I am conducting research on plant-microbe interactions and require a large quantity of sterilized soil for my experiments. While autoclaving is impractical for such volumes, I have adopted a method involving moistening the soil and incubating it at 80°C for 24 hours. This process effectively eliminates odors, but I am uncertain about its efficacy in achieving complete sterilization.
It is unclear whether increasing the temperature to 90°C or extending the incubation duration would be more appropriate. Additionally, I have been unable to find similar sterilization methods in the literature. I am concerned about potential negative reviews from journal editors regarding this unconventional approach.
Could you please provide insights into the effectiveness of this sterilization method and suggest any alternative approaches? Your expertise in this area would be greatly appreciated.
Kadir Aslan According to the work of Nowak, A., and H. Wronkowska. "On the efficiency of soil sterilization in autoclave." Zentralblatt für Mikrobiologie 142.7 (1987): 521-525, sterilization for I hour at 121°C for three successive days (variant "3 X I h") could not achieve high efficiency. Bacteria (Bacillus spp). and fungi (Aspergillus sp., Mucor sp., Ppenicillium spp.) were isolated in 8 days after the treatment in significant numbers (up to 235 cells per g).
Sterilization for 2 hours at 121°C (variant "I X 2 h") was more efficient and only from 0 to 11 CFU/g were found. We had very similar results.
Indeed, 80°C can kill plant pathogenic bacteria and some fungi, but spore-forming microbes like bacilli will stay alive.
Thank you for yor answer sir, so even if 24h in 80C is not enough? What kind of proteins can be stay functional after 24h at 80 or 90 degree İ cant still understand
Kadir Aslan According to the work of Beladjal, L., Gheysens, T., Clegg, J.S. et al. Life from the ashes: survival of dry bacterial spores after very high temperature exposure. Extremophiles 22, 751–759 (2018). https://doi.org/10.1007/s00792-018-1035-6, dry Bacillus spores can survive even after 420°C.
Autoclaving and heat sterilization can cause physical and chemical changes to the soil that may impact the output of your research questions depending on your focus. Of course each method has its limitations and the selection of the best for your use case will need to take into account all the dimensions of your experimental work. For impacts on physical structure it is worth reading this article :Li, H., Liu, L., Li, C. et al. Efficiency of Different Soil Sterilization Approaches and Their Effects on Soil Particle Size Distribution. J Soil Sci Plant Nutr 23, 3979–3990 (2023). https://doi.org/10.1007/s42729-023-01315-2 There is also an interesting comparison paper "Sterilize Methods Comparison for Soils" | International Journal of Methodology (aijr.org) Article Sterilize Methods Comparison for Soils: Cost, Time, and Efficiency
In previous experimentations for large volumes I have used gamma irradiation but again this doesnt come without issues.
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