Tailored Nanoparticles With the Potential to Reduce Ruminant Methane Emissions.

Eric Altermann,Wayne Young,Ron S Ronimus,Kerri Reilly,Stefan Muetzel

doi:10.3389/fmicb.2022.816695

Abstract

Agricultural methane produced by archaea in the forestomach of ruminants is a key contributor to rising levels of greenhouse gases leading to climate change. Functionalized biological polyhydroxybutyrate (PHB) nanoparticles offer a new concept for the reduction of enteric methane emissions by inhibiting rumen methanogens. Nanoparticles were functionalized in vivo with an archaeal virus lytic enzyme, PeiR, active against a range of rumen Methanobrevibacter species. The impact of functionalized nanoparticles against rumen methanogens was demonstrated in pure cultures, in rumen batch and continuous flow rumen models yielding methane reduction of up to 15% over 11 days in the most complex system. We further present evidence of biological nanoparticle fermentation in a rumen environment. Elevated levels of short-chain fatty acids essential to ruminant nutrition were recorded, giving rise to a promising new strategy combining methane mitigation with a possible increase in animal productivity.

Highlights

Climate change presents an increasingly serious threat to all ecosystems (Overpeck and Udall, 2020; Soroye et al, 2020; Tabari, 2020; Witze, 2020)
Methanobrevibacter is the dominant taxonomic archaeal genus in the rumen (Vaidya et al, 2020) and M. ruminantium M1 and M. gottschalkii D5 have been selected as representative members of the rumen (Kittelmann et al, 2013)
Comparing the efficacy of single- and dual-fusion PeiR displaying nanoparticles against rumen methanogens was achieved by analyzing shortterm kinetics and sustained inhibition over time

Summary

Introduction

Climate change presents an increasingly serious threat to all ecosystems (Overpeck and Udall, 2020; Soroye et al, 2020; Tabari, 2020; Witze, 2020). The contribution of anthropogenic emissions, and in particular ruminant methane emissions has been recognized for decades (Johnson, 1974; Sawyer et al, 1974; Burch, 2020; Ku-Vera et al, 2020; Ribeiro et al, 2020; Wolski et al, 2020), pressure on agricultural systems, the need to balance land use and food prices, coupled to an increasing demand to feed a growing population limit the ability to reduce animal numbers (Bustamante et al, 2014; Stevanovic et al, 2017; White and Hall, 2017). Enteric methane emissions predominantly stem from the microbial fermentation of feed in the forestomach of ruminants where a specialized group of archaea, commonly known as methanogens, converts free hydrogen through the reduction of carbon dioxide. The rate of methane production and methanogen growth rates are dependent on a range of factors such as free and dissolved hydrogen, pH, and ruminal passage rates (Janssen, 2010). A range of strategies is currently being pursued to mitigate enteric methane emissions aiming to reduce the number or metabolic activity of rumen methanogen and include such diverse concepts as farm system changes (Chiavegato et al, 2015), animal genetics and breeding (Gonzalez-Recio et al, 2020), forage optimization (Warner et al, 2017), diet interventions (Borsting et al, 2020), methanogen inhibitors (Hristov et al, 2015), vaccines (Subharat et al, 2016), and natural additives (Belanche et al, 2020)

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