In vitro screening of Kluyveromyces strains isolated from Fiore Sardo cheese for potential use as probiotics

Identification of novel probiotic lactic acid bacteria from soymilk waste using the 16s rRNA gene for potential use in poultry

Background and Aim

In-feed antibiotics have been used as antibiotic growth promoters (AGPs) to enhance the genetic potential of poultry. However, the long-term use of AGPs is known to lead to bacterial resistance and antibiotic residues in poultry meat and eggs. To address these concerns, alternatives to AGPs are needed, one of which is probiotics, which can promote the health of livestock without having any negative effects. In vitro probiotic screening was performed to determine the ability of lactic acid bacteria (LAB) isolated from soymilk waste to be used as a probiotic for livestock.

Materials and Methods

Four LAB isolates (designated F4, F6, F9, and F11) isolated from soymilk waste were used in this study. In vitro testing was performed on LAB isolates to determine their resistance to temperatures of 42°C, acidic pH, bile salts, hydrophobicity to the intestine, and ability to inhibit pathogenic bacteria. A promising isolate was identified using the 16S rRNA gene.

Result

All LAB isolates used in this study have the potential to be used as probiotics. On the basis of the results of in vitro testing, all isolates showed resistance to temperatures of 42°C and low pH (2.5) for 3 h (79.87%-94.44%) and 6 h (76.29%-83.39%), respectively. The survival rate at a bile salt concentration of 0.3% ranged from 73.24% to 90.39%, whereas the survival rate at a bile salt concentration of 0.5% ranged from 56.28% to 81.96%. All isolates showed the ability to attach and colonize the digestive tract with a hydrophobicity of 87.58%-91.88%. Inhibitory zones of LAB against pathogens ranged from 4.80-15.15 mm against Staphylococcus aureus, 8.85-14.50 mm against Salmonella enteritidis, and 6.75-22.25 mm against Escherichia coli. Although all isolates showed good ability as probiotics, isolate F4 showed the best probiotic ability. This isolate was identified as Lactobacillus casei strain T22 (JQ412731.1) using the 16S rRNA gene.

Conclusion

All isolates in this study have the potential to be used as probiotics. However, isolate F4 has the best probiotic properties and is considered to be the most promising novel probiotic for poultry.

Evaluation of Potential Probiotic Properties and In Vivo Safety of Lactic Acid Bacteria and Yeast Strains Isolated from Traditional Home-Made Kefir

Probiotics are known for their health-promoting resources and are considered as beneficial microorganisms. The current study focuses on the isolation, and on a complete in vitro and in vivo characterization, of yeast and lactic acid bacteria acquired from traditional homemade kefir in order to assess their potentiality as probiotic candidates. In particular, the isolates Pichia kudriavzevii Y1, Lactococcus lactis subsp. hordniae LAB1 and Lactococcus lactis subsp. lactis LAB2 were subjected to in vitro characterization to evaluate their suitability as probiotics. Resistance to acid and bile salts, auto-aggregation, co-aggregation, hydrophobicity, and biofilm production capability were examined, as well as their antioxidant activity. A safety assessment was also conducted to confirm the non-pathogenic nature of the isolates, with hemolysis assay and antibiotic resistance assessment. Moreover, mortality in the invertebrate model Galleria mellonella was evaluated. Current findings showed that P. kudriavzevii exhibited estimable probiotic properties, placing them as promising candidates for functional foods. Both lactic acid bacteria isolated in this work could be classified as potential probiotics with advantageous traits, including antimicrobial activity against enteric pathogens and good adhesion ability on intestinal cells. This study revealed that homemade kefir could be a beneficial origin of different probiotic microorganisms that may enhance health and wellness.

Probiotic Characterization of LAB isolated from Sourdough and Different Traditional Dairy Products Using Biochemical, Molecular and Computational Approaches

The aim of this study was to identify and isolate lactic acid bacteria (LAB) from indigenous sourdough and dairy samples in Iran, and to assess their probiotic properties in vitro. A total of 560 potential LAB isolates were examined, and 87 demonstrated high survival rates in artificial gastrointestinal fluids without hemolytic activity. The selected isolates exhibited significant auto-aggregation (18.35 to 79.42%) and co-aggregation abilities (20.16 to 71.26%). Additionally, the isolates displayed varying degrees of cell surface hydrophobicity (12.32 to 76.24%). Results indicated that 19 LAB isolates had cholesterol assimilation rates exceeding 30%. Moreover, forty strains tested negative for all twelve assessed pathogenic genes and exhibited good adhesion to human intestinal epithelial cells (13.47 to 49.12%). Furthermore, 24 isolates formed strong biofilms, 29 formed moderate biofilms, and 23 formed weak biofilms. Except for isolates ABRIIFBI-8, ABRIIFBI-16, ABRIIFBI-23, ABRIIFBI-43, ABRIIFBI-56, and ABRIIFBI-62, most isolates were capable of producing exopolysaccharides. Consequently, LAB strains naturally occurring in sourdough and traditional dairy samples were suggested as potential probiotic candidates for incorporation into functional foods.

Milk and Its Derivatives as Sources of Components and Microorganisms with Health-Promoting Properties: Probiotics and Bioactive Peptides

Milk is a source of many valuable nutrients, including minerals, vitamins and proteins, with an important role in adult health. Milk and dairy products naturally containing or with added probiotics have healthy functional food properties. Indeed, probiotic microorganisms, which beneficially affect the host by improving the intestinal microbial balance, are recognized to affect the immune response and other important biological functions. In addition to macronutrients and micronutrients, biologically active peptides (BPAs) have been identified within the amino acid sequences of native milk proteins; hydrolytic reactions, such as those catalyzed by digestive enzymes, result in their release. BPAs directly influence numerous biological pathways evoking behavioral, gastrointestinal, hormonal, immunological, neurological, and nutritional responses. The addition of BPAs to food products or application in drug development could improve consumer health and provide therapeutic strategies for the treatment or prevention of diseases. Herein, we review the scientific literature on probiotics, BPAs in milk and dairy products, with special attention to milk from minor species (buffalo, sheep, camel, yak, donkey, etc.); safety assessment will be also taken into consideration. Finally, recent advances in foodomics to unveil the probiotic role in human health and discover novel active peptide sequences will also be provided.

