Search

The yeast microflora of various dairy products sold in Russia was studied using RFLP analysis of the 5.8S-ITS rDNA fragment and sequencing of the D1/D2 domain of 26S rDNA. Most of the fermented milk products studied were dominated by lactose-utilizing yeasts Kluyveromyces and Debaryomyces and by lactose-negative yeasts Saccharomyces, Monosporozyma, Pichia, Geotrichum, and Yarrowia. The yeast Kluyveromyces marxianus was present in most of the fermented milk products studied, while the related species K. lactis was found only in some samples of ayran, curds, and cheese. The dominance of K. marxianus is apparently associated with their physiological characteristics (thermo- and osmotolerance), which provide these yeasts with better adaptation to industrial fermentation conditions. The dominant species in mixed-fermentation dairy products, Saccharomyces cerevisiae and Monosporozyma unispora, were completely absent in cheeses and lactic acid fermentation products. In general, the species composition of yeasts largely depended on the fermented milk product, the type of milk, and the specific manufacturer. [ABSTRACT FROM AUTHOR]

Blue mould disease is one of the most common postharvest apple diseases caused by Penicillium expansum. Some antagonistic yeasts have been used through laboratory experimentation to control the postharvest diseases of apples, but their control effectiveness needs further improvement. Induction of antagonistic yeasts by elicitors is an effective method that improves the biocontrol effectiveness of the yeast. Our previous study demonstrated that alginate oligosaccharide (AOS) significantly enhanced the biocontrol effectiveness of Debaryomyces hansenii in combating postharvest diseases in apples. Furthermore, the yeast's potential physiological biocontrol mechanisms have been previously documented. However, the molecular mechanisms associated with this were unclear. This study investigated the possible molecular mechanisms behind the enhanced efficacy of biological control by D. hansenii Y3 when cultured with AOS, based on transcriptome and proteome analysis. There were 408 differential genes and 114 differential proteins induced by AOS, which were mainly involved in enhancing the growth, reproduction, metabolism, stress resistance and energy synthesis, and more. These improvements collectively contribute to the heightened antagonistic efficacy of D. hansenii Y3. Our findings offer a valuable reference for future investigations into the utilisation of antagonistic yeasts for preventing and managing postharvest diseases in fruits and vegetables. [ABSTRACT FROM AUTHOR]

The African fig fly, Zaprionus indianus Gupta (Diptera: Drosophilidae), is an ecologically diverse pest species that interacts with and feeds on various microbial pathogens including bacteria and yeast found in decomposing fruits. However, the interaction of Z. indianus with its microbial community and microbial pathogens is obscure. To determine the presence of fungal pathogens, we collected wild Z. indianus from the northwestern part of the Indian subcontinent. Based on molecular identification and phylogenetic analysis, Debaryomyces hansenii (Zopf) Lodder & Kreger‐van Rij (isolate ziha1) was the most commonly observed fungus associated with Z. indianus. Furthermore, we identified two more opportunistic fungal pathogens: Aspergillus flavus Link (isolate zias2), and Pichia kudriavzevii Boidin, Pignal & Besson (isolate zibd3). The interaction of isolated fungi with Z. indianus was evaluated in terms of larval mortality, adult emergence, and fecundity. Debaryomyces hansenii ziha1 resulted in 90% emergence rate for adults, and did not cause significant mortality in the larval stage. In contrast, A. flavus zias2 and P. kudriavzevii zibd3 showed a significant reduction in fecundity and caused 99% and 74% larval mortality of Z. indianus, respectively. In the laboratory oviposition preference assay, mated females of Z. indianus preferred D. hansenii ziha1 supplemented food with a positive oviposition index compared to the uninfected control and compared to food infected with P. kudriavzevii zibd3 or A. flavus zias2. These findings underscore Z. indianus' potential to act as a reservoir for both symbiotic and pathogenic fungal species, some of which may be further harnessed for effective fruit fly pest control strategies. [ABSTRACT FROM AUTHOR]

Rare Earth Elements (REE), also known as Lanthanides (Ln3+), are a group of 17 elements showing peculiar physical and chemical properties. Unlike technological applications, very little is known about the physiological role and toxicity of Ln3+ on biological systems, in particular on microorganisms (e.g., bacteria), which represent the most abundant domains on our planet. Up to now, very limited studies have been conducted due to Ln3+ precipitation with some anions commonly present in the culture media. Therefore, the development of a minimal medium is essential to allow the study of Ln3+-microbial interactions, limiting considerably the precipitation of insoluble salts. In this regard, a new minimal culture medium capable of solubilizing large amounts of Ln3+ and allowing the growth of different microbial taxa was successfully developed. Assays have shown that the medium is capable of solubilizing Ln3+ up to 100 times more than other common culture media and allowing the growth of 63 bacteria and 5 fungi. The kinetic growth of one yeast and one Gram-positive bacterium has been defined, proving to support superior growth and biomass compared to other commonly used minimal media. Moreover, the sensitivity and uptake/absorption of a Bacillus stratosphericus strain were tested, highlighting its capability to tolerate concentrations up to 10 mM of either Cerium, Gadolinium or Lanthanum and accumulate different quantities of the three. [ABSTRACT FROM AUTHOR]

The aim of this research was to determine the influence of yeast strains (previously isolated from the fermentation process) on selected quality parameters of sauerkraut. For this purpose, shredded and salted (2.5% w/w) cabbage of the Galaxy variety was fermented in the absence of oxygen with the addition of 2 × 106 cells of a selected yeast culture. The control sample was spontaneously fermented sauerkraut without yeast addition. The obtained sauerkraut was analysed in terms of the content of selected organic acids, sugars and polyols (HPLC), selected volatile compounds (HS-SPME-GC-TOFMS), colour (CieLAB) and aroma (QDA). Yeast P. fermentans, Rh. mucilaginosa and W. anomalus reduced crucial sauerkraut components such as lactic acid, glycerol, and certain volatile compounds, leading to decreased aroma intensity and acceptability. Additionally, an increase in glucosinolate decomposition products was observed. Conversely, D. hansenii positively influenced sauerkraut quality by enhancing lactic acid content and exhibiting similar volatile characteristics to those of the control. Two of the three samples fermented with D. hansenii received high sensory analysis scores akin to those of the control. Sauerkraut fermented with Cl. lusitaniae yeast contained elevated levels of volatile compounds—alcohols, esters and lactones—resulting in an intense floral aroma, albeit receiving lower overall ratings due to deviation from the typical profile. [ABSTRACT FROM AUTHOR]

The main objective of this work was to evaluate the combined effect of a biotechnology process, based on selected yeast strains, and a high-pressure homogenization (HPH) treatment on the microbiological quality, structural organization of proteins, chitin content, and antioxidant activity of a mixture of cricket powder (Acheta domesticus) and water. Compared to untreated samples, the cricket matrix treated with HPH four times at 180 MPa promoted the growth of the inoculated Yarrowia lipolytica and Debaryomyces hansenii strains. HPH did not affect the concentration of chitin; however, the combination with microorganisms tended to reduce the content. Although the antioxidant activity increased from 0.52 to 0.68 TAC mM/TE after a 48 h incubation in the control, it was further improved by the combination of HPH and D. hansenii metabolism, reaching a value of 0.77 TAC mM/TE. The combination of the two approaches also promoted a reduction in the intensity of bands with molecular weights between 31 and 21.5 kDa in favor of bands with a lower molecular weight. In addition, HPH treatment reduced the number of accessible thiols, suggesting protein structure changes that may further impact the technological properties of cricket powder. [ABSTRACT FROM AUTHOR]

