Yeast Cell Wall Components Research Articles

33 Beyond bacteria: Impact of live yeast as a probiotic on the intestinal health of dogs

Abstract Inactivated yeast and yeast-based products are commonly used in pet food to improve palatability, contribute to dietary protein content, and improve gastrointestinal functionality. However, the use of viable yeast Saccharomyces as a probiotic may contribute to additional beneficial effects on dogs and cats. Considering that, in this presentation, we will focus on the use of viable yeast as a probiotic for dogs. A study conducted at the Federal University of Parana, Brazil, observed that Beagle dogs supplemented with a probiotic yeast presented reduced fecal concentrations of total biogenic amines, ammonia, and aromatic compounds and greater fecal concentrations of butyrate. The supplemented dogs also presented an improvement in dysbiosis index, a greater abundance of Bifidobacterium and Turicibacter, and a reduced abundance of Escherichia coli in feces. In addition, control group dogs presented upregulation in microbial genes related to virulence factors (such as lipopolysaccharide export system), antibiotic resistance, and osmotic stress, compared with the probiotic group. These results may indicate a possible protective effect of the yeast probiotic against potential pathogenic bacteria in the gut. The mechanisms by which yeast probiotics may contribute to gastrointestinal functionality in dogs and cats are not fully elucidated. However, they are usually attributed to the stimulation of brush edge disaccharidases; competition for adhesion sites against potential pathogens; stimulation of nonspecific immunity; neutralization of toxins; and direct effect against potentially pathogenic microorganisms. Many of these mechanisms are influenced directly by yeast cell wall components, such as mannans and beta-glucans. One of the main mechanisms of action of mannans is the elimination of bacteria with pathogenic potential that present type-1 fimbriae, such as some strains of E. coli and Salmonella, preventing their adhesion and colonization to the host mucosa. This may also contribute to the establishment of beneficial bacteria in the gut. We can conclude that viable yeast Saccharomyces as a probiotic may have promising beneficial effects on intestinal functionality of dogs.

A Minimalist Pathogen-Like Sugar Nanovaccine for Enhanced Cancer Immunotherapy.

Pathogen-mimicking nanoparticles have emerged at the forefront of vaccine delivery technology, offering potent immune activation and excellent biocompatibility. Among these innovative carriers, mannan, a critical component of yeast cell walls, shows promise as an exemplary vaccine carrier. Nevertheless, it faces challenges like unpredictable immunogenicity, rapid elimination, and limited antigen loading due to high water solubility. Herein, mannan with varying carbon chain ratios is innovatively modified, yielding a series of dodecyl chains modified mannan (Mann-C12). Through meticulous screening, a mannan variant with a 40% grafting ratio is pinpointed as the optimal vaccine carrier. Further RNA sequencing confirms that Mann-C12 exhibits desired immunostimulatory characteristics. Coupled with antigen peptides, Mann-C12/OVA257-280 nanovaccine initiates the maturation of antigen-presenting cells by activating the TLR4 and Dectin-2 pathways, significantly boosting antigen utilization and sparking antigen-specific immune responses. In vivo, experiments utilizing the B16-OVA tumor model underscore the exceptional preventive capabilities of Mann-C12/OVA257-280. Notably, when combined with immune checkpoint blockade therapy, it displays a profound synergistic effect, leading to marked inhibition of tumor growth. Thus, the work has yielded a pathogen-like nanovaccine that is both simple to prepare and highly effective, underscoring the vast potential of mannan-modified nanovaccines in the realm of cancer immunotherapy.

A Yeast Cell Wall Derived Hybrid Hydrogel with Photothermal and Immune Combined Modality Therapy for Enhanced Anti-Melanoma Efficacy.

