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

Abstract

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.

Keywords: clinical trial; constipation; fibroin; lactic acid bacteria; sericin.

Fig. 1.

Flow diagram of the subjects in the present trial.

Fig. 2.

Statistical analysis of the fecal microbiota before and after the intake period. (A) Changes in the relative abundance of each item from baseline were compared between the test (n=25) and placebo (n=25) groups. (B) The relative abundances before and after the intake period in each group were compared individually. Data are shown as a box plot with medians (lines inside boxes), means (cross marks), 25–75 percentiles (limits of boxes), whiskers indicating the 95% data range, and outliers indicated by circles. The statistical analyses were performed using the Mann–Whitney U test and Wilcoxon’s signed rank test for inter- (A) and intra-group (B) analyses, respectively. ^†p<0.1, *p<0.05, **p<0.01, ***p<0.001.