Microbial Composition of Water Kefir Grains and Their Application for the Detoxification of Aflatoxin B1.

Water kefir grains (WKGs), the starter used to develop a traditional beverage named water kefir, consist of a symbiotic mixture of probiotics with diverse bioactivities, but little is known about their abilities to remove mycotoxins that have serious adverse effects on humans and animals. This study investigated the ability of WKGs to remove aflatoxin B1 (AFB1), one of the most toxic mycotoxins, under different settings, and determined the mechanism of absorption mediated by WKGs and the effect of WKGs on the toxicity induced by AFB1 and the reduction in AFB1 in cow milk and tea soups. The results showed the WKGs used herein were dominated by Lactobacillus, Acetobacter, Phenylobacterium, Sediminibacterium, Saccharomyces, Issatchenkia, and Kodamaea. HPLC analysis demonstrated that the WKGs effectively removed AFB1 at concentrations ranging from 1 to 5 µg/mL, pH values ranging from 3 to 9, and temperatures ranging from 4 to 45 °C. Additionally, the removal of AFB1 mainly depended on absorption, which was consistent with the Freundlich and pseudo-second-order kinetic models. Moreover, only 49.63% of AFB1 was released from the AFB1-WKG complex after four washes when the release of AFB1 was non-detectable. Furthermore, WKG treatment caused a dramatic reduction in the mutagenicity induced by AFB1 according to an Ames test and reduced more than 54% of AFB1 in cow milk and three tea soups. These results suggested that WKGs can act as a potential bio-absorbent with a high binding ability to detoxify AFB1 in food and feed via a chemical action step and multi-binding sites of AFB1 absorption in a wide range of scenarios.

Correlation between the regulation of intestinal bacteriophages by green tea polyphenols and the flora diversity in SPF mice.

Green tea polyphenols (GTP) play an important role in shaping the gut microbiome, comprising a range of densely colonizing microorganisms, including bacteriophages. Previous studies focused on the effect of GTP on the bacteria in the gut microbiota. However, little is known about the role of GTP in the bacteriophage composition of healthy intestines. In this study, SPF male C57BL/6J mice were divided into a polyphenol-free diet group and a tea polyphenol diet group where drinking water was supplemented with 0.1% GTP for 28 days. The ultra-deep metagenomic sequencing of virus-like particle preparations and bacterial 16S rRNA sequencing were performed on mouse stool samples. Changes in the gut bacteriome, bacteriophages, and bacterial-bacteriophage correlations were then compared between the groups. The results revealed an abundance of Firmicutes, a significant decrease in Bacteroidetes, and a significant increase in the ratio of F/B after GTP exposure. The GTP altered the abundance (relative abundance > 1.00%) of Bifidobacterium (regulation rate of 89.78% and the abundance up-regulated by 0.89%) and Akkermansia (regulation rate of 99.70% and the abundance down-regulated by 1.77%). The abundance of Faecalibaculum (regulation rate of 60.17%) increased by 24.38% following GTP treatment. The GTP also altered the abundance of Salmonella phage (regulation rate of 98.64% and the abundance up-regulated by 3.16%) and that of Gordonia_phage_Yakult (regulation rate of 99.99% and the abundance down-regulated by 5.44%). It significantly increased the intestine's lytic phages and reduced the temperate phages by 29.22%. The dominant microorganisms (relative abundance >1.00%) of Bifidobacterium and Dubosiella had a significantly negative relationship with the Faecalibacterium phage and a significantly positive relationship with the Lactobacillus prophage. Exposure to GTP positively promoted changes in the gut bacteriophage community and interaction network in the microbial community of the SPF mice. These findings highlight the importance of "profitable" bacteriophage-bacteria relationships and reveal a potential mechanism of GTP towards the regulation of intestinal flora via intestinal phage communities.

Antibiofilm activities of the cinnamon extract against Vibrio parahaemolyticus and Escherichia coli.

Vibrio parahaemolyticus and Escherichia coli are two major foodborne pathogens. In this paper, the antibiofilm activities of the ethanol extract of cinnamon against these two bacteria were studied in detail. The antibacterial activity and the MIC of the extract were determined, and the inhibition and removing effects of the extract on the biofilms of V. parahaemolyticus and E. coli were investigated. The biofilms stained with fluorescein isothiocyanate (FITC) and concanavalin A (Con A) were also observed by confocal laser scanning microscope (CLSM). The results indicated that the extract exhibited high antibacterial activity, with the MIC against V. parahaemolyticus and E. coli was 6.25 mg/mL. The effects on V. parahaemolyticus biofilm were significant with the inhibition rate of 75.46% at MIC, and the eradication rate of 93.26% at 32MIC, respectively. As to E. coli, the inhibition rate was 48.18% at MIC, and the eradication rate was 46.16% at 8MIC. Meanwhile, the extract could notably reduce the metabolic activities and the secretion of EPS in biofilm, it inhibited 78.57% EPS formation in V. parahaemolyticus biofilm at MIC, and eliminated 61.28% EPS in mature biofilm at 4MIC. CLSM images showed that the EPS of the treated biofilm became thinner and biofilm structure was looser, when compared with the untreated control. This study elucidated that the cinnamon extract was effective to prevent biofilm formation and eradicate mature biofilms of V. parahaemolyticus and E. coli.

