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Decomposition of waste DNA with extended autoclaving under unsaturated steam
 
Tetsushi Suyama and Mamoru Kawaharasaki
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Surprisingly, the efficiency of template removal was higher in the encapsulated samples than in the non-encapsulated ones. The triplicate samples without screw caps (where the air was replaced by steam as in the usual autoclaving) retained (7.63 ± 0.32) × 108, (2.11 ± 0.02) × 108, and (8.24 ± 0.02) × 108 copies/tube of template activity after autoclaving at 121°C for 40 min. The key factor behind the high efficiency template removal in the samples encapsulated with air may be oxygen, since template activity was also protected by replacing air with pure nitrogen gas or reducing oxygen using an oxygen absorber (Ageless, Mitsubishi Gas Chemical Company Inc., Tokyo, Japan) prior to encapsulation.

Extended autoclaving for disposal of laboratory DNA waste

In order to determine the influence of solution composition, TE buffer and water samples were tested. Figure 2 shows a time course of the decline in template activity of autoclaved encapsulated and non-encapsulated samples in three different solutions. The samples exchanged with water (Figure 2A) and TE (Figure 2B) could be decontaminated much more easily, and the encapsulation methods were effective in all cases studied. Although the processing speed varied among the different conditions, removal of activity was completed in 80 min regardless of the solution composition and the presence or absence of encapsulation with air.





In conclusion, although we believe not autoclaving DNA waste is advisable for avoiding laboratory contamination, if autoclaving is unavoidable, it is better to encapsulate the waste in tightly capped tubes or bottles and to process at 121°C for 80 min (not 20 min). Encapsulation with oxygen (air) seems favorable for quick removal of template activity. It would also be a good idea to develop a special steamer that does not exhaust steam and air, as this will help to minimize DNA contamination.

Author contributions

MK proposed this project; TS conducted almost all of the experiments.

Acknowledgments

This work was performed at the Bio-measurement research group of Biomedical Research Institute at AIST. The authors wish to thank Yuji Sekiguchi (leader of the research group) and Masanao Oda (previous director of the Institute) for encouragement on conducting this work.

Competing interests

This work was performed at the Bio-measurement research group of Biomedical Research Institute at AIST. The authors wish to thank Yuji Sekiguchi (leader of the research group) and Masanao Oda (previous director of the Institute) for encouragement on conducting this work.

Correspondence
Address correspondence to Tetsushi Suyama, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan. E-mail: [email protected]">[email protected]

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