Construction of an autonomously replicating plasmid in n-alkane-assimilating yeast, Candida tropicalis

A transformation system using the autonomously replicating plasmid in the n-alkane-assimilating and asporogenic diploid yeast, Candida tropicalis, was developed. For the cloning of a DNA fragment containing a potential autonomously replicating sequence (ARS) from the genomic DNA of C. tropicalis, the ura3 mutant obtained using ethylmethane sulfonate as the host and the URA3 gene amplified by PCR using the C. tropicalis genomic DNA as a selectable marker were prepared. Comparison of ARSs among yeasts revealed that the consensus sequence found in S. cerevisiae was also present in C. tropicalis. The autonomously replicating plasmid containing the putative ARS as the shuttle vector, capable of replicating in both E. coli and C. tropicalis, was first constructed. The transformation system using this plasmid, in addition to the integrative transformation system, will be applicable to genetic studies of C. tropicalis.     

Killer strains of Saccharomyces: application for apple wine production

The aim of this study was to evaluate possible application of killer strains Saccharomyces paradoxus CBS 3702 (K1), S. cerevisiae CBS 6505 (K2) and S. capensis CBS 7903 (K3) for apple wine production. Apple musts were obtained from Jonagold apples. The optimal pH value of killer toxins activity, the temperature of their formation and the spectrum of activity against selected wine spoilage fungal strains were analysed. The influence of yeast strains on the chemical composition, volatile profile and sensory properties of apple wines was determined using high‐performance liquid chromatography and gas chromatography methods. The pH values of 4.2 (K1, K3) and 4.6 (K2), and a temperature of 28 °C, were optimal for the action of toxins. The analysed killer strains inhibited growth of seven of the 11 tested wine spoilage fungal strains. The samples obtained using the S. cerevisiae killer strain were characterized by the highest fermentation rate, highest ethanol concentration and a balanced level of volatiles, but their taste was described as bitter. S. capensis gained the highest scores in the sensory evaluation. It could be used for semi‐sweet or semi‐dry cider production, because of the lower amounts of ethanol formation but higher synthesis of glycerol, volatile esters and higher alcohols. Copyright © 2016 The Institute of Brewing & Distilling     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.     

Predictive model of Vibrio parahaemolyticus growth and survival on salmon meat as a function of temperature

The growth and survival curves of a strain of pandemic Vibrio parahaemolyticus TGqx01 (serotype O3:K6) on salmon meat at different storage temperatures (range from 0 °C to 35 °C) were determined. In order to model the growth or inactivation kinetics of this pathogen during storage, the modified Gompertz and Weibull equations were chosen to regress growth and survival curves, respectively, and both equations produced good fit to the observed data (the average R² value equals to 0.990 for modified Gompertz and 0.920 for Weibull equation). The effect of storage temperature on the specific growth rate (μ) was modeled by square root type equation, and the relationship between μ and lag time (λ) was described by a rule of μ × λ = constant. The shape factor (n) and scale factor (b) values of the Weibull equations versus the temperature (°C) were plotted and the temperature effects on these parameters were described by two linear empirical equations. The predicted growth and survival curves from the model were compared to real enumeration results, using the correlation coefficient (R²), bias factor (B_f) and accuracy factor (A_f), to assess the performance of the established model. The results showed that the overall predictions for V. parahaemolyticus TGqx01 growth or inactivation on salmon at tested temperatures agreed well with observed plate counts, and the average R², B_f and A_f values were 0.958, 1.019 and 1.035, respectively.     

Heat-adaptation induced thermotolerance in Staphylococcus aureus: Influence of the alternative factor σ

