Abstract
Wet heat treatments are widely used sterilization techniques for inactivating dangerous and resistant sporulating bacteria. The effectiveness of such treatments depends upon the thermodynamics of water uptake by the spore as well as the kinetics of phase transformations in the hydrated spore core. The mechanism behind these chemical and physical processes remains unknown because the thermodynamic properties of the spore core constituents are not well understood. Here, we use reactive molecular dynamics simulations to calculate the vibrational density of states and specific heat of hydrated calcium dipicolinate as well as the free energy of hydration based on Jarzynski's inequality. These two quantities are used to construct a phase diagram of hydrated calcium dipicolinate, indicating the extent of hydration at different pressures and temperatures, which can be used to identify potential regimes for wet-heat sterilization of bacterial spores.
Highlights
We use reactive molecular dynamics simulations to calculate the vibrational density of states and specific heat of hydrated calcium dipicolinate as well as the free energy of hydration based on Jarzynski’s inequality
Wet-heat treatments like boiling, steaming, and autoclaving are the most commonly employed strategies to inactivate bacterial spores and prevent their re-germination. These sterilization techniques rely on the interplay of high temperature and increased water content in the cores of bacterial spores which contain metabolic enzymes, proteins, genetic materials, and salts of dipicolinic acid (DPA) with a divalent cation such as Ca2þ, Mg2þ, and Mn2þ
The specific heat capacity contribution of added water to calcium dipicolinate (Ca-DPA) decreases with hydration. These two thermodynamic properties are used to construct a phase diagram of the spore core showing the extent of hydration at different pressures and temperatures, which can be used to identify potential regimes for wet-heat sterilization
Summary
(Received 15 July 2018; accepted 29 August 2018; published online 12 September 2018) We use reactive molecular dynamics simulations to calculate the vibrational density of states and specific heat of hydrated calcium dipicolinate as well as the free energy of hydration based on Jarzynski’s inequality.
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