Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-02-28
2002-11-12
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S377000, C528S380000, C527S300000, C525S437000, C435S041000, C435S117000, C435S130000, C435S135000, C435S136000, C435S146000, C435S874000, C435S877000
Reexamination Certificate
active
06479621
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a novel polyhydroxyalkanoate (may be abbreviated as PHA, hereinafter). Also, it relates to a very effective method for manufacturing such PHA using microorganisms capable of producing PHA and accumulating it in the cell.
Hitherto, many microorganisms have reportedly produced poly-3-hydroxybutyric acid (may be abbreviated as PHB) or other PHAs and accumulated them in the cell (“Biodegradation Plastic Handbook”, Biodegradable Plastic Research Association, NTS, Co. Ltd., P178-197). As in the case of conventional plastics, these polymers can be used for producing various kinds of products through melt processing and the like. Furthermore, since they are biodegradable they are advantageously degraded completely by microorganisms in the natural world, and do not remain in the natural environment to cause pollution unlike many conventional synthetic polymers. Also, they have good biocompatibility, and applications as medical soft materials and the like are expected.
It is known that these PHAs may have various compositions and structures depending on types of microorganisms for use in production thereof and culture medium compositions, culture conditions and the like, and until now, studies have been made on control of these compositions and structures, principally in terms of improvement of properties of PHA.
For example, it has been reported that
Alcaligenes eutropus
H16, ATCC No. 17699 and its mutants produce copolymers of 3-hydroxybutyric acid (may be abbreviated as 3HB, hereinafter) and 3-hydroxyvaleric acid (may be abbreviated as 3HV) in various composition ratios, by changing carbon sources during their culture (Japanese Patent Application Publication (Kokoku) No. 6-15604, Japanese Patent Application Publication (Kokoku) No. 7-14352, Japanese Patent Application Publication (Kokoku) No. 8-19227).
In Japanese Patent Application Laid-Open No. 5-74492, a method in which the copolymer of 3HB and 3HV is produced by bringing Methylobacterium sp., Paracoccus sp., Alcaligenes sp. and Pseudomonas sp. into contact with primary alcohol having three to seven carbons is disclosed.
In Japanese Patent Application Laid-Open No. 5-93049 and Japanese Patent Application Laid-Open No. 7-265065, it is disclosed that binary copolymers of 3HB and 3-hydroxyhexanoic acid (may be abbreviated as 3HHx, hereinafter) are produced by culturing
Aeromonas caviae
) with oleic acid or olive oil as carbon sources.
In Japanese Patent Application Laid-Open No. 9-191893, it is disclosed that
Comamonas acidovoranas
IFO 13852 produces polyester having 3HB and 4-hydroxybutyric acid as monomer unit through culture using gluconic acid and 1,4-butandiol as carbon sources.
Also, currently, studies are vigorously carried out as to PHA composed of 3-hydroxyalkanoate (may be abbreviated as 3HA hereinafter) of medium-chain-length: abbreviated as mcl) having up to about twelve carbons. Synthetic pathways of PHA can be classified broadly into two types, and specific examples thereof will be shown in the following (1) and (2).
(1) Synthesis using &bgr; oxidation
In Japanese Patent No. 2642937, it is disclosed that PHA having monomer unit of 3-hydroxyalkanoate having six to twelve carbons is produced by giving acyclic aliphatic hydrocarbons as carbon sources to
Pseudomonas oleovorans
ATCC 29347. Also, in Appl. Environ. Microbiol, 58 (2), 746 (1992), it is reported that
Pseudomonas resinovorans
produces polyester having 3-hydroxybutyric acid, 3-hydroxyhexanoic acid, 3-hydroxyoctanoic acid and 3-hydroxydecanoic acid (amount ratio 1:15:75:9) as monomer unit, with octanoic acid as a sole carbon source, and produces polyester having 3-hydroxybutyric acid, 3-hydroxyhexanoic acid, 3-hydroxyoctanoic acid and 3-hydroxudecanoic acid (amount ratio 8:62:23:7) as monomer unit, with hexanoic acid as a sole carbon source. Here, it is believed that the 3HA monomer unit having chain length larger than that of stock fatty acid are by way of fatty acid synthetic pathway that is described in (2).
