Viable Yeast Research Articles

Microbial quality and Aflatoxin levels of sorghum grains (Sorghum bicolor) irradiated with gamma rays, low energy electron beam (LEEB) and high energy electron beam (HEEB)

Sorghum grains (Sorghum bicolor) are used as food components for man as well as feed for animals. However, there have been reported cases of microbial contamination on sorghum grains. The present study investigated the comparative effects of gamma rays, low energy electron beam (LEEB) and high energy electron beam (HEEB) on the microbial quality and mycotoxin levels of sorghum grains. Sorghum grains were purchased from a local market in Accra, Ghana, and packaged in zip-lock bags. Samples were exposed to irradiation doses of 2, 4, 6, 8, and 10 kGy, and the un-irradiated sorghum grains served as control. For LEEB, the ILU-6 accelerator (250 keV) was used, and for HEEB ELEKTRONIKA 10-10 accelerator (9 MeV) was used. Gamma Chamber 5000 Co-60 source was used for gamma irradiation. Total viable counts, total coliforms, Bacillus cereus, Staphylococcus aureus, Salmonella spp, yeasts, and molds counts were determined using standard methods. Aflatoxins B1, B2, G1, and G2 were also evaluated. The presumptive yeast and molds were further analyzed using MALDI-TOF. All three sources of irradiation significantly reduced the microbial populations of the sorghum grains, and subsequently eliminated the microorganisms at high doses. However, at 10 kGy, total viable counts as well as yeasts and molds were still detected for LEEB. Aspergillus flavus was identified as an organism associated with the sorghum grains. The aflatoxin levels were below the detection limits. Gamma rays and HEEB were more effective than LEEB.

Microbial communities of a variety of 75 homemade fermented vegetables.

Fermentation is an ancient practice of food preservation. Fermented vegetables are popular in Eastern European and Asian countries. They have received a growing interest in Western countries, where they are mainly manufactured at domestic and artisanal scales and poorly characterized. Our aim was to investigate the microbial communities and the safety of French homemade fermented vegetables, in the frame of a citizen science project. Fermented vegetables and the data associated with their manufacture were collected from citizens and characterized for pH, NaCl concentration, and microbiology by culturomics and 16S DNA metabarcoding analysis. Lactic acid bacteria (LAB) and yeast isolates were identified by 16S rRNA gene sequencing and D1/D2 domains of the large subunit of the rRNA gene, respectively. The 75 collected samples contained 23 types of vegetables, mainly cabbage, followed by carrots and beets, and many mixtures of vegetables. They were 2 weeks to 4 years old, and their median pH was 3.56, except for two samples with a pH over 4.5. LAB represented the dominant viable bacteria. LAB concentrations ranged from non-detectable values to 8.7 log colony-forming units (CFU)/g and only depended on the age of the samples, with the highest most frequently observed in the youngest samples (<100 days). The 93 LAB isolates identified belonged to 23 species, the two mains being Lactiplantibacillus pentosus/plantarum and Levilactobacillus brevis. The other microbial groups enumerated (total aerobic bacteria, halotolerant bacteria, Gram-negative bacteria, and acetic acid bacteria) generally showed lower concentrations compared to LAB concentrations. No pathogenic bacteria were detected. Viable yeasts were observed in nearly half the samples, at concentrations reaching up to 8.0 log CFU/g. The 33 yeast clones identified belonged to 16 species. Bacterial metabarcoding showed two main orders, namely, Lactobacillales (i.e., LAB, 79% of abundance, 177 of the 398 total ASVs) and Enterobacterales (19% of abundance, 191 ASVs). Fifteen LAB genera were identified, with Lactiplantibacillus and Levilactobacillus as the most abundant, with 41 and 12% of total reads, respectively. Enterobacterales members were mainly represented by Enterobacteriaceae and Yersiniaceae. This study is the first wide description of the microbiota of a large variety of homemade fermented vegetables and documents their safety.

