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Temperature-dependency on the inactivation of Saccharomyces pastorianus by low-pressure carbon dioxide microbubbles
Fumiyuki Kobayashi1, Sachiko Odake1
1Faculty of Applied Life Science, Nippon Veterinary and Life Science University, Musashino, Tokyo Japan.
Abstract:
Temperature-dependency on cell membrane injury and inactivation of Saccharomyces pastorianus by low-pressure carbon dioxide microbubbles (MBCO2) was investigated. The number of surviving S. pastorianus cells after MBCO2 treatment detected with yeast and mould agar (YMA, an optimum agar) was higher than that with YMA adding 2.5 g/L sodium chloride and yeast nitrogen base agar (a minimum agar). However, the decrease of the surviving number by thermal treatment was not changed among above agars used. The fluorescence polarization (FP), which indicated the phase transition of the membrane of S. pastorianus cells treated with MBCO2 increased with increasing temperature. The activity of the alkaline phosphatase (AP), a periplasmic enzyme, in S. pastorianus cells after MBCO2 and thermal treatments increased with the FP but was reduced by further increasing temperature. The FP and AP activities after MBCO2 treatment increased at a temperature lower than the temperature of the thermal treatment. In addition, intracellular pH of S. pastorianus decreased by the MBCO2 treatment at lower temperature with increasing pressure. Therefore, it was revealed that phase transition of the cell membrane and inactivation of S. pastorianus was caused by MBCO2 treatment at lower temperature than thermal treatment and that the effect was induced by the dissolved CO2 and increased with increasing pressure.
Insights
Low-pressure carbon dioxide microbubbles (MBCO2) cause cell membrane changes and inactivation in Saccharomyces pastorianus at lower temperatures than thermal treatments. This effect is linked to dissolved CO2 and increases with pressure.
Area of Science:
- Microbiology
- Biophysics
- Food Science
Background:
- Understanding microbial inactivation is crucial for food preservation and biotechnology.
- Cell membrane integrity is vital for microbial survival and function.
- Carbon dioxide microbubbles (MBCO2) offer a novel non-thermal inactivation method.
Purpose of the Study:
- To investigate the temperature-dependency of cell membrane injury and inactivation of Saccharomyces pastorianus using MBCO2.
- To compare the effects of MBCO2 treatment with thermal treatment on S. pastorianus.
- To elucidate the mechanisms underlying MBCO2-induced microbial inactivation.
Main Methods:
- Treatment of S. pastorianus with MBCO2 at varying temperatures and pressures.
- Assessing cell viability using yeast and mould agar (YMA) and modified agars.
- Measuring membrane fluidity using fluorescence polarization (FP).
- Quantifying alkaline phosphatase (AP) activity as an indicator of cell membrane damage.
- Monitoring intracellular pH changes.
Main Results:
- MBCO2 treatment caused increased FP and AP activity in S. pastorianus, indicating membrane phase transition and enzyme leakage.
- These effects occurred at lower temperatures compared to thermal treatments.
- Cell inactivation by MBCO2 was dependent on dissolved CO2 concentration and pressure.
- Intracellular pH decreased with MBCO2 treatment at lower temperatures and increased pressure.
Conclusions:
- MBCO2 induces cell membrane phase transition and inactivation of S. pastorianus at temperatures lower than thermal methods.
- Dissolved CO2 and increased pressure are key factors in MBCO2-induced inactivation.
- MBCO2 represents a promising non-thermal technology for microbial control.
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