This study characterized a novel intracellular α-glucosidase, produced by Debaryomyces hansenii. The enzyme was purified through ultra-filtration, ammonium sulfate precipitation, chromatography Q-Sepharose and Sephacryl S-200 column. SDS-PAGE analysis confirmed the molecular weight of the purified protein to be 125 kDa. The enzyme exhibited maximum activity at pH 4.5and 50 °C and stability at pH 4.0 – 6.0 at 30 – 60 °C. The optimum isomalto-oligosaccharides (IMOs) bio-synthesis temperature using 400 g/L maltose was evaluated to be 35 °C with an optimum enzyme unit determined as 4.34 U g−1. The enzyme exhibits maximum maltose utilization of 78%, with or without inorganic salts, and was inhibited by ZnCl 2 , CoCl 2 and CuSO 4. Using maltose, the K m and V max values were 7.55 µM and 909 µmol/ml/mg respectively. In 3 L bioreactor, 4.34 U of enzyme produced IMOs with 47% purity utilizing 400 g/L maltose at 35 °C for 14 h. Furthermore, low purity IMOs was passed through cationic ion exchange resins to obtain high purity IMOs by separating glucose and maltose. This pioneering study produced high purity IMOs with 89% purity and 60% yield with greater conversion efficiency using a purified enzyme with a higher concentration of maltose and chromatographic method, which were confirmed by HPLC. [Display omitted] • Highly active α-glucosidase from D.hansenii was homogenized and purified. • Optimization studies enhanced isomaltooligosaccharides (IMOs) purity and yield. • Production of IMOs (47% purity) through biotransformation in a 3 L bioreactor. • High purity IMOs (89%) production using chromatographic separation. • IMOs component distribution confirmed by HPLC-RID. [ABSTRACT FROM AUTHOR]

The halotolerant non-conventional yeast Debaryomyces hansenii can grow in media containing high concentrations of salt (up to 4 M), metabolize alternative carbon sources than glucose, such as lactose or glycerol, and withstand a wide range of temperatures and pH. These inherent capabilities allow this yeast to grow in harsh environments and use alternative feedstock than traditional commercial media. For example, D. hansenii could be a potential cell factory for revalorizing industrial salty by-products, using them as a substrate for producing new valuable bioproducts, boosting a circular economy. In this work, three different salty by-products derived from the dairy and biopharmaceutical industry have been tested as a possible feedstock for D. hansenii 's growth. The yeast was not only able to grow efficiently in all of them but also to produce a recombinant protein (Yellow Fluorescent Protein, used as a model) without altering its performance. Moreover, open cultivations at different laboratory scales (1.5 mL and 1 L) were performed under non-sterile conditions and without adding fresh water or any nutritional supplement to the cultivation, making the process cheaper and more sustainable. [Display omitted] • D. hansenii can thrive in high-salt containing feedstocks for producing recombinant proteins. • Side-streams with high salt content are used without sterilization in lab-scale fermentations. • No addition of fresh water to the media is needed, waste-streams can be used directly from the source. [ABSTRACT FROM AUTHOR]

The extracted olive pomace (EOP) is an industrial lignocellulosic by-product of olive pomace oil extraction, currently mainly used for energy production through combustion. In this work, the hemicellulosic fraction of EOP was selectively hydrolyzed by diluted acid hydrolysis to obtain pentose-rich hydrolysates that can potentially be upgraded by Debaryomyces hansenii, targeting xylitol production. The monosaccharides and degradation by-products released along the pre-treatment were quantified and several detoxification methods for the removal of potentially toxic compounds were evaluated, including pH adjustment to 5.5, the use of anion-exchange resins, adsorption into activated charcoal, concentration by evaporation, and membrane techniques, i.e., nanofiltration. The latter approach was shown to be the best method allowing the full removal of furfural, 41% of 5-hydroxymethylfurfural, 54% of acetic acid, and 67% of the phenolic compounds present in the hydrolysate. The effects of the supplementation of both non-detoxified and detoxified hydrolysates were also assessed. The non-detoxified hydrolysate, under aerobic conditions, supported the yeast growth and xylitol production at low levels. Supplementation with the low-cost corn steep liquor of the nanofiltration detoxified hydrolysate showed a higher xylitol yield (0.57 g/g) compared to the non-detoxified hydrolysate. The highest xylitol productivity was found in hydrolysate detoxified with anionic resins (0.30 g/L·h), which was 80% higher than in the non-detoxified culture medium. Overall, the results showed that EOP dilute acid hydrolysates can efficiently be used for xylitol production by D. hansenii if detoxification, and supplementation, even with low-cost supplements, are performed. [ABSTRACT FROM AUTHOR]

ABSTRACTThe objective of this experiment was to select D. hansenii isolates that are stable in dry fermented sausage (DFS) production and can positively affect the quality. D. hansenii isolates were examined for production of biogenic amines, β-glucuronidase, β-glucosidase, proteolytic, and lipolytic enzymatic activities. The acid and salt tolerance of D. hansenii isolates were also examined. DFS inoculated with selected D. hansenii isolates were analyzed for microorganisms, weight loss, Aw, and pH. DFS was also subjected to analyses of color, texture profile, reducing sugar, volatile basic nitrogen (VBN), lipid oxidation, and free fatty acid. Twenty-two D. hansenii isolates were isolated. None of these D. hansenii isolates produced biogenic amines, and all strains were negative for β-glucuronidase and β-glucosidase activities. After examining these strains for proteolysis, lipolysis, and salt and acid tolerance, D. hansenii isolates SMFM2021-C14, SMFM2021-S8, and SMFM2021-SL3 were selected to be used in DFS. During the processing of DFS, the groups treated with D. hansenii isolate SMFM2021-S8 or SMFM2021-SL3 showed lower (p

Abstract Background The development of a sustainable business model with social acceptance, makes necessary to develop new strategies to guarantee the growth, health, and well-being of farmed animals. Debaryomyces hansenii is a yeast species that can be used as a probiotic in aquaculture due to its capacity to i) promote cell proliferation and differentiation, ii) have immunostimulatory effects, iii) modulate gut microbiota, and/or iv) enhance the digestive function. To provide inside into the effects of D. hansenii on juveniles of gilthead seabream (Sparus aurata) condition, we integrated the evaluation of the main key performance indicators coupled with the integrative analysis of the intestine condition, through histological and microbiota state, and its transcriptomic profiling. Results After 70 days of a nutritional trial in which a diet with low levels of fishmeal (7%) was supplemented with 1.1% of D. hansenii (17.2 × 105 CFU), an increase of ca. 12% in somatic growth was observed together with an improvement in feed conversion in fish fed a yeast-supplemented diet. In terms of intestinal condition, this probiotic modulated gut microbiota without affecting the intestine cell organization, whereas an increase in the staining intensity of mucins rich in carboxylated and weakly sulphated glycoconjugates coupled with changes in the affinity for certain lectins were noted in goblet cells. Changes in microbiota were characterized by the reduction in abundance of several groups of Proteobacteria, especially those characterized as opportunistic groups. The microarrays-based transcriptomic analysis found 232 differential expressed genes in the anterior-mid intestine of S. aurata, that were mostly related to metabolic, antioxidant, immune, and symbiotic processes. Conclusions Dietary administration of D. hansenii enhanced somatic growth and improved feed efficiency parameters, results that were coupled to an improvement of intestinal condition as histochemical and transcriptomic tools indicated. This probiotic yeast stimulated host-microbiota interactions without altering the intestinal cell organization nor generating dysbiosis, which demonstrated its safety as a feed additive. At the transcriptomic level, D. hansenii promoted metabolic pathways, mainly protein-related, sphingolipid, and thymidylate pathways, in addition to enhance antioxidant-related intestinal mechanisms, and to regulate sentinel immune processes, potentiating the defensive capacity meanwhile maintaining the homeostatic status of the intestine.

The effects of various yeast species isolated from raw-milk cheese were evaluated in Beyaz cheese. Four batches of cheeses were produced, in which the control cheese involved only commercial starter culture while YL, DH and KL cheeses were produced with the incorporation of individual Yarrowia lipolytica, Debaryomyces hansenii and Kluyveromyces lactis, respectively. The chemical composition, microbial counts, sensory attributes, volatile compounds and textural properties of cheeses were determined on days 1, 30, and 60 during the ripening period. The results obtained demonstrated that chemical, microbial and sensory properties of cheese varied depending on yeast species. The cheese with Y. lipolytica was the most preferred and it contained more short chain fatty acids, particularly butyric acid. This result could be due to the higher fat content and advanced lipolytic activity. The ripening index of DH was found to be higher than the other cheeses, showing an advanced proteolytic activity in relation to lower hardness in the texture profile. K. lactis was associated with lactose metabolism and promoted the development of Lactococcus spp. The results highlighted a potential use of yeasts as adjunct cultures in Beyaz cheese to develop the sensory properties such as texture and flavor. [ABSTRACT FROM AUTHOR]

