Quantitative in vitro assay to evaluate the capability of yeast cell wall fractions from Trichosporon mycotoxinivorans to selectively bind gram negative pathogens

Effect of dietary direct-fed microbial and yeast cell walls on cecal digesta microbiota of layer chicks inoculated with nalidixic acid resistant Salmonella Enteritidis

Salmonella enterica serovar Enteritidis (SE) has consistently been the most common serotype associated with the foodborne Salmonellosis worldwide. In this study, the effect of a dietary direct-fed microbial (DFM) and yeast cell walls (YCW) under a challenge of nalidixic acid resistant SE strain using layer chicks has been investigated. A total of 160 newly hatched Dekalb White female chicks were randomly assigned into 2 experimental groups (80 birds/treatment), control group (CON) and treatment group (DY). Chicks were fed ad libitum a non–medicated-corn-soy based diet and DY was supplemented with the combination of DFM and YCW. At 8 days of age, 2.1 × 10⁹ CFU/bird of the SE was given to all chicks by oral administration. On 3 days postinoculation (dpi), 20 chicks/group were euthanized and all cecal contents were collected for analysis. On 6, 10, and 14 dpi, the cecal contents were sampled from 16 chicks per group. The number of SE in the cecal contents was counted using culture-based methods. A 16S rRNA-based microbiota analysis was performed for additional microbial profiling. The CON and DY showed difference (P ≤ 0.05) in β diversity throughout the trial. Prevalence of SE in cecal contents was lower (P ≤ 0.05) in DY across all time-points. Lower abundance of Salmonella spp. was also shown in DY by liner discriminant analysis effect size (LEfSe). DY increased (P ≤ 0.05) diversity of bacterial species in the cecal contents in DY at 10 and 14 dpi. For the SE challenged birds, SE reduction in DY was observed at 3 dpi and until the end of the trial at 14 dpi confirming a numerically larger difference between groups as well as an increase in bacterial species diversity in DY. It could be hypothesized that the SE reduction shown immediately after the challenge and the greater SE reduction shown after 10 dpi may be the synergistic effect of the combined feed additives.

A Multi-Scale Approach to Investigate Adhesion Properties of Pseudomonas aeruginosa PAO1 to Geotrichum candidum LG-8, a Potential Probiotic Yeast

This study investigated properties of Pseudomonas aeruginosa PAO1 adhesion to Geotrichum candidum LG-8 cells in variable pH and salt conditions. The primary mechanism was revealed by multi-scale microscopy technics. The adhesion of PAO1 to the living fungus occurred within 1 h and was limited at concentrations of bile salts higher than 0.5%. The adhesion efficiency gradually increased to 58.1% with the pH increasing from 2.0 to 7.0 and then decreased to 48.2% at pH 9.0. However, the dead LG-8 has an advantage over the living ones to adhere PAO1 in same pH and bile salt conditions. Optical microscopy showed that both unsterilized and sterilized G. candidum LG-8 cells removed approximately one hundred fold bacteria in 4 h. Laser scanning confocal microscopy (LSCM) analysis indicated that polysaccharides of the fungus contributed to adhesion. Scanning electron microscopy (SEM) analysis proved that syrup-like EPS (extracellular polymeric substances) of LG-8 coating PAO1 was in part a mechanism. Atomic force microscopy (AFM) showed roughness of the LG-8 surface changed in the adhesion process. Furthermore, a pedestal-like structure of bacteria was observed by transmission electron microscopy (TEM) analysis, indicating that the bacteria were also actively involved in the adhesion process. G. candidum LG-8 is a potential candidate for the control of P. aeruginosa PAO1 in the food industry and immunodeficiency patients.

