A Search for Diastatic Enzymes Endogenous to Humulus lupulus and Produced by Microbes Associated with Pellet Hops Driving “Hop Creep” of Dry Hopped Beer

Abstract

A search was conducted for the sources of diastatic enzymes driving the over attenuation and continued fermentation of dry hopped beer known as “hop creep”. Microbial cultivation using starch containing media and assays of amylase enzyme activity were used to isolate and identify microbes from pellet hops that are potential sources of amylases associated with but exogenous to hops (Humulus lupulus). Bacteria and fungi associated with pellet hops produced amylases but did not produce hop creep in assays using finished beer and fermenting wort with added microbes. Cannabis sativa flower produced over attenuation of fermenting wort equivalent to that seen with hops. Comparative bioinformatic analysis of the Cannabis sativa proteome and H. lupulus genome revealed the genetic potential of H. lupulus to produce endogenous amylase enzymes. Sequence similarity of amylases annotated in the C. sativa proteome to previously unidentified genes in H. lupulus revealed 13 genes likely encoding amylases. PCR and sequencing confirmed the occurrence of genes that appear to encode α-amylase and β-amylase in the Citra® hop cultivar. Identifying a genetic basis for hop creep contributes knowledge that may lead to new approaches for controlling hop creep produced by endogenous amylases of H. lupulus.

Keywords:

• Hop diastatic power
• amylase
• bacteria
• fungi
• Cannabis sativa

Acknowledgements

This work was inspired by the TSC Project for Excellence in Microbial Ecology. Heavy Seas Beer provided laboratory space and analytical instrumentation.

Disclosure statement

No potential conflict of interest was reported by the authors.