Extraction and detection of endogenous soybean DNA from fermented foods

We examined rapid and simple genomic DNA extraction method to detect material soybeans from natto (fermented soybeans) and soy sauce. Genomic DNA was extracted from natto and soy sauce by CTAB or alkaline lysis methods. Genomic DNA solutions from natto by both extraction methods were of adequate purity and yield for applying PCR, resulting that amplifications of the expected 100 bp fragment using the soybean specific primer pair were detected. When genomic DNA was extracted from soy sauce, the DNA solutions by alkaline lysis method were of a sufficient purity (A260/A280 = 1.5–2.0), but those by CTAB method were insufficient (A260/A280 = 1.2–1.7). In addition, the amplification products from the genomic DNA solutions by CTAB method were not detected. Thus, these results suggested that the desirable genomic DNA was not extracted from soy sauce by CTAB method, although it was possible to extract it by alkaline lysis method. Furthermore, when genomic DNA was extracted from natto and soy sauce using FTA® card, which can preserve nucleic acids dried on the card just by applying a sample to it, the amplification was detected. It is found that an endogenous gene (lectin 1 gene) of material soybeans can be extracted by rapid and simple methods, and detected from fermented foods as natto and soy sauce.