Silk-derived sericin/fibroin mixture drink fermented with plant-derived Lactococcus lactis BM32-1 improves constipation and related microbiota: a randomized, double-blind, and placebo-controlled clinical trial.

We previously showed through clinical trials that one plant-derived lactic acid bacteria (LAB) can improve constipation. We preliminarily found that the plant-derived LAB Lactococcus lactis BM32-1 can grow in a mixture of sericin and fibroin, which are extracted from silk and have been reported to help promote health. Thus, in the present study, we evaluated the favorable effect of a sericin/fibroin mixture (S/F-M), which was extracted from silk prepared from cocoons reared in an aseptic rearing system using an artificial diet, fermented with the BM32-1 strain through a clinical trial. The trial was conducted at Hiroshima University from June to October 2022 as a double-blind, placebo-controlled, randomized parallel-group comparative study with 50 eligible subjects (aged 23-71) who had an average defecation frequency of less than 5 times per week. The subjects were instructed to drink 100 mL of fermented S/F-M or placebo every day. After the 12 weeks of the clinical trial period, the average defecation frequency increased significantly-1.4 times higher than that at baseline in the test group-as compared with the placebo group. Furthermore, the fecal microbiota was also compared before and after treatment, revealing that intake of the fermented S/F-M significantly multiplied the relative abundance of the genera Enterococcus and Clostridium, which have been reported to contribute to the amelioration of constipation by improving the gut microbiota and producing butyric acid, respectively. In conclusion, the S/F-M fermented using the BM32-1 strain improves defecation frequency through alteration of the gut microbiota.

Transcriptional profiling of geniposide bioconversion into genipin during gardenia fructus extract fermentation by Lactobacillus (Lactiplantibacillus) plantarum SN13T.

Lactiplantibacillus plantarum SN13T is a probiotic plant-derived lactic acid bacterium that can grow in various medicinal plant extracts. In this study, we fermented an aqueous extract of gardenia fructus, the fruit of a medicinal plant, with SN13T, such that the bioactivity of the extract was potentiated after fermentation to suppress the release of inflammatory mediators, such as nitric oxide (NO), reactive oxygen species (ROS), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), as well as downregulate inflammatory genes in lipopolysaccharides (LPS)-stimulated RAW 264.7 cells. This increased antioxidant and anti-inflammatory activity was mediated through bioconversion of the iridoid glycoside geniposide to its aglycone genipin via the supposed hydrolytic action of ß-glucosidases harbored by SN13T. In the complete genome of SN13T, ten putative genes encoding ß-glucosidases of glycosyl hydrolase (GH) family 1 organized among eight gene operons were identified. Transcriptional profiling revealed that two 6-phospho-ß-glucosidase genes, pbg9 and SN13T_1925, located adjacently in the gene operon SN13T_1923, were transcribed significantly more than the remaining genes during fermentation of the gardenia extract. This suggests the role of these ß-glucosidases in bioconversion of geniposide to genipin and the subsequent enhanced bioactivity of the gardenia fructus extract after fermentation with SN13T.

Non-pathogenic Heyndrickxia coagulans (Bacillus coagulans) 29-2E inhibits the virulence of pathogenic Salmonella Typhimurium by quorum-sensing regulation.

Bacteria produce and release small signal molecules, autoinducers, as an indicator of their cell density. The system, called a quorum-sensing (QS) system, is used to control not only virulence factors but also antibiotic production, sporulation, competence, and biofilm formation in bacteria. Different from antibiotics, QS inhibitors are expected to specifically repress the virulence factors in pathogenic bacteria without inhibiting growth or bactericidal effects. Therefore, since QS inhibitors have little risk of antibiotic-resistant bacteria emergence, they have been proposed as promising anti-bacterial agents. In the present study, we aimed to find new QS inhibitors that prohibit the signaling cascade of autoinducer 3 (AI-3) recognized by a QseCB two-component system that regulates some virulence factors of pathogens, such as enterohemorrhagic Escherichia coli (EHEC) and Salmonella enterica subsp. enterica serovar Typhimurium. We have established the method for QS-inhibitor screening using a newly constructed plasmid pLES-AQSA. E. coli DH5α transformed with the pLES-AQSA can produce ß-galactosidase that converts 5-bromo-4-chloro-3-indolyl ß-d-galactopyranoside (X-gal) into blue pigment (5-bromo-4-chloro-indoxyl) under the control of the QseCB system. By screening, Heyndrickxia coagulans (formerly Bacillus coagulans) 29-2E was found to produce an exopolysaccharide (EPS)-like water-soluble polymer that prohibits QseCB-mediated ß-galactosidase production without antibacterial activities. Further, the simultaneous injection of the 29-2E strain significantly improves the survival rate of Salmonella Typhimurium-infected silkworm larvae (from 0% to 83.3%), suggesting that the substance may be a promising inhibitor against the virulence of pathogens without risk of the emergence of antibiotic-resistant bacteria.