Supercritical fluid disruption of and extraction from microbial cells

DETAILED DESCRIPTION The invention combines the beneficial aspects of explosive decompression and supercritical fluid extraction.
First, a solvent that is a gas at ambient conditions and that has a critical temperature between 0.
degree.
and 100.
degree.
C.
is selected.
Preferably, the critical temperature is between 0.
degree.
and 50.
degree.
C.
This solvent is brought to near-critical pressure or higher and to near-critical temperature.
The solvent then is combined with a slurry of intact cells to saturate the cells with the solvent under the prescribed conditions.
Next, the pressure is released, preferably suddenly, to cause a pressure drop which results in partial disruption of the cell membrane and release of solvent and other materials from the cell.
Surprisingly, the cell walls are less fragmented than when using conventional microbial cell disruption techniques, and yet the yield of proteins and nucleic acids from the cells is greatly improved.
Further, the cells are exposed to minimal shear forces and there is no heat generation which would adversely affect yield.
According to one aspect of the invention, conditions are applied to allow preferential collection of proteins or nucleic acids.
First, the mixture of solvent and cells is maintained at just below the critical temperature of the solvent while subjecting the mixture to pressures at or above the critical pressure of the solvent.
When the pressure is released, proteins are selectively expressed from the cell, with little or no nucleic acids expressed.
After removing the solvent containing the expressed protein, new solvent optionally may be added and the mixture then may be repressurized and maintained at a temperature above the solvent's critical temperature.
Explosive decompression under these conditions results in nucleic acids being released from the cells, along with additional proteins.
Preferably, the solvent when combined with the cells result in a mixture having a pH that is close to the pH at which the cells are normally cultured