Eubiotics for Food Security at Farm Level: Yeast Cell Wall Products and Their Antimicrobial Potential Against Pathogenic Bacteria

Conversion of β-1,6-Glucans to Gentiobiose using an endo-β-1,6-Glucanase PsGly30A from Paenibacillus sp. GKG

A plethora of di- and oligosaccharides isolated from the natural sources are used in food and pharmaceutical industry. An enzymatic hydrolysis of fungal cell wall β-glucans is a good alternative to produce the desired oligosaccharides with different functionalities, such as the flavour enhancer gentiobiose. We have previously identified PsGly30A as a potential yeast cell wall degrading β-1,6-glycosidase. The aim of this study is to characterise the PsGly30A enzyme, a member of the GH30 family, and to evaluate its suitability for the production of gentiobiose from β-1,6-glucans. An endo-β-1,6-glucanase PsGly30A encoding gene from Paenibacillus sp. GKG has been cloned and overexpressed in Escherichia coli. The recombinant enzyme has been active towards pustulan and yeast β-glucan, but not on laminarin from the Laminaria digitata, confirming the endo-β-1,6-glucanase mode of action. The PsGly30A shows the highest activity at pH 5.5 and 50 °C. The specific activity of PsGly30A on pustulan (1262±82 U/mg) is among the highest reported for GH30 β-1,6-glycosidases. Moreover, gentiobiose is the major reaction product when pustulan, yeast β-glucan or yeast cell walls have been used as a substrate. Therefore, PsGly30A is a promising catalyst for valorisation of the yeast-related by-products.

Invited review: "Probiotic" approaches to improving dairy production: Reassessing "magic foo-foo dust"

The gastrointestinal microbial consortium in dairy cattle is critical to determining the energetic status of the dairy cow from birth through her final lactation. The ruminant's microbial community can degrade a wide variety of feedstuffs, which can affect growth, as well as production rate and efficiency on the farm, but can also affect food safety, animal health, and environmental impacts of dairy production. Gut microbial diversity and density are powerful tools that can be harnessed to benefit both producers and consumers. The incentives in the United States to develop Alternatives to Antibiotics for use in food-animal production have been largely driven by the Veterinary Feed Directive and have led to an increased use of probiotic approaches to alter the gastrointestinal microbial community composition, resulting in improved heifer growth, milk production and efficiency, and animal health. However, the efficacy of direct-fed microbials or probiotics in dairy cattle has been highly variable due to specific microbial ecological factors within the host gut and its native microflora. Interactions (both synergistic and antagonistic) between the microbial ecosystem and the host animal physiology (including epithelial cells, immune system, hormones, enzyme activities, and epigenetics) are critical to understanding why some probiotics work but others do not. Increasing availability of next-generation sequencing approaches provides novel insights into how probiotic approaches change the microbial community composition in the gut that can potentially affect animal health (e.g., diarrhea or scours, gut integrity, foodborne pathogens), as well as animal performance (e.g., growth, reproduction, productivity) and fermentation parameters (e.g., pH, short-chain fatty acids, methane production, and microbial profiles) of cattle. However, it remains clear that all direct-fed microbials are not created equal and their efficacy remains highly variable and dependent on stage of production and farm environment. Collectively, data have demonstrated that probiotic effects are not limited to the simple mechanisms that have been traditionally hypothesized, but instead are part of a complex cascade of microbial ecological and host animal physiological effects that ultimately impact dairy production and profitability.

New biomarkers underlying acetic acid tolerance in the probiotic yeast Saccharomyces cerevisiae var. boulardii

Evolutionary engineering experiments, in combination with omics technologies, revealed genetic markers underpinning the molecular mechanisms behind acetic acid stress tolerance in the probiotic yeast Saccharomyces cerevisiae var. boulardii. Here, compared to the ancestral Ent strain, evolved yeast strains could quickly adapt to high acetic acid levels (7 g/L) and displayed a shorter lag phase of growth. Bioinformatic-aided whole-genome sequencing identified genetic changes associated with enhanced strain robustness to acetic acid: a duplicated sequence in the essential endocytotic PAN1 gene, mutations in a cell wall mannoprotein (dan4Thr192del), a lipid and fatty acid transcription factor (oaf1Ser57Pro) and a thiamine biosynthetic enzyme (thi13Thr332Ala). Induction of PAN1 and its associated endocytic complex SLA1 and END3 genes was observed following acetic acid treatment in the evolved-resistant strain when compared to the ancestral strain. Genome-wide transcriptomic analysis of the evolved Ent acid-resistant strain (Ent ev16) also revealed a dramatic rewiring of gene expression among genes associated with cellular transport, metabolism, oxidative stress response, biosynthesis/organization of the cell wall, and cell membrane. Some evolved strains also displayed better growth at high acetic acid concentrations and exhibited adaptive metabolic profiles with altered levels of secreted ethanol (4.0-6.4% decrease), glycerol (31.4-78.5% increase), and acetic acid (53.0-60.3% increase) when compared to the ancestral strain. Overall, duplication/mutations and transcriptional alterations are key mechanisms driving improved acetic acid tolerance in probiotic strains. We successfully used adaptive evolutionary engineering to rapidly and effectively elucidate the molecular mechanisms behind important industrial traits to obtain robust probiotic yeast strains for myriad biotechnological applications. KEY POINTS: •Acetic acid adaptation of evolutionary engineered robust probiotic yeast S. boulardii •Enterol ev16 with altered genetic and transcriptomic profiles survives in up to 7 g/L acetic acid •Improved acetic acid tolerance of S. boulardii ev16 with mutated PAN1, DAN4, OAF1, and THI13 genes.

