Inactivation of bacteria and yeast using high-frequency ultrasound treatment.
High-frequency (850 kHz) ultrasound was used to inactivate bacteria and yeast at different growth phases under controlled temperature conditions. Three species of bacteria, Enterobacter aerogenes, Bacillus subtilis and Staphylococcus epidermidis as well as a yeast, Aureobasidium pullulans were considered. The study shows that high-frequency ultrasound is highly efficient in inactivating the bacteria in both their exponential and stationary growth phases, and inactivation rates of more than 99% were achieved. TEM observation suggests that the mechanism of bacteria inactivation is mainly due to acoustic cavitation generated free radicals and H2O2. The rod-shaped bacterium B. subtilis was also found to be sensitive to the mechanical effects of acoustic cavitation. The study showed that the inactivation process continued even after ultrasonic processing cessed due to the presence of H2O2, generated during acoustic cavitation. Compared to bacteria, the yeast A. pullulans was found to be more resistant to high-frequency ultrasound treatment.
School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand; School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Institute of Food and Agricultural Standardization, China National Institute of Standardization, Beijing 10088, China.
Shengpu
S
Gao
School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand. Electronic address: y.hemar@auckland.ac.nz.
Yacine
Y
Hemar
School of Chemistry, University of Melbourne, VIC 3010, Australia.
Muthupandian
M
Ashokkumar
School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand; School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Sara
S
Paturel
School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Gillian D
GD
Lewis
D001203:Ascomycota / Q000502:physiology* / Q000648:ultrastructure; D001419:Bacteria / Q000648:ultrastructure; D018407:Bacterial Physiological Phenomena; D050296:Microbial Viability; D046529:Microscopy, Electron, Transmission; D013010:Sonication
Aureobasidium pullulans; Bacillus subtilis; Bacteria inactivation; Enterobacter aerogenes; High-frequency ultrasound; Staphylococcus epidermidis; Yeast