The role of σ^B in the Staphylococcus aureus heat-shock induced thermotolerance was investigated. Survival curves at 58 °C of S. aureus strain Newman and its isogenic ΔsigB mutant were obtained for native and heat-shocked cells (45 °C for 5–120 min) in exponential and stationary phase of growth. The magnitude of the acquisition of thermotolerance at 58 °C depended on the growth phase and on the duration of the heat shock. Stationary growth phase cells were always more heat tolerant than exponentially growing cells and thermotolerance increased with heat-shock duration up to 120 min. S. aureus cells were able to increase their heat tolerance in the absence of the σ^B factor. In stationary phase, whereas in the parental strain the thermotolerance was increased by a factor of 12 after a heat shock of 120 min at 45 °C (δ values at 58 °C for native and heat-shocked cells were 0.63 and 7.22 min, respectively), in the mutant strain it increased 43 fold (δ values 0.09 and 3.87 min). The addition of chloramphenicol to the adaptation medium resulted in a lower increase in heat tolerance but did not prevent it completely, suggesting that S. aureus can partially increase its thermotolerance without “de novo” protein synthesis. Both the number of non-damaged cells and the proportion of cells able to repair sublethal damage were higher for heat-shocked cells.     

Effect of X-ray treatments on inoculated Escherichia coli O157: H7, Salmonella enterica, Shigella flexneri and Vibrio parahaemolyticus in ready-to-eat shrimp

This study was conducted to evaluate the inactivation effect of X-ray treatments on Escherichia coli O157: H7, Salmonella enteric (S. enterica), Shigella flexneri (S. flexneri) and Vibrio parahaemolyticus (V. parahaemolyticus) artificially inoculated in ready-to-eat (RTE) shrimp. A mixed culture of three strains of each tested pathogen was used to inoculate RTE shrimp. The shrimp samples were inoculated individually with selected pathogenic bacteria then aseptically placed in sterile plastic cups and air-dried at 22 °C for 30 min (to allow bacterial attachment) in the biosafety cabinet prior to X-ray treatments. The inoculated shrimp samples were then placed in sterilized bags and treated with 0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 2.0, 3.0 and 4.0 kGy X-ray at ambient temperature (22 °C and 60% relative humidity). Surviving bacterial populations were evaluated using a non-selective medium (TSA) with the appropriate selective medium overlay for each bacterium; CT-SMAC agar for E. coli O157: H7, XLD for S. enterica and S. flexneri and TCBS for V. parahaemolyticus. More than a 6 log CFU reduction of E. coli O157: H7, S. enterica, S. flexneri and V. parahaemolyticus was achieved with 2.0, 4.0, 3.0 and 3.0 kGy X-ray, respectively. Furthermore, treatment with 0.75 kGy X-ray significantly reduced the initial microflora on RTE shrimp samples from 3.8 ± 0.2 log CFU g⁻¹ to less than detectable limit (<1.0 log CFU g⁻¹).     

Effect of the FAA1 gene disruption of sake yeast on the accumulation of ethyl caproate in sake mash

Fatty acid activation gene (FAA1) in sake yeast Kyokai no. 701 (K701) was disrupted to investigate the accumulation of ethyl caproate in sake mash. Ethyl caproate, recognized as an important apple-like flavor in sake, is generated by fatty acid synthesis in yeast cells. The disruptant for the FAA1 gene (K701Δfaa1) exhibited a reduced growth rate in a medium containing cerulenin and myristic acid or oleic acid compared with that of the parental strain (K701). In a sake brewing test in which the rice used was polished to 60% of its original size, the fermentation ability of K701Δfaa1 was inferior to that of K701 but the production of ethyl caproate by K701Δfaa1 was 1.6-fold higher than that by K701. These results suggest that the FAA1 gene in sake yeast plays an important role in sake brewing and the accumulation of ethyl caproate.     

A study on Saccharomyces cerevisiae and Candida utilis cell wall capacity for binding magnesium

The capacity for binding magnesium by bakery's yeast strain Saccharomyces cerevisiae No. 102 (Pure Culture Collection, Faculty Food Technology, Warsaw) and fodder yeast strain Candida utilis (ATCC 9950) was investigated in media supplemented with that element. The capacities of C. utilis (ATCC 9950) and S. cerevisiae (No. 102) biomass for binding magnesium were not statistically different in the first 24 h. In the next 24 h of cultivation the cells of C. utilis (ATCC 9950) were still able to bind magnesium ions, whereas those of S. cerevisiae (No. 102) released a part of previously bound magnesium to the medium. The major part of magnesium bound by the cells of C. utilis (ATCC 9950) was accumulated in cytosole. It was opposite to the cells of bakery yeast S. cerevisiae (No. 102) that accumulated magnesium mainly in the cell wall. The cells of C. utilis (ATCC 9950) yeast were smaller and their cell walls were thinner as compared to those of S. cerevisiae (No. 102) yeast. The thickness of the external mannoprotein layers was similar in both strains analyzed.     

