School of Food Science

Research Description by UI PhD Student

My name is Aleksandra Checinska and I am a PhD student in the University of Idaho Environmental Science and Water Resources program (

I work in the Food Research Center under direction of UI SFS faculty member Dr. Andrzej Paszczynski. In our laboratory, we developed a new sterilization method which uses supercritical fluid carbon dioxide modified with a small amount of hydrogen peroxide.


Supercritical fluid carbon dioxide has gas-like and liquid-like properties and is particularly useful for sterilization applications. The method is as gentle as pasteurization, but as effective as autoclaving and is very efficient at the inactivation of bacterial vegetative cells, endospores and biofilms.

Sterilization of many items, such as food, medical supplies and industrial materials or equipment, is required in many industries. However, current sterilization methods have to be chosen specifically to match requirements for such items to be sterilized. Moreover, some microorganisms have become more resistant and are more difficult to kill by standard procedures. The latest examples are Bacillus pumilus SAFR-032 that is not inactivated by the sterilization procedures of NASA clean room facilities or Bacillus sporothermodurans that survives milk ultra high temperature treatment.

Therefore, it is important to work on new sterilization method development, but it is also necessary to understand the mechanisms of resistance to heat, chemical agents or ionizing radiation. In my research, I have investigated resistance of Bacillus pumilus endospores to hydrogen peroxide. Currently, I am studying the heat resistance mechanism of other Bacilli endospores. Two of my papers are included below.

1.   Checinska, A., M. Burbank, and A. J. Paszczynski. 2012. Protection of Bacillus pumilus spores by catalases. Applied and Environmental Microbiology (published online).

2.   Checinska, A., I. A. Fruth, T. L. Green, R. L. Crawford, and A. J. Paszczynski. 2011. Sterilization of biological pathogens using supercritical fluid carbon dioxide containing water and hydrogen peroxide. Journal of Microbiological Methods 87:70-75.

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