Shaping the chromatic characteristics of red wines by using biofilm-detached cells of Starmerella bacillaris strains

The aim of this study was to evaluate the effects of 10 Starmerella bacillaris strains inoculated as planktonic or biofilm-detached cells on the chromatic characteristics of Montepulciano d’Abruzzo wine. Wines inoculated with biofilm-detached cells of St. bacillaris were characterized by a higher content of glycerol and viable yeast cells and a lower content of ethanol than those obtained with planktonic cells. Pyruvic acid content ranged from 45.99 mg/L to 48.19 mg/L and from 41.13 mg/L to 45.9 mg/L in wines fermented with biofilm-detached and planktonic cells, respectively. Wines obtained with biofilm-detached cells showed levels of anthocyanins ranging from 506.8 mg/L to 659.9 mg/L, while those fermented with free cells of St. bacillaris ranged from 518 mg/L to 612.6 mg/L. Similarly, the content of polyphenols was higher in wines inoculated with biofilm-detached cells. The different amounts of these compounds resulted in differences in the wine's color. Wines obtained with biofilm-detached cells of St. bacillaris had lower b* and h* values than those obtained with planktonic cells. These wines also showed higher a* values, indicating the presence of a stronger red color than the others, and lower clarity (L*). Moreover, the data obtained highlighted that it is possible to predict the color of young wines from must measurements. Further studies will be done to evaluate the role of other non-Saccharomyces yeasts, grown under different aggregation states, in the definition of wine color.

Kicking sleepers out of bed: Macrophages promote reactivation of dormant Cryptococcus neoformans by extracellular vesicle release and non-lytic exocytosis.

Macrophages play a key role in disseminated cryptococcosis, a deadly fungal disease caused by Cryptococcus neoformans. This opportunistic infection can arise following the reactivation of a poorly characterized latent infection attributed to dormant C. neoformans. Here, we investigated the mechanisms underlying reactivation of dormant C. neoformans using an in vitro co-culture model of viable but non-culturable (VBNC; equivalent of dormant) yeast cells with bone marrow-derived murine macrophages (BMDMs). Comparative transcriptome analysis of BMDMs incubated with log, stationary phase or VBNC cells of C. neoformans showed that VBNC cells elicited a reduced transcriptional modification of the macrophage but retaining the ability to regulate genes important for immune response, such as NLRP3 inflammasome-related genes. We further confirmed the maintenance of the low immunostimulatory capacity of VBNC cells using multiplex cytokine profiling, and analysis of cell wall composition and dectin-1 ligands exposure. In addition, we evaluated the effects of classic (M1) or alternative (M2) macrophage polarization on VBNC cells. We observed that intracellular residence sustained dormancy, regardless of the polarization state of macrophages and despite indirect detection of pantothenic acid (or its derivatives), a known reactivator for VBNC cells, in the C. neoformans-containing phagolysosome. Notably, M0 and M2, but not M1 macrophages, induced extracellular reactivation of VBNC cells by the secretion of extracellular vesicles and non-lytic exocytosis. Our results indicate that VBNC cells retain the low immunostimulatory profile required for persistence of C. neoformans in the host. We also describe a pro-pathogen role of macrophage-derived extracellular vesicles in C. neoformans infection and reinforce the impact of non-lytic exocytosis and the macrophage profile on the pathophysiology of cryptococcosis.

Evaluating the quality of soy residue‐supplemented Korean traditional rice wine and its lactic acid bacteria

