Destruction ofBacillus licheniformisspores by microwave irradiation

Abstract

Aims: To investigate the sporicidal mechanisms of microwave irradiation on Bacillus licheniformis spores. Methods and Results: We measured spore viability and the release of DNA and proteins, and performed transmission electron microscopy (TEM). A microwave oven (0·5 kW) was modified to output power at 2·0 kW, which allowed a shorter sterilization cycle. A 2·0 kW microwave treatment at the boiling temperature for 1 min did not kill all spores, but killed most spores. The spore inactivation rate was faster than that of boiling and 0·5 kW microwave oven. In contrast to boiling and 0·5 kW microwave treatments, the 2·0 kW microwave resulted in significant leakage of proteins and DNA from spores due to injury to the spore structure. TEM revealed that 2·0 kW microwave irradiation affected spore cortex hydrolysis and swelling, and ruptured the spore coat and inner membrane. Conclusions: These results suggest that 2·0 kW microwave irradiation ruptures the spore coat and inner membrane, and is significantly different from boiling. Significance and Impact of the Study: This study provides information on the sporicidal mechanisms of microwave irradiation on B. licheniformis spores.

Fate of antibiotic resistance bacteria and genes during enhanced anaerobic digestion of sewage sludge by microwave pretreatment

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Purification of bacterial genomic DNA in less than 20 min using chelex-100 microwave: examples from strains of lactic acid bacteria isolated from soil samples

“…In contrast, the Chelex 100-Microwave method is efficient with both types of bacteria. This may be because cellular lysis in this method is caused by the rotation and friction of cell molecules when in the microwave oven (Ling et al 1991;Kim et al 2009), and not by enzymatic collision alone (data not shown).…”

Inactivation of Clostridium sporogenes and Geobacillus stearothermophilus spores with the use of microwave and steam sterilizers and microwave oven

“…In the suspension of Bacillus licheniformis spores subjected to microwaves with the capacity of 2 kW, numerous proteins and DNA were noted, which got outside through destroyed spore coats. the activity of the protein cotA located in the spore capsule, which did not change its properties during classic boiling, was completely inhibited [21].…”