(2) Synthesis using fatty acid synthesis routs
In Int. J. Biol. Macromol., 16 (3), 119 (1994), it is reported that Pseudomonas sp.61-3 strain produces polyester having as monomer unit 3-hydroxyalkanoic acids such as 3-hydroxybutyric acid, 3-hydroxyhexanoic acid, 3-hydroxyoctanoic acid, 3-hydroxydecanoic acid and 3-hydroxydodecanoic acid, and 3-hydroxyalkenoic acids such as 3-hydroxy-5-cis-decenoic acid and 3-hydroxy-5-cis-dodecenoic acid, with sodium gluconate as a sole carbon source.
By the way, biosynthesis of PHA is usually performed by PHA synthase using as a matrix “D-3-hydroxyacyl-CoA” produced as intermediates of various metabolism pathways in cells.
Here, “CoA” refers to “coenzyme A”. And, as described in the above prior art of (1), if using fatty acids such as octanoic acid and nonanoic acid as carbon sources, the biosynthesis of PHA is performed with “D-3-hydroxyacyl-CoA” produced in the “&bgr;-oxidation cycle” as a starting substance.
Reactions through which PHA is biosynthesized by way of the “&bgr;-oxidation cycle” are shown in the following.
On the other hand, as described in the above prior art of (2), if PHA is biosynthesized using saccharides such as glucose, the biosynthesis is performed using the “D-3-hydroxyacyl-CoA” converted from “D-3-hydroxyacyl-ACP” produced in the “fatty acid synthetic pathway” as start substance.
Here, “ACP” refers to “acyl carrier protein”.
By the way, as described previously, both any PHA being synthesized in above (1) and (2) is PHA composed of monomer unit having alkyl groups on the side chain, that is “usual PHA”. However, if considering more widespread application of microorganism producible PHA like this, for example application as functional polymers, it is expected that PHA having substituents other than alkyl groups (e.g. phenyl groups) incorporated in the side chain is extremely useful. Examples of other substituents include unsaturated hydrocarbons, ester groups, allyl groups, cyano groups, halogenated hydrocarbons and epoxide.
For synthesis of PHA having such substituents incorporated therein (hereinafter, referred to as “unusual PHA” as necessary), for example, a report as to PHA having aryl groups and the like in terms of synthesis using &bgr; oxidation is found in Macromolecules, 24, p 5256-5260 (1991). Specifically, it is reported that
Pseudomonas oleovorans
produces 160 mg of PHA per liter of culture medium (the ratio of dry weight to the cell is 31.6%), containing as monomer unit 3HV, 3-hydroxyheptanoic acid, 3-hydroxynonanoic acid, 3-hydroxyundecanoic acid and 3-hydroxy-5-phenylvaleric acid (may be abbreviated as 3HPV, hereinafter) in the amount ratio of 0.6:16.0:41.1:1.7:40.6 using 5-phenylvaleric acid (may be abbreviated as PVA) and nonanoic acid (mole ratio of 2:1 and total concentration of 10 mmol/L), and produces 200 mg of PHA per liter of culture medium (the ratio of dry weight to the cell mass is 39.2%), containing as monomer unit 3HHx, 3-hydroxyoctanoic acid, 3-hydroxydecanoic acid and 3HPV in the amount ratio of 7.3:64.5:3.9:24.3 using PVA and octanoic acid (mole ration of 1:1, and total concentration of 10 mmol/L). It is thought that PHA in this report is synthesized principally by way of the &bgr;-oxidation from the fact that nonanoic acid and octanoic acid are used.
Related descriptions are also found in Macromol. Chem., 191, 1957-1965 (1990) and Chirality, 3, 492-494 (1991), and the change of polymer properties that is probably caused by contained 3HPV is recognized.
As described above, for microorganism producible PHA, those having various kinds of compositions and structures have been obtained by varying types of microorganisms for use in their production, culture compositions, culture conditions and the like, but they cannot be appropriate yet in terms of properties when their application as plastics is considered. In order to further expand the application range of microorganism producible PHA, it is important to consider the improvement of properties more widely, and for this purpose
Honma Tsutomu
Imamura Takeshi
Kenmoku Takashi
Kobayashi Shin
Kozaki Shinya
Acquah Samuel A.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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