How do hypertonic solutions kill bacteria and fungi?
A hypertonic solution has a higher concentration of solute, and a lower concentration of water than the cell. This will cause a net movement of water out of the cell and into the solution by the process of osmosis. If the concentration difference is too great, the bacteria and fungi cells will become dehydrated to the point that it will kill them. The dehydration causes the substances inside the cell to be at too high a concentration for survival. Chemical reactions necessary for life will not be able to be carried out.
This video discusses how hypertonic solutions remove water from plant cells.