The present study explores the effects of two supplementation levels of Debaryomyces hansenii (1.1% and 2.2%) as a probiotic in a reference low fish meal-based diet on the skin mucosal tissue in Sparus aurata. This study includes the evaluation of fish performance coupled with a holistic study of the skin mucosa: i) a transcriptomic study of the skin tissue, and ii) the evaluation of its secreted mucus both in terms of skin mucosal-associated biomarkers and its defensive capacity by means of co-culture analysis with two pathogenic bacteria. Results showed that after 70 days of diet administration, fish fed the diet supplemented with D. hansenii at 1.1% presented increased somatic growth and a better feed conversion ratio, compared to fish fed the control diet. In contrast, fish fed the diet including 2.2% of the probiotic presented intermediate values. Regarding gene regulation, the probiotic administration at 1.1% resulted in 712 differentially expressed genes (DEGs), among which 53.4% and 46.6% were up- and down-regulated, respectively. In particular, D. hansenii modulated some skin biological processes related to immunity and metabolism. Specifically, D. hansenii administration induced a strong modulation of some immune biological-related processes (61 DEGs), mainly involved in B- and T-cell regulatory pathways. Furthermore, dietary D. hansenii promoted the skin barrier function by the upregulation of anchoring junction genes (23 DEGs), which reinforces the physical defense against potential skin damage. In contrast, the skin showed modulated genes related to extracellular exosome and membrane organization (50 DEGs). This modulated functioning is of great interest, particularly in relation to the increased skin mucus defensive capacity observed in the bacterial co-culture in vitro trials, which could be related to the increased modulation and exudation of the innate immune components from the skin cells into the mucus. In summary, the modulation of innate immune parameters coupled with increased skin barrier function and cell trafficking potentiates the skin's physical barrier and mucus defensive capacity, while maintaining the skin mucosa's homeostatic immune and metabolic status. These findings confirmed the advantages of D. hansenii supplementation in low fish meal-based diets, demonstrating the probiotic benefits on cultured marine species. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to evaluate the effect of Debaryomyces hansenii isolated from dry-aged beef on the tenderness and flavor attributes of low-grade beef during dry aging. Methods: Five D. hansenii strains were isolated from dry-aged beef samples. The rump of low-grade beef was inoculated with individual D. hansenii isolates and subjected to dry aging for 4 weeks at 5°C and 75% relative humidity. Microbial contamination levels, meat quality attributes, and flavor attributes in the dry-aged beef were measured. Results: Of the five isolates, the shear force of dry-aged beef inoculated with SMFM201812-3 and SMFM201905-5 was lower than that of control samples. Meanwhile, all five isolates increased the total free amino acid, glutamic acid, serine, glycine, alanine, and leucine contents in dry-aged beef. In particular, the total fatty acid, palmitic acid, and oleic acid contents in samples inoculated with D. hansenii SMFM201905-5 were higher than those in control samples. Conclusion: These results indicate that D. hansenii SMFM201905-5 might be used to improve the quality of beef during dry aging. [ABSTRACT FROM AUTHOR]

Desalter effluent (DE) is typically discharged into a petroleum wastewater treatment plant, but its high salt concentration deteriorates the biological treatment. This study used various dilution rates to investigate the treatment of a synthetic DE containing dodecane under saline conditions using a halotolerant yeast, Debaryomyces hansenii, to determine the optimum substrate concentration for use in continuous stirred‐tank reactors (CSTRs). A literature review indicated that this study was the first to examine the biological treatment of DE using D. hansenii in a CSTR system. At a low dodecane substrate concentration, DE did not inhibit D. hansenii growth, and the experimental data approached the Monod model, with μmax and Ks selected as 0.08 h−1 and 1575 mg L−1, respectively. The optimum removal of chemical oxygen demand (95.7% and 85%) was obtained at dilution rates of 0.007 and 0.026 d−1. Using D. hansenii in a CSTR system appeared to be a sustainable approach for the biological treatment of DE. Scale‐up of these laboratory findings to the industrial scale is required to confirm that petroleum DE can be treated using equalization and filtration tanks as a continuous bioreactor. Adjusting the dilution rate can provide sufficient time for biodegradation and hydrocarbon removal from high salt DE by halotolerant yeasts like D. hansenii. [ABSTRACT FROM AUTHOR]

The effluent from a petroleum desalting unit contains salts, emulsifiers, hydrocarbons (mainly n‐dodecane), and other contaminants. Conventional wastewater treatment cannot be used to treat this salt‐containing effluent; thus, alternative approaches must be explored. In this study, a halo‐tolerant yeast, Debaryomyces hansenii, was investigated for the removal of varying concentrations of n‐dodecane in a simulated desalter effluent (SDE). Then, the removal of n‐dodecane was optimized using response surface methodology (RSM). The effects of pH, salt, temperature, and n‐dodecane concentration were evaluated, and a mathematical model was developed and verified. The results showed that complete removal of n‐dodecane was achieved at 20°C and a salt concentration of 1–5 g L−1. The main factors in COD removal are temperature, n‐dodecane concentration, pH, and the interaction between n‐dodecane and temperature. Salt concentration does not affect COD removal or the growth rate of D. hansenii in a SDE. Applying RSM suggested that interactional effects among the operational variables include temperature, n‐dodecane concentration, and pH on the yeast's removal rate. Overall, it can be concluded that the use of D. hansenii could be a viable solution at a wide range of salt concentrations (1–5 g L−1) for desalter wastewater treatment in petroleum refining. [ABSTRACT FROM AUTHOR]

The aim of this research was to determine the influence of yeast strains (previously isolated from the fermentation process) on selected quality parameters of sauerkraut. For this purpose, shredded and salted (2.5% w/w) cabbage of the Galaxy variety was fermented in the absence of oxygen with the addition of 2 × 106 cells of a selected yeast culture. The control sample was spontaneously fermented sauerkraut without yeast addition. The obtained sauerkraut was analysed in terms of the content of selected organic acids, sugars and polyols (HPLC), selected volatile compounds (HS-SPME-GC-TOFMS), colour (CieLAB) and aroma (QDA). Yeast P. fermentans, Rh. mucilaginosa and W. anomalus reduced crucial sauerkraut components such as lactic acid, glycerol, and certain volatile compounds, leading to decreased aroma intensity and acceptability. Additionally, an increase in glucosinolate decomposition products was observed. Conversely, D. hansenii positively influenced sauerkraut quality by enhancing lactic acid content and exhibiting similar volatile characteristics to those of the control. Two of the three samples fermented with D. hansenii received high sensory analysis scores akin to those of the control. Sauerkraut fermented with Cl. lusitaniae yeast contained elevated levels of volatile compounds—alcohols, esters and lactones—resulting in an intense floral aroma, albeit receiving lower overall ratings due to deviation from the typical profile.

The present study explores the effects of two supplementation levels of Debaryomyces hansenii (1.1% and 2.2%) as a probiotic in a reference low fish meal-based diet on the skin mucosal tissue in Sparus aurata. This study includes the evaluation of fish performance coupled with a holistic study of the skin mucosa: i) a transcriptomic study of the skin tissue, and ii) the evaluation of its secreted mucus both in terms of skin mucosal-associated biomarkers and its defensive capacity by means of co-culture analysis with two pathogenic bacteria. Results showed that after 70 days of diet administration, fish fed the diet supplemented with D. hansenii at 1.1% presented increased somatic growth and a better feed conversion ratio, compared to fish fed the control diet. In contrast, fish fed the diet including 2.2% of the probiotic presented intermediate values. Regarding gene regulation, the probiotic administration at 1.1% resulted in 712 differentially expressed genes (DEGs), among which 53.4% and 46.6% were up- and down-regulated, respectively. In particular, D. hansenii modulated some skin biological processes related to immunity and metabolism. Specifically, D. hansenii administration induced a strong modulation of some immune biological-related processes (61 DEGs), mainly involved in B- and T-cell regulatory pathways. Furthermore, dietary D. hansenii promoted the skin barrier function by the upregulation of anchoring junction genes (23 DEGs), which reinforces the physical defense against potential skin damage. In contrast, the skin showed modulated genes related to extracellular exosome and membrane organization (50 DEGs). This modulated functioning is of great interest, particularly in relation to the increased skin mucus defensive capacity observed in the bacterial co-culture in vitro trials, which could be related to the increased modulation and exudation of the innate immune components from the skin cells into the mucus. In summary, the modulation of innate immune parameters coupled with increased skin barrier function and cell trafficking potentiates the skin’s physical barrier and mucus defensive capacity, while maintaining the skin mucosa’s homeostatic immune and metabolic status. These findings confirmed the advantages of D. hansenii supplementation in low fish meal-based diets, demonstrating the probiotic benefits on cultured marine species.