The effect of traditional treatment for melanoma is quite limited, especially for its recurrence. As the major components of yeast cell wall, chitin and β-glucan exhibit good immune activation effect and are promising candidates for adjuvant. Therefore, melanoma cell membrane (CM) and indocyanine green (ICG) was loaded in a chitin and β-glucan hybrid hydrogel to achieve an enhanced anti-melanoma therapy. The novel hybrid hydrogel was prepared, and its physicochemical properties were examined. Its effect towards melanoma prevention and treatment was evaluated via a melanoma-bearing mice model. The CM-ICG-hybrid hydrogel was successfully prepared with excellent injectability, self-healing, drug loading, rheological, in vitro and in vivo photothermal stability, and retention properties. It also exhibited good cellular and in vivo safety profiles. In the primary melanoma mice model, it quickly ablated the in-situ melanoma, effectively inhibited the tumor growth, increased the survival rate of melanoma-bearing mice, and increased the level of IFN-γ and TNF-α. In the distal secondary melanoma model, it efficiently prevented the reoccurrence of melanoma and activated the memory T cells. In both models, a synergistic effect of photothermal therapy and immune therapy was found. The hydrogel effectively recruited CD3+ CD4+ T cells and CD3+ CD8+ T cells, inhibited the proliferation of melanoma cells, and induced the apoptosis of melanoma cells. The hybrid hydrogel was successfully prepared, and it showed excellent efficacy towards melanoma prevention and treatment due to its efficient tumor ablation and immune activation capability.

Early life supplementation with a natural blend containing turmeric, thymol, and yeast cell wall components to optimize rumen anatomical and microbiological development and productivity in dairy goats

Ruminants are born with an anatomically, microbiologically, and metabolically immature rumen. Optimizing the rearing of young ruminants represent an important challenge in intensive dairy farms. Therefore, the objective of this study was to evaluate the effects of dietary supplementation of young ruminants with a plant extract blend containing turmeric, thymol, and yeast cell wall components such as mannan oligosaccharides and β-glucans. One hundred newborn female goat kids were randomly allocated to 2 experimental treatments, which were unsupplemented (CTL) or supplemented with the blend containing plant extracts and yeast cell wall components (PEY). All animas were fed with milk replacer, concentrate feed, and oat hay, and were weaned at 8 wk of age. Dietary treatments lasted from wk 1 to 22 and 10 animals from each treatment were randomly selected to monitor feed intake, digestibility, and health-related indicators. These latter animals were euthanized at wk 22 of age to study the rumen anatomical, papillary, and microbiological development, whereas the remaining animals were monitored for reproductive performance and milk yield during the first lactation. Results indicated that PEY supplementation did not lead to feed intake or health issues because PEY animals tended to have a higher concentrate intake and lower diarrheal incidence than CTL animals. No differences between treatments were noted in terms of feed digestibility, rumen microbial protein synthesis, health-related metabolites, or blood cell counts. Supplementation with PEY promoted a higher rumen empty weight, and rumen relative proportion to the total digestive tract weight, than CTL animals. This was accompanied with a higher rumen papillary development in terms of papillae length and surface area in the cranial ventral and caudal ventral sacs, respectively. The PEY animals also had higher expression of the MCT1 gene, which is related to volatile fatty acid absorption by the rumen epithelium, than CTL animals. The antimicrobial effects of the turmeric and thymol could explain the decreased the rumen absolute abundance of protozoa and anaerobic fungi. This antimicrobial modulation led to a change in the bacterial community structure, a decrease in the bacteria richness, and to the disappearance (i.e., Prevotellaceae_UCG-004, Bacteroidetes_BD2-2, Papillibacter, Schwartzia, and Absconditabacteriales_SR1) or decline of certain bacterial taxa (i.e., Prevotellaceae_NK3B31_group, and Clostridia_UCG-014). Supplementation with PEY also decreased the relative abundance of fibrolytic (i.e., Fibrobacter succinogenes and Eubacterium ruminantium) and increased amylolytic bacteria (Selenomonas ruminantium). Although these microbial changes were not accompanied with significant differences in the rumen fermentation, this supplementation led to increased body weight gain during the preweaning period, higher body weight during the postweaning period, and higher fertility rate during the first gestation. On the contrary, no residual effects of this nutritional intervention were noted on the milk yield and milk components during the first lactation. In conclusion, supplementation with this blend of plant extracts and yeast cell wall component in early life could be considered as a sustainable nutritional strategy to increase body weight gain and optimize the rumen anatomical and microbiological development in young ruminants, despite having minor productive implications later in life.