Co-metabolism of citrate and maltose byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain: effect on growth, end-products and sourdough fermentation

Growth, substrates and end-product formation of the maltose and citrate co-metabolization byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain were initially studied in synthetic medium. Compared to maltose (19 g/l) fermentation, the co-metabolization of maltose (10 g/l) plus citrate (9 g/l) caused faster cell growth, increased the concentrations of lactic acid and especially of acetic acid (from 0.7 g/l to 2.9 g/l), produced succinic acid (0.5 g/l) and reduced ethanol synthesis. Highest activities of acetate kinase, the same of lactate dehydrogenase and a reduced alcohol dehydrogenase activity were detected in cytoplasmic extracts of cells growing on maltose plus citrate. The breakdown of citrate depended upon the continuous presence of maltose in the growth medium. Upon depletion of citrate, the cells continued through the normal maltose fermentation, having a diauxic metabolic curve as shown by impedance measurements. Concentrations of citrate from 3 g/l to 15 g/l led to increases of acetic acid from 1.25 g/l to 5.55 g/l. Since maltose was naturally present during sourdough fermentation, the addition of 9 g citrate per kg wheat dough enabled the co-metabolization of maltose and citrate byL. brevis subsp.lindneri CB1. Compared with traditional sourdough fermentation, faster cell growth, a higher acetic acid concentration and a reduced quotient of fermentation were obtained by co-metabolism.     

Contribution of wild yeasts to the formation of volatile compounds in inoculated wine fermentations

The aim of this work was to study the contribution of wild yeasts to the volatile composition of wine in inoculated fermentations. To do so, Parellada must, sterilized and inoculated with Saccharomyces cerevisiae strain Na33 (pure inoculated fermentation), inoculated Parellada must (mixed inoculated fermentation) and Parellada must that fermented with its wild yeasts (control fermentation) were used. From the results obtained in the pure inoculated fermentation it can be seen that S. cerevisiae produced appreciable quantities of isoamyl acetate, ethyl hexanoate, ethyl octanoate, and ethyl decanoate. However, the wild yeasts also contributed to the synthesis of esters since the total concentration of these substances was higher in the mixed inoculated fermentation than in the pure inoculated fermentation. 2-Phenylethyl acetate was only synthesized by wild yeasts when they did not compete with S. cerevisiae. The concentration of total alcohols was similar in the three samples; the important production of isobutanol and 2-phenylethanol in the control fermentation is noteworthy. As regards the acids, the greatest concentration corresponded to the mixed inoculated fermentation. The wild yeasts contributed to the synthesis of these compounds to a significant extent and S. cerevisiae synthesized appreciable amounts of short-chain fatty acids.     

Profile of volatile compounds during papaya juice fermentation by a mixed culture of Saccharomyces cerevisiae and Williopsis saturnus

This study investigated the formation and utilization of volatile compounds during papaya juice fermentation by a mixed culture of Saccharomyces cerevisiae and Williopsis saturnus. Time-course papaya juice fermentations were carried out using pure cultures of S. cerevisiae var. bayanus R2 and W. saturnus var. mrakii NCYC2251 and a mixed culture of the two yeasts at a ratio of 1:1000 (R2:NCYC2251). Changes in S. cerevisiae cell population, Brix, sugar consumption and pH were similar in the mixed culture and in the S. cerevisiae monoculture. There was an early growth arrest of W. saturnus in the mixed culture fermentation. A range of volatile compounds were produced during fermentation including fatty acids, alcohols, aldehydes and esters and some volatile compounds including those initially present in the juice were utilized. The mixed culture fermentation of S. cerevisiae and W. saturnus benefited from the presence of both yeasts, with more esters being produced than the S. cerevisiae monoculture and more alcohols being formed than the W. saturnus monoculture. The study suggests that papaya juice fermentation with a mixed culture of S. cerevisiae and W. saturnus may be able to result in the formation of more complex aroma compounds and higher ethanol level than those using single yeasts.     