Background: The development of a sustainable business model with social acceptance, makes necessary to develop new strategies to guarantee the growth, health, and well-being of farmed animals. Debaryomyces hansenii is a yeast species that can be used as a probiotic in aquaculture due to its capacity to i) promote cell proliferation and differentiation, ii) have immunostimulatory effects, iii) modulate gut microbiota, and/or iv) enhance the digestive function. To provide inside into the effects of D. hansenii on juveniles of gilthead seabream (Sparus aurata) condition, we integrated the evaluation of the main key performance indicators coupled with the integrative analysis of the intestine condition, through histological and microbiota state, and its transcriptomic profiling. Results: After 70 days of a nutritional trial in which a diet with low levels of fishmeal (7%) was supplemented with 1.1% of D. hansenii (17.2 × 105 CFU), an increase of ca. 12% in somatic growth was observed together with an improvement in feed conversion in fish fed a yeast-supplemented diet. In terms of intestinal condition, this probiotic modulated gut microbiota without affecting the intestine cell organization, whereas an increase in the staining intensity of mucins rich in carboxylated and weakly sulphated glycoconjugates coupled with changes in the affinity for certain lectins were noted in goblet cells. Changes in microbiota were characterized by the reduction in abundance of several groups of Proteobacteria, especially those characterized as opportunistic groups. The microarrays-based transcriptomic analysis found 232 differential expressed genes in the anterior-mid intestine of S. aurata, that were mostly related to metabolic, antioxidant, immune, and symbiotic processes. Conclusions: Dietary administration of D. hansenii enhanced somatic growth and improved feed efficiency parameters, results that were coupled to an improvement of intestinal condition as histochemical and transcriptomic tools indicated. This probiotic yeast stimulated host-microbiota interactions without altering the intestinal cell organization nor generating dysbiosis, which demonstrated its safety as a feed additive. At the transcriptomic level, D. hansenii promoted metabolic pathways, mainly protein-related, sphingolipid, and thymidylate pathways, in addition to enhance antioxidant-related intestinal mechanisms, and to regulate sentinel immune processes, potentiating the defensive capacity meanwhile maintaining the homeostatic status of the intestine. [ABSTRACT FROM AUTHOR]

This study assessed the effect of replacing pork lard with coconut oil and Debaryomyces hansenii inoculation on the biotransformation of amino acids into volatile compounds in a meat model system. Yeast counts, solid-phase microextraction, and gas chromatography/mass spectrometry were used to assess yeast growth and volatile production, respectively. Yeast growth was confirmed until 28 d, although the volatile profile changed until 39 d. Forty-three volatiles were quantified, and their odor activity values (OAVs) were calculated. The presence of fat and yeasts contributed to differences in volatiles. In pork lard models, a delayed formation of lipid-derived aldehyde compounds was observed, whereas in coconut oil models, the generation of acid compounds and their respective esters was enhanced. Yeast activity affected amino acid degradation, which produced an increase in branched-chain aldehydes and alcohols. The aroma profile in the coconut models was influenced by hexanal, acid compounds, and their respective esters, whereas in pork lard models, aroma was affected by methional (musty, potato) and 3-methylbutanal (green, cocoa). The yeast inoculation contributed to the generation of 3-methylbutanoic acid (cheesy) and phenylethyl alcohol (floral). The type of fat and yeast inoculation produced a differential effect on the aroma. [ABSTRACT FROM AUTHOR]

Yeasts play a critical role in the flavor formation of dry-cured ham. In this study, 41 yeast isolates from the dry-cured ham at different processing stages were evaluated for their technological properties. Debaryomyces hansenii was the most dominant yeast and has been detected at each phase of dry-cured ham, followed by Candida zeylanoides which was mainly detected in salting phase. Yarrowia bubula and Yarrowia alimentaria were found at the first two-phase of dry-cured ham. All isolates of yeast showed enzymatic activities against milk protein and tributyrin, while only 4 strains displayed proteolytic activity on meat protein. Yeast strains were grown in a meat model medium and volatile compounds were identified. The result showed that inoculated yeast strains could promote the production of volatiles and there were significant differences among strains. D. hansenii S25 showed the highest production of volatile compounds, followed by the strain C. zeylanoides C4. D. hansenii S25 was the highest producer of alcohols showing the highest production of benzeneethanol and 3-(methylthio)-1-propanol. Based on OAV and PLS analysis, D. hansenii S25 was strongly correlated with overall flavor and key volatile compounds of dry-cured ham, which could be selected as potential starter cultures.

This study investigated the effect of different Bacillus spp. and Debaryomyces spp., which are screened from Melopsittacus undulates crop milk on growth performance, intestinal morphology, intestinal microflora and antioxidant abilities in broilers. By screening the Bacillus spp. and Debaryomyces spp. from parrot’s crop milk, the properties of these microbial were examined in vitro accordingly. In animal experiments, 480 1-day-old Ross 308 broilers were randomly divided into 6 treatments as control (corn-soybean meal), Bacillus velezensis with 5 × 106 cfu/kg feed (BV), Bacillus subtilis with 5 × 106 cfu/kg feed (BS), Debaryomyces hansenii with 5 × 106 cfu/kg feed (DH), B. velezensis + Saccharomyces cerevisiae with 5 × 106 cfu/kg feed (BV + SC), and B. velezensis + D. hansenii with 5 × 106 cfu/kg feed (BV + DH). The results showed that chickens in BV, BV + SC, and BV + DH groups showed significantly higher body weight and average weight gain than control group at 21 days of age. Biochemistry of triglyceride values in BV and BV + SC had significantly decreased than in control group. Intestinal lactic acid bacteria were significantly higher in BV and BS groups than in the control group in ileum. The villus height of jejunum in BV + SC and BV + DH was significantly higher than in the control group. Glutathione peroxidase activity was significantly higher in BV, BS, BV + SC groups than in the control group, but immune assays had no significant differences among the groups. Based on the results of animal growth performance, the number of lactic acids, intestinal morphology, antioxidant activity, and immune system, BV and BV + SC groups possess better feed additives for broiler chickens.HIGHLIGHTS Bacillus spp. and Debaryomyces spp. affect on growth performance, intestinal morphology, intestinal microflora and antioxidant abilities in broiler chickens. Broilers with feed additives of Bacillus velezensis, Debaryomyces hansenii, Saccharomyces cerevisiae have higher body weight and average weight gain B. velezensis and B. velezensis + Saccharomyces cerevisiae groups possess better feed additives for broiler chickens.

Some yeast strains have been proposed as probiotics to improve the health of cultured fish. Cobia is a tropical benthopelagic fish species with potential for marine aquaculture; however, one of the main limitations to its large-scale production is the high mortality of fish larvae. In this study, we evaluated the probiotic potential of autochthonous yeasts from the intestines of cobia. Thirty-nine yeast isolates were recovered from the intestinal mucosa of 37 adult healthy cobia by culture methods. Yeasts were identified by sequencing of the ITS and D1/D2 regions of the 28S rRNA gene and typed by RAPD-PCR using the M13 primer. Yeast strains with unique RAPD patterns were characterized in terms of their cell biomass production ability; anti-Vibrio, enzymatic, and hemolytic activity; biofilm production; hydrophobicity; autoaggregation; polyamine production; safety; and protection of cobia larvae against saline stress. Candida haemuloni C27 and Debaryomyces hansenii C10 and C28 were selected as potential probiotics. They did not affect the survival of larvae and showed biomass production >1 g L−1, hydrophobicity >41.47%, hemolytic activity γ, and activity in more than 8 hydrolytic enzymes. The results suggest that the selected yeast strains could be considered as potential probiotic candidates and should be evaluated in cobia larvae. [ABSTRACT FROM AUTHOR]

The main objective of this work was to evaluate the combined effect of a biotechnology process, based on selected yeast strains, and a high-pressure homogenization (HPH) treatment on the microbiological quality, structural organization of proteins, chitin content, and antioxidant activity of a mixture of cricket powder (Acheta domesticus) and water. Compared to untreated samples, the cricket matrix treated with HPH four times at 180 MPa promoted the growth of the inoculated Yarrowia lipolytica and Debaryomyces hansenii strains. HPH did not affect the concentration of chitin; however, the combination with microorganisms tended to reduce the content. Although the antioxidant activity increased from 0.52 to 0.68 TAC mM/TE after a 48 h incubation in the control, it was further improved by the combination of HPH and D. hansenii metabolism, reaching a value of 0.77 TAC mM/TE. The combination of the two approaches also promoted a reduction in the intensity of bands with molecular weights between 31 and 21.5 kDa in favor of bands with a lower molecular weight. In addition, HPH treatment reduced the number of accessible thiols, suggesting protein structure changes that may further impact the technological properties of cricket powder.