The therapeutic effects of fermented milk with lactic acid bacteria from traditional Daqu on hypertensive mice

Lactic acid bacteria (LAB), a type of microorganism widely used in functional foods, has gained notable research attention in recent years. Certain strains possess the proteolytic ability to release potentially antihypertensive peptides from dairy proteins, which prompted us to explore the LAB strains from an understudied and unique ingredient, Daqu. We screened for 67 strains of LAB strains from traditional Daqu using the calcium dissolution ring method. Sixteen strains exhibiting angiotensin-converting enzyme inhibition (ACE-I) activity exceeding 50% were chosen for 16S rDNA sequencing and safety assessment. It is noteworthy that Enterococcus faecium CP640 and Lacticaseibacillus rhamnosus CP658 exhibited significant ACE-I activity, which was the result of strain fermentation in reconstituted skim milk. These 2 strains did not exhibit hemolytic activity or antibiotic resistance. They also did not produce biogenic amines and showed high survival rates in the gastrointestinal tract. Additionally, Enterococcus faecium CP640 and Lacticaseibacillus rhamnosus CP658 fermented milk exhibited a notable reduction in blood pressure levels in spontaneously hypertensive rats (SHR) compared with negative controls in SHR. Importantly, no adverse effect was observed in normal Wistar-Kyoto rats. Through the analysis of physiological, serum, and urine-related indicators, it was observed that Enterococcus faecium CP640 and Lacticaseibacillus rhamnosus CP658 have the potential to promote weight gain in SHR, alleviate excessive heart rate, improve renal function indicators, and effectively regulate blood sugar and uric acid levels in SHR. These 2 strains showed optimal properties in lowering blood pressure and have the potential to be used in functional dairy products in the future.

Kluyveromyces marxianus supplementation ameliorates alcohol-induced liver injury associated with the modulation of gut microbiota in mice

The aim of this study was to evaluate the intervention effect of the potential probiotic Kluyveromyces marxianus YG-4 isolated from Tibetan kefir grains on alcoholic liver disease (ALD). Eight-week-old male C57BL/6J mice were fed with a Lieber-DeCarli (LDC) diet containing ethanol with a progressively increasing concentration from 1% to 4% (vol/vol) to establish an ALD mouse model. Our results suggested that K. marxianus treatment improved ALD, as demonstrated by the reduction of serum ALT and AST levels and the suppression of TLR4/NF-κB-mediated inflammatory response in the liver. K. marxianus administration significantly elevated antioxidant activities of SOD, CAT and GSH-Px, and reduced the MDA level in mice. K. marxianus supplementation repaired the gut barrier by increasing tight junction proteins and the number of goblet cells in the colon of ALD mice. In addition, treatment with K. marxianus restored alcohol-induced gut dysbiosis. Specifically, K. marxianus administration depleted the abundance of Lactobacillus, Coriobacteriaceae_UCG-002 and Candida, while increased that of Allobaculum, Dubosiella and Epicoccum in mice. Our findings open new possibilities for K. marxianus application in ALD treatment.

Microbiome Interconnectedness throughout Environments with Major Consequences for Healthy People and a Healthy Planet

Microbiomes have highly important roles for ecosystem functioning and carry out key functions that support planetary health, including nutrient cycling, climate regulation, and water filtration. Microbiomes are also intimately associated with complex multicellular organisms such as humans, other animals, plants, and insects and perform crucial roles for the health of their hosts. Although we are starting to understand that microbiomes in different systems are interconnected, there is still a poor understanding of microbiome transfer and connectivity. In this review we show how microbiomes are connected within and transferred between different habitats and discuss the functional consequences of these connections. Microbiome transfer occurs between and within abiotic (e.g., air, soil, and water) and biotic environments, and can either be mediated through different vectors (e.g., insects or food) or direct interactions. Such transfer processes may also include the transmission of pathogens or antibiotic resistance genes. However, here, we highlight the fact that microbiome transmission can have positive effects on planetary and human health, where transmitted microorganisms potentially providing novel functions may be important for the adaptation of ecosystems.

Enhanced probiotic potential of Lactobacillus kefiranofaciens OSU-BDGOA1 through co-culture with Kluyveromyces marxianus bdgo-ym6

Introduction

Due to the increasing consumer demand for the development and improvement of functional foods containing probiotics, new probiotic candidates need to be explored as well as novel means to enhance their beneficial effects. Lactobacillus kefiranofaciens OSU-BDGOA1 is a strain isolated from kefir grains that has demonstrated probiotic traits. This species is the main inhabitant of kefir grains and is responsible for the production of an exopolysaccharide (EPS) whit vast technological applications and potential bioactivities. Research has shown that interkingdom interactions of yeast and lactic acid bacteria can enhance metabolic activities and promote resistance to environmental stressors.

Methods

Comparative genomic analyses were performed to distinguish OSU-BDGOA1 from other strains of the same species, and the genome was mined to provide molecular evidence for relevant probiotic properties. We further assessed the cumulative effect on the probiotic properties of OSU-BDGOA1 and Kluyveromyces marxianus bdgo-ym6 yeast co-culture compared to monocultures.

Results

Survival during simulated digestion assessed by the INFOGEST digestion model showed higher survival of OSU-BDGOA1 and bdgo-ym6 in co-culture. The adhesion to intestinal cells assessed with the Caco-2 intestinal cell model revealed enhanced adhesion of OSU-BDGOA1 in co-culture. The observed increase in survival during digestion could be associated with the increased production of EPS during the late exponential and early stationary phases of co-culture that, by enhancing co-aggregation between the yeast and the bacterium, protects the microorganisms from severe gastrointestinal conditions as observed by SEM images. Immune modulation and barrier function for recovery and prevention of flagellin-mediated inflammation by Salmonella Typhimurium heat-killed cells (HKSC) in Caco-2 cells were also measured. OSU-BDGOA1 in mono- and co-culture regulated inflammation through downregulation of pro-inflammatory cytokine expression and increased membrane barrier integrity assessed by TEER, FD4 permeability, and expression of tight junctions.

Discussion

The results of the study warrant further research into the application of co-cultures of yeast and LAB in functional probiotic products and the potential to increase EPS production by co-culture strategies.

Novel yeasts with potential probiotic characteristics isolated from the endogenous ferment of artisanal Minas cheese

Artisanal Minas cheese (QMA) is traditionally elaborate using raw milk and endogenous ferment (pingo - whey or rala - grated ripened cheese). In the present study, 91 yeast strains were isolated and identified from pingo and rala. Eight yeast species were identified by the MALDI-TOF mass spectrometry and confirmed by sequencing of the ITS region. The yeasts' protease and lipase activities were evaluated in addition to probiotic properties such as tolerance to low pH and bile salts, hydrophobicity, autoaggregation, co-aggregation with pathogens, and antimicrobial susceptibility. The rala ferment showed a greater variety of species. Yarrowia lipolytica was the dominant specie (52.7% of isolates), followed by the Kluyveromyces lactis and Kodamaea ohmeri (9.9 and 6.6%, respectively). From the total yeasts evaluated, 74 strains showed positive enzymatic activity: 52 strains showed lipolytic (51 Y. lipolytica and one Trichosporon japonicum) and 44 proteolytic activities (18 Y. lipolytica, 13 K. ohmeri, 11 K. lactis, and 2 Wickerhamiella sp.). All evaluated isolates demonstrated tolerance to pH 2.0, and 69 isolates supported the presence of bile salts. From them, 12 isolates showed the capacity of autoaggregation (> 30%) and hydrophobicity (> 90.0%) and were then selected for co-aggregation and antibiotic resistance assays. All selected isolates showed co-aggregation with Salmonella Enteritidis, Escherichia coli, and Listeria monocytogenes greater than 30%. None of the yeast showed sensibility to the evaluated antibiotics and antagonistic activity against the evaluated pathogens. The results demonstrated that pingo and rala have different yeast composition with different enzymatic activity, which may affect the characteristics of the cheese. Furthermore, some yeast strains: Y. lipolytica (9 strains isolated from rala) and K. ohmeri (3 strains isolated from pingo) demonstrated attractive probiotic potential.

