Year

2015

Season

Spring

Degree Type

Honors Thesis

College

College of Arts and Sciences

Department

Biology

Degree Name

Honors in the Major

First Advisor

Dr. Michael Lentz

Abstract

Many strains of Brettanomyces pose a major threat to the commercial brewing industry by producing phenolic off-flavors, while a few strains contribute desirable characteristics in unique beer styles. This genus of yeast possesses a two-step pathway that converts hydroxycinnamic acids (HCAs) to vinyl and ethyl derivatives that add unwanted flavors and aromas to the final beverage. This project focused on analyzing Brettanomyces yeast isolates for variation in phenolic acid decarboxylase activity (PAD), which catalyzes the first step in the pathway. Each strain was grown in the three different common HCAs (ferulic acid, p-coumaric acid, caffeic acid) to understand each strain’s reactivity to the compound. Strains displayed variation in their PAD activity and growth in HCAs. Most good brewing strains were highly sensative to pcoumaric acid, and displayed significant lags in their growth in p-coumaric and ferulic acid. All strains were highly resistant to caffeic acid. These data show some trends towards differences in good brewing strains and may lead to easier identification methods for yeast strains that may be good for brewing.

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