Impact of Antimicrobial Hops on Gram Positive Bacteria and Microbiome of Air Exposed Silage

Spoilage and pathogenic microorganisms can proliferate in air exposed silages resulting in reduced palatability, nutritive quality and microbial safety. Consequently, environmentally friendly interventions are of interest. In this study, air exposed sorghum-based silage was administered with LipoVital GL-45, consisting of 45% monoglyceride of lauric acid (mixed within a 50% di/triglyceride base) alone or with either Chinook or Galena hops, consisting of 12 to 13 and 3 to 9% α- or β-acids, as well as with an experimental hops β-acids extract containing 45% co- and ad-lupolone. Yeast, molds and aerobes were enumerated on 3M Petrifilm and lactic acid bacteria on Rogosa SL. Most probable number enumeration of anaerobes was with anaerobically prepared Reinforced Clostridial agar. Presumptive spore-forming aerobes and anaerobes were heated (80°C, 10 minutes). The 16S rRNA sequencing was done by an Illumina MiSeq. LipoVital GL-45 combined with Galena hops or β-acid extract had fewer (P < 0.05) lactic acid bacteria compared to untreated controls. The LipoVital GL-45/Galena hops combination exhibited fewer (P < 0.05) heat-sensitive and spore-forming aerobes versus controls. Lower levels (P < 0.05) of nonheated anaerobe silage populations occurred with LipoVital GL-45 combined with the β-acid extract versus controls. No differences in microbiome richness, evenness, relative abundance, and taxonomic differences among treatments were detected but increased Lentilactobacillus and decreased Brevibacillus occurred for all treatments except Chinook hops.