Analysis of residual genomic DNA in crude and refined soybean oil using three different DNA extraction methods

Soybean oil is one of the highly consumed vegetable oil worldwide. Nowadays, usage of genetically modified (GM) soybean seeds for soybean oil production is constantly increasing. The recommended methods for GMO detection are based on analysis of residual DNA in vegetable oil and highly processed food. However, the successful amplification of isolated DNA depends on the efficiency of DNA extraction method.
The purpose of this study was to apply three different DNA extraction methods for analysis of residual genomic DNA in crude and refined soybean oil to obtain high pure of DNA suitable for DNA amplification.
Extraction methods were developed based on the specific binding of DNA molecules to the silica membrane (column) or resin. The isolated DNA was then analyzed by PCR technique using primer pairs, derived from 18S rRNA and 5.8S rRNA gene and soybean lectin gene.
The results showed that amplifiable DNA could not be extracted from crude/refined soybean oil in method 1. In method 2, by pre-treating of oil with PBS and subsequent precipitation with Isopropanol, the amplification was not observed but OD260 was decreased. In method 1 and 2 the DNA was not pure enough to be amplifiable. To remove more effectively contaminant, method 2 was combined with chloroform extraction as method 3. The extracted DNA from all examined oil samples could be amplified.
We believe that the purity of DNA in samples is decisive for amplification and not necessarily the low amount of DNA in samples. Method 3 can be determined as a suitable method for the isolation of the pure DNA.