Genomic and physiological characterization of beer spoiling Megasphaera spp

Area of Science:

• Microbiology
• Brewing Science
• Genomics

Background:

• Beer spoilage bacteria, especially anaerobic Megasphaera species, are a significant concern for the brewing industry.
• Previous genome analyses of Megasphaera spp. primarily focused on mammal-associated species, neglecting beer-borne strains and their stress tolerance.
• The specific adaptations of beer-spoiling Megasphaera to the harsh brewing environment remained largely unexplored.

Purpose of the Study:

• To conduct the first in silico genome comparison of ten beer-spoiling Megasphaera strains from three species: M. cerevisiae, M. paucivorans, and M. sueciensis.
• To investigate the resilience of these beer-spoiling Megasphaera strains to key environmental stressors found in beer.
• To identify genetic factors contributing to the survival of Megasphaera in the challenging brewing niche.

Main Methods:

• In silico genome comparison of ten Megasphaera strains.
• Experimental determination of strain tolerance to iso-alpha-acids, ethanol, and low pH.
• Bioinformatic analysis to identify genes associated with stress survival.

Main Results:

• Beer-spoiling Megasphaera strains demonstrated significant resilience, growing in lager beer with up to 120 IBU of iso-alpha-acids, 7.0% ethanol, and at pH 4.0.
• Genome analysis revealed the presence of specific genes potentially involved in surviving hop, ethanol, and acid stress.
• This study provides the first comprehensive genomic insights into beer-borne Megasphaera species.

Conclusions:

• Beer-spoiling Megasphaera species possess remarkable tolerance to multiple stress factors prevalent in the brewing environment.
• Genomic analysis identified potential genetic mechanisms underlying this resilience, offering targets for future spoilage prevention strategies.
• Understanding these adaptations is crucial for developing effective control measures against Megasphaera contamination in the brewing industry.