Biocontrol and Probiotic Function of Non-Saccharomyces Yeasts: New Insights in Agri-Food Industry

Fermented food matrices, including beverages, can be defined as the result of the activity of complex microbial ecosystems where different microorganisms interact according to different biotic and abiotic factors. Certainly, in industrial production, the technological processes aim to control the fermentation to place safe foods on the market. Therefore, if food safety is the essential prerogative, consumers are increasingly oriented towards a healthy and conscious diet driving the production and consequently the applied research towards natural processes. In this regard, the aim to guarantee the safety, quality and diversity of products should be reached limiting or avoiding the addition of antimicrobials or synthetic additives using the biological approach. In this paper, the recent re-evaluation of non-Saccharomyces yeasts (NSYs) has been reviewed in terms of bio-protectant and biocontrol activity with a particular focus on their antimicrobial power using different application modalities including biopackaging, probiotic features and promoting functional aspects. In this review, the authors underline the contribution of NSYs in the food production chain and their role in the technological and fermentative features for their practical and useful use as a biocontrol agent in food preparations.

In-vitro and in-vivo antibacterial activity of potential probiotic Lactobacillus paracasei against Staphylococcus aureus and Escherichia coli

Previous studies documented that Lactobacillus paracasei has obvious in vitro cholesterol-lowering abilities. In this study, initially, L. paracasei was tested in terms of antibacterial properties as well as antibiogram profile. Then, the safety of the mentioned strain was evaluated in rats. Evaluation of antibiotic susceptibility revealed that the L. paracasei strain had high antibiotic resistance to several antibiotics as well as a great ability to autoaggregation. After identification of the probiotic aptitude, six groups of six rats from both sexes were used (three groups of each sex). L. paracasei was administered to the experimental groups via drinking water for 28 days (1 × 108 and 1 × 109, respectively). The negative control group received only tap water during this period. Hematological indicators, serum liver enzyme activity including (alanine transaminase (ALT), alkaline phosphatase (ALP), and aspartate transaminase (AST)) as well as serum creatinine and urea were evaluated at the end of 28 days. The blood and serum factors were not changed significantly during the 28 days. The only noticeable difference was the increase of blood urea in both sexes which was in a normal range. Furthermore, the evaluation of antagonistic properties revealed that L. paracasei had antibacterial aptitude against Escherichia coli and Staphylococcus aureus. In conclusion, this strain has good cholesterol-lowering and antibacterial properties and is a safe supplement in Wistar rats.

Non-saccharomyces yeast probiotics: revealing relevance and potential

Non-Saccharomyces yeasts are unicellular eukaryotes that play important roles in diverse ecological niches. In recent decades, their physiological and morphological properties have been reevaluated and reassessed, demonstrating the enormous potential they possess in various fields of application. Non-Saccharomyces yeasts have gained relevance as probiotics, and in vitro and in vivo assays are very promising and offer a research niche with novel applications within the functional food and nutraceutical industry. Several beneficial effects have been described, such as antimicrobial and antioxidant activities and gastrointestinal modulation and regulation functions. In addition, several positive effects of bioactive compounds or production of specific enzymes have been reported on physical, mental and neurodegenerative diseases as well as on the organoleptic properties of the final product. Other points to highlight are the multiomics as a tool to enhance characteristics of interest within the industry; as well as microencapsulation offer a wide field of study that opens the niche of food matrices as carriers of probiotics; in turn, non-Saccharomyces yeasts offer an interesting alternative as microencapsulating cells of various compounds of interest.

Bioprospecting of the probiotic potential of yeasts isolated from a wine environment

Autochthonous yeasts of oenological origin are adapted to highly stressful and selective environments, which makes them potential candidates for probiotics. The objective of the present study was to explore the probiotic potential of 96 native yeasts of oenological origin, their biosafety, resistance to gastrointestinal tract conditions and adhesion properties. Regarding biosafety, 66 isolates shown negative hemolytic activity, negative urease activity and susceptibility to 3 or more antifungals. After the gastrointestinal resistance test, 15 isolates were selected that showed growth at different temperatures, tolerance to low pH and the presence of bile salts in in vitro tests. In general, survival after simulated conditions of the gastrointestinal tract was high and more restrictive was the duodenal. The results of the adhesion properties showed highly variable hydrophobicity and a high percentage of autoaggregation at 24 h. The maximum production of biofilm was detected in the Pichia strains. Of a total of 96 yeast strains, 15 non-Saccharomyces yeasts presented suitable properties as probiotic candidates. The native winemaking strains performed better than the reference probiotic strain, Saccharomyces cerevisiae var. boulardii CNCM I-745, which reaffirms that these strains are promising probiotic candidates and further studies are necessary to confirm their probiosis.

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.

Technological characterisation and probiotic traits of yeasts isolated from Sha'a, a Cameroonian maize-based traditional fermented beverage

The current trend in starter selection is to combine both technological and probiotic properties to standardise and make functional artisanal fermented beverages such as Sha'a whose properties are very variable due to the lack of a known starter. The objective of this work was to study technological and probiotic properties of yeasts isolated from Sha'a sold in Bamenda, Bafoussam, Bonabérie, Dschang, Foumbot, Mbouda and Njombé (Cameroon). The isolated yeasts were studied for their ability to produce CO₂ from glucose, to grow in the presence of 8% ethanol, 20% glucose and pH 3, to assimilate maltose and to produce ethanol. Then, the survival of the pre-selected isolates was assessed in simulated gastric (pH 2 and 3) and intestinal juices, followed by self-aggregation, co-aggregation, hydrophobicity, haemolysin, gelatinase, biogenic amine production, antibiotic and antifungal susceptibility, bile salt hydrolase and antiradical activity. The selected isolates were identified by sequencing the 5.8S/28S rRNA gene. From the 98 isolates obtained, 66 produced CO₂ from glucose and 16 were then selected for their ability to grow in the presence of 8% ethanol, 20% glucose, pH 3 and maltose. The overall survival of isolates ranged from 4.12 ± 1.63 to 104.25 ± 0.19% (LT16) and from 0.56 ± 0.20 to 96.74 ± 1.60% (LT66) at pH 3 and pH 2 respectively. All of them have remarkable surface hydrophobicity properties. Based on principal component analysis, 5 isolates were selected as the best. However, only 3 of them, LT16 (the most promising), LT25 identified as Saccharomyces cerevisiae and LT80 as Nakaseomyces delphensis, do not produce a virulence factor. The latter can deconjugate bile salts with a maximum percentage of 60.54 ± 0.12% (LT16) and the highest inhibition of DPPH° radicals was 55.94 ± 1.14% (LT25). In summary, the yeast flora of Sha'a contains yeasts capable of fermenting and producing ethanol while producing bioactive compounds that would benefit the consumer.