Marine Microalgae Biomolecules and Their Adhesion Capacity to Salmonella enterica sv. Typhimurium

Different molecules have been tested as analog receptors due to their capacity to bind bacteria and prevent cell adhesion. By using in vitro assays, the present study characterized the aqueous and alkaline extracts from microalgae Pavlova lutheri and Pavlova gyrans and evaluated the capacity of these extracts to adhere to enterobacteria (Salmonella Typhimurium). The aqueous and alkaline extracts of both species were fractionated via freeze-thawing, giving rise to soluble and insoluble (precipitate) fractions in cold water. The obtained fractions were studied using thermogravimetric, methylation analyses, and using 1D and 2D NMR techniques. The cold-water-soluble fractions obtained from the aqueous extracts were mainly composed of highly branched (1→3),(1→6)-β-glucans, whereas the cold-water-precipitate fractions were constituted by (1→3)-β-glucans. The alkaline extract fractions showed similar compositions with a high protein content, and the presence of glycosides (sulfoquinovosylglycerol (SQG), digalactosylglycerol (DGG)), and free fatty acids. The linear (1→3)-β-glucans and the alkaline extract fractions showed an adhesion capacity toward Salmonella. The chemical composition of the active fractions suggested that the presence of three-linked β-glucose units, as well as microalgal proteins and glycosides, could be important in the adhesion process. Therefore, these microalgal species possess a high potential to serve as a source of anti-adhesive compounds.

Modified soybean meal polysaccharide with high adhesion capacity to Salmonella

Carbohydrates are known to act as analog receptors for bacteria and therefore are promising alternatives for the control and prevention of bacterial infections. The present study evaluated the chemical structure of modified soybean meal polysaccharides and their capacity to adhere enterobacteria (Salmonella Typhimurium) and to interfere with the bacteria adhesion to the known analogue receptors, using in vitro assays. For this, soybean meal suspensions were subjected to a thermochemical extraction process and structural analyses showed that the fraction with higher adhesion and adhesion-inhibition potential, SAP, was constituted by two types of polysaccharides: a partially depolymerized pectin, of high molar mass, composed of xylogalacturonan and rhamnogalacturonan regions (SAP1, 545.5 kDa), and a (1 → 4)-linked-β-D-galactan of low molar mass (SAP2, 8.7 kDa). The results showed a high affinity of Salmonella for galactans, while high molar mass pectins showed no adhesion capacity. The chemical compositions of the fractions suggested that galactose could be responsible for the recognition process in the adhesion process. Other factors, such as structure and degree of polymerization of the polymers, may also be influencing the adhesion process. Modified soybean meal polysaccharides appear to be a promising alternative agent to antibiotics for the control and prevention of foodborne diseases.

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.

Biobased Sanitizer Delivery System for Improved Sanitation of Bacterial and Fungal Biofilms

Biofilms can persist in food-processing environments because of their relatively higher tolerance and resistance to antimicrobials including sanitizers. In this study, a novel biobased sanitizer composition was developed to effectively target biofilms and deliver chlorine-based sanitizers to inactivate bacterial and fungal biofilms. The biobased composition was developed by encapsulating a chlorine-binding polymer in a biobased yeast cell wall particle (YCWP) microcarrier. This study demonstrates the high affinity of biobased compositions to bind target bacterial and fungal cells and inactivate 5 logs of model pathogenic bacteria and fungi in wash water without and with high organic load (chemical oxygen demand = 2000 mg/L) in 30 s and 5 min, respectively. For the sanitation of biofilms, this biobased sanitizer can inactivate 7 logs of pathogenic bacteria and 3 logs of fungi after 1 h treatment, whereas the 1 h treatment using conventional chlorine-based sanitizer can only achieve 2-3 log reduction for bacterial biofilms and 1-2 log reduction for fungal biofilms, respectively. The enhanced antimicrobial activity can be attributed to three factors: (a) localized high concentration of chlorine bound on the YCWPs; (b) high affinity of YCWPs to bind diverse microbes; and (c) improved stability in an organic-rich aqueous environment. In summary, these unique attributes of biobased carriers will significantly enhance the sanitation efficacy of biofilms, reduce the persistence and transmission of antimicrobial resistant microbes, limit the use of antimicrobial chemicals, and improve the cost-effectiveness of sanitizers.

Assessment of yeast Saccharomyces cerevisiae component binding to Mycobacterium avium subspecies paratuberculosis using bovine epithelial cells

Background

Since yeast Saccharomyces cerevisiae and its components are being used for the prevention and treatment of enteric diseases in different species, they may also be useful for preventing Johne’s disease, a chronic inflammatory bowel disease of ruminants caused by Mycobacterium avium spp. paratuberculosis (MAP). This study aimed to identify potential yeast derivatives that may be used to help prevent MAP infection. The adherence of mCherry-labeled MAP to bovine mammary epithelial cell line (MAC-T cells) and bovine primary epithelial cells (BECs) co-cultured with yeast cell wall components (CWCs) from four different yeast strains (A, B, C and D) and two forms of dead yeast from strain A was investigated.

