Anaerobic Gram-Negative Bacteria in Brewing-A Review. Brian J. Chelack and W. M. Ingledew, Department of Microbiology and Department of Applied Microbiology and Food Science, respectively, University of Saskatchewan, Saskatoon, Canada S7N 0W0. J. Am. Soc. Brew. Chem. 45:0123, 1987.

Until recently, gram-negative bacteria have not been considered to be common spoilers of finished (packaged) beer. In this article, however, two gram-negative, obligately anaerobic, beer spoilers of the genera Pectinatus and Megasphaera are reviewed. Improved detection methods and recent advances in brewing technology leading to lowered O₂ levels in finished beer have led to an increased occurrence of Pectinatus and Megasphaera bacteria. Their discovery, isolation, nutritional requirements, and end product spoilage patterns have now been reported. The impact of these microbes on the brewing industry is discussed.

Keywords: Pectinatus, Megasphaera, Anaerobes, Spoilage bacteria, Beer