The extracted olive pomace (EOP) is an industrial lignocellulosic by-product of olive pomace oil extraction, currently mainly used for energy production through combustion. In this work, the hemicellulosic fraction of EOP was selectively hydrolyzed by diluted acid hydrolysis to obtain pentose-rich hydrolysates that can potentially be upgraded by Debaryomyces hansenii, targeting xylitol production. The monosaccharides and degradation by-products released along the pre-treatment were quantified and several detoxification methods for the removal of potentially toxic compounds were evaluated, including pH adjustment to 5.5, the use of anion-exchange resins, adsorption into activated charcoal, concentration by evaporation, and membrane techniques, i.e., nanofiltration. The latter approach was shown to be the best method allowing the full removal of furfural, 41% of 5-hydroxymethylfurfural, 54% of acetic acid, and 67% of the phenolic compounds present in the hydrolysate. The effects of the supplementation of both non-detoxified and detoxified hydrolysates were also assessed. The non-detoxified hydrolysate, under aerobic conditions, supported the yeast growth and xylitol production at low levels. Supplementation with the low-cost corn steep liquor of the nanofiltration detoxified hydrolysate showed a higher xylitol yield (0.57 g/g) compared to the non-detoxified hydrolysate. The highest xylitol productivity was found in hydrolysate detoxified with anionic resins (0.30 g/L·h), which was 80% higher than in the non-detoxified culture medium. Overall, the results showed that EOP dilute acid hydrolysates can efficiently be used for xylitol production by D. hansenii if detoxification, and supplementation, even with low-cost supplements, are performed.

Exopolysaccharides produced by edible microorganisms exhibit excellent constructive physicochemical and significant biological activity, which provide advantages for the food or pharmaceutical industries. Two novel exopolysaccharides produced by Debaryomyces hansenii DH-1 were characterized, named S1 and S2, respectively. S1, with a molecular weight of 34.594 kDa, primarily consisted of mannose and glucose in a molar ratio of 12.19:1.00, which contained a backbone fragment of α-D-Manp-(1→4)-α-D-Manp-(1→2)-α-D-Glcp-(1→3)-α-D-Manp-(1→3)-β-D-Glcp-(1→4)-β-D-Manp-(1→. S2, with a molecular weight of 24.657 kDa, was mainly composed of mannose and galactose in a molar ratio of 4.00:1.00, which had a backbone fragment of α-D-Manp-(1→6)-β-D-Manp-(1→2)-α-D-Manp-(1→4)-α-D-Galp-(1→3)-β-D-Manp-(1→6)-α-D-Manp-(1→. Both S1 and S2 exhibited good thermal stability and potent hydroxyl radical scavenging activity, with ~98%. Moreover, S1 possessed an additional strong iron-reducing capacity. In vitro antitumor assays showed that S1 and S2 significantly inhibited the proliferation of Hela, HepG2, and PC-9 cancer cells. Moreover, PC-9 was more sensitive to S1 compared with S2. The above results indicate that S1 and S2 have great potential to be utilized as natural antioxidants and candidates for cancer treatment in the food and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to select D. hansenii isolates that are stable in dry fermented sausage (DFS) production and can positively affect the quality. D. hansenii isolates were examined for production of biogenic amines, β-glucuronidase, β-glucosidase, proteolytic, and lipolytic enzymatic activities. The acid and salt tolerance of D. hansenii isolates were also examined. DFS inoculated with selected D. hansenii isolates were analyzed for microorganisms, weight loss, Aw, and pH. DFS was also subjected to analyses of color, texture profile, reducing sugar, volatile basic nitrogen (VBN), lipid oxidation, and free fatty acid. Twenty-two D. hansenii isolates were isolated. None of these D. hansenii isolates produced biogenic amines, and all strains were negative for β-glucuronidase and β-glucosidase activities. After examining these strains for proteolysis, lipolysis, and salt and acid tolerance, D. hansenii isolates SMFM2021-C14, SMFM2021-S8, and SMFM2021-SL3 were selected to be used in DFS. During the processing of DFS, the groups treated with D. hansenii isolate SMFM2021-S8 or SMFM2021-SL3 showed lower (p <.05) hardness values of DFS. The sample treated with D. hansenii SMFM2021-S8 showed lower (p <.05) VBN and lipid oxidation contents than the others. The ratio of ω-6/ω-3 was lower (p <.05) in D. hansenii SMFM2021-SL3 treated group than in the other treatments. These results indicate that D. hansenii isolates SMFM2021-S8 and SMFM2021-SL3 might be useful in producing DFS to improve its quality. [ABSTRACT FROM AUTHOR]

Lupine-based seasoning sauce is produced similarly to soy sauces and therefore generates a comparable microbiota and aroma profile. While the koji state is dominated by Aspergillus oryzae, the microbiome of the moromi differs to soy moromi, especially in yeast composition due to the absence of Zygosaccharomyces rouxii and Debaryomyces hansenii as the dominant yeast. In this study, we monitored the addition of a carbohydrate source on the microbiome and aroma profile of the resulting sauce. Compared to previous studies, the usage of a yeast starter culture resulted in a sparsely diverse microbiota that was dominated by D. hansenii and T. halophilus. This led to a pH below 5 even after four months of incubation and most of the measured aroma compounds were pyrazines and acids. The addition of wheat and buckwheat resulted in a temporary change in the yeast consortium with the appearance of Z. rouxii and additional bacterial genera. The aroma profile differs in the presence of pyrazines and esters. Since no significant differences in the taste and odour of wheat-added and buckwheat-added sauce was sensed, both substrates influence the lupine sauce in a similar way. [ABSTRACT FROM AUTHOR]

This study investigated the effect of different Bacillus spp. and Debaryomyces spp., which are screened from Melopsittacus undulates crop milk on growth performance, intestinal morphology, intestinal microflora and antioxidant abilities in broilers. By screening the Bacillus spp. and Debaryomyces spp. from parrot's crop milk, the properties of these microbial were examined in vitro accordingly. In animal experiments, 480 1-day-old Ross 308 broilers were randomly divided into 6 treatments as control (corn-soybean meal), Bacillus velezensis with 5 × 106 cfu/kg feed (BV), Bacillus subtilis with 5 × 106 cfu/kg feed (BS), Debaryomyces hansenii with 5 × 106 cfu/kg feed (DH), B. velezensis + Saccharomyces cerevisiae with 5 × 106 cfu/kg feed (BV + SC), and B. velezensis + D. hansenii with 5 × 106 cfu/kg feed (BV + DH). The results showed that chickens in BV, BV + SC, and BV + DH groups showed significantly higher body weight and average weight gain than control group at 21 days of age. Biochemistry of triglyceride values in BV and BV + SC had significantly decreased than in control group. Intestinal lactic acid bacteria were significantly higher in BV and BS groups than in the control group in ileum. The villus height of jejunum in BV + SC and BV + DH was significantly higher than in the control group. Glutathione peroxidase activity was significantly higher in BV, BS, BV + SC groups than in the control group, but immune assays had no significant differences among the groups. Based on the results of animal growth performance, the number of lactic acids, intestinal morphology, antioxidant activity, and immune system, BV and BV + SC groups possess better feed additives for broiler chickens. Bacillus spp. and Debaryomyces spp. affect on growth performance, intestinal morphology, intestinal microflora and antioxidant abilities in broiler chickens. Broilers with feed additives of Bacillus velezensis, Debaryomyces hansenii, Saccharomyces cerevisiae have higher body weight and average weight gain B. velezensis and B. velezensis + Saccharomyces cerevisiae groups possess better feed additives for broiler chickens. [ABSTRACT FROM AUTHOR]

