The radiation-induced inactivation of microorganisms in non-aqueous suspension: The effect of selected alcohols and paraffins on the radiation sensitivity of aerated Bacillus pumilus spores.

The effect of model compounds comprising alcohols and paraffins on the radiation sensitivity of B pumilus spores has been carried out with the aim of understanding the radiation-induced inactivation of microorganisms when suspended in non-aqueous medium. This study is a prerequisite to the undertaking of radiation sterilization of non-aqueous pharmaceuticals. Spores of B. pumilus E601 mounted on kaolin powder were suspended in the appropriate organic agent and gamma irradiated under oxic conditions. Spores suspended in paraffins displayed increased radiation response over that for aerated buffered suspensions. Values of inactivation constant ranged between 2X and 5X for that buffer. Less pronounced modification of response was obtained for the alcohols. The results reveal a marked tendency for response to increase with decreasing polarity of the suspending fluid. The partial miscibility of the alcohols in water enabled the examining of the transition from the response characteristic of aerated buffered suspensions to those of the spores in pure organic liquids.