Beer enemy number one: genetic diversity, physiology and biofilm formation ofLactobacillus brevis

Abstract

Lactobacillus brevis is the most significant beer spoilage bacteria worldwide. It is found as a contaminant at all stages of brewing, including during primary and secondary fermentation, storage, filtration and the packaging process. In production with flash pasteurisation and subsequent hygienic filling, avoiding and tracing secondary contaminations is the key to a microbiologically stable product. However, L. brevis strains vary in their spoilage potential and can grow in many different beer types. This study presents a physiological test scheme for growth potential and biofilm formation in various media. It was determined that a large number of L. brevis strains can form biofilms as a first coloniser. The identification of the species alone is therefore not enough to be sure of the spoilage risk, which shows the need for a more in depth differentiation. DNA fingerprint techniques are crucial to differentiate isolates of this species at strain level. The rep-PCR fingerprint system (GTG) 5 was used to differentiate a selected collection of 20 isolates, which were characterised in growth and biofilm formation in various media. The data showed a high variation within the selected isolates. As second step, generated fingerprint clusters of L. brevis were traced back to contamination sources in a German brewery, revealing a high number of isolates with potentially varying growth, spoilage and biofilm potential. L. brevis being the demonstrator species, the PCR system used is a powerful and compatible tracing and troubleshooting tool for all kinds of spoilage bacteria in the brewing industry.

Beer fermentation performance and sugar uptake of Saccharomycopsis fibuligera–A novel option for low-alcohol beer

“…In the next step, DNA concentrations were measured using NanoDrop1000 spectrophotometer (Peqlab Biotechnologie GmbH, Erlangen, Germany) and adjusted to 25 ng/μL, containing 12.5 μl RedTaq Mastermix (2×) 2-fold (Genaxxon bioscience, Ulm, Germany), 10 μl Primer Solution (50 pmol/l), 5 μl PCR-clean double distilled water (ddH 2 O) and 2.5 μl sample DNA. The PCR temperature protocol of the DNA fingerprint amplification and subsequent capillary gel electrophoresis including data processing were described according to Riedl et al (2019) .…”

The enhanced susceptibility of alcohol‐free and low alcohol beers to microbiological spoilage: implications for draught dispense

“…However, whilst some bacteriapathogens (24,35) and obligate anaerobe Megasphaera (33)are sensitive to ethanol, lactic acid bacteria are highly ethanol tolerant (33). Indeed, Lactobacillus brevis has been reported to be the 'most significant beer spoilage bacteria worldwide' (34). The strictly aerobic acetic acid bacteria which are a concern in draught beer (14), utilise ethanol as a substrate and are tolerant (depending on species) to between 8 and 15% ABV (35).…”

Draught beer hygiene: use of microplates to assess biofilm formation, growth and removal

“…Microplates have been used to screen biofilm formation by brewing microorganisms including yeast ( 24 ) , bacteria ( 25 ) and lactic acid bacteria ( 26,27 ) . These studies used pure cultures of brewery organisms at 26‐30°C incubated for one ( 24,26 ) , two ( 25 ) or four days ( 27 ) . Biofilms were grown in rich media (Tryptic Soy, MRS) although Riedl et al ( 26 ) also successfully used beer (wheat, lager, pilsner as is and diluted 50%).…”

“…These studies used pure cultures of brewery organisms at 26‐30°C incubated for one ( 24,26 ) , two ( 25 ) or four days ( 27 ) . Biofilms were grown in rich media (Tryptic Soy, MRS) although Riedl et al ( 26 ) also successfully used beer (wheat, lager, pilsner as is and diluted 50%).…”