Microbial Disruption in High Frequency Cavitating Ultrasound Fields

Cell disruption in a novel 266 kHz system (0.6 ml) that has batch and flow-through capabilities was compared with that achieved with a 20 kHz (2.4 ml) generator. Batch suspensions of Saccharomyces cerevisiae were exposed to cavitation for times up to 5 min. Protein release (an assay of cell disruption) was measured using the Lowry method. The rate of protein release was similar for both systems. Temperature increases for similar cell disruption efficiencies were significantly lower at 266 kHz compared to 20 kHz. For 1 min batch sonications the temperature increase was 2.75 times lower at 266 kHz (8ûC increase) than at 20 kHz (22ûC increase). In a parallel study, detection of surface antigen released from Bacillus spores was measured by the enzyme linked immunosorbent assay (ELISA) technique. Samples sonicated in the 266 kHz system showed a 15-fold increase in assay sensitivity compared to unsonicated spores. The tolerable temperature increase in the 266 kHz flow system suggests that it has potential for increasing bacterial antigen detection in the environment.