Early-life β-glucan exposure enhances disease resilience of broiler chickens to a natural Clostridium perfringens infection

Necrotic enteritis (NE) is an economically important disease in poultry. Colonization by the opportunistic pathogen C. perfringens occurs early after hatch and induces host immune tolerance, which allows it to persist as part of the bird's commensal microflora. β-glucan, a yeast cell wall component, is well characterized for its immunomodulatory capacity, and is a strong driver of innate immune memory. In this study, we assessed the effectiveness of β-glucan to reduce severity of NE, when co-administered with heat-killed C. perfringens via intra-abdominal route at day 1 of age. We found that this early-life exposure in the presence of β-glucan did not reduce intestinal C. perfringens loads or lesion severity during a subsequent NE outbreak. However, it improved ileal morphology, prevented liver and spleen weight decline, and preserved feed efficiency in challenged birds. Molecular analyses revealed metabolic changes consistent with innate immune memory. Together, our results suggest that β-glucan can reduce the negative impacts of NE by influencing the context in which C. perfringens is first encountered.

Yeast mannoproteins are expected to be a novel potential functional food for attenuation of obesity and modulation of gut microbiota.

The yeast mannoproteins (MPs), a major component of yeast cell walls with large exploration potentiality, have been attracting increasing attention due to their beneficial effects. However, the information about the anti-obesogenic activity of MPs is still limited. Thus, the effects of MPs on the high-fat diet (HFD)-induced obesity and dysbiosis of gut microbiota were investigated in this work. The results showed that MPs could significantly attenuate the HFD-induced higher body weight, fat accumulation, liver steatosis, and damage. Simultaneously, the inflammation in HFD-induced mice was also ameliorated by MPs. The pyrosequencing analysis showed that intervention by MPs could lead to an obvious change in the structure of gut microbiota. Furthermore, the prevention of obesity by MPs is highly linked to the promotion of Parabacteroides distasonis (increased from 0.39 ± 0.12% to 2.10 ± 0.20%) and inhibition of Lactobacillus (decreased from 19.99 ± 3.94% to 2.68 ± 0.77%). Moreover, the increased level of acetate (increased from 3.28 ± 0.22 mmol/g to 7.84 ± 0.96 mmol/g) and activation of G protein-coupled receptors (GPRs) by MPs may also contribute to the prevention of obesity. Thus, our preliminary findings revealed that MPs from yeast could be explored as potential prebiotics to modulate the gut microbiota and prevent HFD-induced obesity.

β-1,3-Glucan/chitin unmasking in the Saccharomyces cerevisiae mutant, Δmnn9, promotes immune response and resistance of the Pacific oyster (Crassostrea gigas) to Vibrio coralliilyticus infection

Yeast cells can play a crucial role in immune activation in fish and shellfish predominantly due to the cell wall component β-1,3-glucan, providing protection against bacterial or viral infections. However, the immunostimulatory capacity of dietary yeast cells remains poorly studied in bivalves. To understand the role of yeast cell wall components (mannan, β-glucan and chitin) as immune activators, this study characterized the surface carbohydrate exposure of the wild-type baker's yeast Saccharomyces cerevisiae (WT) and its Δmnn9 mutant, which presents a defective mannan structure, and compared these profiles with that of β-glucan particles, using fluorescein isothiocyanate (FITC)-labeled lectin binding analysis. Then, a first trial evaluated the immunological response in Crassostrea gigas juveniles after being fed for 24 h with an algae-based diet (100A) and its 50% substituted version (based on dry weight) with WT (50A50WT) and Δmnn9 (50A50Y), and the posterior resistance of the juveniles against Vibrio coralliilyticus infection (trial 1). The mRNA expression was measured for β-glucan-binding protein (CgβGBP), Toll-like receptor 4 (CgTLR4), C-type lectin receptor 3 (CgCLec-3), myeloid differentiation factor 88 (CgMyD88), nuclear factor-kappa B (CgNFκB), lysozyme (CgLys), interleukin 17-5 (CgIL17-5), and superoxide dismutase (CgSOD), in oysters, before and 24 h after the bacterial inoculation. A second trial tested the effect of incorporating Δmnn9 into the 100A diet for 24 h at different substitution levels: 0, 5, 10, 25, and 50% (100A, 95A5Y, 90A10Y, 75A25Y, and 50A50Y), followed by the bacterial challenge with V. coralliilyticus (trial 2). Our findings showed that the outer cell wall surface of WT is largely composed of mannan, while Δmnn9 presents high exposure of β-glucan and chitin, exhibiting similar FITC-lectin binding profiles (fluorescence intensity) to β-glucan particles. A significantly higher survival after the bacterial challenge was observed in oysters fed on 50A50Y compared to those fed 50A50WT and 100A in trial 1. This better performance of 50A50Y was supported by significantly higher gene expressions of CgLys, CgSOD, CgMyD88, and CgβGBP compared to 100A, and CgSOD and CgNFκB in relation to those fed on 50A50WT, prior to the bacterial inoculation. Furthermore, improved survival was observed in oysters fed 50A50Y compared to those offered lower Δmnn9 levels and 100A in trial 2. The superior performance of Δmnn9-fed oysters is mostly associated with the elevated presence of unmasked β-glucans on Δmnn9 cell wall surface, facilitating their interactions with oyster hemocytes. Further studies are needed to evaluate administration dose and frequency of Δmnn9 to develop strategies for long-term feeding.

