A detection method for recombinant DNA from genetically modified soybeans and processed foods containing them

A method using polymerase chain reaction (PCR) was designed for the detecti on of food or food ingredients derived from genetically modified soybeans ( GMS), imported from the United States, in a mixture with conventional non-g enetically modified soybeans (non-GMS). The presence of recombinant deoxyri bonucleic acid (DNA) in the soybeans could be detected with three different pairs of specific oligonucleotide primers designed from the sequences of t he introduced genes. The soybean intrinsic lectin Le1 gene was used as an i nternal control. The results of the PCR amplification indicated that a meth od using cetyltrimethylammonium bromide (CTAB) was most suitable for DNA ex traction from soybeans and the processed foods. The recombinant DNA could b e detected in dry soybeans containing 0.05% GMS and tofu made from soybeans containing 0.5% GMS. Of 41 commercial tofu samples, recombinant DNA was de tected from 27 tofu samples. It is, however, difficult to carry out PCR on DNA extracted from soybeans steamed at 131 degrees C or on fermented natto, although the Le1 gene was detected from soybeans steamed at 115 degrees C and in the fermented natto when a nested PCR technique was employed.