Investigations into metabolic properties and selected nutritional metabolic byproducts of different non-Saccharomyces yeast strains when producing nonalcoholic beer

Nonalcoholic beers are becoming increasingly popular, in part due to consumers' awareness of a healthier lifestyle. Additionally, consumers are demanding diversification in the product range, which can be offered by producing nonalcoholic beers using non-Saccharomyces yeasts for fermentation to create a wide variety of flavors. So far, little is known about the nutritionally relevant byproducts that these yeasts release during wort fermentation and whether these yeasts can be considered safe for food fermentations. To gain insights into this, the B vitamins of four different nonalcoholic beers fermented with the yeast species Saccharomycodes ludwigii, Cyberlindnera saturnus (two strains), and Kluyveromyces marxianus were analyzed. Furthermore, a total of 16 beers fermented with different non-Saccharomyces yeast strains were analyzed for biogenic amines. Additionally, stress tolerance tests were performed at 37°C and in synthetic human gastric juice in vitro. B vitamins were found in the four nonalcoholic beers in nutritionally relevant amounts so they could serve as a supplement for a balanced diet. Biogenic amines remained below the limit of determination in all 16 beers, and thus likely had no influence, while the stress tolerance tests gave a first indication that seven yeast strains could possibly tolerate the human gastric juice milieu.

Yeasts from Iranian traditional milk kefir samples: isolation, molecular identification and their potential probiotic properties

Milk kefir is a fermented dairy product with numerous attributed health benefits due to the presence of a complex eukaryotic and prokaryotic microbiota. In this study, a total number of 26 yeast isolates were obtained from eight kefir samples from three different cities of Iran. The isolates belonged to Kluyveromyces marxianus, Saccharomyces cerevisiae, Pichia fermentans and P. kudriavzevii. The potential probiotic characteristics of the isolates were evaluated based on their ability to tolerate the stimulated condition of the gastrointestinal tract. In addition, hemolytic activity, adherence to different solvents, auto-aggregation, adhesion to the epithelial intestine-derived cells and antimicrobial activity of the selected isolates were evaluated. Overall, four yeast strains (three strains of S. cerevisiae and one strain of P. fermentans) showed resistance and survival ability against the gastrointestinal physiological conditions including acidic pH, presence of bile salt and digestive enzymes. They were able to grow at 37 °C and had the capacity to adhere to epithelial intestine-derived cells. These results suggest that the selected strains can be proper candidates as probiotic yeast strains for the development of novel functional foods.

Mycobiota composition and changes across pregnancy in patients with gestational diabetes mellitus (GDM)

The gut mycobiota has never been studied either during pregnancy or in patients with gestational diabetes (GDM). This study aimed to analyze the fecal mycobiota of GDM patients during the second (T2) and third (T3) trimester of pregnancy and to compare it with the mycobiota of pregnant normoglycemic women (controls). Forty-one GDM patients and 121 normoglycemic women were studied. GDM mycobiota was composed almost exclusively by the Ascomycota phylum; Basidiomicota accounted for 43% of the relative frequency of the controls. Kluyveromyces (p < 0.001), Metschnikowia (p < 0.001), and Pichia (p < 0.001) showed a significantly higher frequency in GDM patients, while Saccharomyces (p = 0.019), were more prevalent in controls. From T2 to T3, a reduction in fungal alpha diversity was found in GDM patients, with an increase of the relative frequency of Candida, and the reduction of some pro-inflammatory taxa. Many associations between fungi and foods and nutrients were detected. Finally, several fungi and bacteria showed competition or co-occurrence. Patients with GDM showed a predominance of fungal taxa with potential inflammatory effects when compared to normoglycemic pregnant women, with a marked shift in their mycobiota during pregnancy, and complex bacteria-fungi interactions.

Exploring biotechnological and functional characteristics of probiotic yeasts: A review

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In this review, the probiotic attributes of yeasts other than Saccharomyces boulardii and the various applications of probiotic yeast in biotechnology have been explored.

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This review comprises of the probiotic attributes, antagonistic activity against pathogens, plant growth promoting attributes, industrial application and their biotherapeutic potentials.

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Advanced and additional studies on non-Saccharomyces yeasts are necessary prior to administer these yeasts as potential probiotics for health and wellbeing.

Probiotics are vital and beneficial organisms which offers the health benefits to the host organisms. The fungal probiotic field is one of the developing fields nowadays. Yeast has an enormous and diverse group of microorganisms that is attracting and expanding the attention from researchers and industries. Saccharomyces boulardii, the only patented strain belonging to yeast genera for the human use, has been broadly evaluated for its probiotic effect. Yeasts belonging to the genera Debaryomyces, Pichia, Yarrowia, Meyerozyma, Kluyveromyces etc.., have attained more interest because of their beneficial and probable probiotic features. These yeast probiotics produce VOCs (Volatile organic compounds), mycocins and antimicrobials which shows the antagonistic effect against pathogenic fungi and bacteria. Additionally, those yeasts have been recorded as good plant growth promoting microorganisms. Yeast has an important role in environmental applications such as bioremediation and removal of metals like chromium, mercury, lead etc., from waste water. Probiotic yeasts with their promising antimicrobial, antioxidant, anticancer properties, cholesterol assimilation and immunomodulatory effects can also be utilized as biotherapeutics. In this review article we have made an attempt to address important yeast probiotic attributes.

