Selective Quenching of Peracetic Acid by Sodium Dithionite Enables Rapid, Non-Thermal Sterilization for Euglena gracilis Cultivation

TL;DR

A new method using sodium dithionite quickly and selectively removes peracetic acid, enabling effective sterilization without harming the growth of Euglena gracilis.

Contribution

A selective and rapid quenching method for peracetic acid using sodium dithionite, independent of pH and nitrogen compounds.

Findings

Sodium dithionite reduced PAA completely within 5 seconds, regardless of pH or nitrogen compounds.

Selective removal of PAA allowed residual H2O2 to remain, supporting better growth of Euglena gracilis.

PAA-treated medium with quenching led to higher paramylon production compared to autoclaved medium.

Abstract

Peracetic acid (PAA) has strong biocidal activity against bacteria, fungi, and spores, even with short contact times. PAA-mediated sterilization is therefore an attractive method for sterilization of growth media that have heat-labile components or when polymer-based equipment is used. However, residual PAA and co-existing hydrogen peroxide (H2O2) can inhibit the growth of cultivated species, necessitating a fast and reliable quenching strategy that does not require rinsing. In contrast to Fe–EDTA-based catalytic decomposition that is strongly influenced by pH, buffers, and organic nitrogen, we demonstrate a fundamentally different, stoichiometric quenching strategy using sodium dithionite that enables instantaneous and selective removal of PAA. Na2S2O4 preferentially reduced PAA over H2O2 in a 0.03% PAA solution and achieved complete PAA reduction within 5 s, independent of pH and in the presence of nitrogen compounds. By adjusting the Na2S2O4 dose, PAA could be selectively removed while allowing a small fraction of H2O2 to remain. When applied to the cultivation of Euglena gracilis, which tolerates low levels of H2O2, the PAA–Na2S2O4-treated medium resulted in greater cell growth and higher paramylon production than autoclaved medium.

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