Results

The CWCs from all four yeast strains and the other two forms of dead yeast from strain A reduced MAP adhesion to MAC-T cells and BECs in a concentration-dependent manner after 6-h of exposure, with the dead yeast having the greatest effect.

Conclusions

The following in vitro binding studies suggest that dead yeast and its’ CWCs may be useful for reducing risk of MAP infection.

Influence of Feeding Enzymatically Hydrolyzed Yeast Cell Wall on Growth Performance and Digestive Function of Feedlot Cattle during Periods of Elevated Ambient Temperature

In experiment 1, eighty crossbred steers (239±15 kg) were used in a 229-d experiment to evaluate the effects of increasing levels of enzymatically hydrolyzed yeast (EHY) cell wall in diets on growth performance feedlot cattle during periods of elevated ambient temperature. Treatments consisted of steam-flaked corn-based diets supplemented to provide 0, 1, 2, or 3 g EHY/hd/d. There were no effects on growth performance during the initial 139-d period. However, from d 139 to harvest, when 24-h temperature humidity index averaged 80, EHY increased dry matter intake (DMI) (linear effect, p<0.01) and average daily gain (ADG) (linear effect, p = 0.01). There were no treatment effects (p>0.10) on carcass characteristics. In experiment 2, four Holstein steers (292±5 kg) with cannulas in the rumen and proximal duodenum were used in a 4×4 Latin Square design experiment to evaluate treatments effects on characteristics of ruminal and total tract digestion in steers. There were no treatment effects (p>0.10) on ruminal pH, total volatile fatty acid, molar proportions of acetate, butyrate, or estimated methane production. Supplemental EHY decreased ruminal molar proportion of acetate (p = 0.08), increased molar proportion of propionate (p = 0.09), and decreased acetate:propionate molar ratio (p = 0.07) and estimated ruminal methane production (p = 0.09). It is concluded that supplemental EHY may enhance DMI and ADG of feedlot steers during periods of high ambient temperature. Supplemental EHY may also enhance ruminal fiber digestion and decrease ruminal acetate:propionate molar ratios in feedlot steers fed steam-flaked corn-based finishing diets.

Quantitative evaluation of E. coli F4 and Salmonella Typhimurium binding capacity of yeast derivatives

The target of the present study was to quantify the capacity of different commercially available yeast derivatives to bind E. coli F4 and Salmonella Typhimurium. In addition, a correlation analysis was performed for the obtained binding numbers and the mannan-, glucan- and protein contents of the products, respectively. In a subsequent experiment, different yeast strains were fermented and treated by autolysis or French press to obtain a concentrated yeast cell wall. The capacity of yeast cell wall products to bind E. coli F4 and Salmonella Typhimurium was assessed with a quantitative microbiological microplate-based assay by measuring the optical density (OD) as the growth parameter of adhering bacteria. Total mannan and glucan were determined by HPLC using an isocratic method and a Refractive Index (RI) Detector. Total protein was determined by Total Kjeldahl Nitrogen (TKN). Statistical analyses were performed with IBM SPSS V19 using Spearman correlation and Mann Whitney U Test.

Different yeast derivatives show different binding numbers, which indicate differences in product quality.

Interestingly, the binding numbers for Salmonella Typhimurium are consistently higher (between one and two orders of magnitude) than for E. coli F4.

We could demonstrate some statistical significant correlations between the mannan- and glucan content of different yeast derivatives and pathogen binding numbers; however, for the different yeast strains fermented under standardized laboratory conditions, no statistically significant correlations between the mannan- and glucan content and the binding numbers for E. coli and Salmonella Typhimurium were found.

Interestingly, we could demonstrate that the yeast autolysis had a statistically significant difference on E. coli binding in contrast to the French press treatment. Salmonella binding was independent of these two treatments.

As such, we could not give a clear statement about the binding factors involved. We propose that many more factors apart from mannan- and glucan content, such as cell wall structure, strain diversity, structural diversity, structural surroundings, and non-specific interactions play important roles in pathogen immobilization.