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Dry heat inactivation of bacterial spores and influence of spore moisture content on z values as related to spacecraft sanitation
Inactivation of viruses and rickettsiae by heat - bibliography
Inactivation by heavy ions of esterase activity of dried trypsin as function of temperature during irradiation
Inactivation of T4 bacteriophage by tritium decay incorporated into DNA and phage protein
Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components
Thermal inactivation of microbes relating to spacecraft sterilization
Empirically based kinetic model describing synergistic inactivation of dry Bacillus subtilis by combined heat and gamma radiation environment
Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components
Purification and reversible inactivation of isocitrate dehydrogenase /ICDH/ of Halobacterium cutirubrums, overcoming difficulties in purifying halophilic enzymes
Nicotinamide adenide dinucleotide phosphate /NADP/ specific isocitrate dehydrogenase /ICDH/ inactivation from obligate halophile at low NaCl levels
Thermal inactivation curves of Bacillus subtilis spores for decontamination of interplanetary space vehicle components
Evaluation equipment for terminal sterilization process on unmanned landers and determination of thermal inactivation curve of B. subtilis var. niger spores
Moisture effects on thermal inactivation of microbial spores for spacecraft sterilization
Spacecraft sterilization by microbial inactivation, comparing thermoradiation and dry heat methods
Data showing that 90 C was a more effective temperature than 125 C for the destruction of Bacillus subtilis var. niger when the head-space moisture was fixed at 474 micrograms H2O/ml have been confirmed and are summarized. The influence of head-space moisture at 90 C was investigated and it was observed that as the head-space moisture was increased 474 micrograms H2O/ml, there was a corresponding increase in lethality of the system. This moisture level corresponded to 100% relative humidity at 90 C, and additional water in the cans should have had no effect. A profound descrease was observed in the destruction of the organisms when additional water was added. The discontinuity observed in these data is troublesome and must be resolved as the first step in an orderly exploration of low temperature inactivation of B. subtilis var. niger.
An experimental sterilization facility was developed to simulate conditions that will be encountered during terminal sterilization of space vehicles. The system consists of a temperature controlled oven with a nitrogen gas stream containing a known concentration of water. Moisture analyzers are utilized to monitor the gas flowing over spore samples contained in the oven. In its original configuration, no provision was made for the control of water vapor during the sterilization cycle. Because moisture profoundly influences the thermal inactivation of bacterial spores, an upper limit for the moisture content in the gas used to sterilize the space vehicle was established (25% RH at 0 C STP). Accordingly, a controller was developed and installed to provide these conditions in the experimental sterilization facility.
The thermal inactivation curve for Bacillus subtilis var. niger spores on the Viking lander is examined. Tests were conducted at 113 C and 25% RH, and over a wide range of temperatures using .001% RH and additions of P2O5 to dry the environment. Results show the 25% RH environment did not significantly reduce the survival curve, while the survival curves for spores treated under the drier .001% RH environment was reduced by a factor of 3.
The mechanism for thermal inactivation of bacterial spores under moist or dry heat was studied. Experimental conditions were established relating to spore loss of heat resistance and loss of optical density as a measure of the rate and extent of germination in spore suspensions. Events occurring during germination were correlated with phase darkening (refractility and non-refractility of spores), stainability characteristics of heat and non-heat treated spores, morphological characteristics, and studies on swelling of spores by an increase in packed cell volume.