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

This study is about the isolation of yeast from fermented dairy and non-dairy products as well as the characterization of their survival in in vitro digestion conditions and tolerance to bile salts. Promising strains were selected to further investigate their probiotic properties, including cell surface properties (autoaggregation, hydrophobicity and coaggregation), physiological properties (adhesion to the HT-29 cell line and cholesterol lowering), antimicrobial activities, bile salt hydrolysis, exopolysaccharide (EPS) producing capability, heat resistance and resistance to six antibiotics. The selected yeast isolates demonstrated remarkable survivability in an acidic environment. The reduction caused by in vitro digestion conditions ranged from 0.7 to 2.1 Log₁₀. Bile salt tolerance increased with the extension in the incubation period, which ranged from 69.2% to 91.1% after 24 h. The ability of the 12 selected isolates to remove cholesterol varied from 41.6% to 96.5%, and all yeast strains exhibited a capability to hydrolyse screened bile salts. All the selected isolates exhibited heat resistance, hydrophobicity, strong coaggregation, autoaggregation after 24 h, robust antimicrobial activity and EPS production. The ability to adhere to the HT-29 cell line was within an average of 6.3 Log₁₀ CFU/mL after 2 h. Based on ITS/5.8S ribosomal DNA sequencing, 12 yeast isolates were identified as 1 strain for each Candidaalbicans and Saccharomyces cerevisiae and 10 strains for Pichia kudriavzevii.

In Vitro Study of Probiotic, Antioxidant and Anti-Inflammatory Activities among Indigenous Saccharomyces cerevisiae Strains

Nowadays, the interest toward products containing probiotics is growing due to their potential health benefits to the host and the research is focusing on search of new probiotic microorganisms. The present work was focused on the characterization of indigenous Saccharomyces cerevisiae strains, isolated from different food matrixes, with the goal to select strains with probiotic or health-beneficial potential. A preliminary screening performed on fifty S. cerevisiae indigenous strains, in comparison to a commercial probiotic strain, allowed to individuate the most suitable ones for potential probiotic aptitude. Fourteen selected strains were tested for survival ability in the gastrointestinal tract and finally, the strains characterized for the most important probiotic features were analyzed for health-beneficial traits, such as the content of glucan, antioxidant and potential anti-inflammatory activities. Three strains, 4LBI-3, LL-1, TA4-10, showing better attributes compared to the commercial probiotic S.cerevisiae var. boulardii strain, were characterized by interesting health-beneficial traits, such as high content of glucan, high antioxidant and potential anti-inflammatory activities. Our results suggest that some of the tested S. cerevisiae strains have potential as probiotics and candidate for different applications, such as dietary supplements, and starter for the production of functional foods or as probiotic to be used therapeutically.

Evaluation of the Potential Probiotic Yeast Characteristics with Anti-MRSA Abilities

Methicillin-resistant Staphylococcus aureus (MRSA) is a disreputable pathogenic bacterium that has been proven to colonize the intestinal tract. The goal of this study is to find anti-MRSA probiotic yeast from food and evaluate its probiotic characteristics and safety. Finally, 15 strains were isolated from fruit peel with anti-MRSA ability. Using DNA sequence analysis, they were identified as the genus Hanseniaspora (7 strains) and Starmerella (8 strains). Starmerella bacillaris CC-PT4 (CGMCC No. 23573) that was isolated from the grape peel has good auto-aggregation ability and hydrophobicity, and can tolerate 0.3% bile, pH 2, simulated gastric fluid (SGF), and simulated intestinal fluid (SIF). Strikingly, Starmerella bacillaris CC-PT4, like commercial probiotic Saccharomyces boulardii CNCM I-745 (Florastor ^®), can adapt to the temperature of the human body (37 ℃). After safety assessment, this strain is sensitive to amphotericin B and cannot produced β-hemolytic activities. Overall, this study provides a new candidate for probiotic yeast with anti-MRSA ability.

Survivability of Kluyveromyces marxianus Isolated From Korean Kefir in a Simulated Gastrointestinal Environment

Kluyveromyces marxianus accounts for > 90% of the yeast population of kefir, and recently, its probiotic potential has been actively explored with a focus on its health benefits and safety. Herein, the survivability of five kefir-isolated K. marxianus strains (Km A1–A5) in a simulated gastrointestinal (GI) environment was evaluated and compared with those of commercial probiotic yeast, Saccharomyces boulardii MYA-796. To further explore the potential to survive in the host GI tract, biochemical activities, hydrophobicity assay, biofilm formation, auto-aggregation analysis, and phenol tolerance of the strains were assessed. K. marxianus A4 exhibited the best survivability among all tested strains, including the clinically proven probiotic yeast strain S. boulardii MYA-796 (p = 0.014) in the artificial GI tract ranging from pH 2.0 to 7.5. In addition, the five K. marxianus strains and S. boulardii MYA-796 displayed different assimilation of lactose, xylitol, D-sorbitol, and DL-lactate, indicating that K. marxianus metabolized a wide range of substances and, thus, might be more feasible to nourish themselves in the host GI tract for survival. K. marxianus strains showed a greater hydrophobicity of cell surface, abilities to biofilm formation and auto-aggregation, and phenol tolerance than S. boulardii MYA-796, suggesting greater potential for survival in the host GI tract.

The Bacterial and Fungal Microbiota of “Robiola di Roccaverano” Protected Designation of Origin Raw Milk Cheese

Robiola di Roccaverano is an artisanal Protected Designation of Origin (PDO) soft cheese made with raw goat’s milk and by the addition of Natural Milk Culture (NMC) to drive the fermentation process. Cheeses collected from five different dairy plants were analyzed for their bacterial and fungal microbiota diversity. Lactococcus lactis and Leuconostoc mesenteroides were the main bacterial population, while Galactomyces candidum and Kluyveromyces marxianus constituted the core mycobiota but many other minor taxa were observed, suggesting a high level of complexity in fungal composition by these cheeses compared to bacteria population.

In Vitro Characterisation Revealed Himalayan Dairy Kluyveromyces marxianus PCH397 as Potential Probiotic with Therapeutic Properties

Recently, probiotics have gained much attention for their roles against various clinical conditions. Obesity is a worldwide health problem that triggers various other major complications like type 2 diabetes (T2D) and cancers, including colorectal cancer (CRC). Earlier, Kluyveromyces marxianus PCH397 isolated from yak (Bos grunniens) milk has been characterised by us for its efficient β-galactosidase-producing ability, an important probiotic property. In the present study, yeast PCH397 has been evaluated for various parameters for its probiotic use. PCH397 exhibited tolerance to GI tract conditions (low pH, pancreatin, pepsin, and bile salts) with 78 to 99% survivability, possessed around 81% cell surface hydrophobicity, and 96% autoaggregation ability. The cell-free extract (CFE) and cell-free supernatant (CFS) from PCH397 improved insulin sensitisation by enhancing 2-NBDG (a glucose analogue) uptake in 3T3-L1 adipocytes, an approach useful in T2D treatment. They also exhibited lower intracellular lipid accumulation, triglyceride storage, and reactive oxygen species in differentiated adipocytes, indicating their anti-adipogenic ability. Also, CFE and intact cells (ICs) exhibited 73.33 ± 1.11% and 34.88 ± 2.80% DPPH radical scavenging activity, respectively. Furthermore, CFS showed a cytotoxic effect on SW-480 colorectal cancer (CRC) cells and induced the cell cycle phase arrest after 24 h of treatment. In conclusion, these results demonstrate that K. marxianus PCH397 could be used as a potential probiotic yeast and presents a therapeutic potential against obesity, T2D, and colon cancer.

