Ketobiotics by Poly-3-Hydroxybutyrate: A Novel Prebiotic Activation of Butyrate-Producing Bacteria through 3-Hydroxybutyrate Donation to the Microbiota

Since the first target of poly-3-hydroxybutyrate (PHB), a simple bioplastic, is the microbiota, it has gained attention from the public and academia because of its promising function as a prebiotic food stuff for butyrate-producing bacteria. Since mammalian digestive enzymes cannot hydrolyze PHB, it passes through the small intestine and reaches the large intestine, allowing the gut microbiota to produce 3-Hydroxybutyrate (3HB) by the depolymerization of PHB around them. As a result, they become an energy substrate that promotes the growth of butyrate-producing bacteria and induces slight acidification of the gut environment. Thus, PHBs may be used as novel prebiotics to improve the gut environment. Based on this background, studies have proposed donating this ketone body to microbiota-mediated prebiotics, termed "ketobiotics", to act as a microbial activator of the animal gut. Ketobiotics may help maintain the gut health of pets and industrial animals, including enhancing human antiaging in the future. Therefore, this review discusses the potential use of the prebiotic action of ketobiotics for activating butyrate-producing bacteria from other prebiotic strategies, initiated by the direct donation of 3HB to microbiota in the large intestine.