Method for producing polyhydroxyalkanoic acid
Embodiments of the invention relate to the microbial production of polyhydroxyalkanoic acids, or polyhydroxyalkanoates (PHA), from substrates which cannot be used as a source of carbon and/or energy for microbial growth or PHA synthesis and which have microbial and environmental toxicity. According to one embodiment of the invention, a process for the production of PHA is provided wherein an enzyme such as methane monooxygenase is used to convert volatile organic compounds into PHA through the use of microorganisms that are unable to use volatile organic compounds as a source of carbon for growth or PHA production.
1. A method for causing the intracellular synthesis of a polyhydroxyalkanoate (PHA) from one or more non-methane volatile organic compounds (VOC's), comprising:
a) providing one or more non-methane VOC's;
b) providing a culture of microorganisms capable of metabolizing said one or more non-methane VOC's to produce a metabolized compound, wherein said culture is capable of incorporating a carbon contained within said metabolized compound into the PHA, wherein said culture is also capable of metabolizing methane, wherein said culture comprises methanotrophic and/or non-methanotrophic PHA-synthesizing microorganisms;
c) providing a growth-culture medium that regulates the metabolism of said culture in which the availability of copper ions and/or iron ions to said culture is increased to cause said culture to produce particulate methane monooxygenase;
d) exposing said culture in said growth-culture medium to said one or more non-methane VOC's, thereby causing or allowing said culture to convert said one or more non-methane VOC's into said metabolized compound; and
e) manipulating said growth-culture medium to cause or allow said culture to use carbon contained within said metabolized compound for the intracellular synthesis of said PHA.
2. The method of claim 1 , further comprising adding an additional source of carbon to the growth-culture medium to induce the PHA-synthesizing microorganisms to synthesize a PHA having a different molecular structure as compared to said PHA synthesized from said carbon contained within said metabolized compound, wherein said additional source of carbon is valeric acid.
3. The method of claim 1 , further comprising exposing said culture in said growth-culture medium to methane prior to, while, and/or after exposing said culture to said non-methane organic compounds.
4. The method of claim 3 , wherein said exposing to said methane occurs while said culture is exposed to said non-methane organic compounds by exposing said culture to a gaseous mixture comprising said methane and said non-methane organic compounds.
5. The method of claim 1 , wherein said culture comprises methanotrophic microorganisms, non-methanotrophic microorganisms, and/or heterotrophic microorganisms.
6. The method of claim 1 , wherein said methanotrophic PHA-synthesizing microorganisms comprise one or more methane monooxygenases (MMO), and wherein said organic compounds are capable of inhibiting the metabolic function of said MMOs.
7. The method of claim 1 , wherein manipulating said growth-culture medium comprises altering the concentration of one or more compounds within said growth-culture medium to alter the substrate specificity of methane monooxygenase (MMO).
8. The method of claim 7 , wherein said one or more compounds comprises iron and wherein said substrate specificity is altered to reduce the inhibition of said MMO.
9. The method of claim 1 , wherein said one or more non-methane organic compounds are obtained from one or more of the following sources: a landfill, a wastewater treatment system, a coal mine, a natural gas system, an agricultural waste management system, and a ruminant animal operation.
10. The method of claim 1 , wherein the mass of PHA produced is about 5-80% of the mass of said methanotrophic and/or non-methanotrophic PHA-synthesizing microorganisms.
11. The method of claim 1 , wherein said culture comprises naturally-occurring microorganisms, genetically-engineered microorganisms, or combinations thereof.
12. The method of claim 1 , wherein manipulating said growth-culture medium to cause or allow said culture to produce said PHA comprises adjusting the availability of an essential growth nutrient.
13. The method of claim 12 , wherein said nutrient is selected from the group consisting of oxygen, nitrogen, magnesium, calcium, sodium, sulphur, and potassium.
14. The method of claim 1 , wherein a single culture metabolizes said compound into an intracellular metabolized compound, and wherein said single microorganism converts said intracellular metabolized compound into said PHA.
15. The method of claim 1 , wherein said metabolized compound is produced intracellularly and/or extracellularly.
16. A method for intracellular synthesis of a polyhydroxyalkanoate (PHA) from one or more non-methane volatile organic compounds VOC's, comprising:
a) contacting a culture comprising methanotrophic and/or non-methanotrophic PHA-synthesizing microorganisms grown in a growth-culture medium with one or more non-methane VOC's, wherein said culture is capable of i) metabolizing said one or more non-methane VOC's to produce a metabolized compound and ii) incorporating a carbon contained within said metabolized compound into PHA, wherein said contacting induces said culture to convert said one or more non-methane VOC's into said metabolized compound,
b) increasing the availability of copper ions and/or iron ions to said culture in said culture medium to cause said culture to produce particulate methane monooxygenase; and
c) manipulating said growth-culture medium to cause said culture to use carbon contained within said metabolized compound for the intracellular generation of said PHA, wherein the manipulation is an adjustment in the availability of a nutrient selected from the group consisting of oxygen, nitrogen, magnesium, calcium, sodium, sulphur and potassium.