TITLE:
Effects of Spent Craft Brewers’ Yeast on Fermentation and Methane Production by Rumen Microorganisms
AUTHORS:
Virginia L. Pszczolkowski, Robert W. Bryant, Brittany E. Harlow, Glen E. Aiken, Langdon J. Martin, Michael D. Flythe
KEYWORDS:
Antimicrobials, Brewing, Co-Product, Feed Supplement, Feed Efficiency, Hops Acids, Humulus Lupulus, Plant Secondary Metabolite, Phytochemicals
JOURNAL NAME:
Advances in Microbiology,
Vol.6 No.9,
August
17,
2016
ABSTRACT: 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.