Evaluation of dietary mycotoxin control strategies on nursery pig growth performance and blood measures.

A total of 4,318 pigs (337 × 1,050, PIC; initially 6.5 ± 0.08 kg) were used in a 35-day study to evaluate dietary mycotoxin control strategies on nursery pig performance and blood measures. Pigs were weaned at approximately 21 d of age and randomly allotted to 1 of 5 dietary treatments in a randomized complete block design with blocking structure including sow farm origin, date of entry into facility, and average pen BW. A total of 160 pens were used with 80 double-sided 5-hole stainless steel fence line feeders, with feeder serving as the experimental unit. For each feeder, 1 pen contained 27 gilts and 1 pen contained 27 barrows. There were 16 replications per dietary treatment. A common phase 1 diet was fed to all pigs in pelleted form for 7 day prior to treatment diets. Experimental treatments were fed from days 7 to 42 after weaning (days 0 to 35 of the study) and included a low deoxynivalenol (DON) diet (1.12 ± 0.623 mg/kg), high DON diet (2.34 ± 1.809 mg/kg), high DON+ 0.50% sodium metabisulfite (SMB), high DON+ one of two mitigating products; 0.30% Technology1, or 0.30% Technology1+. Technology1 and 1+ are comprised of clays, yeast cell wall components, and a blend of plant extracts. Technology1+ also contains SMB. Overall (days 0 to 35), pigs fed high DON had decreased (P < 0.05) final BW, ADG, and ADFI compared with low DON. Additionally, pigs fed high DON+SMB had increased (P < 0.05) ADG compared with all other treatments. An improvement (P < 0.05) in G:F was observed in pigs fed high DON + SMB or high DON + Technology1+ compared with the low DON or high DON + Technology1 diets with high DON diets intermediate. Pigs fed high DON + SMB or high DON + Technology1 diets had reduced (P < 0.05) total removals and mortality compared with pigs fed low DON diets with high DON and high DON + Technology1+ intermediate. Liquid chromatography/mass spectrometry analysis of circulating blood collected on day 35 revealed that pigs fed high DON or high DON + Technology1 had increased (P < 0.05) DON concentrations compared to low DON with high DON + SMB and high DON + Technology1+ intermediate. In summary, pigs fed high DON diets had reduced performance compared with pigs fed low DON. Sodium metabisulfite in high DON diets provided a benefit in growth performance with ADG and G:F exceeding growth performance in the low DON diet while, the improved G:F ratio combined with other immunometabolic changes (gamma glutamyltransferase and creatine kinase) associated with Technology1+ warrant further investigation.

Preparation of Yeast Cells for Staining.

Staining yeast cells for the presence and location of antigens is particularly challenging. They are small, making the resolution of any antigen difficult; they have a thick cell wall that antibodies cannot penetrate and that is difficult to remove; and they grow in suspension, making handling difficult. In addition, background problems can be especially severe, particularly with polyclonal antibodies, because many antisera contain antibodies to yeast cell wall components. In this protocol, yeast cells are treated with paraformaldehyde, the cell wall is removed by enzymic digestion, and the spheroplasts are attached to poly-l-lysine-coated slides. After cell lysis, the cells are ready to be stained as per normal. Except in unusual circumstances, the detection reagent should be fluorochrome-labeled.

