Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing oxygen-containing organic compound
Patent
1995-05-12
1997-04-22
Lilling, Herbert J.
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing oxygen-containing organic compound
435146, 4352521, 435829, 435872, C08G 6306, C12P 762
Patent
active
056228473
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION relates to a process for the separation of solid materials from microorganisms.
It may be advantageous to separate protein from microorganisms either because the protein itself is required or because other components of the microorganisms are required to be separated from protein.
An example of the latter case is in the production of plastics materials using microorganisms. Polyhydroxyalkanoic acids (PHA) are useful plastics materials which can be produced by this means and it is necessary if they are to be produced in an acceptable state of purity to free them from other cellular material which includes proteins.
It is known to break down cells containing PHA by heat and then to solubilise and preferably to decompose proteinaceous material for example by the use of enzymes. However, there is a tendency for proteins to denature during such treatment and this may make them resistant to the action of solubilising and decomposing agents for example enzymes; they are then difficult to remove from the PHA.
The PHA is preferably a thermoplastic hydroxybutyrate polyester, which may be a copolymer comprising other hydroxyalkanoate units for example hydroxyvalerate units. Usually it will be of D(-) configuration and suitably comprises up to 30% and preferably 3 to 25% hydroxyvalerate units, the balance being preferably substantially all hydroxybutyrate units, these percentages being by weight. Its molecular weight is suitably at least 50,000 and preferably at least 100,000 for example at least 500,000.
We have now found that if microorganisms are grown in a fermentation stage at a fermentation temperature at which they multiply rapidly and are then conditioned to render them susceptible to thermal shock in a conditioning stage by cooling them substantially below the fermentation temperature, to a conditioning temperature which is preferably by at least 10.degree. C. and more preferably by at least 20.degree. C. below the fermentation temperature without any substantial freezing, preferably maintained at the conditioning temperature for at least 1 hour and preferably at least 3 and more preferably at least 4 hours for example 4 to 12 hours, and then subjected to a protein separation stage by heating them to a protein separation temperature 10.degree. to 150.degree. C. and preferably 15.degree. to 120.degree. C. for example 20.degree. to 65.degree. C. above the fermentation temperature without permitting any substantial recovery from the conditioning effect, that the separation of protein is improved compared with that obtained if no conditioning stage is provided. The fermentation, cooling and heating stages are preferably carried out in the presence of water. Thus the severity of the heat treatment and thus of the denaturing of the proteins may be less for a similar level of protein removal and/or more protein may be removed. The separated protein may be removed from the remaining cellular material immediately or after further processing. If desired protein removal may be carried out in the presence of a surfactant.
Thus the invention comprises a process in which a solid component is recovered from a microorganism which comprises growing the microorganism at a fermentation temperature, conditioning it to render it susceptible to thermal shock in a conditioning stage by cooling it substantially below the fermentation temperature without any substantial freezing, solubilising protein contained in the microorganism by heating the microorganism in water to a protein solubilisation temperature 10.degree. C. to 150.degree. C. above the fermentation temperature without permitting any substantial recovery from the conditioning stage and separating one or more components of the cell as solids from the protein (optionally after decomposition of the protein).
The maximum rate of heating is suitably 0.05.degree. to 20.degree. C. and preferably 1.degree. to 10.degree. C. per second and the maximum rate of cooling is suitably 0.01.degree. to 20.degree. C. and preferably 1.degree. to 10.degree. C. per second. The a
Cumming Robert H.
Rees Paul
Watson Julie S.
Lilling Herbert J.
Zeneca Limited
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