AbstractBackground and ObjectivesTraditional Korean rice wine (makgeolli), contains various microorganisms, including lactic acid bacteria (LAB). This study investigated the utilization of biji, a by‐product of soy processing, as a substitute for rice in makgeolli fermentation. We evaluated the functional properties of biji‐makgeolli and examined the probiotic properties of LAB isolated from it.FindingsBiji‐makgeolli exhibited lower sugar and alcohol contents and higher pH and acidity than 100% rice makgeolli (control). Moreover, biji‐makgeolli displayed higher total viable cells (5.54–6.32 log CFU/g), yeast (4.23–6.59 log CFU/g), and LAB (5.44–6.48 log CFU/g) than control (5.26, 2.59, and 5.23 log CFU/g), which increased with biji addition. Furthermore, biji‐makgeolli showed higher total phenolic content, antioxidant capacity, and α‐glucosidase inhibitory activity, increasing with biji addition. Three LAB strains were isolated from makgeolli, identified as Pediococcus pentosaceus)‐KX886792 in control (CW) and P. pentosaceus‐KX886790 (RW), and Lactobacillus coryniformis (RM) in 50% biji replaced makgeolli. All groups (CW, RW, and RM) survived exposure to pH 3 for 3 h and 0.3% bile salts for 24 h and exhibited the ability to adhere to HT‐29 cells. RW (20.7%) and RM (27.5%) showed antioxidant effects, having higher ABTS+ values than CW (7.5%). The expression of tumor necrosis factor‐α and interleukin‐8 was significantly suppressed in RW and RM compared with that in CW. RW and RM showed antimicrobial activity against Escherichia coli. Additionally, RM was active against Staphylococcus aureus and exhibited a cholesterol‐lowering effect.ConclusionsBiji enhances the antioxidant capacity of makgeolli, and LAB isolated from biji‐makgeolli exhibit potential probiotic properties.Significance and NoveltyBiji is a potential additive for producing plant‐derived LAB in makgeolli and developing functional foods.

Using dielectrophoretic spectra to identify and separate viable yeast cells.

Immotile yeast cells were transiently moved in nonuniform sinusoidal electric fields using multiple pairs of micro-parallel cylindrical electrodes equipped with a sequential signal generator (SSG) to analyze cell viability at a clinical scale for the brewery/fermentation industry. Living yeast cells of Saccharomyces cerevisiae during the exponential-stationary phase, with a cell density of 1.15 × 105 cells mL-1 were suspended in sucrose medium. The conductivity (σs) was adjusted to 0.01 S m-1 with added KCl. Cells exposed in electric field strengths ranging from 32.89 to 40.98 kV m-1, exhibited positive dielectrophoresis (pDEP) with the lower critical frequencies (LCF) at 85.72 ± 3.59 kHz. The optimized value of LCF was shifted upwards to 780.00 ± 83.67 kHz when σswas increased to 0.10 S m-1. Dielectrophoretic and LCF spectra (translational speed of cells vs. electric field frequencies) of yeast suspensions during positive dielectrophoresis were analyzed in terms of the dielectric properties of the cell membrane and cytoplasm which reflect yeast cell viability and metabolic health status. The dielectrophoretic collection yield of cells using positive dielectrophoresis was reported on the monitor of sequential signal generator software to evaluate the number of living and dead cells through a real-time image processing analyzer. The spectra of both positive dielectrophoresis of the living and dead cells had distinguishable dielectric properties. The conductivity of the yeast cytoplasm (σc) of the dead cells was significantly less (≈ ≤ 0.05 S m-1) than that of the living yeast cells which typically had a cytoplasmic conductivity of ≈ 0.2 S m-1. This difference between viable and non-viable cells is sufficient for cell separation procedures. KEY POINTS: • Dielectrophoresis can be used to separate viable and non-viable yeast cells, • Cellular dielectric properties can be derived from the analysis of their dielectric spectra, • Cytoplasmic conductivity of viable cells is ≈ 0.2 S m-1 while that of non-viable cells ≈ ≤ 0.05 S m-1.

The effects of double gelatin containing chitosan nanoparticles-calcium alginate coatings on the stability of chicken breast meat.