Effects of microbial-derived biotics (meta/pharma/post-biotics) on the modulation of gut microbiome and metabolome; general aspects and emerging trends

Potential effects of metabiotics (probiotics effector molecules or signaling factors), pharmabiotics (pro-functional metabolites produced by gut microbiota (GMB)) and postbiotics (multifunctional metabolites and structural compounds of food-grade microorganisms) on GMB have been rarely reviewed. These multifunctional components have several promising capabilities for prevention, alleviation and treatment of some diseases or disorders. Correlations between these essential biotics and GMB are also very interesting and important in human health and nutrition. Furthermore, these natural bioactives are involved in modulation of the immune function, control of metabolic dysbiosis and regulation of the signaling pathways. This review discusses the potential of meta/pharma/post-biotics as new classes of pharmaceutical agents and their effective mechanisms associated with GMB-host cell to cell communications with therapeutic benefits which are important in balance and the integrity of the host microbiome. In addition, cutting-edge findings about bioinformatics /metabolomics analyses related to GMB and these essential biotics are reviewed.

Nutrient intake, digestibility and ruminal characteristics of lambs supplemented with probiotic

The aim of this study was to evaluate the inclusion of different levels of probiotic in the diets of lambs, on ruminal characteristics, intake and digestibility of nutrients. The treatments were 0 (control group), 2, 4 and 6 g/day of probiotic doses, supplied orally and individually to the lambs. Four crossbred Santa Inês X Texel lambs were used, and the experimental design was a Latin square, with four treatments and four periods. Samples of diet, orts, feces, and ruminal fluid were collected from each animal. Intake and apparent digestibility variables were not different (p > 0.05) among the levels of probiotic evaluated. The average daily feed intake of lambs ranged from 1.27 to 1.28 kg of DM/day, and no significant differences (p > 0.05) were obtained between the levels of probiotics used in the diet. The percentage distribution of protozoa was not significant according to the different doses of probiotics used. A positive linear effect was obtained between the pH of the rumen fluid and the probiotic used, indicating that the highest pH values were obtained when the animals received the higher dose of 6 g probiotic; indicative that its use provides a ruminal environment closer to neutrality. The methylene blue reduction test in ruminal fluid samples did not differ between the different doses of probiotics used. The increasing levels of the probiotic in the diet of lambs are related to an increase in ruminal pH, without changing the levels of intake and digestibility of nutrients.

Effects of Saccharomyces cerevisiae hydrolysate on growth performance, immunity function, and intestinal health in broilers

The current study was performed to explore the effects of dietary supplementation of Saccharomyces cerevisiae hydrolysate (SCH) on growth performance, immune function, and intestinal health in broiler chicken. A total of 300 Ross 308 male broilers (1-day-old) were randomly assigned to 2 dietary treatments including a basal diet (control group), and a basal diet supplemented with SCH feed additive (500 mg/kg in starter and grower phase, and 250 mg/kg in finisher phase). Each treatment had 6 replicates with 25 birds each. The results showed that the addition of SCH promoted growth during d 15 to 28 (P < 0.05). Although the addition of SCH had no significant effect on the intestinal relative indexes, it significantly increased the jejunum villus height (VH) and the ratio of villus height to crypt depth (VCR) of jejunum, and decreased the crypt depth (CD) of ileum (P < 0.05). Furthermore, SCH addition significantly downregulated the mRNA expression of immunomodulatory genes (TNF-α, IL-1β, and IL-6), and upregulated the tight junction genes (ZO-1 and Claudin-1) (P < 0.05). High throughput sequencing analysis of bacterial 16S rRNA revealed that dietary SCH supplementation altered cecum microbiota. Alpha diversity analysis showed that a higher bacterial richness in cecum of broilers fed with SCH. The composition of cecum microbiota regulated by SCH addition was characterized by an increased abundance of Firmicutes and a reduced abundance of Bacteroidetes. At the genus level, dietary SCH resulted in a decrease of Bacteroides and an increase of short-chain fatty acids (SCFA) -producing bacteria including Lactobacillus and Faecalibacterium. Taken together, dietary SCH supplementation can stimulate the growth of broilers by regulating the intestinal immunity and barrier function, and improving the intestinal morphology, which may be related to the enhancement of bacterial diversity and the changes of intestinal microbial composition.