Background: Mannitol is a polyol sugar widely used in pharmaceutical and food industries which can be produced by bioconversion. Using of resting cells and methanol as a carbon source are strategies to increase the efficiency of mannitol production by increasing NAD(P)H needed in the reduction process. Objectives: This research aimed to optimize bioconversion condition by using resting cells of methylotrophic yeasts with methanol and fructose as carbon source and substrate, respectively. Methods: Several isolates were used including Candida sp, Debaryomyces nepalensis and Debaryomyces hansenii and three species suspected to be yeast isolated from a local paddy field. The methylotrophic characteristic of the yeasts was screened by turbidometry. The optimization of fermentation condition was conducted by varying cultivation time (24-96 hours), resting cell concentration (30-140 mg/mL), fructose concentration (7.5-15%), ammonium sulphate concentration (0.25-0.75%) and aeration condition (50-80%). Quantitative analysis of the mannitol was conducted by HPLC with NH2 column and Refractive Index Detector. Results: D. hansenii showed the highest yield value in mannitol production (23.17%), followed by D. nepalensis, Isolate A and Candida sp. (6.52%, 6.50% and 4.38%, respectively). Variation of bioconversion condition using D. hansenii showed that the highest resting cell concentration (140 mg/mL) incubated for 72 hours, moderate fructose concentration (10%), the highest ammonium sulphate concentration (0.75%) and moderate aeration condition (70%) would result in the highest yield value of mannitol (60%). Conclusion: This finding showed the potency of D. hansenii in mannitol production and gave preliminary information of its optimum fermentation condition. [ABSTRACT FROM AUTHOR]

Blueberry (Vaccinium corymbosum L.) is a crop with great potential for exportation and is very important for its antioxidant properties. However, this fruit is susceptible to different factors of deterioration and attack by pathogens. Botrytis cinerea is the main cause of post-harvest losses in this crop. Antagonistic yeasts from the Debaryomyces hansenii species, which is of marine origin, have been proposed as an alternative method for fungal control. For this reason, this study evaluated the in vitro and in vivo antagonistic capacity of the yeast against B. cinerea. The in vitro growth of the fungus was inhibited by 90% and germination was reduced by 100%, and through the production of volatile organic compounds, the growth of the pathogen was inhibited by 32.5%. Photographic evidence by electron microscopy revealed the effects caused by D. hansenii on B. cinerea. The incidence study showed a 50% reduction in the incidence of the disease caused by B. cinerea in blueberries, while quality parameters—such as soluble solids, titratable acidity, and pH—presented stable values, delaying the maturation process of the fruits. Likewise, the rate of reduction in firmness and physiological weight loss was lower, and the blueberries preserved their quality for a longer time. [ABSTRACT FROM AUTHOR]

Pollutants, such as polycyclic aromatic hydrocarbons (PAHs), e.g., benzo(a)pyrene (BaP), are common components of contaminating mixtures. Such compounds are ubiquitous, extremely toxic, and they pollute soils and aquatic niches. The need for new microorganism-based remediation strategies prompted researchers to identify the most suitable organisms to eliminate pollutants without interfering with the ecosystem. We analyzed the effect caused by BaP on the growth properties of Candida albicans, Debaryomyces hansenii, Rhodotorula mucilaginosa, and Saccharomyces cerevisiae. Their ability to metabolize BaP was also evaluated. The aim was to identify an optimal candidate to be used as the central component of a mycoremediation strategy. The results show that all four yeast species metabolized BaP by more than 70%, whereas their viability was not affected. The best results were observed for D. hansenii. When an incubation was performed in the presence of a cytochrome P450 (CYP) inhibitor, no BaP degradation was observed. Thus, the initial oxidation step is mediated by a CYP enzyme. Additionally, this study identified the D. hansenii DhDIT2 gene as essential to perform the initial degradation of BaP. Hence, we propose that D. hansenii and a S. cerevisiae expressing the DhDIT2 gene are suitable candidates to degrade BaP in contaminated environments. [ABSTRACT FROM AUTHOR]

Oil palm empty fruit bunch (OPEFB) is the largest biomass waste from the palm oil industry. The OPEFB has a lignocellulose content of 34.77% cellulose, 22.55% hemicellulose, and 10.58% lignin. Therefore, this material's hemicellulose and cellulose content have a high potential for xylitol and ethanol production, respectively. This study investigated the integrated microaerobic xylitol production by Debaryomyces hansenii and anaerobic ethanol semi simultaneous saccharification and fermentation (semi-SSF) by Saccharomyces cerevisiae using the same OPEFB material. A maximum xylitol concentration of 2.86 g/L was obtained with a yield of 0.297 g/gxylose. After 96 h of anaerobic fermentation, the maximum ethanol concentration was 6.48 g/L, corresponding to 71.38% of the theoretical ethanol yield. Significant morphological changes occurred in the OPEFB after hydrolysis and xylitol and ethanol fermentation were shown from SEM analysis. [ABSTRACT FROM AUTHOR]

Biosurfactants are surface active, amphiphilic, multifunctional, non-toxic and biodegradable alternatives to chemical surfactants. The present study reported biosurfactant production from yeast Debaryomyces hansenii CBS767 using soybean oil as the low-cost carbon source. Characterization of extracellularly synthesized biosurfactant revealed it as of glycolipid type. D. hansenii was able to synthesize the biosurfactant at diverse physiochemical conditions of temperature, pH, percentage of soyabean oil and incubation period. Isolated cell free extract displayed reducing activity as evident by synthesis of silver nanoparticles of size between 23.7 and 77.5 nm. This reducing action might be due to the presence of certain reducing metabolites in cell extract. Silver nanoparticles displayed distinct spherical morphology. This implies surface functionality of the biosurfactant as capping agent helping in regulating the process of nanoparticle aggregation. To aid the future optimization of biosurfactant production from D. hansenii, five support vector machine models were developed, trained and evaluated utilizing experimental optimization datasets. Significant prediction of E24, oil displacement and surface tension using these models encourage the use of machine learning in the future assessment of biosurfactant production. [ABSTRACT FROM AUTHOR]

The exploration of alternatives to the use of chemical preservatives in food is a topic that has attracted great attention. The implementation of regulations associated with the reduction of these elements directly affects the production of cured meat products, with the premise of looking for more "natural" alternatives. From a previously identified collection of 24 strains of Debaryomyces hansenii, isolated from dry meat products of the "Valle de los Pedroches" (Córdoba), a screening was carried out to determine which strains had inhibitory potential against a battery of fungi belonging to the genera Aspergillus, Penicillium, and Candida. After a series of general trials, four strains showing the greatest potential were selected by a streak inhibition assay performed at several concentrations of NaCl. The inhibitory activity of the selected D. hansenii strains was later evaluated by measuring their fungal antagonistic diffusible and volatile compound production following radial inhibition and mouth-to-mouth approaches, respectively. Growth aspects, sporulation, and morphology changes were also considered during these assays. The results support ideas already raised in previous studies, such as the presence of D. hanseniii could imply a reduction of pathogenic fungi in food. Autochthonous yeast strains inhibited not only the mycelial growth, but also sporulation, which strengthens the biocontrol activity of this yeast. Our results show that, under certain conditions, all tested D. hansenii strains were able to alter the growth/development of fungi, being especially evident in the cases of Penicillium expansum and Aspergillus niger. Finally, our research can facilitate the future comparison of results in this area, since we contributed to standardize the methodology described to date, we quantified the number of yeast cells and spores used during the experiments, we homogenized growth conditions for both, yeasts, and molds, and applied an image analyzer software to quantify the growth of the studied microorganisms in solid media. [ABSTRACT FROM AUTHOR]

Overall, 180 yeasts and bacteria isolated from the peel of citrus fruits were screened for their in vitro antagonistic activity against Penicillium digitatum and P. italicum, causative agents of green and blue mold of citrus fruits, respectively. Two yeast and three bacterial isolates were selected for their inhibitory activity on mycelium growth. Based on the phylogenetic analysis of 16S rDNA and ITS rDNA sequences, the yeast isolates were identified as Candida oleophila and Debaryomyces hansenii while the bacterial isolates were identified as Bacillus amyloliquefaciens, B. pumilus and B. subtilis. All five selected isolates significantly reduced the incidence of decay incited by P. digitatum and P. italicum on 'Valencia' orange and 'Eureka' lemon fruits. Moreover, they were effective in preventing natural infections of green and blue mold of fruits stored at 4 °C. Treatments with antagonistic yeasts and bacteria did not negatively affect the quality and shelf life of fruits. The antagonistic efficacy of the five isolates depended on multiple modes of action, including the ability to form biofilms and produce antifungal lipopeptides, lytic enzymes and volatile compounds. The selected isolates are promising as biocontrol agents of postharvest green and blue molds of citrus fruits. [ABSTRACT FROM AUTHOR]

This study assessed the effect of replacing pork lard with coconut oil and Debaryomyces hansenii inoculation on the biotransformation of amino acids into volatile compounds in a meat model system. Yeast counts, solid-phase microextraction, and gas chromatography/mass spectrometry were used to assess yeast growth and volatile production, respectively. Yeast growth was confirmed until 28 d, although the volatile profile changed until 39 d. Forty-three volatiles were quantified, and their odor activity values (OAVs) were calculated. The presence of fat and yeasts contributed to differences in volatiles. In pork lard models, a delayed formation of lipid-derived aldehyde compounds was observed, whereas in coconut oil models, the generation of acid compounds and their respective esters was enhanced. Yeast activity affected amino acid degradation, which produced an increase in branched-chain aldehydes and alcohols. The aroma profile in the coconut models was influenced by hexanal, acid compounds, and their respective esters, whereas in pork lard models, aroma was affected by methional (musty, potato) and 3-methylbutanal (green, cocoa). The yeast inoculation contributed to the generation of 3-methylbutanoic acid (cheesy) and phenylethyl alcohol (floral). The type of fat and yeast inoculation produced a differential effect on the aroma.

