Table 2.

Inactivation Characteristics of B. pumilus SAFR-032 and B. subtilis 168 Spores after Plasma Treatment with and without Hydrogen Peroxide as Process Gas

				LD90 value (in s)b		Spore inactivation constant (SIC)c
Plasma (flux in sccm)	Power (in W)	Pressure (in Pa)	Hydrogen peroxide concentration (in %)a	Bacillus pumilus SAFR-032	Bacillus subtilis 168	Bacillus pumilus SAFR-032	Bacillus subtilis 168
H2 (20 sccm)	100	5	n.a.	184.1±12.3*	73.6±8.5	(1.2±0.1)×10−2*	(3.1±0.3)×10−2
H2 (20 sccm)	400	5	n.a.	40.3±3.0*	19.7±2.3	(5.5±0.4)×10−2*	(9.8±1.0)×10−2
H2 (20 sccm)	400	25	n.a.	44.5±4.7*	29.4±3.6	(5.0±0.4)×10−2*	(7.3±0.6)×10−2
H2/O2 (10:10 sccm)	400	10	n.a.	38.7±3.8*	23.6±2.9	(6.9±0.8)×10−2*	(1.1±0.2)×10−1
H2 (20 sccm)	400	5	30	13.6±1.5*	9.2±0.8	(1.6±0.2)×10−1*	(2.5±0.3)×10−1
n.a.	n.a.	n.a.	30	55.1±6.7*	19.5±2.1	(4.2±0.5)×10−2*	(1.1±0.2)×10−1
n.a.	n.a.	n.a.	60	16.7±1.8*	11.3±1.2	(1.2±0.2)×10−1*	(1.7±0.2)×10−1

^aFour milliliters of 90°C heated and evaporated hydrogen peroxide in two concentrations (30% and 60%) were used for the spore inactivation. n.a.=not applied.

Data are expressed as averages and standard deviations (n=3). Asterisks indicate LD₉₀ and SIC values that were significantly different (P values of ≤0.05) than the respective values obtained from spores of B. subtilis 168.

^bLD₉₀ value, i.e., time (in seconds) needed to reduce one order of magnitude of the initial spore population.

^cSpore inactivation constant (SIC) was determined from the slope of the dose-effect curves as described by Moeller et al. (2007, 2009, 2010).