In Vitro Characterization and Identification of Potential Probiotic Yeasts Isolated from Fermented Dairy and Non-Dairy Food Products

Characterization and Biological In Vitro Screening of Probiotic Yeast Strains Isolated from Algerian Fruits

Interest in Saccharomyces and non-Saccharomyces yeasts as biotechnological agents is growing worldwide. Here, Kluyveromyces marxianus GBC2 and two Saccharomyces cerevisiae strains FBZ4 and FBK9 were isolated from pomegranate (Punica granatum) and fig (Ficus carica), respectively, and extensively characterized for their probiotic attributes and health benefits. Overall, these strains were found to be γ-hemolytic, non-cytotoxic against Caco-2 cells, and sensitive to therapeutic antifungals. In terms of probiotic characterization, the strains were able to survive at pH 2 and in 1% bile and had high hydrophobicity and self-aggregation properties, which could explain their ability to form biofilm on a polystyrene and adhere to Caco-2 cells. Adhesion rates of 23.52%, 14.05%, and 9.44% were recorded at 37 °C for K. marxianus GBC2, S. cerevisiae FBK9, and S. cerevisiae FBZ4, respectively. Furthermore, biological screening showed a cholesterol assimilation of 54.32% for K. marxianus GBC2 and almost 33% for both Saccharomyces, more than 73% α-amylase inhibition, and good antioxidant potential for all strains; however, only K. marxianus GBC2 showed antibacterial activity against Staphylococcus aureus ATCC 25923. In light of these findings, the strains could be potential candidates for the development of novel functional foods and for probiotic applications.

Probiotic and Functional Attributes of Yeasts Isolated from Different Traditional Fermented Foods and Products

Though numerous bacteria have been used as probiotics by industries, at present, Saccharomyces boulardii and Saccharomyces cerevesiae are the only yeast probiotics which are industrially exploited. In view of this, yeast probiotics were isolated from traditional fermented foods and products collected from different parts of Karnataka, India. In this work, we have studied the probiotic attributes of ten yeast isolates isolated from different traditionally fermented foods and products. About 73 yeast isolates were initially isolated by serially diluting the samples and plating on the Potato Dextrose Agar (PDA) plates. The spot assay was performed to screen the yeast isolates against test pathogens. Ten isolates were selected based on their significant antimicrobial activity. These isolates were subjected to biochemical characterization and then assessed for probiotic properties. The ability of probiotics to endure at pH 2.0 and tolerate bile conditions (0.3%) are crucial attributes for the survival in the gastrointestinal tract (GIT). The yeast isolates were also assessed for cell surface hydrophobicity and autoaggregation capabilities. All the ten isolates showed endurance in GIT tract and > 40% of adhesion. The study further examined cholesterol assimilation, antioxidant and antagonistic properties of the yeasts. Subsequently, the molecular characterization was performed by isolating the DNA of yeast isolates by phenol-chloroform method and identified molecularly through sequencing of D1/D2 regions. The isolates tested negative for gelatinase and DNase and were non-haemolytic indicating they are safe for consumption. Among ten isolates, Meyerozyma guillermondii (MYSY23), Meyerozyma caribbica (MYSY22) and Meyerozyma guillermondii (MYSY19) showed significant results for all probiotic and functional characteristics with greater than 65% survivability in GIT tract and > 50% of antagonistic activity against test pathogens and also proved non-cytotoxic and safe. These findings suggest that yeasts with significant probiotic attributes could be recommended for various probiotic application.

Unraveling the potential nutritional benefits of fermented date syrup waste: Untargeted metabolomics and carbohydrate metabolites of in vitro digested fraction

Valorization of fruit by-products is a crucial area of research for the development of innovative bio-based products. This study investigated the physicochemical properties and health-promoting benefits of date syrup waste, both fermented by Pichia cecembensis or Pichia kudriavzevii (FDSW), and unfermented (CDSW). Metabolomics profiles of these samples were identified post in vitro digestion. FDSW exhibited 42 volatile compounds, including 9 new ones, and contained (-)-epicatechin, tyrosol, and gallic acid. Bioaccessible fractions of FDSW demonstrated substantial α-amylase inhibition, with percentages of 40.7 % and 53.9 %, respectively. FDSW displayed superior cytotoxicity against Caco2 and MCF-7 cancer cell lines, with an average of ∼75 % and 56 %, respectively. Untargeted metabolomics analysis revealed an increase in secondary metabolites, totaling 27 metabolites. LC-QTOF analysis of bioaccessible carbohydrate metabolites in FDSW identified two phytochemical groups, alkaloids, and terpenoids. This study underscores the potential of FDSW for producing value-added bio-based products with desirable characteristics and health benefits.

