[ConservativeMind]

Additional sources:

Clostridium butyricum

https://en.m.wikipedia.org/wiki/Clostridium_butyricum

Butyrate Producers as Potential Next-Generation Probiotics: Safety Assessment of the Administration of Butyricicoccus pullicaecorum to Healthy Volunteers

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6222043/

[ConservativeMind]

Another study:

A four-strain probiotic exerts positive immunomodulatory effects by enhancing colonic butyrate production in vitro

https://www.sciencedirect.com/science/article/pii/S037851731830838X