Viability of the use of mycotoxin adsorbent in the finishing of Texel lambs in confinement

The objective of the present study was to evaluate the viability of a mycotoxin adsorbent based on beta-glucans from cell walls of Saccharomyces cerevisiae and bentonites in the diets of confined lambs of the Texel breed. Twenty-four lambs (12 males and 12 females) with an average weight of 18.6 kg ± 1.6 were divided into two groups: treated (with adsorbent) and control. The animal diets contained the mycotoxins aflatoxin B1, fumonisin B1 and B2, zearalenone, and deoxynivalenol in concentrations within guidance levels. The animals were slaughtered with body weight of approximately 26.4 kg. The performance and carcass variables of the lambs were evaluated. The daily weight gain was higher in the treated group (216.24 g) than in the control group (185.90 g). The averages for loin eye area, subcutaneous fat thickness, and marbling were 13.93 cm², 2.66 mm, and 3.20 in the treated group and 12.16 cm², 2.6 mm, and 3.25 in the control group, respectively. The true, hot, and cold carcass yield, and the carcass cooling losses did not differ between groups. The carcasses were similar in conformation and fat finishing degree, with averages of 3.95 and 3.83, respectively. To the best of our knowledge, this is the first study to evaluate the effect of a mycotoxin additive in the diet of finishing lambs. The use of mycotoxin adsorbent in confined lambs was feasible, and its use resulted in greater daily weight gain in lambs and average net profit.

Structure, preparation, modification, and bioactivities of β-glucan and mannan from yeast cell wall: A review

In order to solve the antibiotic resistance, the research on antibiotic substitutes has received an extensive attention. Many studies have shown that β-glucan and mannan from yeast cell wall have the potential to replace antibiotics for the prevention and treatment of animal diseases, thereby reducing the development and spread of antibiotic-resistant bacterial pathogens. β-Glucan and mannan had a variety of biological functions, including improving the intestinal environment, stimulating innate and acquired immunity, adsorbing mycotoxins, enhancing antioxidant capacity, and so on. The biological activities of β-glucan and mannan can be improved by chemically modifying its primary structure or reducing molecular weight. In this paper, the structure, preparation, modification, and biological activities of β-glucan and mannan were reviewed, which provided future perspectives of β-glucan and mannan.

Prebiotics and the poultry gastrointestinal tract microbiome

Feed additives that can modulate the poultry gastrointestinal tract and provide benefit to bird performance and health have recently received more interest for commercial applications. Such feed supplements offer an economic advantage because they may directly benefit poultry producers by either decreasing mortality rates of farm animals, increasing bird growth rates, or improve feed efficieny. They can also limit foodborne pathogen establishment in bird flocks by modifying the gastrointestinal microbial population. Prebiotics are known as non-digestible carbohydrates that selectively stimulate the growth of beneficial bacteria, thus improving the overall health of the host. Once prebiotics are introduced to the host, 2 major modes of action can potentially occur. Initially, the corresponding prebiotic reaches the intestine of the chicken without being digested in the upper part of the gastrointestinal tract but are selectively utilized by certain bacteria considered beneficial to the host. Secondly, other gut activities occur due to the presence of the prebiotic, including generation of short-chain fatty acids and lactic acid as microbial fermentation products, a decreased rate of pathogen colonization, and potential bird health benefits. In the current review, the effect of prebiotics on the gastrointestinal tract microbiome will be discussed as well as future directions for further research.

Effect of Yeast Culture (Saccharomyces cerevisiae) on Broilers: A Preliminary Study on the Effective Components of Yeast Culture

Simple Summary

The value of yeast culture (YC) as alternative feed additives in poultry farming has been proven. YC is a nutrient-rich and complex micro-ecological fermentation product containing various metabolites. However, the major or specific effective components of YC and their importance in poultry farming are unknown. Herein, we screened the “effective ingredients” of YCs obtained from different fermentation times based on metabolomics and animal feeding experiments. Glycine, fructose, inositol, galactose, and sucrose were identified as potential effective metabolites in YCs. These findings provide an important basis for objective, accurate, and quick evaluation of the quality of YC products, as well as a scientific understanding of their functions.