Identification and characterization of Dekkera bruxellensis, Candida pararugosa, and Pichia guilliermondii isolated from commercial red wines

Yeast isolates from commercial red wines were characterized with regards to tolerances to molecular SO₂, ethanol, and temperature as well as synthesis of 4-ethyl-phenol/4-ethyl-guaiacol in grape juice or wine. Based on rDNA sequencing, nine of the 11 isolates belonged to Dekkera bruxellensis (B1a, B1b, B2a, E1, F1a, F3, I1a, N2, and P2) while the other two were Candida pararugosa (Q2) and Pichia guilliermondii (Q3). Strains B1b, Q2, and Q3 were much more resistant to molecular SO₂ in comparison to the other strains of Dekkera. These strains were inoculated (10³–10⁴ cfu/ml) along with lower populations of Saccharomyces (<500 cfu/ml) into red grape juice and red wine incubated at two temperatures, 15 °C and 21 °C. Although Saccharomyces quickly dominated fermentations in grape juice, B1b and Q2 grew and eventually reached populations >10⁵ cfu/ml. In wine, Q3 never entered logarithmic growth and quickly died in contrast to Q2 which survived >40 days after inoculation. B1b grew well in wine incubated at 21 °C while slower growth was observed at 15 °C. Neither Q2 nor Q3 produced 4-ethyl-phenol or 4-ethyl-guaiacol, unlike B1b. However, lower concentrations of volatile phenols were present in wine incubated at 15 °C compared to 21 °C.     

Control of food spoiling bacteria in cooked meat products with nisin,lacticin 3147, and a lacticin 3147-producing starter culture

Nisin, in the form of the commercial product Nisaplin, and lacticin 3147 in whey powdered form were added to minced pork-meat in amounts of 0.15% (w/w) and 1.5% (w/w), respectively. The meat was cooked and inoculated with a Staphylococcus aureus strain of meat origin and a Listeria innocua strain at a level of 10⁷ or 10⁵ CFU g^–1. The batches were stored vacuum-packaged for 21 days at 8 °C. Nisin and lacticin 3147 immediately reduced the L. innocua population at the time of inoculation. Nisin showed higher inhibitory activity than lacticin 3147. During the storage period, a slight L. innocua growth was observed in the batches inoculated with the larger inoculum, and a bacteriostatic effect was observed against Listeria in the batches inoculated with 10⁵ CFU g^–1. Nisin maintained a constant S. aureus population in the cooked batch inoculated with 10⁷ CFU g^–1, although the bacteriocin was capable of reducing the amount of S. aureus by 90% in the batch inoculated with 10⁵ CFU g^–1. On the other hand, lacticin 3147 did not show an inhibitory effect against S. aureus in the cooked meat. The starter culture Lactococcus lactis DPC 303-T4 (containing the conjugative plasmid encoding production of lacticin 3147) was inoculated in a portion of a Longissimus dorsi pork muscle with brine. L. lactis DPC 303-T4 performed a good fermentation, but lacticin 3147 production was not found after 7 days at 12 °C of storage.     

Diversity of lactic acid bacteria in suan-tsai and fu-tsai, traditional fermented mustard products of Taiwan

Fu-tsai and suan-tsai are spontaneously fermented mustard products traditionally prepared by the Hakka tribe of Taiwan. We chose 5 different processing stages of these products for analysis of the microbial community of lactic acid bacteria (LAB) by 16S rRNA gene sequencing. From 500 LAB isolates we identified 119 representative strains belonging to 5 genera and 18 species, including Enterococcus (1 species), Lactobacillus (11 species), Leuconostoc (3 species), Pediococcus (1 species), and Weissella (2 species). The LAB composition of mustard fermented for 3 days, known as the Mu sample, was the most diverse, with 11 different LAB species being isolated. We used sequence analysis of the 16S rRNA gene to identify the LAB strains and analysis of the dnaA, pheS, and rpoA genes to identify 13 LAB strains for which identification by 16S rRNA gene sequences was not possible. These 13 strains were found to belong to 5 validated known species: Lactobacillus farciminis, Leuconostoc mesenteroides, Leuconostoc pseudomesenteroides, Weissella cibaria, and Weissella paramesenteroides, and 5 possibly novel Lactobacillus species. These results revealed that there is a high level of diversity in LAB at the different stages of fermentation in the production of suan-tsai and fu-tsai.     

