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. 1987 Sep;53(9):2133–2137. doi: 10.1128/aem.53.9.2133-2137.1987

Mechanism of microwave sterilization in the dry state.

D K Jeng 1, K A Kaczmarek 1, A G Woodworth 1, G Balasky 1
PMCID: PMC204070  PMID: 3118807

Abstract

With an automated computerized temperature control and a specialized temperature measurement system, dry spores of Bacillus subtilis subsp. niger were treated with heat simultaneously in a convection dry-heat oven and a microwave oven. The temperature of the microwave oven was monitored such that the temperature profiles of the spore samples in both heat sources were nearly identical. Under these experimental conditions, we unequivocally demonstrated that the mechanism of sporicidal action of the microwaves was caused solely by thermal effects. Nonthermal effects were not significant in a dry microwave sterilization process. Both heating systems showed that a dwelling time of more than 45 min was required to sterilize 10(5) inoculated spores in dry glass vials at 137 degrees C. The D values of both heating systems were 88, 14, and 7 min at 117, 130, and 137 degrees C, respectively. The Z value was estimated to be 18 degrees C.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Angelotti R., Maryanski J. H., Butler T. F., Peeler J. T., Campbell J. E. Influence of spore moisture content on the dry-heat resistance of Bacillus subtilis var. niger. Appl Microbiol. 1968 May;16(5):735–745. doi: 10.1128/am.16.5.735-745.1968. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Cope F. W. Superconductivity--a possible mechanism for non-thermal biological effects of microwaves. J Microw Power. 1976 Sep;11(3):267–270. doi: 10.1080/00222739.1976.11689004. [DOI] [PubMed] [Google Scholar]
  3. Fox K., Pflug I. J. Effect of temperature and gas velocity on dry-heat destruction rate of bacterial spores. Appl Microbiol. 1968 Feb;16(2):343–348. doi: 10.1128/am.16.2.343-348.1968. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Furia L., Hill D. W., Gandhi O. P. Effect of millimeter-wave irradiation on growth of Saccharomyces cerevisiae. IEEE Trans Biomed Eng. 1986 Nov;33(11):993–999. doi: 10.1109/TBME.1986.325865. [DOI] [PubMed] [Google Scholar]
  5. Goldblith S. A., Wang D. I. Effect of Microwaves on Escherichia coli and Bacillus subtilis. Appl Microbiol. 1967 Nov;15(6):1371–1375. doi: 10.1128/am.15.6.1371-1375.1967. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Gurney T. R., Quesnel L. B. Thermal activation and dry-heat inactivation of spores of Bacillus subtilis MD2 and Bacillus subtilis var. niger. J Appl Bacteriol. 1980 Apr;48(2):231–247. doi: 10.1111/j.1365-2672.1980.tb01222.x. [DOI] [PubMed] [Google Scholar]
  7. Lechowich R. V., Beuchat L. R., Fox K. I., Webster F. H. Procedure for evaluating the effects of 2,450-megahertz microwaves upon Streptococcus faecalis and Saccharomyces cerevisiae. Appl Microbiol. 1969 Jan;17(1):106–110. doi: 10.1128/am.17.1.106-110.1969. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Lin J. C. Health aspects of radio and microwave radiation. J Environ Pathol Toxicol. 1979 Jul-Aug;2(6):1413–1432. [PubMed] [Google Scholar]
  9. Lohmann S., Manique F. Microwave sterilization of vials. J Parenter Sci Technol. 1986 Jan-Feb;40(1):25–30. [PubMed] [Google Scholar]
  10. Molin G., Ostlund K. Dry-heat inactivation of Bacillus subtilis var. niger spores with special reference to spore density. Can J Microbiol. 1976 Mar;22(3):359–363. doi: 10.1139/m76-055. [DOI] [PubMed] [Google Scholar]
  11. Rohrer M. D., Bulard R. A. Microwave sterilization. J Am Dent Assoc. 1985 Feb;110(2):194–198. doi: 10.14219/jada.archive.1985.0250. [DOI] [PubMed] [Google Scholar]
  12. Rohrer M. D., Terry M. A., Bulard R. A., Graves D. C., Taylor E. M. Microwave sterilization of hydrophilic contact lenses. Am J Ophthalmol. 1986 Jan 15;101(1):49–57. doi: 10.1016/0002-9394(86)90464-2. [DOI] [PubMed] [Google Scholar]
  13. Vela G. R., Wu J. F. Mechanism of lethal action of 2,450-MHz radiation on microorganisms. Appl Environ Microbiol. 1979 Mar;37(3):550–553. doi: 10.1128/aem.37.3.550-553.1979. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Wayland J. R., Brannen J. P., Morris M. E. On the interdependence of thermal and electromagnetic effects in the response of Bacillus subtilis spores to microwave exposure. Radiat Res. 1977 Jul;71(1):251–258. [PubMed] [Google Scholar]

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