Effects of oriental medicinal plants on the reduction of methane production mediated by microbial population

Abstract

Methane plays a major role in greenhouse gas emissions contributing to climate change. Therefore, reducing methane production by ruminants is a primary goal but significant challenge. In this study, five oriental medicine plant extracts (OMPEs), Hypericum ascyron L. (HYA), Rhododendron mucronulatum (RHM), Zizyphus jujube var. inermis (ZIJ), Vitis vinifera L. (VIV), and Rhus succedanea L. (RHS), with different polyphenol and flavonoid contents were evaluated for their effects on in vitro ruminal fermentation parameters, gas profiles, and changes in the microbial population of targeted groups including cellulolytic bacteria and methanogenic archaea (M. archaea). The total polyphenol and flavonoid content of the OMPEs was in the range of 30.53–266.62 mg GAE·g-1 and 4.95–125.43 mg CHE·g-1, respectively. Each OMPE was tested at a fixed dose (50 mg·L-1) after 48 h incubation in a batch culture system. Total gas production in the RHM treatment was significantly higher than that in the control group after 24 h of incubation, whereas methane production decreased by 34.08–41.01% in the RHM, ZIJ, VIV, and RHS treatment groups. Quantification of microbial populations showed that the relative abundance of two Ruminococcus species was decreased by treatment of all OMPEs whereas the relative abundance of Fibrobacter succinogenes increased. The abundance of M. archaea was reduced by VIV and RHS treatment groups. In conclusion, this study suggests that polyphenols and flavonoids extracted from OMPEs have potential to reduce methane production in ruminants, which should be further validated testing in vivo feeding trials for implementation. Highlight Some oriental medicine plants rich in polyphenol and/or flavonoid contents can be used to mitigate ruminant methane production. Supplementation of Vitis vinifera L. and Rhus succedanea L. extracts could reduce methane production and the abundance of methanogenic archaea.