Disintegration of Cells and Protein Recovery

In order to prepare intracellular substances from microorganisms the barrier of the cell envelope has to be disrupted. Since this barrier is usually very resistant, the methods available for the preparation of substances with unstable activity are restricted due to the inactivation occasioned by some disintegration processes. Some methods, usually applying physico-mechanical shearing stress, are inherently well suited to disintegrate cells to release unstable substances. In other cases, when more inert substances like e.g. nutrients are prepared from microbes, denaturing treatments like cell envelope disruption by heating followed by enzymatic dissolution of the protoplasm may be advantageous. Some recent results with disintegration by freeze-pressing are described. Procedures giving selective release of certain cell constituents and ways to influence the yield qualitatively are also reported. The main obstacle to the disintegration of microorganisms lies in their tough cell walls. In the true bacteria (Eubacteriales), the mechanicallyresistant part of the wall is the murein which can be considered as a giant bag-shaped macromolecule. Consequently, covalent bonds have to be broken in order to disrupt the bacteria. In other microbes analogous conditions often exist. Table 1. Methods for disintegration of microorganisms. Chemical Alkaline or detergent breakdown Solvent extraction Enzymatic digestion Freeze-thawing Physical Heat-treatment rupture Osmotic disruption Decompression Crystal transformation Sonic vibration Mechanical Agitation with abrasive particles Grinding Pressure extrusion