Initial screening for inhibitory activity of essential oils on growth of Fusarium verticillioides, F. proliferatum and F. graminearum on maize-based agar media

An in vitro initial screening of a range of 37 essential oils on inhibition of mycelial growth of Fusarium verticillioides, F. proliferatum and F. graminearum under different temperature (20–30°C) and water activity (a_w) (0.95–0.995) conditions was made. The basic medium was a 3% maize meal extract agar. The maize meal agar was modified with glycerol to a range of water activity conditions and the essential oils were incorporated at different concentrations (0, 500, 1000 μg ml⁻¹). Cinnamon leaf, clove, lemongrass, oregano and palmarosa oils were the products tested suitable for being used as novel preservatives in the control of the three Fusarium species studied. Although water activity was determinant for the growth of the isolates, in general, the preservative effects of the oils were not linked to a_w. However, a trend to a higher inhibition by the oils when a_w was low was observed. Temperature had a minor importance in the inhibitory effect of the preservatives. In vivo studies may be required to confirm the usefulness of the results obtained.     

Variations of internal pH in typical Italian sourdough yeasts during co-fermentation with lactobacilli

The effects of organic acids (lactic and acetic) and extracellular pH (pHex) on the intracellular pH (pHi) of Saccharomyces cerevisiae and Candida milleri during co-fermentation with lactobacilli were investigated by using Fluorescence-Ratio-Imaging-Microscopy (FRIM). Yeasts were grown in a system that partially mimics sourdough composition, using individual fermentation and combinations with lactic acid bacteria. Fermentations were carried out at 25 °C for 22 h at an initial pH of 5.3. The two yeast species grew equally well during the co-fermentations with lactobacilli. Our results reveal large differences in pHi values between the two yeast species, primarily in relation with pHex changes, while the concentration of organic acids did not seem to affect the pHi. Moreover, the pHi of S. cerevisiae seemed to be affected by maltose consumption. The pH gradient (difference between internal and external pH) of S. cerevisiae remained rather constant, ranging from 2.0 to 2.5. C. milleri instead exhibited a higher pHi, that remained constant throughout the experiments and was unaffected by pHex and/or sugar consumption. Thus, the pH gradient of C. milleri varied much more than that of S. cerevisiae, ranging from 2.3 to 3.8. Our results suggest that the two yeast species have different pHi regulation mechanisms.     

Performance of wild Saccharomyces and Non-Saccharomyces yeasts as starter cultures in dough fermentation and bread making

The use of wild Saccharomyces and non-Saccharomyces yeasts might result in bread with different and attractive sensory characteristics. This study aimed to evaluate the performance of Saccharomyces and non-Saccharomyces yeasts as starter culture in dough fermentation to bread making and the physicochemical parameters and aromatic profile of bread. All 26 wild yeasts strains isolated from Brazilian Cerrado fruit and tree bark were osmotolerant, and 19.4% were able to ferment maltose. Candida tropicalis ART101.3 and Saccharomyces cerevisiae SC5952 had the best growth capacity under high concentrations of glucose and maltose. Also, they were resistant to lyophilisation. Kinetic parameters of bioreactor cultivations showed high cell growth and lower generation time with 10 g L⁻¹ maltose. Bread produced with C. tropicalis ART101.3 and the control bread had similar physicochemical properties and acceptance of consumers. Bread with S. cerevisiae SC5951 had a lower specific volume and a different colour than control bread; however, the consumers found no significant difference. More than 70% of the consumers demonstrated purchase intention of bread produced with both wild yeasts. The present study shows the potential of native Cerrado yeasts to be used and exploited in industrial processes and contributes to the diversification of bread starter cultures.     

