima that could negatively affects the growth of the apiculate yeast in co-cultures. The slowest rate of O2 consumption of H. valbyensis strain, in comparison with M. pulcherrima, was probably not involved in the bioprotective effect. Non-targeted metabolomic analyses of M. pulcherrima and H. valbyensis co-culture indicate that the interaction between both strains particularly impact lysin and tryptophan metabolisms.

Fermentation Kinetic and Alpha-Amylase Inhibition Studies of Mao Wine Fermented by Three Commercial Saccharomyces cerevisiae Yeasts

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. HIGHLIGHTS Mao wines were produced by 3 commercial cerevisiae yeast strains Lalvin K1-V1116 yeast exhibits the highest capacity in converting sugar to alcohol Lalvin K1-V1116 is the most suitable yeast for making mao wine The chosen kinetic models are appropriate for kinetic studies of fermentation process The efficacy of Mao wine in inhibiting the activity of alpha-amylase is quite low GRAPHICAL ABSTRACT