Enhanced microbial inactivation by carbon dioxide through mechanical effects

Abstract

The development of efficient and sustainable microbial inactivation approaches is an important objective. Dense-Phase-Carbon-Dioxide and related approaches, which utilize high pressure CO2, were reported to be feasible methods. However, a major challenge is the enhancement of sustainability and economic viability by reducing the necessary temperatures, energy and time. Here we report on a new approach that exploits added mechanical forces due to sudden depressurization in<15 s of near critical/liquid/gaseous CO2 and concomitant pressure drops in narrow sub-millimeter diameter mini tubes. The efficiency of the new "Multi-Phase-Pressure-Drop" method was determined with Escherichia coli DH5α as a function of starting inactivation pressure (40–82 bar), pressure drop (26–77 bar) and operation temperature (25, 30 and 45 °C) and increased from 0.2 ± 0.2 log to 3.7 ± 0.4 log by raising the inactivation pressure and the pressure drop. Bacteria viability and morphology studies confirmed damage and disintegration of bacteria, consistent with effects of added mechanical forces.