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Letter

Metabolic engineering of diacetyl shortens industrial lager maturation to four days

Knocking out an ILV2 bypass and overexpressing BDC1 means cold storage is no longer a time tax on lager.

Yu Qian1†, Beichen Zheng1, Lena Vogt2

* Equal contribution · † Corresponding author

B.E.E.R. 647, 278–281 (2026)

Received: 18 May 2026
Accepted: 20 August 2026
Published: 15 September 2026
DOI: 10.1038/sbeer-026-18470-6

Abstract

Diacetyl is the rate-limiting off-flavour of lager maturation. In industrial strain W34/70 we combined knockout of an ILV2 bypass with overexpression of α-acetolactate decarboxylase BDC1, cutting the diacetyl peak below 40 µg L⁻¹ so that packaging thresholds are met at the end of primary fermentation. In three replicates in 1,200 hL fermenters, maturation fell from 14 days to 4, with an ester profile indistinguishable from the control. The strain was built by a self-cloning path and introduces no heterologous markers.

Subject: Microbes and yeast

Lager’s “time tax” is spent mainly waiting for diacetyl reduction1. Metabolic engineering is not a new idea, but most schemes rely on heterologous genes or disturb ester balance.

Stainless-steel beer fermenters
Fig. 1 | Industrial mash and fermenters. A self-cloned strain cut maturation from 14 days to 4 at 1,200 hL scale.

Three plant trials showed foam stability and mouthfeel scores indistinguishable from the parent (p = 0.41). Shorter cold storage also frees tank time — equivalent to growing the brewery a new fermenter.

Methods

  1. CRISPR–Cas9 self-cloning edits; plant trials on a 1,200 hL lager line in Jinan.
  2. Diacetyl by GC–ECD, threshold 100 µg L⁻¹.

Data availability. Strain sequences and process curves are in the supplementary materials.

Acknowledgements. An anonymous plant partner supplied tank time.

Author contributions. Q.Y. designed the work; Z.B.C. carried out the edits; L.V. supervised metabolic analysis.

Competing interests. Qilu University of Technology has filed a Chinese invention-patent application on the strain.

Authors and affiliations

  1. 1. Sino-German Beer Technology Centre, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China
  2. 2. Carlsberg Research Laboratory, Copenhagen, Denmark

Corresponding author: Yu Qian (yqian@qlu.beer)

References

  1. 1. Krogerus, K. & Gibson, B. Diacetyl and its control. J. Inst. Brew. 119, 86–97 (2013).
  2. 2. Duong, C. T. et al. ILV6 allele and diacetyl. Appl. Microbiol. Biotechnol. 92, 1083–1093 (2011).
  3. 3. Gibson, B. et al. Yeast engineering for beer. FEMS Yeast Res. 17, fox009 (2017).