Evaluation of the probiotic potential of yeast isolated from kombucha in New Zealand

The current study investigated the in vitro probiotic potential of yeast isolated from kombucha, a tea beverage fermented with a symbiotic culture of acetic acid bacteria and yeast. A total of 62 yeast strains were previously isolated from four different commercial kombucha samples sold in New Zealand. Fifteen representative isolates belonging to eight different species were evaluated for their growth under different conditions (temperature, low pH, concentrations of bile salts, and NaCl). Cell surface characteristics, functional and enzymatic activities of the selected strains were also studied in triplicate experiments. Results showed that six strains (Dekkera bruxellensis LBY1, Sachizosaccharomyces pombe LBY5, Hanseniaspora valbyensis DOY1, Brettanomyces anomalus DOY8, Pichia kudraivzevii GBY1, and Saccharomyces cerevisiae GBY2) were able to grow under low-acid conditions (at pH 2 and pH 3) and in the presence of bile salts. This suggests their potential to survive passage through the human gut. All 15 strains exhibited negative enzymatic activity reactions (haemolytic, gelatinase, phospholipase, and protease activities), and thus, they can be considered safe to consume. Notably, two of the fifteen strains (Pichia kudraivzevii GBY1 and Saccharomyces cerevisiae GBY2) exhibited desirable cell surface hydrophobicity (64.60-83.87%), auto-aggregation (>98%), co-aggregation, resistance to eight tested antibiotics (ampicillin, chloramphenicol, colistin sulphate, kanamycin, nalidixic acid, nitrofurantoin, streptomycin, and tetracycline), and high levels of antioxidant activities (>90%). Together, our data reveal the probiotic activities of two yeast strains GBY1 and GBY2 and their potential application in functional food production.

Investigating the antidiabetic efficacy of dairy-derived Lacticaseibacillus paracasei probiotic strains: modulating α-amylase and α-glucosidase enzyme functions

The current study aims to evaluate and characterize the probiotic andantidiabetic properties of lactic acid bacteria (LAB) obtained from milk and other dairy-based products. The strains were tested physiologically, biochemically, and molecularly. Based on biochemical tests and 16S rRNA gene amplification and sequencing, all three isolates RAMULAB18, RAMULAB19, and RAMULAB53 were identified as Lacticaseibacillus paracasei with homology similarity of more than 98%. The inhibitory potential of each isolate against carbohydrate hydrolysis enzymes (α-amylase and α-glucosidase) was assessed using three different preparations of RAMULAB (RL) isolates: the supernatant (RL-CS), intact cells (RL-IC), and cell-free extraction (RL-CE). Additionally, the isolate was evaluated for its antioxidant activity against free radicals (DPPH and ABTS). The strain's RL-CS, RL-CE, and RL-IC inhibited α-amylase (17.25 to 55.42%), α-glucosidase (15.08-59.55%), DPPH (56.42-87.45%), and ABTS (46.35-78.45%) enzymes differently. With the highest survival rate (>98%) toward tolerance to gastrointestinal conditions, hydrophobicity (>42.18%), aggregation (>74.21%), as well as attachment to an individual's colorectal cancer cell line (HT-29) (>64.98%), human buccal and chicken crop epithelial cells, all three isolates exhibited extensive results. All three isolates exhibited high resistance toward antibiotics (methicillin, kanamycin, cefixime, and vancomycin), and other assays such as antibacterial, DNase, hemolytic, and gelatinase were performed for safety assessment. Results suggest that the LAB described are valuable candidates for their significant health benefits and that they can also be utilized as a beginning or bio-preservative tradition in the food, agriculture, and pharmaceutical sectors. The LAB isolates are excellent in vitro probiotic applicants and yet additional in vivo testing is required.

Isolation of Yeasts from Some Homemade Fermented Cow-Milk Products of Sikkim and Their Probiotic Characteristics

Dahi and chhurpi are the homemade, mildly acidic and mouthfeel fermented dairy products of Sikkim in India. Since yeasts co-exist among traditional fermented dairy foods, we believe that some species of yeasts may have some probiotic properties. Hence, the present study is aimed at screening some probiotic yeasts from dahi and chhurpi. A total of 3438 yeasts were isolated from 40 samples of dahi (1779 isolates) and 40 chhurpi (1659 isolates) and were preliminarily screened for probiotic properties on the basis of survival in low pH, resistance to bile salts and the percentage of hydrophobicity, out of which only 20 yeasts were selected for in vitro and genetic screening of probiotic properties. Saccharomyces cerevisiae DJT-2 and Debaryomyces prosopidis CPA-55 showed the highest hydrophobicity of 97.54% and 98.33%, respectively. S. cerevisiae DRC-42 and S. cerevisiae CGI-29 showed 93.88% and 91.69% auto-aggregation, respectively. All yeasts showed co-aggregation properties against pathogenic bacteria. Kluyveromyces marxianus DPA-41 and Pichia kudriavzevii CNT-3 showed excellent deconjugation activities. Probiotic genes for acid tolerance, bile tolerance, adhesion and antimicrobial activity were detected in S. cerevisiae DAO-17, K. marxianus DPA-41, S. cerevisiae CKL-10 and P. kudriavzevii CNT-3. Based on the results of in vitro and genetic screening of probiotic yeasts strains, S. cerevisiae DAO-17 (dahi), S. cerevisiae CKL-10 (chhurpi), P. kudriavzevii CNT-3 (chhurpi) and K. marxianus DPA-41(dahi) were selected as the potential probiotic yeasts.