Preliminary assays in distilled water
Cold distilled water (20 ml in 50 ml sterile tube) was inoculated
to 5 log cfu/ml with each yeast; samples were treated by a VC Vibra
Cell Ultrasound (US) equipment, model VC 130 (Sonics and Mate-
rials Inc., Newtown, CT, USA); the equipment works at 20 kHz
(frequency) e 130 W (acoustic energy). The probe (5 60 mm;
diameter the active component of horn) was put 2 cm below the
surface of the water. US treatments differed for duration (from 2 to
6 min), pulse (from 2 to 6 s), and percentage of the acoustic energy
(from 40 to 80%). The mean transducer efficiency was 70% (h); the
acoustic power or energy supplied (WA) into the media was: