Polyhydroxyalkanoate production methods and materials and microorganisms used in same
Embodiments of the invention relate generally to methods to generate microorganisms and/or microorganism cultures that exhibit the ability to produce polyhydroxyalkanoates (PHA) from carbon sources at high efficiencies. In several embodiments, preferential expression of, or preferential growth of microorganisms utilizing certain metabolic pathways, enables the high efficiency PHA production from carbon-containing gases or materials. Several embodiments relate to the microorganism cultures, and/or microorganisms isolated therefrom.
1. A method for enhancing polyhydroxyalkanoate (PHA) production in a methanotrophic culture by reducing copper concentrations to effect particulate methane monooxygenase (pMMO) production, the method comprising:
(a) contacting a culture of methanotrophic microorganisms with a medium comprising copper, one or more additional nutrients, and a carbon-containing gas that can be metabolized by said culture;
(b) incubating said culture in said medium to cause growth of said culture; and
(c) inducing a selection pressure on said culture to transform said culture into a culture that generates PHA preferentially through particulate methane monooxygenase (pMMO) by:
(i) reducing the concentration of copper in said medium to cause production of soluble methane monooxygenase (sMMO) and/or pMMO by said culture, wherein said concentration of copper causes the production of sMMO in some methanotrophic microorganisms;
(ii) reducing the concentration of one or more of said nutrients in said medium to cause said culture to generate PHA from said carbon-containing gas using said soluble methane monooxygenase (sMMO) or said pMMO,
wherein PHA is generated by pMMO at a greater rate as compared to sMMO,
(iii) returning the culture to the growth conditions of step (b),
wherein microorganisms having higher intracellular concentrations of pMMO and PHA grow at a greater rate as compared to those with lower intracellular pMMO and PHA concentrations; and
(iv) repeating steps (i), (ii) and (iii), wherein said repetitions selectively favor growth of microorganisms that produce PHA via pMMO, thereby facilitating the pMMO-mediated production of PHA at reduced copper concentrations, and resulting in a culture comprising microorganisms that use pMMO to produce PHA.
2. The method of claim 1 , wherein said culturing is performed under non-sterile conditions.
3. The method of claim 1 , wherein said intracellular PHA concentrations are least 71% of total dry cell weight of said methanotrophic microorganisms.
4. The method of claim 1 , wherein said one or more nutrients comprises at least one of the nutrients selected from the group consisting of aluminum, boron, calcium, carbon, carbon dioxide, cobalt, iron, magnesium, molybdenum, nitrogen, oxygen, phosphorus, potassium, sodium, and zinc.
5. The method of claim 1 , wherein said copper concentration is controlled to be between about 0.001 micromolar and about 1000 micromolar.
6. The method of claim 1 , wherein one or more of said additional nutrients comprises dissolved oxygen and wherein the method further comprises increasing the concentration of dissolved oxygen in said culture media to preferentially select for methanotrophic microorganisms exhibiting reduced pigmentation.
7. The method of claim 1 , wherein at least a portion of said PHA-producing methanotrophic microorganisms of step (c) do not (i) possess the gene encoding for sMMO, (ii) express a functional sMMO or (iii) express the gene encoding sMMO.
8. The method of claim 1 , wherein said culture of methanotrophic microorganisms comprises microorganisms of a genus selected from a group consisting of: Methylosinus, Methylocystis, Methylococcus, Methylobacterium , and Pseudomonas.
9. The method of claim 1 , wherein said intracellular PHA is produced at concentrations having a ratio of PHA to non-PHA biomass exceeding 3:1 on a dry weight basis.
10. The method of claim 1 , wherein said copper concentration is between about 0.001 micromolar and about 1000 micromolar, and
wherein said intracellular PHA is produced at concentrations having a ratio of PHA to non-PHA biomass exceeding 3:1 on a dry weight basis.
11. The method of claim 1 , wherein said copper concentration is between about 0.001 micromolar and about 1000 micromolar,
wherein the microorganisms exhibit ethylmalonyl-CoA pathway activity at copper concentrations between about 0.001 micromolar and about 1000 micromolar,
wherein said microorganisms exhibit pMMO activity at copper concentrations between about 0.001 micromolar and about 1000 micromolar, and
wherein the intracellular PHA is produced at concentrations having a ratio of PHA to non-PHA biomass exceeding 3:1 on a dry weight basis.
12. The method of claim 1 , further comprising extracting the produced intracellular PHA.
13. The method of claim 12 , wherein the extracting comprises a solvent extraction of the intracellular PHA from the microorganisms..