Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing oxygen-containing organic compound
Patent
1995-10-10
1997-11-25
Lilling, Herbert J.
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing oxygen-containing organic compound
435144, 435267, 435270, 4353171, 435800, 435803, 435820, 435829, C12P 762, C12P 748, C12N 108
Patent
active
056911742
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/GB94/00741 filed Apr. 7, 1994.
This invention relates to the recovery of plastics materials from microorganisms.
It is known to produce plastics materials which can be formed into shaped articles for example by heating them (plastic) from microorganisms. These are generally polyhydroxyalkanoates, for example polymers which comprise hydroxybutyric acid residues (PHB). The homopolymer is found widely in naturally occurring microorganisms and it is known from European patent specifications 52499 and 69497 that copolymers may also be produced. Co-polymers of hydroxybutyric and hydroxyvaleric acid have now become well known.
Although it is possible to grow micro organisms which contain large quantities of plastic for example 60% or more and even 80% or more by weight based on the dry cell weight of the microorganisms, it is normally necessary to remove other components of the cellular material from it before the plastic can be used satisfactorily.
It is known from European patent specification 145,233 that digestion of the cells with certain enzymes (proteases and phospholipases) is useful in this respect and treatment with surfactants is also disclosed. After such treatment and washing it was disclosed that the product could be further treated with hydrogen peroxide. Whilst the multistage process produces product of good purity, it is complex and consequently expensive.
We have now found that the process may be improved by using an oxidising agent (for example hydrogen peroxide) in the presence of a chelating agent. It is then possible to carry out an oxidation treatment in the presence of non-plastic cellular material or decomposition products thereof which enables a separation stage for the removal of such unwanted material prior to the oxidation treatment to be omitted.
It is thus possible to carry out a decomposition and/or solubilisation stage of such material (for example with one or more enzymes as aforesaid) and to treat the product of such a stage with an oxidising agent with less or even no intermediate purification.
We have also surprisingly found that good results may be obtained if the oxidation stage is the first chemical treatment and indeed even if it is the only chemical treatment. It may however be desirable in order to secure particularly high level of purity to carry out a subsequent chemical treatment also.
This invention comprises a process of recovering plastic, from a plastic producing microorganism in which non plastic material is removed from the plastic by a process which comprises chemically reacting non plastic material of the microorganisms in a stage of chemical solubilisation of non plastic material with an oxidising agent in the presence of a chelating agent.
The invention also comprises a process of producing a plastic, for example PHB which comprises growing a plastic producing microorganism under conditions conducive to plastic accumulation characterised in that non plastic material is removed from the product by a process which comprises chemically reacting non plastic material of the microorganism, optionally after physical treatment to condition the microorganism for subsequent processing, for example by disrupting its cell wall by a stage of chemical solubilisation of non plastic material with an oxidising agent in the presence of a chelating agent which stage is preferably the first or only chemical treatment stage.
The quantity of the chelating agent used varies according to a number of factors. In order to grow the microorganisms it is necessary to supply inorganic nutrients, for example iron, manganese and/or copper ions, and in general the quantity of chelating agent must be increased if the quantity of polyvalent metal ions is increased. If the quantity of chelating agent is too high or too low the process becomes less efficient, and the optimum quantity required should be established experimentally.
Suitable chelating agents include ethylenediamine tetra acetic acid, citric acid and diethylene triami
REFERENCES:
Biotech Abs 94-08787 WO9410289 (May 11, 1994).
Ito et al: "Degradation of RNA in Escherichia coli induced by sodium chloride", Agricultural and Biological Chemistry, vol. 41, No. 2, 1977, pp. 257-263 (see whole document).
Hughes: "Action of oxygenated water on DNA in the presence of ferrous ions and light", Chemical Abstracts, vol. 70, No. 7, 1969, abstract No. 25618r. p. 8, see abstract & Biochemical and Biophysical Research Communications, vol. 166, No. 3, 1968, pp. 720-722.
Liddell John Macdonald
Locke Timothy John
Lilling Herbert J.
Zeneca Limited
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