The Microbial Diversity and Biofilm-Forming Characteristic of Two Traditional Tibetan Kefir Grains

In this study, a high-throughput sequencing technique was used to analyze bacterial and fungal diversity of two traditional Tibetan kefir grains from Linzhi (K1) and Naqu (K2) regions. Comparative bioinformatic analyses indicated that Lactobacillus kefiranofaciens, L. kefiri and Kluyveromyces marxianus were the main dominant strains in K1 and K2. In order to research the relationship of the growth of kefir grains, the biofilm and the extracellular polysaccharides (EPS) produced by microorganisms, the proliferation rate of kefir grains, the yield and chemical structure of EPS and the optimal days for biofilm formation were determined. The results showed that the growth rate, the yield of EPS and the biofilm formation ability of K1 were higher than K2, and the optimal day of their biofilm formation was the same in 10th day. Additionally, the live cells, dead cells and EPS in biofilm formation of K1 and K2 were observed by fluorescence microscope to clarify the formation process of kefir grains. To determine the influence of microbial interactions on biofilm and the formation of kefir grains, the essential role of microbial quorum sensing needs further attention.

Novel Yeasts Producing High Levels of Conjugated Linoleic Acid and Organic Acids in Fermented Doughs

Traditional fermented foods are obtained by a complex consortium of autochthonous microorganisms producing a wide variety of bioactive compounds, thus representing a reservoir of strains with new functional properties. Here, doughs obtained using five different wholegrain flours were singly fermented with selected yeast strains, which were evaluated for their functional traits. Lactate, volatile fatty acids and conjugated linoleic acid isomers produced by fermented doughs were detected by HPLC, while dough anti-inflammatory capacity was measured on human peripheral blood mononuclear cells by flow cytometry. Yeast potential probiotic activity was assessed by evaluating their resistance to simulated gastric and intestinal fluids. For the first time we report evidence of yeast strains producing high levels of the conjugated linoleic acid (CLA) isomer CLA 10-12tc and propionic acid, which are known for their specific health benefits. Moreover, such yeast strains showed an anti-inflammatory capacity, as revealed by a significantly decreased production of the strongly pro-inflammatory cytokine IL-1β. All our Saccharomyces cerevisiae strains were remarkably resistant to simulated gastric and intestinal fluids, as compared to the commercial probiotic strain. The two strains S. cerevisiae IMA D18Y and L10Y showed the best survival percentage. Our novel yeast strains may be exploited as valuable functional starters for the industrial production of cereal-based innovative and health-promoting fermented foods.

Mycobiota Composition of Robiola di Roccaverano Cheese along the Production Chain

Robiola di Roccaverano is a Protected Designation of Origin (PDO) cheese from the Piedmont region of Italy. In this study, the mycobiota occurring during Robiola di Roccaverano production was elucidated. Samples of milk, Natural Milk Cultures (NMC), curd, 5- and 15-days ripened cheese were collected from one dairy plant and the mycobiota was analyzed by the metataxonomic approach. Milk samples showed a high diversity and Cladosporium, Kluyveromyces marxianus, Geotrichum candidum and Debaryomyces hansenii were found with higher relative abundance. This mycobiota remains quite stable in NMC and curd matrices although the relative abundance of K. marxianus and G. candidum yeasts increased significantly and shaped the fungal composition of 5- and 15-day ripened cheese.

Potential probiotic yeast isolated from an Indonesian indigenous fermented fish (Ikan Budu)

Budu is a fermented food resulting from the activities of microorganisms like lactic acid bacteria and yeast. Budu, therefore, serves as a source of probiotics that can have beneficial effects on livestock and humans. Nonetheless, their selection has to be done with caution. The current study purposed to find out whether budu has desirable probiotic properties. This was done by determining its pH, bile acid tolerance, hydrophobicity, and inhibition of pathogens such as Staphylococcus aureus, Salmonella enteritidis, and Escherichia coli. An in vitro experiment was conducted using three Saccharomyces cerevisiae (coded as SC 11, SC 12, and SC 21) in the preparation of budu. The whole experiment was repeated four times. The budus were tested for their probiotic properties (low pH, bile salts, hydrophobicity, and inhibition of pathogenic bacteria). The results showed that the three Saccharomyces cerevisiae survived in gastric juice and bile acid, exhibited good hydrophobicity, and could inhibit pathogenic bacteria, both gram-positive and negative pathogens. They were able to survive at pH 2 for 3 h (40.70 to 55.1%), at pH 2 for 5 h (35.25 to 46.88%), in 0.3% bile acid incubated for 3 h (69.69 to 86.56%), in 0.3% bile acid incubated for 5 h (82.22 to 88.18%) and hydrophobicity ability of 97.0 to 98.1%. The inhibition activity against pathogenic bacteria, that is, Escherichia coli was 2.50 to 3.81 mm, Staphylococcus aureus was 1.66 to 3.71 mm, and Salmonella enteritidis was 1.20 to 2.64 mm.

Microbiological quality and safety of Brazilian artisanal cheeses

The establishment of norms that regulates the production and trade of Brazilian Artisanal Cheeses (BAC) has been stimulating many small farmers for this activity. The predominance of lactic acid bacteria (LAB) is a typical characteristic of BAC, which confers desirable attributes to artisanal cheeses. However, these products can be contaminated by other microbial groups, including those that indicate hygienic failures during production and may cause spoilage, or even microorganisms that pose risks to consumers' health. A systematic review of the literature published from January 1996 to November 2020 was carried out to identify scientific data about production characteristics and microbiological aspects of BAC, with a major focus on quality and safety status of these traditional products. Studies that fulfilled the inclusion criteria indicated that artisanal chesses produced in Brazil still do not satisfactorily meet the microbiological criteria established by the national laws, mainly due to the high counts of coagulase-positive Staphylococcus and coliforms. Despite low prevalence, pathogens such as Salmonella and Listeria monocytogenes were isolated in some BAC. This review contributed to better understanding microbiological aspects of BAC, the data compiled by the authors highlight the need to improve hygiene practices along the production chain of these traditional cheeses.

