A Combined In Vitro and In Vivo Assessment of the Safety of the Yeast Strains Kluyveromyces marxianus A4 and A5 Isolated from Korean Kefir

A comparative evaluation of the kefir yeast Kluyveromyces marxianus A4 and sulfasalazine in ulcerative colitis: anti-inflammatory impact and gut microbiota modulation

Although only Saccharomyces boulardii has been studied for ulcerative colitis (UC), probiotic yeasts have immense therapeutic potential. Herein, we evaluated the kefir yeast Kluyveromyces marxianus A4 (Km A4) and its anti-inflammatory effect with sulfasalazine in BALB/c mice with dextran sulfate sodium (DSS)-induced colitis. Oral administration continued for 7 days after the mice were randomly divided into seven groups: control (CON, normal mice administered with saline), DSS-induced colitis mice administered saline (DSS), and DSS-induced colitis mice administered sulfasalazine only (S), Km A4 only (A4), Km A4 plus sulfasalazine (A4 + S), S. boulardii ATCC MYA-796 (Sb MYA-796) only (Sb), and Sb MYA-796 plus sulfasalazine (Sb + S). The β-glucan content of Km A4 was significantly higher than that of Sb MYA-796 (P < 0.05). Body weight gain (BWG) significantly correlated with colon length, cyclooxygenase-2 (Cox-2) levels, and Bacteroides abundance (P < 0.05). In colitis-induced mice, the A4 + S group had the lowest histological score (6.00) compared to the DSS group (12.67), indicating the anti-inflammatory effects of this combination. The A4 + S group showed significantly downregulated expression of interleukin (Il)-6, tumor necrosis factor-α (Tnf-α), and Cox-2 and upregulated expression of Il-10 and occludin (Ocln) compared to the DSS group. Mice treated with A4 + S had enhanced Bacteroides abundance in their gut microbiota compared with the DSS group (P < 0.05). Bacteroides were significantly correlated with all colitis biomarkers (BWG, colon length, Il-6, Tnf-α, Il-10, Cox-2, and Ocln; P < 0.05). The anti-inflammatory effects of Km A4 could be attributed to high β-glucan content and gut microbiota modulation. Thus, treatment with Km A4 and sulfasalazine could alleviate UC.

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.

Gut microbiota modulation via short-term administration of potential probiotic kefir yeast Kluyveromyces marxianus A4 and A5 in BALB/c mice

Kefir yeast, Kluyveromyces marxianus, has been evaluated for its potential probiotic properties-survivability, non-pathogenicity, and antioxidant and anti-microbial activities. However, host gut microbiota modulation of kefir yeasts remains unclear. Here, we compared kefir yeast strains K. marxianus A4 (Km A4) and K. marxianus A5 (Km A5) with Saccharomyces boulardii ATCC MYA-796 (Sb MYA-796) by investigating their adherence to colorectal adenocarcinoma (Caco-2) cells and gut microbiota modulation in BALB/c mice. The kefir yeast strains exhibited higher intestinal cell adhesion than Sb MYA-796 (p < 0.05). Bacteroidetes, Bacteroidales, and Bacteroides were more abundant in the 1 × 108 CFU/mL of Km A4 treatment group than in the control group (p < 0.05). Moreover, 1 × 108 CFU/mL of Km A5 increased Corynebacteriales and Corynebacterium compared to the 1 × 108 CFU/mL of Km A4 treatment group (p < 0.01). The results showed that Km A4 and Km A5 had good Caco-2 cell adhesion ability and modulated gut microbiota upon short-term administration in healthy mice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01268-3.

Update of the list of qualified presumption of safety (QPS) recommended microbiological agents intentionally added to food or feed as notified to EFSA 17: suitability of taxonomic units notified to EFSA until September 2022

The qualified presumption of safety (QPS) approach was developed to provide a regularly updated generic pre-evaluation of the safety of microorganisms, intended for use in the food or feed chains, to support the work of EFSA's Scientific Panels. The QPS approach is based on an assessment of published data for each agent, with respect to its taxonomic identity, the body of relevant knowledge and safety concerns. Safety concerns identified for a taxonomic unit (TU) are, where possible, confirmed at the species/strain or product level and reflected by 'qualifications'. In the period covered by this Statement, new information was found leading to the withdrawal of the qualification 'absence of aminoglycoside production ability' for Bacillus velezensis. The qualification for Bacillus paralicheniformis was changed to 'absence of bacitracin production ability'. For the other TUs, no new information was found that would change the status of previously recommended QPS TUs. Of 52 microorganisms notified to EFSA between April and September 2022 (inclusive), 48 were not evaluated because: 7 were filamentous fungi, 3 were Enterococcus faecium, 2 were Escherichia coli, 1 was Streptomyces spp., and 35 were taxonomic units (TUs) that already have a QPS status. The other four TUs notified within this period, and one notified previously as a different species, which was recently reclassified, were evaluated for the first time for a possible QPS status: Xanthobacter spp. could not be assessed because it was not identified to the species level; Geobacillus thermodenitrificans is recommended for QPS status with the qualification 'absence of toxigenic activity'. Streptoccus oralis is not recommended for QPS status. Ogataea polymorpha is proposed for QPS status with the qualification 'for production purposes only'. Lactiplantibacillus argentoratensis (new species) is included in the QPS list.

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.

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.