A process for treating a microorganism-containing stream includes the steps ofpassing the stream (12) through a chamber (14), pressurizing the stream (12)in the chamber to a pressure greater than 14.7 p.s.i.g., introducing a feedgas (16) into the pressurized stream (12) such that the feed gas (16) issoluable within the microorganisms, and depressurizing the stream (12) so asto cause the soluablized feed gas (16) to expand within the microorganisms soas to rupture the cell walls of the microorganisms. The feed gas (16) can becarbon dioxide, air, nitrogen, methane, or mixtures thereof.
