THE KINETICS OF BACILLUS-SUBTILIS SPORE INACTIVATION ON FILTER-PAPER BY UV-LIGHT AND UV-LIGHT IN COMBINATION WITH HYDROGEN-PEROXIDE

Inactivation of spores of Bacillus subtilis (ATCC 6633) on two differe nt grades of cellulose filter paper (Whatman Grades 2 and 6), by ultra violet light (u.v.), at an intensity of approximately 4.5 Wm(-2) and a t fluences of up to 2 x 10(3) Jm(-2), and u.v. in the presence of hydr ogen peroxide, is described in terms of multi-target and single hit-si ngle target kinetic expressions. Wet spores were inactivated at rates ranging from 6.7 to 10.6 higher than that of dry spores on both grades of filter paper. In addition, spore inactivation was up to 5.6 times more rapid on Grade 2 filter paper. Synergistic inactivation was seen to occur when spores were irradiated in the presence of 1% (w/v) hydro gen peroxide with rates up to 5.3 times higher than with treatment sol ely by u.v. The results obtained are discussed in general terms with p articular reference to surface characteristics which might provide shi elding to micro-organisms from incident u.v. light.