Introduction: Debaryomyces hansenii is a yeast widely used in meat fermentations as starter for the purpose of improving the aromatic quality of the final product. However, it has not been the subject of an extensive study regarding phenotypic characteristics important for starter selection, such as the capacity to grow at abiotic stress conditions occurring during fermentation, the ability to generate desirable aromas and the absence of virulence traits in yeasts. Aims: The aim of this study was to screen 60 strains of D. hansenii isolated from assorted foods for their potential application as starters in dry‐cured fermented sausages manufacture. Methods: The abiotic stress factors tested were low aw and pH and high concentration of salt, acetic acid and lactic acid. The phenotypic virulence traits explored were growth at 37°C, pseudohyphal and biofilm generation, invasiveness and enzymatic activities present in virulent yeasts. The generation of desirable meat aromas was tested in models containing aroma precursors applying an olfactory analysis. A quantitative profiling of stress tolerance was used to test the potential performance of selected strains in meat fermentations. Results: The results demonstrated that most strains displayed no virulence trait or were only positive for biofilm production. Moreover, the strains showed large heterogeneity regarding their tolerance to abiotic stress factors, although most of them could grow at intermediate to high levels of the traits. The sensory analysis was the criteria determining the selection of starter strains. Conclusions: The evaluation of the phenotypic traits demonstrates that D. hansenii is a safe yeast, it is able to tolerate the stress in meat fermentation and it is able to generate desirable aromas. Significance and Impact of the Study: The results of this study confirm the adequacy of selected D. hansenii strains to be applied as starters in meat products. [ABSTRACT FROM AUTHOR]

Debaryomyces hansenii has been employed to study, initially, the influence of the oxygen availability on D-xylose to xylitol fermentation, as this parameter is considered as one of the most critical variables for this bio alcohol accumulation. Apart from the air supplied in the fermentation process through the stirring vortex (0.0 v/v/min), additional aeration rates (0.1–2.0 v/v/min) effects were discussed. Furthermore, a change in the fermentative medium composition as well as a comparative analysis of D. hansenii behavior with respect to fermentation of D-glucose and D-xylose mixtures solutions, with the aim of producing both xylitol and ethanol bioproducts, were performed. For these purposes, specific growth rates, biomass productivities, specific substrate-uptake rates, overall biomass yields, specific xylitol formation rates and overall xylitol yields values have been calculated, applying a differential method to the kinetic data. Aeration influence was clearly evinced since a faster D-xylose metabolism, for aeration values close to 1.0 v/v/min, was noted. This yeast exhibited a sequential substrate consumption, firstly D-glucose and then D-xylose. The maximum xylitol yield (0.32 kg kg– 1) was obtained for 0.5 v/v/min airflow, remarking a significant reduction of this parameter for both above and below the quoted air supply value. [ABSTRACT FROM AUTHOR]

The use of preservatives such as nitrite and salt is a widespread practice in meat industry. For many years it has resulted in benefits like extending the shelf life of cured meat products. The EU has published new regulations to reduce the content of preservatives in foods as recent investigations have concluded that its excessive usage is related to health issues, so new alternatives are needed. Debaryomyces hansenii is a non-conventional yeast with known biocontrol possibilities. It can be found in many of environments and is the most frequent yeast isolated from sausages and dry meat products. The LRC2 strain used in this work is an isolate from Iberian Pork Loin, characterized biochemically and molecularly. The potential of D. hansenii LRC2 strain was evaluated following a volatile compounds inhibition assay. Then a scale-up trial was performed by inoculating a battery of Iberian Pork loins followed by a quality study of the final product. This was carried out through physical and microbial analysis as the identification of volatile compound profiles with GC-IMS. Finally, sensory tests were performed by a group of trained panellists and regular consumers. Results in our research show that the production of volatile compounds from LRC2 inhibited the activity of unwanted molds in all the conditions studied. The inhibition rates surpassed 75% in all cases, strengthening the hypothesis of its potential preservative effect in cured meat products. When testing the yeast inoculation effect and the reduction of preservatives in Iberian Pork Loins, a loss of sensory quality is observed when preservatives are drastically reduced reducing the panellists' grades by more than 3 points on a 1–9 scale in overall quality. In all conditions, the LRC2 inoculated loins showed significant fewer mold populations than the non-inoculated ones, improving the safety food level of the final product. This study confirms that the application of natural yeast-based alternatives is a feasible option for the new meat industry needs. • D. hansenii strain LRC2 addition has a minimal impact on the Pork Loin qualities. • D. hansenii strain LRC2 inhibits fungi through volatile compounds production. • Very low preservative levels harm volatile and sensory profiles of pork loin. • D. hansenii LRC2 addition improves the safety of loins with reduced preservatives. [ABSTRACT FROM AUTHOR]

The antioxidant yeast strains isolated from the traditional dry sausage of northern China were screened, and their antioxidant role in dry sausage was evaluated. The survival abilities of seven strains were relatively superior when exposed to 12 mM H 2 O 2 after 48 h, and these were subsequently inoculated into dry sausage. Among them, Debaryomyces hansenii HRB1 and Rhodotorula mucilaginosa SH9 treatments yielded lower peroxide value (0.48 and 0.51 mmol/kg, respectively), thiobarbituric acid reactive substance value (0.51 and 0.50 mg MDA/kg, respectively), and carbonyl content (8.67 and 8.70 nmol/kg protein, respectively) values (P < 0.05), indicating the superior antioxidant activity of these two strains. Meanwhile, yeast inoculation reduced the alcohol content and increased the ester content in the dry sausage. In particular, the level of hexanal, a byproduct of lipid oxidation, was reduced. A sensory evaluation demonstrated that the inoculated dry sausage had the higher salty taste and the lower sour taste and rancid taste. Overall, D. hansenii HRB1 not only effectively inhibited lipid and protein oxidation and reduced the perception of oxidative taste, but also enhanced the aroma profile of dry sausage and improved overall sensory quality. This study offers a novel perspective for the development of antioxidant starters and enhancement of fermented meat product quality. • Survival abilities of seven strains were superior when exposed to 12 mM H 2 O 2. • Inoculation with D. hansenii HRB1 and R. mucilaginosa SH9 inhibited lipid oxidation. • Dry sausage inoculated with D. hansenii HRB1 yielded the lowest carbonyl content. • Inoculation with D. hansenii HRB1 reduced the hexanal content of dry sausage. • Inoculation with D. hansenii HRB1 reduced the rancid odour of dry sausage. [ABSTRACT FROM AUTHOR]

