Molecular switches
Genetically modified microorganisms that have the ability to convert carbon substrates into chemical products such as 2,3-BDO; 1,4-BDO; isobutyraldehyde; isobutanol; 1-butanol; n-butanol; ethanol; fatty alcohols; and fatty acid methyl ester are disclosed. For example, genetically modified methanotrophs that are capable of generating 2,3-BDO; 1,4-BDO; isobutyraldehyde; isobutanol; 1-butanol; n-butanol; ethanol; fatty alcohols; and fatty acid methyl ester at high titers from a methane source are disclosed. Methods of making these genetically modified microorganisms and methods of using them are also disclosed. These microorganisms and methods make use of molecular switches to regulate gene expression.
1. A vector comprising:
(a) genes encoding the following polypeptides: (i) an acetolactate synthase comprising an amino acid sequence that is at least 90% identical to SEQ ID NO: 1; (ii) an alpha-acetolactate decarboxylase comprising an amino acid sequence that is at least 90% identical to SEQ ID NO: 9; and (iii) an acetoin reductase comprising an amino acid sequence that is at least 90% identical to SEQ ID NO: 11; and
(b) a promoter driving the expression of such genes, the promoter being pMxAF or pXoxF.
2. The vector of claim 1 , wherein the genes encode the following polypeptides: an acetolactate synthase comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 1; an alpha-acetolactate decarboxylase comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 9; and an acetoin reductase comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 11.
3. A method of making a genetically modified methanotroph capable of converting a C1 carbon to a multicarbon product, the method comprising transforming a methanotroph with the vector of claim 1 , wherein the methanotroph is selected from the genera Methylobacter, Methylomicrobium, Methylomonas, Methylocaldum, Methylococcus, Methylosoma, Methylosarcina, Methylothermus, Methylohalobius, Methylogaea, Methylovulum, Crenothrix, Clonothrix, Methylosphaera, Methylocapsa, Methylocella, Methylosinus, Methylocystis , or Methyloacidophilum.
4. A method of making a multicarbon product, the method comprising:
a) contacting a methanotroph with the vector of claim 1 , thereby generating a genetically-modified methanothroph; and
b) growing the genetically-modified methanotroph to produce the multicarbon product;
wherein the methanotroph is selected from the genera Methylobacter, Methylomicrobium, Methylomonas, Methylocaldum, Methylococcus, Methylosoma, Methylosarcina, Methylothermus, Methylohalobius, Methylogaea, Methylovulum, Crenothrix, Clonothrix, Methylosphaera, Methylocapsa, Methylocella, Methylosinus, Methylocystis , or Methyloacidophilum.
5. The method of claim 4 , wherein the multicarbon product is 2,3-butanediol.
6. The method of claim 4 , further comprising contacting the multicarbon product with a SiO 2 -supported cesium dihydrogen phosphate (CsH 2 PO 4 ) catalyst to produce a second multicarbon product.
7. The method of claim 4 , wherein step a) further comprises contacting the genetically-modified methanotroph with media comprising a rare earth metal that can activate or repress the promoter.
8. The method of claim 7 , wherein the rare earth metal is lanthanum.
9. The method of claim 8 , wherein the lanthanum is present at a concentration of at least 0.5 μM.
10. The vector of claim 2 , wherein:
(a) the acetolactate synthase comprises an amino acid sequence that is at least 98% identical to SEQ ID NO: 1; (b) the alpha-acetolactate decarboxylase comprises an amino acid sequence that is at least 98% identical to SEQ ID NO: 9; and (c) the acetoin reductase comprises an amino acid sequence that is at least 98% identical to SEQ ID NO: 11.
11. The method of claim 3 , wherein the methanotroph is from the species Methylococcus capsulatus.
12. The method of claim 4 , wherein the methanotroph is from the species Methylococcus capsulatus.
13. The vector of claim 2 , wherein:
(a) the acetolactate synthase comprises the amino acid sequence of SEQ ID NO: 1; (b) the alpha-acetolactate decarboxylase comprises the amino acid sequence of SEQ ID NO: 9; and (c) the acetoin reductase comprises the amino acid sequence of SEQ ID NO: 11.