Bioscience of Microbiota, Food and Health最新文献

Streptococcus thermophilus is widely used for producing fermented dairy products such as yogurt and cheese. Some S. thermophilus strains possessing the cell-wall protease PrtS show high proteolytic activity and fast acidification properties, which are very useful in industrial starters. However, few S. thermophilus strains possessing the prtS gene have been isolated from the environment. To clarify whether or not S. thermophilus strains possessing the prtS gene are present in Japan, we isolated S. thermophilus from raw milk collected in Japan from 2011 to 2017 and investigated the strains for the presence of prtS by PCR. A total of 172 S. thermophilus strains were isolated, and 59 strains were confirmed to possess prtS. We measured fermentation times of 59 prtS-positive strains in skim milk broth and found that 53 strains showed fast acidification properties, finishing fermentation within 10 hr. However, the remaining 6 prtS-positive strains showed slow acidification properties, and they had several amino acid mutations in PrtS compared with fast acidifying S. thermophilus LMD-9 and 4F44. These results demonstrate that S. thermophilus strains possessing prtS are prevalent in Japan and that some prtS-positive strains could lose their fast acidifying properties through mutations in PrtS.

In the present study, we investigated the glucose-decreasing action of lactic acid bacteria (LAB). The finding of this study could be helpful for people in controlling their blood sugar levels. The LAB candidate was isolated from a Japanese fermented food and identified as Pediococcus pentosaceus by an analysis of its genome sequence. Postprandial blood glucose elevation was investigated using oral starch tolerance tests in mice. Normal mice were fed starch and lyophilized cells of P. pentosaceus QU 19 at the same time. Even without pre-administration of P. pentosaceus QU 19, elevation of the blood glucose level was significantly suppressed by the intake of P. pentosaceus QU 19 at the same time as oral administration of starch. According to the results for its survival in simulated digestive juice and the reduction of blood glucose level in mice, P. pentosaceus QU 19 has potential hypoglycemic activity. In vitro measurements revealed that the glucose-decreasing action of P. pentosaceus QU 19 is probably caused by the glucose assimilation of the strain, not the inhibition of carbohydrate-splitting enzymes which has been reported for other LABs previously. These findings indicate that specific strains of LAB, especially P. pentosaceus QU 19, and foods fermented by LAB may be beneficial for people who must manage glucose ingestion.

Food contamination by fungi and mycotoxins presents a problem for food safety even today. Since lactic acid (LA) has Generally Recognized As Safe (GRAS) status, the aim of this research was to determine its potential in protection of food against mycological and mycotoxicological contamination. In this study, LA showed an inhibitory effect on the growth of food-borne fungi (Penicillium aurantiogriseum K51, Aspergillus parasiticus KB31, Aspergillus versicolor S72, and Aspergillus niger K95) and on biosynthesis of sterigmatocystin (STE). For the antifungal effect of LA on the growth of food-borne fungi, the disc diffusion and microdilution methods were performed. The effect of LA on the STE biosynthesis by A. versicolor was determined using an LC-MS/MS technique. The largest inhibition zone was observed for A. versicolor (inhibition zone of 24 ± 0.35 mm), while there were no inhibition zones for A. niger and A. parasiticus at all tested LA concentrations. The minimal inhibitory concentration (MIC) of LA on fungi ranged from 25.0 mg/mL to 50.0 mg/mL, while the minimum fungicidal concentrations (MFCs) ranged from 50.0 mg/mL to 100.0 mg/mL. Complete inhibition of STE biosynthesis by A. versicolor was observed at an LA concentration of 50.0 mg/mL. The obtained results showed that LA could be efficient for protection of food against mycological and STE contamination.

Recent evidence suggests that gut microbiota-derived metabolites affect many biological processes of the host, including appetite control and weight management. Dysbiosis of the gut microbiome in obesity influences the metabolism and excretion of gut microbiota byproducts and consequently affects the physiology of the host. Since identification of the gut microbiota-host co-metabolites is essential for clarifying the interactions between the intestinal flora and the host, we conducted this systematic review to summarize all human studies that characterized the gut microbiota-related metabolites in overweight and obese individuals. A comprehensive search of the PubMed, Web of Science, and Scopus databases yielded 2,137 articles documented up to July 2018. After screening abstracts and full texts, 12 articles that used different biosamples and methodologies of metabolic profiling and fecal microbiota analysis were included. Amino acids and byproducts of amino acids, lipids and lipid-like metabolites, bile acids derivatives, and other metabolites derived from degradation of carnitine, choline, polyphenols, and purines are among the gut microbiota-derived metabolites which showed alterations in obesity. These metabolites play an important role in metabolic complications of obesity, including insulin resistance, hyperglycemia, and dyslipidemia. The results of this study could be useful in development of therapeutic strategies with the aim of modulating gut microbiota and consequently the metabolic profile in obesity.