111 Evaluation of Dietary Mycotoxin Control Strategies on Nursery Pig Growth Performance and Blood Measures

Abstract A total of 4,318 pigs (337×1050, PIC; initially 6.5±0.08kg) were used in a 35-d trial to evaluate dietary mycotoxin control strategies on nursery pig performance and blood measures. Pigs were weaned at 21-d of age and randomly allotted to 1 of 5 dietary treatments. A total of 160 pens were used with 80 double-sided 5-hole stainless steel fence line feeders, with feeder serving as the experimental unit. For each feeder, 1 pen contained 27 gilts and 1 pen contained 27 barrows. There were 16 replications/treatment. A common phase 1 diet was fed in pelleted form for 7-d prior to treatment diets. Experimental treatments were fed from d 7 to 42 after weaning (d0 to 35 of study) and included a low deoxynivalenol (DON) diet (1.12±0.623 mg/kg), high DON diet (2.34±1.809 mg/kg), high DON+ sodium metabisulfite (SMB), high DON+ 1 of 2 mitigating products; Technology1, or Technology1+. Technology1 and 1+ are comprised of clays, yeast cell wall components and a blend of plant extracts. Technology1+ also contains SMB. Overall (d0 to 35), pigs fed high DON had decreased (P &amp;lt; 0.05) final BW, ADG, and ADFI compared with low DON. Additionally, pigs fed high DON+SMB had increased (P&amp;lt;0.05) ADG compared with all other treatments. An increase (P &amp;lt; 0.05) in G:F was observed in pigs fed high DON+SMB or high DON+Technology1+ compared with low DON or high DON+Technology1 with high DON intermediate. Analysis of dried blood spots collected on d 35 revealed pigs fed high DON or high DON+Technology1 had increased (P &amp;lt; 0.05) DON concentrations compared with low DON with high DON+SMB and high DON+Technology1+ intermediate. In summary, pigs fed high DON had reduced performance compared with low DON. Sodium metabisulfite supplementation to high DON led to ADG and G:F that exceeded low DON, whereas Technology1+ resulted in similar ADG and improved G:F compared with low DON.

Role of nitric oxide on zymosan-induced inhibition of crop emptying in chicks

Zymosan, a component of yeast cell walls, reduces feed passage through the digestive tract in chicks (Gallus gallus), although the mechanism mediating this effect is poorly understood. Nitric oxide (NO) is associated with a variety of biological actions including effects on the immune system. In addition, it has been suggested that NO is involved in relaxation of the digestive tract and affects feed passage in mammals. It is therefore possible that NO might be related to zymosan-induced reduction of feed passage in chicks. However, the role of NO on the effect of zymosan feed passage has not been clarified yet. Thus, the purpose of the present study was to investigate whether NO is associated with zymosan-induced alteration of feed passage in chicks. Intraperitoneal (IP) injection of zymosan significantly increased plasma nitrate and nitrite (NOx) concentrations at 6 h after injection. Zymosan-induced elevation of plasma NOx concentration was abolished by co-injection of S-methylisothiourea (SMT), a selective inhibitor for inducible NO synthase (iNOS), indicating that zymosan facilitated the induction of iNOS. Furthermore, because zymosan increased iNOS mRNA expression in the digestive tract, NO is likely associated with the effect of zymosan on the digestive tract. IP injection of NO donors significantly decreased crop emptying rate, suggesting that NO functions as an inhibitor of crop emptying. This result implied that zymosan stimulates NO production by the induction of iNOS in the digestive tract and thereby inhibits crop emptying rate. However, the co-injection of SMT did not attenuate the inhibitory effect of zymosan on crop emptying. The present study provides evidence that some changes in the digestive tract caused by zymosan are mediated by iNOS-induced NO in chicks, but NO does not mediate the effect of zymosan on feed passage through the crop.

