The interaction of microplastics with the ruminal ecosystem in vitro

Area of Science:

• Environmental Science
• Microbiology
• Animal Science

Background:

• Mismanaged plastic waste leads to microplastic (MP) contamination in environments.
• Farm animals are increasingly exposed to MPs through contaminated feed.
• The interaction between MPs and the rumen microbiome is not well understood.

Purpose of the Study:

• To investigate the in vitro interactions between various microplastics and the rumen microbiome.
• To assess the impact of different MP types, sizes, and doses on rumen fermentation and microbial activity.

Main Methods:

• Utilized the Hohenheim Gas Test for in vitro incubation of five MP chemical species in two particle-size classes and six doses.
• Incubations were performed with rumen fluid and either hay or barley.
• Analyzed cumulative gas production, pH, dry-matter disappearance, volatile fatty acids, metaproteomics, and metabolomics.

Main Results:

• Microplastics consistently reduced cumulative gas production regardless of polymer type, particle size, or dose.
• Total dry-matter degradation was enhanced dose-dependently by MP exposure.
• Metaproteomics revealed shifts in microbial communities (Bacteroidetes to Firmicutes) and altered protein abundances in barley incubations.

Conclusions:

• Rumen microbes interact with and partially degrade microplastics.
• Progressive MP size reduction in the rumen may lead to translocation into animal tissues.
• Further in vivo studies are crucial to understand animal health and food safety implications.