The influence of precultivation parameters on the catabolism of branched-chain amino acids by Staphylococcus xylosus and Staphylococcus carnosus

The influence of precultivation parameters on the ability of Staphylococcus xylosus and Staphylococcus carnosus to convert branched-chain amino acids—leucine, isoleucine and valine—into volatile flavour compounds was investigated using resting cells in a defined reaction medium. The studied precultivation parameters were: growth phase, temperature, NaCl concentration and the concentration of leucine, isoleucine and valine (only for S. xylosus). Flavour compounds were sampled by automatic static headspace collection and separated/quantified using gas chromatography/flame ionization detection (GC/FID).Main catabolic products from degradation of leucine, isoleucine and valine were the flavour intensive branched-chain acids: 2- and 3-methylbutanoic and 2-methylpropanoic acids. The precultivation parameters altered the production of the branched-chain acids significantly, but to various degrees for S. xylosus and S. carnosus.Production of branched-chain acids by S. carnosus was only influenced slightly by the growth phase and not by changing the NaCl concentration between 4.0% and 10.0% (w/w). Lowering the temperature from 28°C to 18°C significantly decreased S. carnosus’ generation of branched-chain acids. In contrast, S. xylosus was significantly influenced by all precultivation parameters, in particular by the growth phase. Cells taken from growing cultures had a much higher production of branched-chain acids compared to cells taken from stationary cultures. Addition of leucine and valine to the precultivation medium enhanced the production of branched-chain acids whereas addition of isoleucine had the opposite effect.     

Production of ethanol from liquefied cassava starch using co-immobilized cells of Zymomonas mobilis and Saccharomyces diastaticus

Co-immobilized cells of Saccharomyces diastaticus and Zymomonas mobilis produced a high ethanol concentration compared to immobilized cells of S. diastaticus during batch fermentation of liquefied cassava starch. The co-immobilized cells produced 46.7 g/l ethanol from 150 g/l liquefied cassava starch, while immobilized cells of yeast S. diastaticus produced 37.5 g/l ethanol. The concentration of ethanol produced by immobilized cells was higher than that by free cells of S. diastaticus and Z. mobilis in mixed-culture fermentation. In repeated-batch fermentation using co-immobilized cells, the ethanol concentration increased to 53.5 g/l. The co-immobilized gel beads were stable up to seven successive batches. Continuous fermentation using co-immobilized cells in a packed bed column reactor operated at a flow rate of 15 ml/h (residence time, 4 h) exhibited a maximum ethanol productivity of 8.9 g/l/h.     

Probiotic potential of Saccharomyces cerevisiae and Kluyveromyces marxianus isolated from West African spontaneously fermented cereal and milk products

The yeast species Saccharomyces cerevisiae and Kluyveromyces marxianus are associated with fermentation of West African indigenous foods. The aim of this study was to characterize potential probiotic properties of S. cerevisiae and K. marxianus isolates from the West African milk products lait caillé and nunu and a cereal-based product mawè. The strains (14 in total) were identified by 26S rRNA gene sequencing and characterized for survival at gastrointestinal stress (bile salts and low pH) and adhesion to Caco-2 intestinal epithelial cells. Selected yeast isolates were tested for their effect on the transepithelial electrical resistance (TEER), using the intestinal epithelial cell line Caco-2 and for maintenance of intracellular pH (pH_i) during perfusion with gastrointestinal pH (3.5 and 6.5). All tested yeasts were able to grow in bile salts in a strain-dependent manner, exhibiting a maximum specific growth rate (μ_max) of 0.58–1.50 h⁻¹. At pH 2.5, slow growth was observed for the isolates from mawè (μ_max of 0.06–0.80 h⁻¹), whereas growth of yeasts from other sources was mostly inhibited. Yeast adhesion to Caco-2 cells was strain specific and varied between 8.0% and 36.2%. Selected strains of S. cerevisiae and K. marxianus were able to maintain the pH_i homeostasis at gastrointestinal pH and to increase TEER across the Caco-2 monolayers, indicating their potential to improve intestinal barrier functions. Based on overall results, strains of K. marxianus and S. cerevisiae from mawè exhibited the highest probiotic potential and might be recommended for further development as starter cultures in West African fermented products.