Rapid Detection of Genetically Modified Ingredients in Soybean Products by Real-Time Loop-Mediated Isothermal Amplification

Abstract

A real-time turbidimeter loop-mediated isothermal amplification (LAMP) assay was developed for the rapid, sensitive, and convenient detection of genetically modified (GM) ingredients in soybean products obtained from local supermarkets in China. Specific primers were designed based on the published sequence of <i>lectin</i>, <i>nos</i> terminator and endogenous genes of two GM soybean strains (GTS40-3-2 and MON89788). The total genomic DNA of soybean-made products was extracted by cetyltrimethylammonium bromide (CTAB) method. Then, the genomic DNA was used as template for LAMP assay. The results showed that this real-time turbidimeter LAMP assay was specific and sensitive enough to amplify DNA from soybean products. The limit of detection (LOD) of <i>lectin</i> and MON89788 was 0.01% (weight of GM soybean/weight of non-GM soybean), roughly equivalent to four copies of soybean genomic DNA in DNA mixture within one hour; and the LOD of <i>nos</i> and GTS40-3-2 was 0.1%, roughly equivalent to forty copies of soybean genomic DNA within 1 hour. The sensitivity reaches to 0.01%, which meets the requirements of the European Union (EU). In practical application, the total detectable ratio in soybean-made products was the same as that of PCR, suggesting that LAMP method was accurate and sensitive.