Bauer Torsten, Hammes Walter P, Haase Norbert U, Hertel Christian
Institute of Food Technology, University of Hohenheim, 70593 Stuttgart, Germany.
Environ Biosafety Res. 2004 Oct-Dec;3(4):215-23. doi: 10.1051/ebr:2005005.
The effect of food components on degradation of DNA by DNase I (EC 3.1.21.1) was monitored by electrotransformation of Escherichia coil, making it possible to determine the number of plasmid molecules capable of giving rise to transformed cells. The transformation frequency increased linearly with the plasmid number within the range of 2 x 10(6) to 2 x 10(10). DNA degradation was reduced by one order of magnitude in the presence of 0.05% (w.v(-1)) maltol or 1 mM putrescine. Complete inhibition of degradation was observed with > or = 0.2% (w.v(-1)) maltol, > or = 0.01% (w.v(-1)) octyl gallate or > or = 0.5 mM of spermine. To monitor degradation of plant DNA during food processing, a real-time PCR system was established. The ratio of copy numbers of a potato gbss DNA fragment of 325 bp and a nested 96 bp fragment was determined. The latter served as internal reference for normalization. The system made it possible to exclude process-dependent changes of DNA concentration in the food matrix. Processing of genetically modified potatoes to dried potato sticks, crisps or flakes was studied and drying steps were shown to exert the strongest effect on DNA degradation, resulting in a drop of the ratio from 0.73 to 0.16.
通过大肠杆菌的电转化监测食物成分对脱氧核糖核酸酶I（EC 3.1.21.1）降解DNA的影响，从而能够确定能够产生转化细胞的质粒分子数量。在2×10⁶至2×10¹⁰的范围内，转化频率随质粒数量呈线性增加。在存在0.05%（w/v⁻¹）麦芽酚或1 mM腐胺的情况下，DNA降解降低了一个数量级。当麦芽酚含量≥0.2%（w/v⁻¹）、没食子酸辛酯含量≥0.01%（w/v⁻¹）或精胺含量≥0.5 mM时，观察到降解被完全抑制。为了监测食品加工过程中植物DNA的降解情况，建立了一个实时聚合酶链反应系统。测定了325 bp的马铃薯颗粒结合淀粉合成酶DNA片段与嵌套的96 bp片段的拷贝数之比。后者用作标准化的内部参照。该系统能够排除食品基质中DNA浓度的加工相关变化。对转基因马铃薯加工成干薯条、薯片或薯片进行了研究，结果表明干燥步骤对DNA降解的影响最大，导致该比值从0.73降至0.16。
