Combination of an Immunomagnetic Separation Method and a Chromogenic Oligonucleotide Array for the Detection of Beer-Spoilage Lactic Acid Bacteria

J. Am. Soc. Brew. Chem. 71(1):57-62, 2013 For the brewing industry, the possibility of beer spoilage by lactic acid bacteria (LAB) or by wild yeasts is always a concern. Contamination by certain LAB, such as Lactobacillus brevis, L. casei, L. plantarum, Pediococcus claussenii, P. damnosus, and P. inopinatus, may result in the deterioration of beer quality. Thus, monitoring of these spoilage organisms during the brewing process is critical to quality control. When concentrations of spoilage organisms in the brewing samples are low and, thus, difficult to detect, collection and concentration of these spoilage organisms prior to the application of diagnostic methods are important. Although the membrane filtration method can be used even if filters of the correct pore sizes are chosen, it is still possible that some LAB cells will go through the membrane filters. Another drawback of membrane filtration is membrane fouling, which restricts the beer volume to be filtered. In this study, polyclonal antibodies against beer-spoilage bacteria were prepared by rabbit immunization. The antibodies were then conjugated to magnetic beads for the capture and concentration of major beer-spoilage LAB. The captured cells were subsequently discriminated to species level by a commercially available oligonucleotide array. The combination of immunomagnetic separation with an oligonucleotide array allowed the simultaneous and sensitive detection of several major beer-spoilage LAB species in the brewing samples within 8 hr. This method is accurate and time-saving and can be used for routine monitoring and control of the spoilage organisms during the beer brewing process.