Biotechnological approaches for the production of designer cheese with improved functionality

Cheese is a product of ancient biotechnological practices, which has been revolutionized as a functional food product in many parts of the world. Bioactive compounds, such as peptides, polysaccharides, and fatty acids, have been identified in traditional cheese products, which demonstrate functional properties such as antihypertensive, antioxidant, immunomodulation, antidiabetic, and anticancer activities. Besides, cheese-making probiotic lactic acid bacteria (LAB) exert a positive impact on gut health, aiding in digestion, and improved nutrient absorption. Advancement in biotechnological research revealed the potential of metabolite production with prebiotics and bioactive functions in several strains of LAB, yeast, and filamentous fungi. The application of specific biocatalyst producing microbial strains enhances nutraceutical value, resulting in designer cheese products with multifarious health beneficial effects. This review summarizes the biotechnological approaches applied in designing cheese products with improved functional properties.

Influence of Autochthonous Putative Probiotic Cultures on Microbiota, Lipid Components and Metabolome of Caciotta Cheese

The present study was undertaken to produce probiotic Caciotta cheeses from pasteurized ewes' milk by using different combinations of autochthonous microbial cultures, containing putative probiotic strains, and evaluate their influence on gross composition, lipid components, sensory properties and microbiological and metabolite profiles of the cheeses throughout ripening process. A control cheese was produced using commercial starter cultures. The hydrophilic molecular pools (mainly composed by amino acids, organic acids, and carbohydrates) were characterized by means of 1H NMR spectroscopy, while the cholesterol, α-tocopherol and fatty acid composition by HPLC-DAD/ELSD techniques. Conventional culturing and a PCR-DGGE approach using total cheese DNA extracts were used to analyze cheese microbiota and monitor the presence and viability of starters and probiotic strains. Our findings showed no marked differences for gross composition, total lipids, total cholesterol, and fatty acid levels among all cheeses during ripening. Differently, the multivariate statistical analysis of NMR data highlighted significant variations in the cheese' profiles both in terms of maturation time and strains combination. The use of autochthonous cultures and adjunct probiotic strains did not adversely affect acceptability of the cheeses. Higher levels of lactobacilli (viability of 108-109 cfu/g of cheese) were detected in cheeses made with the addition of probiotic autochthonous strains with respect to control cheese during the whole ripening period, suggesting the adequacy of Caciotta cheese as a carrier for probiotic bacteria delivery.

Novel probiotic lactic acid bacteria isolated from indigenous fermented foods from West Sumatera, Indonesia

Background and Aim:

Probiotics play an important role in maintaining a healthy gut and consequently promote good health. This study aimed to find novel probiotic lactic acid bacteria (LAB) from indigenous fermented foods of West Sumatera, Indonesia.

Materials and Methods:

This study utilized 10 LAB previously isolated from fermented buffalo milk (dadih), fermented fish (budu), and fermented cassava (tape) which have the ability to produce gamma-aminobutyric acid. The study commenced with the screening of LAB for certain properties, such as resistance to acid and bile salts, adhesion to mucosal surface, and antagonism against enteric pathogens (Escherichia coli, Salmonella Enteritidis, and Staphylococcus aureus). The promising isolates were identified through biochemical and gram staining methods.

Results:

All isolates in this study were potential novel probiotics. They survived at a pH level of 2.5 for 3 h (55.27-98.18%) and 6 h (50.98-84.91%). Survival in bile at a concentration of 0.3% was 39.90-58.61% and the survival rate was 28.38-52.11% at a concentration of 0.5%. The inhibitory diameter ranged from 8.75 to 11.54 mm for E. coli, 7.02 to 13.42 mm for S. aureus, and 12.49 to 19.00 mm for S. Enteritidis. All the isolates (84.5-92%) exhibited the ability to adhere to mucosal surfaces. This study revealed that all the isolates were potential probiotics but N16 proved to be superior because it was viable at a pH level of 2 (84.91%) and it had a good survival rate in bile salts assay (55.07%). This isolate was identified as Lactobacillus spp., Gram-positive bacilli bacteria, and tested negative in both the catalase and oxidase tests.

Conclusion:

All the isolates in this study may be used as probiotics, with isolate N16 (Lactobacillus spp.) as the most promising novel probiotic for poultry applications based on its ability to inhibit pathogenic bacteria.

Kluyveromyces marxianus: An emerging yeast cell factory for applications in food and biotechnology

Several yeasts, which are eukaryotic microorganisms, have long been used in different industries due to their potential applications, both for fermentation and for the production of specific metabolites. Kluyveromyces marxianus is one of the most auspicious nonconventional yeasts, generally isolated from wide-ranging natural habitats such as fermented traditional dairy products, kefir grain, sewage from sugar industries, sisal leaves, and plants. This is a food-grade yeast with various beneficial traits, such as rapid growth rate and thermotolerance that make it appealing for different industrial food and biotechnological applications. K. marxianus is a respiro-fermentative yeast likely to produce energy by either respiration or fermentation pathways. It generates a wide-ranging specific metabolites and could contribute to a variety of different food and biotechnological industries. Although Saccharomyces cerevisiae is the most widely used dominant representative in all aspects, many applications of K. marxianus in biotechnology, food and environment have only started to emerge nowadays; some of the most promising applications are reviewed here. The general physiology of K. marxianus is outlined, and then the different applications are discussed: first, the applications of K. marxianus in biotechnology, and then the recent advances and possible applications in food, feed and environmental industries. Finally, this review provides a discussion of the main challenges and some perspectives for targeted applications of K. marxianus in the modern food technology and applied biotechnology in order to exploit the full potential of this yeast which can be used as a cell factory with great efficiency.

Probiotic characterization of Pediococcus strains isolated from Iranian cereal-dairy fermented product: Interaction with pathogenic bacteria and the enteric cell line Caco-2

In present study, we investigated the probiotic potential of three Pediococcus spp. isolated from Iranian traditional fermented cereal-dairy product, Tarkhineh. These 3 strains were identified as Pediococcus acidilactici VKU2, P. acidilactici IAH-5 and P. pentosaceus DHR005 by 16S rRNA gene sequencing. All the strain were found tolerate to pH 3 and 0.3% oxall for 3 h as well as simulated gastric and intestinal juice. P. acidilactici IAH-5 showed the highest cholesterol removal (67.52%), hydroxyl radical scavenging activity (58.32%), hydrophobicity (40.3%) and auto-aggregation (48%). Pediococcus spp. inhibited the growth of tested pathogens (Escherichia coli ATCC 25922, Pseudomonas aeruginosa PTCC 1707, Salmonella typhimurium PTCC 1609, and Staphylococcus aureus ATCC 25923) which the most susceptible strain was S. aureus. In competition assay, P. acidilactici IAH-5 was able to inhibited adhesion of 67.3% of S. typhimurium and in inhibition assay 45.8% of the pathogenic adhesion to Caco-2 cells were decreased. P. acidilactici VKU2 and P. acidilactici IAH-5 showed 16.32 and 12.25% adhesion to simulated epithelial cell line which were also confirmed by scanning electron microscopy. Pediococcus spp. did not showed DNase production or hemolytic activity which confirm its safety aspects. Our findings suggested that the P. acidilactici IAH-5 has the best properties with probiotic features and cholesterol assimilation for its application as novel bio-therapeutic and bio-preservation agents.

