Carbohydrate Metabolism Differentiates <i>Pectinatus</i> and <i>Megasphaera</i> Species Growing in Beer
2024
Manuel J. Arnold | Stefan W. Ritter | Matthias A. Ehrmann | Yohanes N. Kurniawan | Koji Suzuki | Thomas M. Becker | Wolfgang Liebl
Obligate anaerobic beer spoilage bacteria have been a menace to the brewing industry for several decades. Technological advances in the brewing process aimed at suppressing aerobic spoilers gave rise to problems with obligate anaerobes. In previous studies, the metabolic spectrum of <i>Pectinatus</i> and <i>Megasphaera</i> species has been described, but their metabolism in the beer environment remains largely unknown. We used high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME-GCMS) to further characterize beer spoiled by 30 different strains from six beer-spoiling species of <i>Pectinatus</i> and <i>Megasphaera</i> (<i>P. cerevisiiphilus</i>, <i>P. frisingensis</i>, <i>P. haikarae</i>, <i>M. cerevisiae</i>, <i>M. paucivorans</i>, and <i>M. sueciensis</i>). We detected differences in carbohydrate utilization and the volatile organic compounds (volatilome) produced during beer spoilage by all six species. We were able to show that glycerol, one of the basic components of beer, is the common carbon source used by all strains. It appears that this carbon source allows for anaerobic beer spoilage by <i>Pectinatus</i> and <i>Megasphaera</i> despite the spoilage-preventing intrinsic barriers of beer (iso-α-acids, ethanol, low pH, scarce nutrients); thus, extrinsic countermeasures are key for prevention.
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