Development of microbial inspection for beer industry

Beer has been recognized as a microbiologically stable beverage, due to its hostile characteristics (e.g., presence of ethanol, low pH, high CO2 content), which prevent microbial growth. Despite these hostile characteristics, a limited number of microbes are able to grow in beer. However, emergence of novel beer-spoilage microbial strains, and the rise in popularity of non-traditional beverages (e.g., non-alcoholic beverages) having lower microbiological stability than traditional beer beverages, could result in a surge of microbiological beer-spoilage incidents. The increasing number of beer-spoilage microbes will eventually outpace many of the current detection methods, which rely heavily on species-specific, PCR-based detection methods. A more universal detection method that is not restricted by species characterization, i.e., "species-independent", and a comprehensive species identification method that allows accurate determination of a broader range of microbial species are needed. These reasons prompted us to develop a species-independent, PCR-based detection method by utilizing beer-spoilage specific gene markers, e.g., hop tolerance genes horA and horC, and a new user-friendly, third-generation DNA sequencing technology (MinION)-based microbial identification method with high accuracy and wide coverage for quality control laboratories in breweries. Furthermore, we have successfully demonstrated the applicability of third-generation DNA sequencing technology for concurrent analysis of multiple target genes, providing a way for simultaneous species identification and detection of specific gene markers for intra-species discrimination. The wide application of the third-generation sequencing technology, the inexpensive initial capital investment cost, and the moderate running costs will surely help this technology become more widely adopted in breweries as part of the arsenal to combat emerging beer-spoilage microbes.