Additive effect of multi-strain mixtures. Additive Effect of Multi-strain Mixtures of Dead Bacterial Strains on Human Gut Microbiota in an In Vitro Model of Human Intestinal Microbiota

Probiotics exert their beneficial effects by improving the intestinal environment. Heat-inactivated probiotics may have similar effects. However, little is known about whether single strains or multi-strain mixtures (MSMs) are better, regardless of whether the bacteria are alive or dead. This study examined the gut-improving efficacy of MSMs consisting of four dead bacterial strains using an in vitro model that simulates the human gut environment. In the in vitro model, human feces were inoculated with a single strain or MSM, and the microbial composition and fermentation products were assessed. The 16S rRNA gene sequences showed that the MSMs tended to change the microbial community structure more than single strains did. Furthermore, results of the microbial diversity analysis showed that despite differences among single strains, MSMs increased with an increase in any single strain. A similar trend was observed for fermentation products. Among the analyzed parameters, those for which the highest number of people improved were observed most frequently with MSMs. These results suggest that MSMs made from dead bacteria exert additive effects that may provide new health benefits to more people.