Recovery and characterization of residual DNA from beer as a prerequisite for the detection of genetically modified ingredients

In an attempt to recover polymerase chain reaction (PCR)-amplifiable DNA fr om beer, the performance of three different extraction methods was compared . Efficient DNA enrichment, by selective binding to either a membrane or a silica matrix, proved an essential requirement for the procedure to be succ essful. To identify its origin, the extracted DNA was subjected to PCR usin g primer pairs specific for eukaryotes, plants or yeast, respectively. It w as shown that samples of six beer brands tested positive for yeast, whereas the PCR assay for plant DNA was negative in these cases. The data demonstr ate that residual DNA can be recovered from beer, thus opening up the possi bility of monitoring the presence of transgenic genomic sequences.