Heteropolysaccharides from S. cerevisiae show anti-adhesive properties against E. coli associated with Crohn's disease

The Saccharomyces cerevisiae CNCM I-3856 was previously reported to strongly inhibit adherent-invasive Escherichia coli (AIEC) adhesion to intestinal epithelial cells in vitro and to favor AIEC elimination from the gut in a murine model of Crohn's disease in vivo. In order to identify which cell wall components of yeast are responsible for AIEC elimination, constituent polysaccharides of yeast were isolated and their anti-adhesive ability against AIEC adhesion in vitro was screened. A fraction containing mannan, β-glucan and α-glucan extracted from yeast cell-walls was shown to inhibit 95% of AIEC adhesion in vitro and was thus identified as the strongest anti-adhesive yeast cell wall component. Furthermore, this mannan-glucan-containing fraction was shown to accelerate AIEC decolonization from gut in vivo. This fraction could be proposed as a treatment to eliminate AIEC bacteria in patients with Crohn's disease, a microbial trigger of intestinal inflammation.

Candida albicans and Candida glabrata triosephosphate isomerase \u2013 a moonlighting protein that can be exposed on the candidal cell surface and bind to human extracellular matrix proteins

BackgroundTriosephosphate isomerase (Tpi1) is a glycolytic enzyme that has recently been reported also to be an atypical proteinaceous component of the Candida yeast cell wall. Similar to other known candidal “moonlighting proteins”, surface-exposed Tpi1 is likely to contribute to fungal adhesion during the colonization and infection of a human host. The aim of our present study was to directly prove the presence of Tpi1 on C. albicans and C. glabrata cells under various growth conditions and characterize the interactions of native Tpi1, isolated and purified from the candidal cell wall, with human extracellular matrix proteins.ResultsSurface plasmon resonance measurements were used to determine the dissociation constants for the complexes of Tpi1 with host proteins and these values were found to fall within a relatively narrow range of 10− 8-10− 7 M. Using a chemical cross-linking method, two motifs of the Tpi1 molecule (aa 4–17 and aa 224–247) were identified to be directly involved in the interaction with vitronectin. A proposed structural model for Tpi1 confirmed that these interaction sites were at a considerable distance from the catalytic active site. Synthetic peptides with these sequences significantly inhibited Tpi1 binding to several extracellular matrix proteins suggesting that a common region on the surface of Tpi1 molecule is involved in the interactions with the host proteins.ConclusionsThe current study provided structural insights into the interactions of human extracellular matrix proteins with Tpi1 that can occur at the cell surface of Candida yeasts and contribute to the host infection by these fungal pathogens.

SlMAPK3, a key mitogen-activated protein kinase, regulates the resistance of cherry tomato fruit to Botrytis cinerea induced by yeast cell wall and β-glucan

Induced disease resistance of fruit by bio-based compounds is a promising strategy to control fruit decay. This research was aimed at studying the resistance of cherry tomato fruit to Botrytis cinerea induced by the yeast cell wall component from Saccharomyces cerevisiae and investigate a role of MAPKs in regulating the resistance response. The disease resistance of cherry tomato fruit was effectively enhanced by yeast cell wall and β-glucan. The expression of SlMAPK3 (but not of SlMAPK1 and SlMAPK2) was significantly increased by yeast cell wall and β-glucan and reached peak at 1 h. The yeast cell wall component also induced high expression of PR genes (SlPR1, SlPR5 and SlCHI9) and the transcription factors (SlERF1 and SlPti5) that specifically bind to the promoter of PR genes. The expression of PR genes (SlPR1, SlPR5 and SlCHI9) peaked after 24 h (at 24 or 48 h). The peak of SlERF1 and SlPti5 gene expression mostly appeared at around 4 h. It supposed to be a chronological order in the peaks of gene expression profile among SlMAPK3, PR genes and transcription factors. U0126 (1,4-diamino-2,3-dicyano-1,4-bis(o-amino-phenylmercapto)butadiene) significantly inhibited transcription of SlMAPK3, PR genes and transcription factors. The yeast cell wall and β-glucan could not induce high expression of SlMAPK3 and the downstream genes of SlMAPK3 in the U0126 treatment. These findings indicated that the yeast cell wall component that acts as microbe associated molecular patterns (MAMPs) could effectively induce disease resistance in cherry tomato fruit after harvest. The mechanism of induced resistance was associated with the expression of SlMAPK3 and defense-related genes. SlMAPK3, as an important upstream signaling kinase, had a direct regulatory effect on the downstream transcriptional factors (SlERF1 and SlPti5) to activate the expression of PR genes in the yeast cell wall component-induced immune responses in cherry tomato fruit.

