Polyhydroxyalkanoate production from polyols
Organisms are provided which express enzymes such as glycerol dehydratase, diol dehydratase, acyl-CoA transferase, acyl-CoA synthetase β-ketothiolase, acetoacetyl-CoA reductase, PHA synthase, glycerol-3-phosphate dehydrogenase and glycerol-3-phosphatase, which are useful for the production of PHAs. In some cases one or more of these genes are native to the host organism and the remainder are provided from transgenes. These organisms produce poly(3-hydroxyalkanoate) homopolymers or co-polymers incorporating 3-hydroxypropionate or 3-hydroxyvalerate monomers wherein the 3-hydroxypropionate and 3-hydroxyvalreate units are derived from the enzyme catalysed conversion of diols. Suitable diols that can be used include 1,2-propanediol, 1,3 propanediol and glycerol. Biochemical pathways for obtaining the glycerol from normal cellular metabolites are also described. The PHA polymers are readily recovered and industrially useful as polymers or as starting materials for a range of chemical intermediates including 1,3-propanediol, 3-hydroxypropionaldehyde, acrylics, malonic acid, esters and amines.
1. A method for producing poly-3-hydroxypropionate by bacterial fermentation, the method comprising
a) providing bacteria genetically engineered to express a gene encoding a glycerol dehydrogenase or aldehyde dehydrogenase in an effective amount to produce 3-hydroxypropionic acid when provided with glucose or glycerol, wherein the bacteria can convert the 3-hydroxypropionic acid to 3-hydroxypropionyl-CoA, and then polymerize the 3-hydroxypropionyl-CoA to poly-3-hydroxypropionate,
b) providing a substrate containing glucose or glycerol to the bacteria, and
c) culturing the bacteria under conditions wherein 3-hydroxypropionic acid is converted to 3-hydroxypropionyl-CoA, which is then polymerized to poly-3-hydroxypropionate.
2. The method of claim 1 wherein the bacteria is Escherichia coli.
3. Bacteria genetically engineered to express a gene encoding an aldehyde dehydrogenase which can produce 3-hydroxypropionic acid from 3-hydroxypropionaldehyde when provided with glucose or glycerol.
4. The bacteria of claim 3 , where the bacteria is Escherichia coli.
5. A system for making polyhydroxyalkanoates comprising a bacteria genetically engineered to express a gene encoding aldehyde dehydrogenase which can produce 3-hydroxypropionic acid when provided with glucose or glycerol, wherein the bacteria express enzymes to convert the 3-hydroxypropionic acid to 3-hydroxypropionyl-CoA, and polymerize the 3-hydroxypropionyl-CoA to poly-3-hydroxypropionate.
6. The system of claim 5 , where the bacteria is Escherichia coli.
7. The method of claim 1 wherein the bacteria is genetically engineered to express genes encoding a glycerol dehydrogenase and an aldehyde dehydrogenase.
8. The method of claim 1 wherein the bacteria is genetically engineered to express a gene encoding an aldehyde dehydrogenase.
9. The bacteria of claim 3 wherein the bacteria is genetically engineered to express genes encoding a glycerol dehydrogenase and an aldehyde dehydrogenase.
10. The bacteria of claim 3 wherein the bacteria is genetically engineered to express a gene encoding an aldehyde dehydrogenase.