Modified photosynthetic microorganisms with reduced glycogen and their use in producing carbon-based products
Inventors
Roberts, James • Cross, Fred • Warrener, Paul • Kotovic, Kimberly Marie • McCormick, Margaret Mary
Assignees
Publication Number
US-8835137-B2
Publication Date
2014-09-16
Expiration Date
2029-12-22
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Abstract
This disclosure describes genetically modified photosynthetic microorganisms, including Cyanobacteria, that contain one or more mutations or deletions in a glycogen biosynthesis or storage pathway, which accumulate a reduced amount of glycogen as compared to a wild type Cyanobacterium, and which are capable of producing an increased amount of lipids and/or fatty acids. In certain embodiments, the genetically modified photosynthetic microorganisms also contain one or more exogenous genes encoding a diacyglycerol acyltransferase, a phosphatidate phosphatase, and/or an acetyl-CoA carboxylase, and which are capable of producing increased amounts of lipids or fatty acids and/or synthesizing triglycerides.
Core Innovation
The invention provides genetically modified photosynthetic microorganisms, particularly Cyanobacteria, that contain one or more mutations or deletions in the glycogen biosynthesis or storage pathway. These modifications result in the accumulation of a reduced amount of glycogen compared to wild type Cyanobacteria and enable the microorganisms to produce increased amounts of lipids and/or fatty acids.
In certain embodiments, these genetically modified photosynthetic microorganisms also contain one or more introduced genes encoding diacylglycerol acyltransferase (DGAT), phosphatidate phosphatase, and/or acetyl-CoA carboxylase, which enable them to synthesize triglycerides. The modifications achieved by disabling the glycogen biosynthesis or storage pathway, along with the introduction of lipid or triglyceride biosynthesis genes, divert carbon flow from glycogen production to enhanced synthesis of lipids, fatty acids, and triglycerides.
The problem addressed is the inability of Cyanobacteria to produce triglycerides, as they normally lack the enzymes required for triglyceride synthesis and instead store carbon primarily as glycogen. The invention overcomes this limitation by enabling the production of triglycerides and fatty acids in Cyanobacteria, which can be used as feedstock for biofuels and specialty chemicals.
Claims Coverage
The patent contains three independent claims, each introducing a distinct inventive feature related to genetically modified photosynthetic microorganisms and their use.
Genetically modified photosynthetic microorganism with glgC mutation and DGAT expression
A photosynthetic microorganism, specifically a Cyanobacterium, that has reduced expression, reduced activity, or mutation of a glucose-1-phosphate adenyltransferase (glgC) gene, such as by one or more mutations or a complete or partial gene deletion. The microorganism further comprises one or more introduced polynucleotides encoding diacylglycerol acyltransferase (DGAT). As a result, this microorganism accumulates a reduced amount of glycogen and an increased amount of triglycerides, wax esters, or both, compared to a photosynthetic microorganism having only the DGAT expressed without the glgC mutation.
Method for producing a modified photosynthetic microorganism with glgC mutation and DGAT expression
A method comprising modifying a photosynthetic microorganism to have reduced expression, reduced activity, or a mutation in the endogenous glgC gene (by introducing one or more mutations or complete or partial deletions) and further modifying the microorganism to include one or more introduced polynucleotides encoding DGAT. The method results in a Cyanobacterium that accumulates increased triglycerides, wax esters, or both, relative to a microorganism expressing DGAT but without the glgC gene modification.
Method for producing triglyceride or wax ester using modified photosynthetic microorganism
A method comprising cultivating a genetically modified photosynthetic microorganism in suitable media, where the microorganism has reduced expression, reduced activity, or a mutated glgC gene (with one or more mutations or deletions), and comprises one or more introduced polynucleotides encoding DGAT. The cultivated microorganism accumulates an increased amount of triglycerides, wax esters, or both, compared to a microorganism with only the DGAT introduced.
Together, these inventive features protect photosynthetic microorganisms genetically engineered to have diminished glycogen biosynthesis via glgC modification and enhanced lipid, fatty acid, and triglyceride production by introduction of DGAT, methods for producing such organisms, and their use for producing triglycerides and wax esters.
Stated Advantages
Enables genetically modified Cyanobacteria to produce and accumulate increased amounts of triglycerides and fatty acids compared to wild type organisms.
Provides a photosynthetic microorganism capable of serving as an efficient feedstock for the production of biofuels and specialty chemicals.
Allows for production of large amounts of triglycerides from minimal energy and nutrient input using sunlight, water, air, and inorganic nutrients.
Diverts carbon flow from glycogen production to lipid and fatty acid biosynthesis by disabling the glycogen storage pathway.
Documented Applications
Production of triglycerides and fatty acids to serve as feedstock for biofuels and specialty chemicals.
Production of biofuels such as biodiesel from the triglycerides synthesized by the modified Cyanobacteria.
Production of specialty chemicals, including glycerin, derived from triglyceride conversion.
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