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.

Production of β-glucosidase from okara fermentation using Kluyveromyces marxianus

The effective utilization of okara (soybean residue) has become a considerable challenge in recent years. In this paper, the potential advantages of β-glucosidase production from okara fermented by Kluyveromyces marxianus were evaluated and the properties of the β-glucosidase were also characterized. The results showed that okara can significantly induce the production of β-glucosidase from K. marxianus. The β-glucosidase activity was up to 4.5 U/mg under optimized fermentation conditions. The optimal parameters were as follows: fermentation temperature 35 °C, cultivation time 98 h, inoculum concentration 10%, and 30 g/L of okara. After two steps of purification using ammonium sulfate precipitation and Sephadex G-75 column chromatography, the activity of β-glucosidase was 71.4 U/mg. The native enzyme was an approximately 66 kDa dimer consisting of two different subunits (22 and 44 kDa). The kinetic parameters of the K. marxianus β-glucosidase, using pNPG as substrate, were V _max 8.34 μmol min^-1 mg^-1 and K _m 7.42 mM. The β-glucosidase showed high thermostability and acid-alkali tolerance as well as low inhibition by DMSO (10-50%). In conclusion, this study supports the notion that okara fermentation by K. marxianus could be a useful process to produce β-glucosidase.

Microbiological characterization of Gioddu, an Italian fermented milk

Gioddu, also known as "Miciuratu", "Mezzoraddu" or "Latte ischidu" (literally meaning acidulous milk), is the sole variety of traditional Italian fermented milk. The aim of the present study was to elucidate the microbiota and the mycobiota occurring in artisan Gioddu sampled from three Sardinian producers by combining the results of viable counting on selective culture media and high-throughput sequencing. Physico-chemical parameters were also measured. The overall low pH values (3.80-4.22) recorded in the analyzed Gioddu samples attested the strong acidifying activity carried out by lactic acid bacteria during fermentation. Viable counts revealed the presence of presumptive lactococci, presumptive lactobacilli and non-Saccharomyces yeasts. A complex (kefir-like) microbiota of bacteria and yeasts was unveiled through sequencing. In more detail, Lactobacillus delbrueckii was found to dominate in Gioddu together with Streptococcus thermophilus, thus suggesting the establishment of a yogurt-like protocooperation. Unexpectedly, in all the three analyzed batches from two out of the three producers Lactobacillus kefiri was also detected, thus representing an absolute novelty, which suggests the presence of bioactive compounds (e.g. exopolysaccharides) similar to those characterizing milk kefir beverage. Mycobiota population, studied for the very first time in Gioddu, revealed a more complex composition, with Kluyveromyces marxianus, Galactomyces candidum and Geotrichum galactomyces constituting the core species. Further research is needed to disclose the eventual occurence in Gioddu of probiotic cultures and bioactive compounds (e.g. exopolysaccharides, angiotensin-converting enzyme inhibitory peptides and antimicrobial compounds) with potential health-benefits for the consumers.

Production and characterization of volatile compounds and phytase from potentially probiotic yeasts isolated from traditional fermented cereal foods in Nigeria

BACKGROUND

Probiotic strains are incorporated into food substrates to contribute to fermentation process. The technological suitability of such strains to improve the flavor and nutritional value of fermented food is strain-specific. Potentially probiotic yeasts isolated from Nigerian traditional fermented foods were assessed for production of volatile compounds by gas chromatography-mass spectrophotometry. Phytases were characterized for activity and stability at different pH (3-8) and temperatures (25-50 °C).

RESULTS

A total of 45 volatiles compounds were identified from intracellular cell-free extracts of Pichia kluyveri LKC17, Issatchenkia orientalis OSL11, P. kudriavzevii OG32, P. kudriavzevii ROM11, and Candida tropicalis BOM21. They include alcohols (14), carbonyls (13), esters (10), and organic acids (8). Phenylethyl alcohol was the highest higher-alcohol in Issatchenkia orientalis OSL11 (27.51 %). The largest proportion of esters was detected in P. kudriavzevii OG32 (17.38 %). Pichia kudriavzevii OG32 and C. tropicalis BOM21 showed vigorous gowth in minimal medium supplemented with sodium phytate (2 g L-1). Extracellular phytases from P. kudriavzevii OG32 and Candida tropicalis BOM2 showed optimal activiy at pH 4.6 (104.28 U) and pH 3.6 (81.43 U) respectively.

CONCLUSIONS

Results obtained revealed species- and strain-specific potentials of the yeast strains to improve flavor and mineral bioavailability of fermented food products. Therefore, the application of these yeasts as starter cultures during food fermentation process is a very promising method to enhance the flavor profile and enhance mineral bioavailability in indigenous cereal-based fermented food products.

Unveiling the potentials of bacteriocin (Pediocin L50) from Pediococcus acidilactici with antagonist spectrum in a Caenorhabditis elegans model

Human-milk-based probiotics play a major role in the early colonization and protection of infants against gastrointestinal infection. We investigated potential probiotics in human milk. Among 41 Lactic acid bacteria (LAB) strains, four strains showed high antimicrobial activity against Escherichia coli 0157:H7, Listeria monocytogenes ATCC 15313, Bacillus cereus ATCC 14576, Staphylococcus aureus ATCC 19095, and Helicobacter pylori. The selected LAB strains were tested in simulated gastrointestinal conditions for their survival. Four LAB strains showed high resistance to pepsin (82%-99%), bile with pancreatine stability (96%-100%), and low pH (80%-94%). They showed moderate cell surface hydrophobicity (22%-46%), auto-aggregation abilities (12%-34%), and 70%-80% co-aggregation abilities against L. monocytogenes ATCC 15313, S. aureus ATCC 19095, B. cereus ATCC 14576, and E. coli 0157:H7. All four selected isolates were resistant to gentamicin, imipenem, novobiocin, tetracycline, clindamycin, meropenem, ampicillin, and penicillin. The results show that Pediococcus acidilatici is likely an efficient probiotic strain to produce < 3 Kda pediocin-based antimicrobial peptides, confirmed by applying amino acid sequences), using liquid chromatography mass spectrometry and HPLC with the corresponding sequences from class 2 bacteriocin, and based on the molecular docking, the mode of action of pediocin was determined on LipoX complex, further the ¹³C nuclear magnetic resonance structural analysis, which confirmed the antimicrobial peptide as pediocin.