The effects of gelatin coatings (2% and 4%) containing chitosan nanoparticles (ChNPs; 1% and 2%), in combination with calcium-alginate coatings (CA; 2%), on quality attributes and shelf life of chicken breast meat were evaluated at 4°C for 12 days. The results indicated that double-active gelatin-calcium alginate coatings had significant (p < .05) effects on moisture and protein content. Incorporation of ChNPs into double gelatin-CA coatings led to significant reduction (p < .05) in TBARS, pH, and TVB-N values at the end of storage. The counts of total viable count (TVC), coliforms, yeasts, and molds were significantly (p < .05) lower in all coated samples, particularly in treated samples by 4% gelatin containing 2% ChNPs + 2% CA coatings (6.85, 6.78, and 5.91 log CFU/g, respectively, compared with 8.35, 8.76, and 7.71 log CFU/g in control) at the end of keeping time. The results of sensory attributes showed that the coated samples had higher overall acceptability scores compared with the untreated samples. A synergistic relationship between the concentrations of gelatin and ChNPs was observed in maintaining the quality characteristics of meat samples during storage. Therefore, this study aims to evaluate the performance of double gelatin coating containing ChNPs in combination with CA coating in the storage quality improvement of chicken breast meat stored for 12 days at 4 °C to develop novel and practical coatings for meat and meat products.

Effect of Yeast Cell Wall on Gut Health, Immunity and Milk Production of Dairy Cattle in Normal and Heat Stress Conditions. Review

This review focuses on the most recent literature to bring to light the major beneficial effects of the yeast cell wall (YCW) and its products on dairy cattle. These products include viable yeast, yeast culture, nutritional yeast, and fractionated yeast products. The yeast cell wall is one of these products and belongs to the fractionated yeast products used to promote production performance and health in dairy cows. The yeast and YCW were proven to have positive impacts on dairy cattle performance in terms of milk yield, milk components, and overall quality. As well, these products showed beneficial effects under heat stress conditions. The YCW is a natural fermentation derivative of yeast cells such as Saccharomyces cerevisiae species consists mainly of β-glucan (29% to 64%), mannan (31%), and some other compounds like protein (13%), lipids (9%), chitin (1–2%) with β-glucan and mannan being the main bioactive molecules. The mode of action through which YCW elicit their beneficial functions in dairy cow explain their effect on cows' metabolism and digestion, immunity, rumen and intestine health, and subsequent performance and well-being. These modes of action include improving gastrointestinal (GI) tract health, stimulating immune system components as it is considered an immunomodulator additive, mycotoxin binding ability, and improving antioxidant capacity. Therefore, yeast and YCW products are one of the promising areas of ruminant nutrition in dairy cows, not only because of their nutritional and health benefits to dairy cows but also due to their negligible residual effects on dairy cows’ bodies and products.

Fast and Non-Invasive Evaluation of Yeast Viability in Fermentation Processes Using Raman Spectroscopy and Machine Learning

Fermentation processes used for producing alcoholic beverages such as beer, wine, and cider have a long history, having been developed early on across different civilizations. In most instances, yeast strains are used for fermentation processes, e.g., at breweries and wineries. Monitoring of yeast viability, cell count, and growth behavior is essential to ensure a controlled fermentation process. However, classical microbiological techniques to monitor fermentation process parameters are time-consuming and require sampling, along with the risk of contamination. Nowadays, industries are moving toward automation and digitalization. This necessitates state-of-the-art process analytical technologies to ensure an efficient and controlled process to obtain high-quality product outputs. Hence, there is a strong need for a fast, non-invasive, and generally applicable method to evaluate the viability of yeast cells during fermentation to warrant the standardization and purity of produced products in industrial applications. The aim of our study is to discriminate between viable and non-viable yeast in various culture media using Raman spectroscopy (RS) followed by data analysis with machine learning (ML) tools. These techniques allow for rapid, non-invasive analysis addressing the limitations of traditional methods. The present work primarily focuses on the evaluation of RS combined with predictive ML models in a non-real-time setting. Our goal is to adapt these techniques for future application in real-time monitoring and determination of yeast viability in biotechnological processes. We demonstrate that RS, in combination with ML, is a promising tool for non-invasive inline monitoring of fermentation processes.