Yeast as major protein‐rich ingredient in aquafeeds: a review of the implications for aquaculture production

AbstractSustainability concerns associated with protein sources and currently used fishmeal and plant‐based meal have necessitated the quests for novel sustainable ingredients for use in aquafeeds. Yeasts have been proposed as sustainable ingredients particularly because of their potential to valorise non‐food lignocellulosic biomass into valuable protein resources. Prior to now, extensive studies exist on the role of yeast cell wall components in modulating health responses of fish. However, research on its use as a major protein source in fish diets is still in its infancy. The current review collates, synthesises and discusses the prospects of five major yeast species as future protein ingredients with respect to their nutritional adequacy in fish. Nutritional quality of Saccharomyces cerevisiae, Cyberlindnera jadinii, Kluyveromyces marxianus, Blastobotrys adeninivorans and Wickerhamomyces anomalus and their use as replacement for fishmeal and soy protein in the diets of Atlantic salmon and rainbow trout are discussed based on three protein quality indices: chemical score, essential amino acid index and ideal protein concept based on the first limiting amino acids, methionine. The crude protein contents of yeast (40–55%) are lower than that of fishmeal, but comparable with soya bean meal. Compared to fishmeal, the different yeast species have favourable amino acid profiles, except for methionine, lysine, arginine and phenylalanine which are the frequently limiting essential amino acids in Atlantic salmon and rainbow trout. This review also presents future area of research and emphasise the need for large‐scale production of yeast at competitive price to constitute a feasible replacement for fishmeal and soy protein in aquaculture.

The effect of prebiotic components on the quality of yogurt

The aim of our study was to study the effect of prebiotic components on the quality indicators of enriched yogurt. Yogurt was produced by fermenting pasteurized normalized milk with yoghurt sourdough, which included lyophilically dried strains of Streptococcus thrmophilus, Lactobacillus delbrueckii ssp.bulgaricus, Lactobacillus acidophilus, and Bactidiochemia sulphonidae with the addition of lactobacillus cultivar and yeast lactobacillus complex ), in addition, in order to enrich the product with vitamins, minerals and polyphenolic compounds, mashed potatoes from blueberries and dogwood were used. In the course of the study, we evaluated organoleptic, physicochemical and microbiological indicators, carried out a comparative analysis of the content of vitamins and trace elements in a traditional and enriched product. It was established that enrichment of yogurt with a prebiotic complex and fruit and berry puree contributed to the improvement of quality indicators, due to an increase in nutritional value, an increase in the content of vitamins (C, B1, B2, E and PP) and microelements (Ca, K, Mg, P, Fe). The prebiotic properties and immunogenic effects of wheat bran and yeast cell wall components, as well as the polyphenolic compounds of blueberries and cornel berries, make it possible to use yogurt as an adaptogenic product with probiotic, prebiotic neuroprotective, cardioprotective, antioxidant, immunomodulating and anti-inflammatory properties.

Characterization of MORN2 stability and regulatory function in LC3-associated phagocytosis in macrophages.

ABSTRACTMicrotubule-associated protein A1/B1-light chain 3 (LC3)-associated phagocytosis (LAP) is a type of non-canonical autophagy that regulates phagosome maturation in macrophages. However, the role and regulatory mechanism of LAP remain largely unknown. Recently, the membrane occupation and recognition nexus repeat-containing-2 (MORN2) was identified as a key component of LAP for the efficient formation of LC3-recruiting phagosomes. To characterize MORN2 and elucidate its function in LAP, we established a MORN2-overexpressing macrophage line. At a steady state, MORN2 was partially cleaved by the ubiquitin-proteasome system. MORN2 overexpression promoted not only LC3-II production but also LAP phagosome (LAPosome) acidification during Escherichia coli uptake. Furthermore, the formation of LAPosomes containing the yeast cell wall component zymosan was enhanced in MORN2-overexpressing cells and depended on reactive oxygen species (ROS). Finally, MORN2-mediated LAP was regulated by plasma membrane-localized soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) such as SNAP-23 and syntaxin 11. Taken together, these findings demonstrate that MORN2, whose expression is downregulated via proteasomal digestion, is a limiting factor for LAP, and that membrane trafficking by SNARE proteins is involved in MORN2-mediated LAP.

