Effect of cell volume on disintegration by ultrasonics

Wide variations in resistance to ultrasonic disintegration of continuously cultivated Bacillus cereus, Saccharomyces cerevisiae and Escherichia coli could be achieved by corresponding variations in fermenter impeller speed (agitation rate). In all cases examined, the relationship between disintegration constant and impeller speed was found to be linear. Although changes in relative strengths of E. coli were observed with changes in limiting nutrient (nitrogen-limited cells being weaker than carbon-limited cells for any one impeller speed), this was compensated for by the increased volumes of nitrogen-limited cells, and the relationship between disintegration constant and mean cell volume was linear, irrespective of nutrient limitation. Comparisons with other published data confirmed the view that for any one micro-organism, irrespective of cultural conditions, the principal determinand of susceptibility to ultrasonic disintegration was mean cell volume.