Ascending renal infection following experimental candiduria by Candida tropicalis in immunocompromised mice

The present study evaluated renal infection resulting from the implantation of C. tropicalis in the bladder of immunosuppressed mice. Yeasts were implanted in two manners: planktonic and via preformed biofilm on a small catheter fragment (SCF). Renal histopathology and cultures was performed 72 and 144 h after cystotomy was carried out in mice from three groups: group I contained non-contaminated mice implanted with a sterile SCF; group II mice received a sterile SCF plus a yeast suspension containing 1 × 107 yeasts/mL in a planktonic form; group III mice were implanted with a SCF containing preformed C. tropicalis biofilm. Viable yeasts were found in the kidneys of mice from both groups II and III. However, after 72 h the planktonic cells (group II) invaded more quickly than the sessile cells (group III). Over a longer period (144 h), group III exhibited a more invasive infection (50% of the animals presented renal infection and the renal fungal load was 3.2 log10 CFU/g tissue) than in group II, where yeasts were not found. C. tropicalis introduced into the bladder in two ways (in planktonic or biofilm form) were able to reach the kidney and establish a renal fungal infection, causing interstitial disorders. The data of the present study therefore support the hypothesis of an ascending pathway for renal infections by C. tropicalis. Furthermore, the biofilm resulted in a greater and progressive risk of renal infection, attributed to the slow detachment of the yeasts.

Transmission of beneficial yeasts accompanies offspring production in Drosophila-An initial evolutionary stage of insect maternal care through manipulation of microbial load?

Parent-to-offspring transmission of beneficial microorganisms is intimately interwoven with the evolution of social behaviors. Ancestral stages of complex sociality-microbe vectoring interrelationships may be characterized by high costs of intensive parental care and hence only a weak link between the transmission of microbial symbionts and offspring production. We investigate the relationship between yeast symbiont transmission and egg-laying, as well as some general factors thought to drive the "farming" of microscopic fungi by the fruit fly Drosophila melanogaster, an insect with no obvious parental care but which is highly dependent on dietary microbes during offspring development. The process of transmitting microbes involves flies ingesting microbes from their previous environment, storing and vectoring them, and finally depositing them to a new environment. This study revealed that fecal materials of adult flies play a significant role in this process, as they contain viable yeast cells that support larval development. During single patch visits, egg-laying female flies transmitted more yeast cells than non-egg-laying females, suggesting that dietary symbiont transmission is not random, but linked to offspring production. The crop, an extension of the foregut, was identified as an organ capable of storing viable yeast cells during travel between egg-laying sites. However, the amount of yeast in the crop reduced rapidly during periods of starvation. Although females starved for 24 h deposited a smaller amount of yeast than those starved for 6 h, the yeast inoculum produced still promoted the development of larval offspring. The results of these experiments suggest that female Drosophila fruit flies have the ability to store and regulate the transfer of microorganisms beneficial to their offspring via the shedding of fecal material. We argue that our observation may represent an initial evolutionary stage of maternal care through the manipulation of microbial load, from which more specialized feedbacks of sociality and microbe management may evolve.

Alginate-Based 3D A549 Cell Culture Model to Study Paracoccidioides Infection

A three-dimensional (3D) lung aggregate model based on sodium alginate scaffolds was developed to study the interactions between Paracoccidioides brasiliensis (Pb) and lung epithelial cells. The suitability of the 3D aggregate as an infection model was examined using cell viability (cytotoxicity), metabolic activity, and proliferation assays. Several studies exemplify the similarity between 3D cell cultures and living organisms, which can generate complementary data due to the greater complexity observed in these designed models, compared to 2D cell cultures. A 3D cell culture system of human A549 lung cell line plus sodium alginate was used to create the scaffolds that were infected with Pb18. Our results showed low cytotoxicity, evidence of increased cell density (indicative of cell proliferation), and the maintenance of cell viability for seven days. The confocal analysis revealed viable yeast within the 3D scaffold, as demonstrated in the solid BHI Agar medium cultivation. Moreover, when ECM proteins were added to the alginate scaffolds, the number of retrieved fungi was significantly higher. Our results highlight that this 3D model may be promising for in vitro studies of host–pathogen interactions.

