Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1995-04-27
1997-05-06
Kunz, Gary L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
435 6, 435135, 435145, 435259, C07H 100, C07H 2104
Patent
active
056272766
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the degradation of nucleic acids. Nucleic acid degradation is a useful or essential step in many processes involving products derived from biotechnology or fermentation processing generally.
An increasing number of valuable products are produced intracellularly, often in microbial cells, in industrial processes. To extract the product of interest, it is generally necessary to disrupt or lyse the host cells. One of the problems on such lysis is that, as well as the desired products, nucleic acids are released from the cells into the disruption medium. On being released, the nucleic acids uncoil and form networks in solution: this results in an increase in the viscosity of the cell lysate. This high viscosity can be a problem in downstream processing steps, as it can adversely effect mixing, solid/liquid separation, pumping and adsorption processes, to name but a few. Because of this property of nucleic acids, processes which involve cell disruption may require methods for breaking down nucleic acids, so as to enable subsequent processing steps to be carried out in an efficient manner or indeed at all.
There have been previous attempts in the prior art to degrade nucleic acids in industrial processes such as those described above. One possibility is to use heat, as is for example disclosed in EP-A-0145233, in which "heat shock" processes involve heating cells or a cell lysate to a temperature as high as 150.degree. C. or more for a short period of time (generally a few seconds or minutes). While effective, this process is fairly energy-intensive and clearly requires the use of costly equipment if an aqueous medium is to be heated in liquid form significantly above 100.degree. C.
Instead of using heat, nucleic acids can be degraded or removed (for example by precipitation) by the addition of chemical or biological agents. Nucleases are enzymes which hydrolyse nucleic acids and can be added to a cell lysate for that purpose. Purified preparations of nucleases, though, are expensive. A precipitating agent such as polyethylene imine may be significantly cheaper than a nuclease and may effectively remove the nucleic acid from the bulk of the cell lysate.
Although the chemical degradation of nucleic acids will be the route of choice in removing them from a cell lysate, there is a problem in finding a reagent that is effective, inexpensive and, importantly, leaves no detrimental residue after its use.
It has now been found that peroxide can be used as a particularly effective and suitable nucleic acid degrading agent, and it is to this finding that the present invention is addressed. It is believed that this nucleic acid degradation involves a substantial reduction in its molecular weight and that this reduces substantially the viscosity enhancing properties of the nucleic acid.
According to a first aspect of the present invention, there is provided a process of recovering a product from an aqueous preparation which comprises a quantity of nucleic acid sufficient to lead to a viscosity high enough to cause difficulty in a processing stage characterised by a step of degrading the nucleic acid by contacting it with a peroxide before or during the said stage.
According to a second aspect of the present invention, there is provided a process of degrading nucleic acid in a solution which comprises at least 0.1 g/litre, for example 0.5 to 20 g/litre of nucleic acid dissolved in water by contacting it with a peroxide.
According to a third aspect of the present invention, there is provided a process which comprises controlling the viscosity of an aqueous preparation which contains solid particles and at least 0.1 g/litre for example 0.5 to 10 g/litre of nucleic acid which comprises degrading nucleic acid with a peroxide and separating solid particles.
According to a fourth aspect of the present invention, there is provided a process of recovering a polysaccharide or preferably a polyhydroxyalkanoate polymer from cells which comprises degrading cellular material other than the said polymer in which
REFERENCES:
patent: 5118603 (1992-06-01), Popp et al.
Schweitz: "Action de l'eau oxygenee sur le DNA in presence d' ions ferreux et de lumiere", Biochimica et Biophysica Acta, vol 166, 1968.
Kunz Gary L.
Zeneca Limited
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