A comparison of DNA extraction methods and PCR-based detection of GMO in textured soy protein

Abstract

Monitoring the presence of genetically modified organisms (GMOs) in a variety of food is important to many countries, as the law requires that the approved GMOs should be labeled as such. In addition, before genetically modified crops are used to obtain feed for the livestock, tests must be carried out to screen unapproved genetically modified varieties. Therefore, it is necessary to be able to detect and accurately quantify the amount of transgenic material present in food and feed. The analysis of processed soybean used in food and feed involves a number of complications, which negatively affect the DNA extraction. Therefore, the successful selection of DNA extraction methods is important for the detection of specific DNA targets in textured soy protein (TSP). The aim of this study was to compare three methods of DNA extraction from TSP, namely CTAB, modified CTAB and phenol/Chloroform methods. To this end, polymerase chain reaction (PCR) method was used to monitor products derived from GMOs, which specifically amplify the 35S promoter, NOS terminator and EPSPS gene. The results obtained from the modified CTAB method was promising, as the concentrations were higher than those in the CTAB and phenol/Chloroform methods. In addition, the purity of TSP samples was satisfactory. All the soybean samples were evidenced by presence of the lectin gene and 35S promoter, NOS and EPSPS were found in all TSP samples. This is the first report showing that most of genetically modified soy protein does not use the “GMO” label in Iran, which has amplified the need for mandatory labeling systems and reliable and simple methods for routine analysis of genetically modified foods.