Low-temperature decontamination with hydrogen peroxide or chlorine dioxide for space applications

Area of Science:

• Microbiology
• Space Science
• Sterilization Technology

Background:

• Current spacecraft microbial decontamination relies on high-temperature dry heat, which is time-consuming, costly, and limits material choices.
• Space agencies require alternative decontamination methods to prevent biological contamination of extraterrestrial destinations.
• Gaseous decontamination technologies are being investigated as potential replacements for dry-heat microbial reduction.

Purpose of the Study:

• To assess the biological efficacy of vapor hydrogen peroxide (VHP) and chlorine dioxide (CD) gas for spacecraft microbial decontamination.
• To compare the effectiveness and required exposure times of VHP and CD against common spore-forming bacteria.
• To identify potential challenges and areas for improvement in current spacecraft sterilization protocols.

Main Methods:

• Five spore-forming Bacillus species were inoculated onto stainless steel coupons.
• Coupons were exposed to VHP and CD gas within a 20-m³ exposure chamber.
• Microbial reduction was quantified by log reductions in culturable bacteria after specific exposure times.

Main Results:

• VHP achieved 6-log reduction of Bacillus atrophaeus in 20 minutes; CD required 60 minutes for a 5-log reduction.
• Geobacillus stearothermophilus showed similar reduction patterns, with VHP being more rapid.
• Bacillus thuringiensis exhibited higher resistance to both VHP and CD, indicating it as a potential challenge organism.

Conclusions:

• Both VHP and CD demonstrate effectiveness in reducing microbial loads on spacecraft components at lower temperatures.
• Bacillus thuringiensis presents a significant challenge, suggesting current indicator organisms may not fully represent real-world sterilization efficacy.
• Re-evaluating indicator organisms and loading is crucial for developing more realistic and effective spacecraft sterilization procedures.