Mannoproteins from Saccharomyces cerevisiae stimulate angiogenesis by promoting the akt-eNOS signaling pathway in endothelial cells

Mannoproteins (MPs) are a major component of yeast cell walls and consist of high levels of mannose in covalent complexes with proteins. MPs complexly enhance the immune system. We previously isolated a mutant yeast, K48L3, with a higher yield of MP from its cell wall than wild-type Saccharomyces cerevisiae, YPH499. We determined that K48L3 induces the release of nitric oxide in macrophage cells. The present study reports nitric-oxide-mediated angiogenesis by MP from K48L3 and the induction of the Akt/eNOS signal pathway. Western blotting and RT-PCR were used to demonstrate that MP treatment resulted in the upregulation of p-Akt, p-eNOS, and angiogenesis-mediated gene expression. Moreover, the angiogenesis activity of the MPs was demonstrated using three angiogenesis assays, namely, a cell migration assay, a tube-forming assay, and an ex vivo aorta ring assay. Thus, this study demonstrates for the first time that MPs from S. cerevisiae K48L3 induce angiogenesis in HUVECs via the Akt-eNOS-dependent signaling pathway.

Saccharomyces cerevisiae β-glucan-induced SBD-1 expression in ovine ruminal epithelial cells is mediated through the TLR-2-MyD88-NF-κB/MAPK pathway.

Ovine ruminal epithelial cells (ORECs) not only have a physical barrier function but also can secrete host defence peptides (HDPs), such as sheep β-defensin-1 (SBD-1). As a feed additive, Saccharomyces cerevisiae can enhance the host's innate immunity. β-glucan, a cell wall component of Saccharomyces cerevisiae, can stimulate innate immune responses and trigger the up-regulation of SBD-1 in ORECs. The signaling mechanisms involved in β-glucan-induced SBD-1 expression are not completely understood. The aim of this study was to identify the receptors and intracellular pathways involved in the up-regulation of SBD-1 induced by β-glucan. ORECs were cultured, and the regulatory mechanisms of β-glucan-induced up-regulation of SBD-1 were detected using quantitative real-time PCR (qPCR), enzyme-linked immunosorbent assay (ELISA), and western blotting. TLR-2 and MyD88 knockdown or inhibition attenuated β-glucan-induced SBD-1 expression. We also showed that inhibition of MAPK and NF-κB pathways significantly reduced β-glucan-induced SBD-1 expression. These results demonstrate that β-glucan-induced SBD-1 expression is TLR-2-MyD88-dependent and may be regulated by both MAPK and NF-κB pathways. Since NF-κB inhibition had a greater effect on the down-regulation of β-glucan-induced SBD-1 expression, the NF-κB pathway may be the dominant signaling pathway involved in the regulation of defensin expression. Our studies demonstrate that β-glucan-induced SBD-1 expression is mediated through the TLR-2-MyD88-NF-κB/MAPK pathway. Our results would contribute to the understanding of immunological modulations in the gastrointestinal tract triggered by probiotic yeast cell wall components.

Yeast-based vaccines: New perspective in vaccine development and application.

In presently licensed vaccines, killed or attenuated organisms act as a source of immunogens except for peptide-based vaccines. These conventional vaccines required a mass culture of associated or related organisms and long incubation periods. Special requirements during storage and transportation further adds to the cost of vaccine preparations. Availability of complete genome sequence, well-established genetic, inherent natural adjuvant and non-pathogenic nature of yeast species viz. Saccharomyces cerevisiae, Pichia pastoris makes them an ideal model system for the development of vaccines both for public health and for on-farm consumption. In this review, we compile the work in this emerging field during last two decades with major emphases on S. cerevisiae and P. pastoris which are routinely used worldwide for expression of heterologous proteins with therapeutic value against infectious diseases along with possible use in cancer therapy. We also pointed towards the developments in use of whole recombinant yeast, yeast surface display and virus-like particles as a novel strategy in the fight against infectious diseases and cancer along with other aspects including suitability of yeast in vaccines preparations, yeast cell wall component as an immune stimulator or modulator and present status of yeast-based vaccines in clinical trials.