Author(s)

Virginia L. Pszczolkowski¹, Robert W. Bryant², Brittany E. Harlow³, Glen E. Aiken³, Langdon J. Martin¹, Michael D. Flythe^3,4

¹Department of Chemistry, Warren Wilson College, Asheville, NC, USA.
²Asheville Flavor Innovations, LLC, Asheville, NC, USA.
³Forage-Animal Production Research Unit, Agricultural Research Service, USDA, Lexington, KY, USA.
⁴Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, USA.

Saccharomyces cerevisiae is a key component of beer brewing and a major by-product. The leftover, spent brewers’ yeast from large breweries has been used as a protein supplement in cattle; however the possible advantages of spent yeast from smaller craft breweries, containing much higher levels of bioactive hop acids, have not been evaluated. Hops secondary metabolites from the hops (Humulus lupulus L.) used to make beer are concentrated in the yeast during brewing, and have antimicrobial activity against Gram-positive bacteria. Uncultivated suspensions of bovine rumen microorganisms produced less methane during fructose fermentation when exposed to inactivated, and freeze-dried spent craft brewers’ yeast than a bakers’ yeast control. The experiment was repeated with caprine rumen microorganisms and ground grass hay as the substrate. Likewise, in the presence of craft brewers’ yeast less methane was produced (2.7% vs. 6.9% CH₄). Both experiments also revealed a decrease in acetic acid production, but not propionic acid production, when craft brewers’ yeast was included. These results indicated that spent yeast could represent a co-product for craft breweries, and a feed supplement for ruminants that has a favorable impact on methane production.

Antimicrobials, Brewing, Co-Product, Feed Supplement, Feed Efficiency, Hops Acids, Humulus Lupulus, Plant Secondary Metabolite, Phytochemicals

Pszczolkowski, V. , Bryant, R. , Harlow, B. , Aiken, G. , Martin, L. and Flythe, M. (2016) Effects of Spent Craft Brewers’ Yeast on Fermentation and Methane Production by Rumen Microorganisms. Advances in Microbiology, 6, 716-723. doi: 10.4236/aim.2016.69070.