Transgenic barley in brewing: Detection of transgene and heterologous protein levels

Genetically modified (GM) raw materials and products have appeared on the market. The aim was to find out through a model case whether the threshold of 1% of GM contamination in foods is detectable using the present analytical methods. Transgenic barley lines were homozygotized through microspore culture for production of doubled haploid plants. The transgenic and non-transgenic barley samples were malted, mashed and fermented. The produced malts, worts and beers were analyzed in respect to the transgene and the corresponding heterologous protein. The heterologous protein was not detectable from protein extracts of malted grains. However, presence of the heterologous enzyme in the aleurone layer and scutellum of the transgenic malt was verified by immunomicroscopy. This suggested that the heterologous protein was expressed in germinating transgenic seeds. Real-time PCR proved to be repeatable and extremely sensitive for the detection of the transgene. The threshold of 1 part in 1000 (0.1%), nicely in the range of the legal requirements, was obtainable with high confidence. Detectable foreign DNA was also obtainable from wort, but repeated trials of DNA extraction from beer were not successful.