Abstract

This study was aimed at determining the effective ingredients of yeast culture (YC) for animal breeding. First, the contents of YCs obtained from various fermentation times were detected using gas-chromatography. A total of 85 compounds were identified. Next, 336 Arbor Acres (AA) broilers were randomly divided into seven experimental groups and fed a basal diet, diets supplemented with YCs obtained at various fermentation times, or SZ1 (a commercial YC product). A significant increase in body weight gain (BWG) and a significant decrease in feed conversion ratio (FCR) of AA broiler chicks were observed with YC supplementation. Additionally, most of blood and immunological indices were improved with YC supplementation. According to the production performance and the results of multivariate analysis, glycine, fructose, inositol, galactose, and sucrose were found as the potential effective compounds of YC and were involved in metabolic pathways including glycine, serine, and threonine metabolism. Supplementation with diets based on combinations of effective compounds improved weight gain, feed efficiency, serum immunoglobulin A, and immunoglobulin G, but decreased blood urea concentration. These findings suggest YCs as effective and harmless feed additives with improved nutritional properties for broiler chicks.

Decontamination of Mycotoxin-Contaminated Feedstuffs and Compound Feed

Mycotoxins are known worldwide as fungus-produced toxins that adulterate a wide heterogeneity of raw feed ingredients and final products. Consumption of mycotoxins-contaminated feed causes a plethora of harmful responses from acute toxicity to many persistent health disorders with lethal outcomes; such as mycotoxicosis when ingested by animals. Therefore, the main task for feed producers is to minimize the concentration of mycotoxin by applying different strategies aimed at minimizing the risk of mycotoxin effects on animals and human health. Once mycotoxins enter the production chain it is hard to eliminate or inactivate them. This paper examines the most recent findings on different processes and strategies for the reduction of toxicity of mycotoxins in animals. The review gives detailed information about the decontamination approaches to mitigate mycotoxin contamination of feedstuffs and compound feed, which could be implemented in practice.

Equilibrium Isotherm Approach to Measure the Capability of Yeast Cell Wall to Adsorb Clostridium perfringens

Yeast cell wall (YCW) products are currently used as substitutes to antibiotic growth promoters, to improve animal performances, and to reduce the incidence of infectious diseases in livestock. They are claimed to bind enteropathogens, thus interfering with their colonization in the intestinal mucosa. Although the anti-infectious activity of YCW products on Gram-positive pathogens like Clostridium perfringens has been reported in vivo, in vitro evidences on the adsorption of C. perfringens by YCW fractions are not yet available. Preliminary results showed that purified YCW products exert antimicrobial activity toward C. perfringens. Using the adsorption isotherm approach, we measured the ability of YCW products in adsorbing C. perfringens, thus reducing its viability. Dosages of YCW products >1 mg/mL adsorbed 4 Log colony-forming unit (CFU)/mL of C. perfringens in buffered solution. The maximum adsorption of the bacterium was reached in 3 h, whereas only one product of four YCW products retained the adsorption up to 6 h. The analysis of equilibrium isotherms and adsorption kinetics revealed that all products adsorb C. perfringens in a dose- and time-dependent manner, with high affinity and capacity, sequestering up to 4 Log CFU/mg of product. The determination of adsorption parameters allows to differentiate among adsorbents and select the most efficient product. This approach discriminated among YCW products more efficiently than the antimicrobial assay. In conclusion, this study suggests that the ability of YCW products in reducing C. perfringens viability can be the result of an adsorption mechanism.

Potential for Prebiotics as Feed Additives to Limit Foodborne Campylobacter Establishment in the Poultry Gastrointestinal Tract

Campylobacter as an inhabitant of the poultry gastrointestinal tract has proven to be difficult to reduce with most feed additives. In-feed antibiotics have been taken out of poultry diets due to the negative reactions of consumers along with concerns regarding the generation of antibiotic resistant bacteria. Consequently, interest in alternative feed supplements to antibiotics has grown. One of these alternatives, prebiotics, has been examined as a potential animal and poultry feed additive. Prebiotics are non-digestible ingredients by host enzymes that enhance growth of indigenous gastrointestinal bacteria that elicit metabolic characteristics considered beneficial to the host and depending on the type of metabolite, antagonistic to establishment of pathogens. There are several carbohydrate polymers that qualify as prebiotics and have been fed to poultry. These include mannan-oligosaccharides and fructooligosaccharides as the most common ones marketed commercially that have been used as feed supplements in poultry. More recently, several other non-digestible oligosaccharides have also been identified as possessing prebiotic properties when implemented as feed supplements. While there is evidence that prebiotics may be effective in poultry and limit establishment of foodborne pathogens such as Salmonella in the gastrointestinal tract, less is known about their impact on Campylobacter. This review will focus on the potential of prebiotics to limit establishment of Campylobacter in the poultry gastrointestinal tract and future research directions.