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 low energy method for polyhydroxyalkanoate (PHA) production in a methanotrophic culture, 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;
(c) 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,
(d) 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;
wherein PHA is preferentially generated by pMMO,
(e) 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
(f) repeating steps (c), (d) and (e), 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; wherein
the energy required to carry out the process is reduced as compared to other carbon based PHA production methods.
2. The method of claim 1 , wherein each subsequent repetition of steps (c), (d), (e), (f) and (g) results in said culture producing progressively less sMMO and progressively more pMMO.
3. The method of claim 1 , wherein the culture of methanotrophic microorganisms characterized by:
(a) lack of the genetic material encoding soluble methane monooxygenase (sMMO), failure to transcribe DNA encoding sMMO or translate mRNA encoding sMMO, and/or failure to produce a functional sMMO enzyme;
(b) having the genetic material encoding the ethylmalonyl-CoA pathway, transcribing DNA encoding the ethylmalonyl-CoA pathway, and translating mRNA encoding the ethylmalonyl-CoA pathway; and
(c) the capability of producing polyhydroxyalkanoate (PHA) at intracellular PHA concentrations with a ratio of PHA to non-PHA biomass exceeding 3:1 on a dry weight basis.
4. The method of claim 1 , wherein at least a portion of said PHA-producing methanotrophic microorganisms of step (g) do not (i) possess the gene encoding for sMMO, (ii) express a functional sMMO or (iii) express the gene encoding sMMO.
5. 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.
6. The method of claim 1 , wherein said culturing is performed under non-sterile conditions.
7. The method of claim 1 , wherein the one or more additional nutrients comprise carbon, oxygen, magnesium, phosphorus, phosphate, potassium, sulfate, sulfur, calcium, boron, aluminum, chromium, cobalt, iron, nickel, manganese, molybdenum, sodium, nitrogen, nitrate, ammonia, ammonium, urea, amino acids, methane, carbon dioxide, and/or hydrogen.
8. The method of claim 1 , wherein the one or more essential nutrients comprises dissolved oxygen.
9. The method of claim 8 , wherein the dissolved oxygen is present at a concentration of between about 0.00-1.0 ppm.
10. The method of claim 1 , wherein the one or more additional nutrients comprises nitrogen.
11. The method of claim 10 , wherein the nitrogen is present at a concentration of between about 0.01 ppm and 50 ppm.
12. The method of claim 1 , further comprising extracting said generated PHA.
13. The method of claim 1 , wherein said generated PHA comprise at least 71% of total dry cell weight of said methanotrophic microorganisms.
14. The method of claim 1 , wherein said generated PHA is generated at concentrations having a ratio of PHA to non-PHA biomass exceeding 3:1 on a dry weight basis.