Microbial composition and polymer hydrolytic activity of Japanese washed-rind cheeses

Abstract

Since the use of biodegradable polymers for food packaging is becoming popular, it is important to investigate the biodegradable-polymer-hydrolyzing potential of microorganisms in fermented foods. Here, we focused on 4 Japanese washed-rind cheeses. Metagenomic analyses revealed that microbiota in the 4 Japanese washed-rind cheeses was composed of bacteria classified into 515 operational taxonomic units (OTUs) and fungi classified into 74 OTUs. Remarkably, a considerable number of marine bacteria were identified in 3 of 4 cheeses. Further, we isolated a poly(3-hydroxybutyrate) (P(3HB))-degrading bacterium, designated as strain MC1, from one of the cheeses—Muchuri. The strain was a gram-negative, rod-shaped bacterium. It grew well and formed a large clear zone on P(3HB)-containing medium at a temperature range of 30–37 °C, while it did not degrade P(3HB) at 4 °C. The phenotypic properties and phylogenetic inference indicated that strain MC1 is related to Alcanivorax dieselolei B-5T, which is a marine inhabitant. Our study demonstrated that MC1 degrades P(3HB) and that components in cheese promote the degradation of P(3HB) while nutrient-rich conditions suppress it. This suggests that packaging material made of P(3HB) for cheeses could be used under low temperatures and nutrient-rich conditions.