Volatile changes associated with fresh‐cut jackfruit during storage

AbstractHeadspace solid‐phase microextraction and gas chromatography mass spectrometry (HS‐SPME‐GCMS) was performed to study the aroma volatile profile of fresh‐cut jackfruit under different storage temperature conditions (4 and 10°C). Total viable counts (TVC) and yeast and mould count (Y&amp;M) were also simultaneously estimated. Sensory analysis revealed a loss in texture along with an increase in ripeness during storage at both the storage temperatures. It was observed that the volatile profile demonstrated significant changes at different storage temperatures during storage. Principal component analysis performed on volatile compounds allowed to differentiate fresh samples from stored samples, the differential pattern of correlation with volatiles was observed at 4 and 10°C. During storage the ester content increased linearly at both temperatures, however acetate esters predominated initially at 4°C, followed by other non‐acetate esters. In the case of 10°C storage, higher levels of ethyl ester derivatives along with other esters were obtained in the later period of storage due to enhanced microbial activity.

Influence of compression kinetics during tableting of fluidized bed-granulated microorganisms on microbiological and physical-mechanical tablet properties

As tablets are convenient to administer to patients, ensure safe dosing and allow cost-effective production on a large scale, they are the favored dosage form for numerous active pharmaceutical ingredients but also for the administration of viable probiotic microorganisms. Granules with viable yeast cells (Saccharomyces cerevisiae) formed by fluidized bed granulation with dicalcium phosphate (DCP), lactose (LAC) or microcrystalline cellulose (MCC) as carrier materials were tableted using a compaction simulator. Besides the compression stress, the compression speed was systematically studied by varying consolidation time and dwell time. The microbial survival as well as physical properties of the tablets, e.g., porosity and tensile strength, were determined. Higher compression stresses result in lower porosities. While on the one hand this has a detrimental effect on microbial survival (due to increased pressure and shear stress during particle rearrangement / densification), on the other hand it results in higher tensile strengths. At the same compression stress, a prolonged dwell time resulted in lower porosity and thus in lower survival rates but higher tensile strength. Against that, consolidation time showed no significant influence on the considered tablet quality attributes. Since changes of the tensile strength related survival rate were negligible (due to opposite but balancing dependence on porosity), high production speeds could be used for tableting of these granules without additional loss of viability, as long as tablets with the same tensile strength are produced.

Growing conditions of Saccharomyces boulardii for the development of potentially probiotic mead: Fermentation kinetics, viable cell counts and bioactive compounds.

Mead is an alcoholic beverage produced by the fermentation of a diluted honey solution by the action of yeast. Recently, research has shown the potential of S. boulardii for brewing beer and in the development of probiotic alcoholic beverages and, to date, no research has examined for mead production. The aim of this study was to evaluate the growth conditions of S. boulardii for the development of potentially probiotic mead. The findings show that initial wort soluble solids conditions of 30 °Brix and initial concentration of 0.030 g/L of S. boulardii obtain potentially probiotic mead with viable yeast cells of 6.53 Log10 CFU/mL, alcohol content of 5.05%, and has the presence of total phenolics (17.72 mg GAE/100 mL) and natural antioxidants (62.79 and 1.37 µmol TE/100 mL for ABTS and FRAP methods, respectively). In conclusion, S. boulardii has a potential for the development of probiotic mead.

