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.
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