Disentangling the multiple effects of a novel high pressure jet device upon bacterial cell disruption

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High-pressure jet devices (HPJDs) support high throughput and are cost-effective in reducing excess activated sludge. We aimed to identify the dominant mechanism among frictional shear, collision, and cavitation on bacterial cell disruption and intercellular substances eluted by an HPJD. An HPJD was modified to disassociate these three mechanisms so that they could be analyzed separately. Gram-negative and Gram-positive bacteria (Escherichia coli and Bacillus subtilis, respectively) were subjected to treatment by the modified HPJD device. Frictional shear, collision, and cavitation were found to damage 11.12±1.12%, 11.97±1.12%, and 23.70±2.35% of E. coli cell and 5.2±1.57%, 7.81±1.09%, and 28.54±3.45% of B. subtilis cell, respectively. The application of atomic force microscopy (AFM) displayed different morphological changes of E. coli and B. subtilis cells induced by frictional shear, collision, and cavitation. Frictional shear and collision deformed E. coli cells but not severely B. subtilis cells, merely increasing the cell surface roughness. In contrast, cavitation directly contributed to implosion of B. subtilis cells, resulting in higher concentrations of released intracellular DNA, polysaccharide and protein than those by frictional shear and collision. Despite the distinct cell disruption mechanisms, cavitation commonly provided the most intense effect on cell disintegration and the release of intracellular components for both E. coli and B. subtilis.