Provocation: prolonged maturation of beer is of unproven benefit

Approaches to brewing are suffused with dogmatic insistence that certain techniques are unequivocally linked to the delivery of quality products. Amongst these belief sets is the perseverance with prolonged maturation (or ‘conditioning’) times post-fermentation. Historically the justification for these lagering techniques was to allow settling of solids, carbonation, flavour maturation and removal of chill haze entities. As science and technology have advanced it is unequivocally the case that solids and chill haze precursors can be dealt with in short order and without the need for lengthy treatments. &#x0D; Equally it is perfectly possible to deliver specified levels of carbonation without the need for all the carbon dioxide to be introduced via yeast action. However, there remain many who feel that the nature of carbonation differs depending on which approach is taken. Herein lies one of the research areas that the author proposes. The perception of carbonation is not primarily due to bubble release on the palate, but rather is through the detection of carbonic acid. Is there a difference in the availability of this form of the gas depending on the mode of carbonation and to what extent does the adsorption of the carbonic acid on polypeptides in the beer have a role to play? &#x0D; In terms of flavour, the advocates for lagering insist that there needs to be a handling of vicinal diketones, acetaldehyde, and hydrogen sulphide. However, all of these can be controlled through attention to primary fermentation. Then, the proponents for maturation insist that there is a desirable release of non-volatile materials into beer, which substances supposedly benefit the balance and mouthfeel of the lager. These include amino acids and nucleotides. It seems to this author however that the likeliest explanation for the greatly increased levels of these materials and of pH is autolysis of yeast. This, together with the disadvantageous impact of increased free amino nitrogen and higher pH on aspects such as biological stability, flavour stability and foam, should convince any brewer that there is a sound argument for avoiding the prolonged contact of beer with yeast. Indeed, a metabolomic approach to studying changes in non-volatile substances under conditions where there is little or no autolysis, revealed no detectable changes in any entity. &#x0D; The author is open to being convinced that there are yet unidentified materials that are developed (whether through the action of viable yeast or by yeast autolysis) as beer is stored, substances which can be proven through sound organoleptic investigation to benefit the flavour of beer. Perhaps the Japanese term kokumi is what we are looking for here: ‘rich taste’. This is believed to be afforded by γ-glutamyl peptides and, inter alia, these are to be found in yeast extracts. Herein lies the second experimental approach that the author recommends for pursuit.

Study on the fermentation effect of Rhodotorula glutinis utilizing tofu whey wastewater and the influence of Rhodotorula glutinis on laying hens.

Tofu whey wastewater (TWW) is the wastewater of tofu processing, which is rich in a variety of nutrients. Rhodotorula glutinis can make full use of TWW to ferment and reproduce yeast cells, produce carotenoids and other nutrients, improve the utilization value of TWW, and reduce environmental pollution and resource waste. In this study, the nutrient composition changes of TWW treated by Rhodotorula glutinis were analyzed to reformulate TWW medium, and the optimal composition and proportion of TWW medium that can improve the biomass and carotenoids production of Rhodotorula glutinis were explored. Meanwhile, the Rhodotorula glutinis liquid obtained under these conditions was used to prepare biological feed for laying hens, and the effect of Rhodotorula glutinis growing on TWW as substrate on laying performance and egg quality of laying hens were verified. The results showed that the zinc content of TWW after Rhodotorula glutinis fermentation increased by 62.30%, the phosphorus content decreased by 42.31%, and the contents of vitamin B1, B2 and B6 increased to varying degrees. The optimal fermentation conditions of Rhodotorula glutinis in the TWW medium were as follow: the initial pH was 6.40, the amount of soybean oil, glucose and zinc ions was 0.80 ml/L, 16.32 g/L, and 20.52 mg/L, respectively. Under this condition, the biomass of Rhodotorula glutinis reached 2.23 g/L, the carotenoids production was 832.86 μg/g, and the number of effective viable yeast count was 7.08 × 107 cfu/ml. In addition, the laying performance and egg quality of laying hens fed Rhodotorula glutinis biological feed were improved. In this study, we analyzed the composition changes of TWW, optimized the fermentation conditions of Rhodotorula glutinis in TWW medium, explored the influence of Rhodotorula glutinis utilizing TWW on laying layers, and provided a new idea for the efficient utilization of TWW.

