Instrumentation

Cell Disruption Methods (Physical)

Cell Disruption Methods (Physical Methods)

Cell Disruption is a process of releasing biological content from a cell or a process of obtaining intracellular fluid via methods that opens up cell wall. An overall goal in cell disruption is to obtain intracellular fluid without disrupting any of its components.

It is of two types: Mechanical and Non-mechanical.

Non mechanical methods can be classified into physical and chemical methods. Physical methods includes use of osmotic shock, decompression, thermolysis etc. while chemical methods involves use of detergents, solvents and enzymes.

Thermolysis

It refers to breakdown of molecules by action of heat. E.g. Release of cytoplasmic proteins from E.coli (10min at 90 0C), periplasmic proteins of gram negative bacteria are released when cells are heated up to 50 0C. Improved protein release has been obtained after short high temperature shocks, than when at longer temperature exposures at lower values. However, results are highly unreliable, as protein solubility changes with temperature fluctuations.

Freezing and thawing of a cell slurry can cause cells to burst due to formation and melting of ice crystals. Gradual freezing, leading to formation of larger crystals, can cause an extensive damage to cell. On combination with cell grinding, this technique has shown great results. However, it is very costly, and restricted to small-scale laboratories.

Decompression

During explosive decompression, the cell suspension is mixed with pressurized subcritical gas for a specified time, depending on cell type. The gas enters cell and expends on release causing the cell to burst. When gas pressure is suddenly released, gas comes out of solution as expanding bubbles that stretch the membranes of each cell until they rupture and release their contents. E.g. Cell disruption of E.coli by decompression.

 

Decompression Chamber for cell disruption

 

The technique is promising, being gentle on cells, resulting in large debris that are easier to remove in order to obtain desired product. However, low efficiency and high dependency on pressure release and time of contact between cell suspension and gas are its limitations.

 

Osmotic Shock

In this method, cells are first exposed to either high or low salt concentration. Then it is quickly changed to opposite concentrations which leads to osmotic pressure and cell lysis. The reason for cell breakage is quick flow of water from low salt concentration to high salt concentration.

 

Osmotic shock (Cell Disruption Methods)

 

It is not commonly used for cell disruption because of its low efficiency. The efficient disruption would commonly require enzymatic pre-treatment to weaken the cells. In addition, it requires addition of high amounts of salts and water. Also downstream processing costs may be higher due to dilution of products.

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