Plant proteins are known to possess important bioactive peptides and have a positive impact on gut microbial modulation. In this study, we studied the ability of a single dose of a fermented soy protein product (P-SPI) to reduce high blood pressure in spontaneous hypertensive rats (SHR) and how it modulates the gut microbiota after six weeks of feeding. SHRs were fed with P-SPI, Captopril or distilled water once, and their blood pressures were monitored from the first to twelfth-hour post-administration. Consumption of P-SPI significantly reduced systolic and diastolic blood pressures up to the sixth hour by 25 ± 4 mmHg and 40 ± 5 mmHg respectively. P-SPI consumption inhibited serum ACE activity, increased superoxide dismutase activity and nitric oxide levels and reduced malondialdehyde levels in serum. Analysis of fecal microbial 16S rRNA of hypertensive rats revealed a significant reduction in microbial richness and diversity in the gut, while P-SPI consumption improved microbial richness and increased diversity. Also, P-SPI feeding significantly reduced the Firmicutes/Bacteroidetes ratio, increased propionate- and H₂S-producing bacteria and reduced Streptococcaceae and Erysipelotrichales levels. Our results show that P-SPI is a potential antihypertensive functional food which could remodel the altered gut microbiota of hypertensive patients.

In this paper, we investigated the hydrophobicity, ability to adhere to solvents and the pig epithelium and co-aggregation of members of family Enterobacteriaceae and Enterococcus faecalis KGPMF 49. The bacteria used in this study were isolated from traditionally made autochthonous cheese from Southeastern Serbia (Sokobanja). The percentage of adhered bacteria was different in three solvents (chloroform, ethyl acetate and xylene). The highest percentage was detected in the presence of chloroform, and the lowest percentage was detected in the presence of xylene (chloroform < ethyl acetate < xylene). A different degree of co-aggregation of enterobacteria with E. faecalis KGPMF 49 was observed. Klebsiella ornithinolytica KGPMF 8 demonstrated the highest percentage of co-aggregation with E. faecalis KGPMF49 (32.29%). Klebsiella pneumoniae KGPMF 13, K. ornithinolytica KGPMF 9 and Serratia marcescens biogp 1 KGPMF 19 were found to have the ability to adhere to the pig epithelium, whereas Escherichia coli KGPMF 22 showed no such ability. The ability to co-aggregate with other species and the ability to adhere to the pig epithelium are very important characteristics of the isolated bacteria.

Recent evidence suggests that psychological stress is associated with gut microbiota; however, there are no reports of its association with gut microbial structure. This cross-sectional study examined the relationship between psychological stress and gut microbial patterns in young Japanese adults. Analysis of fecal microbiota was performed using terminal restriction fragment length polymorphism (T-RFLP). Psychological stress was assessed using salivary biomarkers, including cortisol, alpha-amylase, and secretory IgA (S-IgA). Fecal microbial patterns were defined using principal component analysis of the T-RFLP profile and were classified into two enterotype-like clusters, which were defined by the B (microbiota dominated by Bacteroides) and BL patterns (microbiota dominated by Bifidobacterium and Lactobacillales), respectively. The Simpson index was significantly higher for the BL pattern than for the B pattern. The salivary cortisol level was significantly lower for the BL pattern than for the B pattern. Salivary alpha-amylase and S-IgA levels showed a negative correlation with the Simpson index. Our results raise the possibility that salivary biomarkers may be involved in the observed differences in microbial patterns.

[This corrects the article on p. 89 in vol. 38, PMID: 31384520.].

The aim of this study was to verify the effect of treatment with isoxanthohumol (IX) on the metabolomics profile of mouse feces to explore the host-intestinal bacterial interactions at the molecular level. The fecal contents of several amino acids in the high-fat diet (HFD) + 0.1% IX group (treated with IX mixed in diets for 12 weeks) were significantly lower than in the HFD group. The fecal contents of the secondary bile acid deoxycholic acid (DCA) in the HFD + 180 mg/kg IX group (orally treated with IX for 8 weeks) were significantly lower than in the HFD group; the values in the HFD group were higher than those in the normal diet (ND) group. Administration of IX changed the fecal metabolomics profile. For some metabolites, IX normalized HFD-induced fluctuations.

Lactobacillus fermentum MTCC 25067 produces a hetero-exopolysaccharide (HePS) when cultured which forms supramolecular networks in the culture medium, increasing the viscosity. In the present study, the viscosity of the bacterial culture reached its maximum at 48 hr of cultivation and then decreased during a stationary growth phase lasting for up to 144 hr. The monosaccharide composition did not change during the stationary growth phase, whereas degradation of HePS molecules was noticeable, leading to partial disintegration of their supramolecular networks. The viscosity values of the HePS purified from the culture and dissolved in a fresh medium indicated little contribution of medium components to the viscosity. Absence of the apparent network structure of the HePS in the surrounding area of bacterial cells was observed during the late growth phase, supporting the idea that the decreases in culture viscosity during the prolonged period of cultivation were caused mainly by reduced interactions between bacterial cells and the intact supramolecular networks as a consequence of decreasing bacterial cell wall integrity and partial degradation of HePS molecules.