Degradation and Detoxification of Aflatoxin B1 by Tea-Derived Aspergillus niger RAF106.

Microbial degradation is an effective and attractive method for eliminating aflatoxin B1 (AFB1), which is severely toxic to humans and animals. In this study, Aspergillus niger RAF106 could effectively degrade AFB1 when cultivated in Sabouraud dextrose broth (SDB) with contents of AFB1 ranging from 0.1 to 4 µg/mL. Treatment with yeast extract as a nitrogen source stimulated the degradation, but treatment with NaNO3 and NaNO2 as nitrogen sources and lactose and sucrose as carbon sources suppressed the degradation. Moreover, A. niger RAF106 still degraded AFB1 at initial pH values that ranged from 4 to 10 and at cultivation temperatures that ranged from 25 to 45 °C. In addition, intracellular enzymes or proteins with excellent thermotolerance were verified as being able to degrade AFB1 into metabolites with low or no mutagenicity. Furthermore, genomic sequence analysis indicated that the fungus was considered to be safe owing to the absence of virulence genes and the gene clusters for the synthesis of mycotoxins. These results indicate that A. niger RAF106 and its intracellular enzymes or proteins have a promising potential to be applied commercially in the processing and industry of food and feed to detoxify AFB1.

Green Tea Polyphenols Modulate Colonic Microbiota Diversity and Lipid Metabolism in High-Fat Diet Treated HFA Mice.

There is an increasing interest in the effect of dietary polyphenols on the intestinal microbiota and the possible associations between this effect and the development of obesity. However, limited information is available on how these polyphenols affect the gut microbiota and lipid metabolism. The co-action of a high-fat diet (HFD) and tea polyphenol (TP) on gut microbiota and lipid metabolism using a human flora-associated (HFA) C57BL/6J mice model is studied. TP reduced serum total cholesterol, triglyceride, low density lipoprotein, glucose (GLU) and insulin (INS) levels of HFD mice in a dose-dependent manner (P < 0.01). TP also significantly increased acetic acid and butyric acid levels in HFA mice. 16S rRNA V3 region Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) profiles showed that HFD mice had significantly reduced microbial diversity. This reduction could be alleviated by TP, with a significant increase in the richness and diversity of colonic microbiota in the high-fat diet with 0.2% TP (TPM) and high-fat diet with 0.05% TP (TPL) groups (P < 0.05). 454 pyrosequencing analysis showed that the HFD group had a significant increase in the Bacteroidetes to Firmicutes (F/B) ratio (P < 0.001), which could effectively be reversed by TP. The results showed that the changes in composition and diversity of colonic microbiota by TP administration suppressed the host body weight and blood lipid increase in high-fat diet HFA mice. PRACTICAL APPLICATION: A high fat diet significantly impacted gut microbiota composition and lipid metabolism in human flora-associated mice, which were largely ameliorated by tea polyphenol (TP). Therefore, TPs may be effectively used in controlling or treating obesity, hyperlipidemia and other related metabolic diseases.

The effect of green tea polyphenols on gut microbial diversity and fat deposition in C57BL/6J HFA mice.

Quantitative and qualitative changes in gut microbial composition have been linked to obesity and obesity-related complications, and eating pattern has been shown to significantly impact the gut microbiome. Meanwhile, tea polyphenols are known to have health benefits such as improving glucose tolerance and decreasing liver fat deposition that may be helpful in combating obesity and obesity-related disorders. We therefore studied the effect of green tea polyphenols on gut microbial diversity and fat deposition in C57BL/6J Human Flora-Associated (HFA) mice, which were divided into five groups: low fat (LF), high fat (HF), high fat + 0.05% tea polyphenols (HF + 0.05% TP), high fat + 0.2% tea polyphenols (HF + 0.2% TP) and high fat + 0.8% tea polyphenols (HF + 0.8% TP). 16S rRNA V6-V8 region PCR-DGGE profiles showed that a high fat diet was associated with a significant reduction in microbial diversity. This reduction could be alleviated by a HF + 0.2% TP diet, with a significant increase in the number of lactic acid bacteria in the HF + 0.2% TP group compared with the LF group (P < 0.05). Body weight (P < 0.05) and fat pad weight (P < 0.001) were significantly increased in the HF compared with the LF group, with notable adipocyte hypertrophy in the HF group, indicating successful establishment of the high fat model. Body weight among the HF + 0.2% TP group and HF + 0.8% TP group (but not the HF + 0.05% TP group) was significantly lower than the body weight in the HF group (P < 0.01). Therefore, tea polyphenols may effectively retard diet-induced weight gain and body fat gain, adipocyte hypertrophy and hepatic steatosis in a dose-dependent manner.