Improving microbiological and physicochemical properties of fresh-cut apples using carvacrol emulsions

The cut or sliced form of apples are more prone to chemical deterioration and microbial growth. In this work, quality changes (physicochemical properties, sensory quality, and microbial growth) of fresh-cut apples stored at 4 °C for 15 days were studied after immersion treatment (water, biopolymer complex; free carvacrol, and carvacrol emulsion). Whey protein isolate/high methoxyl pectin-based carvacrol emulsions effectively delayed the browning process and reduced variation in chemical quality compared to other groups. Apples treated with carvacrol emulsions were more favored by panelists at the middle- and late-stages of storage. Additionally, the presence of carvacrol emulsions improved microbial safety, as demonstrated by the number of viable bacteria (<6 log CFU/g) and yeast and mold (<5 log CFU/g) after 15 d of storage. 16 S rRNA Gene Sequencing was used to identify the bacterial species responsible for the spoilage of fresh-cut apples. These results show that carvacrol emulsions are a potential preservation alternative for fresh-cut apples.

Application of oleaster leaves (Elaeagnus angustifolia L.) essential oil and natural nanoparticle preservatives in frankfurter-type sausages: An assessment of quality attributes and stability during refrigerated storage

The effects of oleaster leave essential oil (OLEOs: 1000 and 2000 ppm) in combination with nisin nanoparticles (200 ppm) and ε-polylysine nanoparticles (2000 ppm) on the physicochemical, microbiological and sensory properties of the emulsion-type sausages without added chemical nitrite/nitrate salts were evaluated during 45 days of storage. Nanoparticle attributes were assessed, including encapsulation efficiency (EE%), zeta potential, nanoparticles size, FTIR analysis, and thermal stability (DSC). Overall, ε-PL nanoparticles (ε-PL-NPs) were thermally more stable and showed higher EE% (91.52%) and zeta potential (37.80%) as compared to nisin nanoparticles (82.85%) and (33.60%), respectively. The use of combined ε-PL-NPs (2000 ppm) + Ni-NPs (200 ppm) with oleaster leaves essential oil (2000 ppm) resulted in a higher pH value (5.88), total phenolic content (10.45 mg/100 g) and lower TBARS (2.11 mg/kg), and also decreased total viable bacteria (1.28 Log CFU/g), Clostridium perfringens (1.43 Log CFU/g), E. coli (0.24 Log CFU/g), Staphylococcus aureus (0.63 Log CFU/g), and molds and yeasts (0.86 Log CFU/g) count in samples at day 45 in comparison to the control (120 ppm nitrite). The consumers approved sensory traits in nitrite-free formulated sausages containing ε-PL-NPs and Ni-NPs combined with OLEOs.

Microbial Decontamination of Red Wine by Pulsed Electric Fields (PEF) after Alcoholic and Malolactic Fermentation: Effect on Saccharomyces cerevisiae, Oenococcus oeni, and Oenological Parameters during Storage.

New techniques are required to replace the use of sulfur dioxide (SO2) or of sterilizing filtration in wineries, due to those methods' drawbacks. Pulsed electric fields (PEF) is a technology capable of inactivating microorganisms at low temperatures in a continuous flow with no detrimental effect on food properties. In the present study, PEF technology was evaluated for purposes of microbial decontamination of red wines after alcoholic and malolactic fermentation, respectively. PEF combined with SO2 was evaluated in terms of microbial stability and physicochemical parameters over a period of four months. Furthermore, the effect of PEF on the sensory properties of red wine was compared with the sterilizing filtration method. Results showed that up to 4.0 Log10 cycles of S. cerevisiae and O. oeni could be eradicated by PEF and sublethal damages and a synergetic effect with SO2 were also observed, respectively. After 4 months, wine treated by PEF after alcoholic fermentation was free of viable yeasts; and less than 100 CFU/mL of O. oeni cells were viable in PEF-treated wine added with 20 ppm of SO2 after malolactic fermentation. No detrimental qualities were found, neither in terms of oenological parameters, nor in the sensory parameters of wines subjected to PEF after storage time.