Microbial antagonists are used to manage both pre- and postharvest diseases of fruit crops. Mixing two types of antagonists has been reported to enhance the viability, stability, and biocontrol efficacy of each strain used individually. In the present study, a co-cultivation system for Debaryomyces hansenii (Y-1) and Bacillus atrophaeus (TE-7) strains was evaluated, and the regulatory mechanism associated with antagonistic activity and postharvest disease control in mango and litchi fruits was investigated. Results indicated that the optimized co-cultivation system for Y-1 and TE-7 (Y + T) significantly promoted the growth of both strains, compared to single cultures, and improved their ability to adapt to co-cultivation conditions. Non-targeted metabolomics revealed that characteristic metabolites, including N-Acetyl-L-glutamic acid, adenine, umbelliferone, and cucurbitacin B significantly accumulated in co-culture, which involved in citrate cycle (TCA cycle), amino acid biosynthesis, phenylpropanoid biosynthesis, and alkaloid biosynthesis. Subsequent in vivo and in vitro assays indicated that the Y + T system, relative to the use of the individual strains, significantly enhanced the inhibition of pathogen growth, increased disease control, and also decreased weight loss and changes in peel color. The co-culture also enhanced the content of total acids (TA) and total soluble solids (TSS) in mango and litchi fruits compared to the control group. These results suggest that the Y + T co-cultivation system is highly effective in antagonistic protection, disease control, and quality maintenance of postharvest fruit. Our study provides new insights into the interactions that occur between biocontrol microorganisms in a co-culture system, and information that can be used for the development of improved strategies for the postharvest preservation of fruit. [Display omitted] • Co-culture system enhanced the growth activity of D. hansenii and B. atrophaeus. • Co-culture system promoted metabolite accumulation, such as cucurbitacin B, etc. • Co-culture fermentation broths inhibited mycelial growth of pathogens in vitro. • Co-culture fermentation broths maintained storage quality of mango and litchi fruits. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of Debaryomyces hansenii isolated from dry-cured ham on the physicochemical properties and sensory quality of dry-cured pork belly were studied. • D. hansenii S20 and S26 inhibited the growth of Enterobacteriaceae during the processing of dry-cured pork belly. • D. hansenii -inoculation contributed to the dry-cured pork belly's increased textural stability by increasing it's hardness and chewiness. • D. hansenii starter increased the content of several essential free amino acids (Thr, Val, Met, Ile, Leu and Phe) in dry-cured pork belly. • The content of four key volatile compounds: hexanal, hexanoic acid, (Z)-2-heptanal, and (E)-2-octenal was higher in dry-cured pork belly inoculated with yeast starters. Dry-cured meat products are gaining attention owing to their distinctive sensory characteristics and health benefits. In this study, two Debaryomyces hansenii strains were investigated for their potential as starter cultures for dry-cured pork belly products. After preliminary screening, these D. hansenii strains, namely, S20 and S26, both exhibiting with excellent aroma-producing capacity in a dry-cured meat model, were selected as single-strain starter cultures. For comparison, a non-inoculated control was also evaluated. In S20- and S26-inoculated pork belly, yeast dominated the microbiota and improved microbiological safety by suppressing Enterobacteriaceae growth. Compared with the non-inoculated control, the inoculated pork belly yielded higher hardness and redness (a*) values. Starter culture inoculation accelerated proteolysis in pork belly, improving the content of total free amino acids (TFFAs) and several essential free amino acids (Thr, Val, Met, Ile, Leu, and Phe) at the end of processing. Moreover, the inoculated samples exhibited higher levels of fat oxidation-derived aldehydes as well as esters, acids, alcohols and other compounds than the non-inoculated control at the end of the 95-day ripening period. Overall, these findings provide new insights into the application of D. hansenii isolated from dry-cured ham to dry-cured pork belly. [ABSTRACT FROM AUTHOR]

Globally, rice is becoming more vulnerable to arsenic (As) pollution, posing a serious threat to public food safety. Previously Debaryomyces hansenii was found to reduce grain As content of rice. To better understand the underlying mechanism, we performed a genome analysis to identify the key genes in D. hansenii responsible for As tolerance and plant growth promotion. Notably, genes related to As resistance (ARR , Ycf 1, and Yap) were observed in the genome of D. hansenii. The presence of auxin pathway and glutathione metabolism-related genes may explain the plant growth-promoting potential and As tolerance mechanism of this novel yeast strain. The genome annotation of D. hansenii indicated that it contains a repertoire of genes encoding antioxidants, well corroborated with the in vitro studies of GST, GR, and glutathione content. In addition, the effect of D. hansenii on gene expression profiling of rice plants under As stress was also examined. The Kyoto Encyclopedia of Genes and Genomes (KEGG) database revealed 307 genes, annotated in D. hansenii -treated rice, related to metabolic pathways (184), photosynthesis (12), glutathione (10), tryptophan (4), and biosynthesis of secondary metabolite (117). Higher expression of regulatory elements like AUX/IAA and WRKY transcription factors (TFs), and defense-responsive genes dismutases, catalases, peroxiredoxin, and glutaredoxins during D. hansenii +As exposure was also observed. Combined analysis revealed that D. hansenii genes are contributing to stress mitigation in rice by supporting plant growth and As-tolerance. The study lays the foundation to develop yeast as a beneficial biofertilizer for As-prone areas. [Display omitted] • DEGs in rice assert with in vitro GST, GR, and genes (ACR2, ACR3, YAP1, YCF1) of D. hansenii. • D. hansenii genome revealed CC: 12304058 bp, G+C-36.18%, CDS: 6072, tRNAs: 243, and rRNAs:17. • D. hansenii modulates genes related to glutathione, auxin, and photosynthesis in rice. [ABSTRACT FROM AUTHOR]

Some yeast strains have been proposed as probiotics to improve the health of cultured fish. Cobia is a tropical benthopelagic fish species with potential for marine aquaculture; however, one of the main limitations to its large-scale production is the high mortality of fish larvae. In this study, we evaluated the probiotic potential of autochthonous yeasts from the intestines of cobia. Thirty-nine yeast isolates were recovered from the intestinal mucosa of 37 adult healthy cobia by culture methods. Yeasts were identified by sequencing of the ITS and D1/D2 regions of the 28S rRNA gene and typed by RAPD-PCR using the M13 primer. Yeast strains with unique RAPD patterns were characterized in terms of their cell biomass production ability; anti-Vibrio, enzymatic, and hemolytic activity; biofilm production; hydrophobicity; autoaggregation; polyamine production; safety; and protection of cobia larvae against saline stress. Candida haemuloni C27 and Debaryomyces hansenii C10 and C28 were selected as potential probiotics. They did not affect the survival of larvae and showed biomass production >1 g L−1, hydrophobicity >41.47%, hemolytic activity γ, and activity in more than 8 hydrolytic enzymes. The results suggest that the selected yeast strains could be considered as potential probiotic candidates and should be evaluated in cobia larvae.

The killer strains of Debaryomyces hansenii and Wickerhamomyces anomalus species secrete antimicrobial proteins called killer toxins which are active against selected fungal phytopathogens. In our research, we attempted to investigate the role of plasma membrane pleiotropic drug resistance (PDR) transporters (Pdr5p and Snq2p) in the mechanism of defense against killer toxins. Saccharomyces cerevisiae mutant strains with strengthened or weakened pleiotropic drug resistance due to increased or reduced number of mentioned PDR efflux pumps were tested for killer toxin susceptibility. The present study demonstrates the influence of the Snq2p efflux pump in immunity to W.anomalus BS91 killer toxin. It was also shown that the activity of killer toxins of D. hansenii AII4b, KI2a, MI1a and CBS767 strains is regulated by other transporters than those influencing W. anomalus killer toxin activity. In turn, this might be related to the functioning of the Pdr5p transporter and a complex cross-talk between several regulatory multidrug resistance networks. To the best of our knowledge, this is the first study that reports the involvement of PDR transporters in the cell membrane of susceptible microorganisms in resistance to killer yeasts' toxins. [ABSTRACT FROM AUTHOR]

This study focused on the isolation and characterization of wild yeasts in Korea. The yeasts were identified by phylogenetically analyzing the D1/D2 domains of the 26S rDNA regions. Consequently, we identified seven strains, NNIBRFG856, NNIBRFG3732, NNIBRFG3734, NNIBRFG3738, NNIBRFG3739, NNIBRFG5497, and NNIBRFG6049, which were confirmed to be Kabatiella microsticta, Pichia membranifaciens, Candida vartiovaarae, Candida sake, Debaryomyces hansenii, Candida railenensis, and Schwanniomyces polymorphus, respectively, all of them being new in Korea. Morphological and cultural characteristics of these yeast species were investigated. None of the strains formed ascospores or pseudomycelia. Moreover, these yeasts grew in a pH range of 4–8. NNIBRFG3732, NNIBRFG3738, NNIBRFG3739, NNIBRFG5497, and NNIBRFG6049 were halotolerant or halophilic, and NNIBRFG3732, NNIBRFG3734, and NNIBRFG6049 grew in vitamin-free medium. NNIBRFG3732, NIBRFG3739, and NNIBRFG6049 grew at 35 °C, but not at 40 °C.