Cyanobacteria having improved photosynthetic activity
Inventors
Roberts, James • Carleton, Michael • CARRIERI, Damian • Hickman, Jason W.
Assignees
Publication Number
US-10760045-B2
Publication Date
2020-09-01
Expiration Date
2034-03-10
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Abstract
This disclosure describes modified photosynthetic microorganisms, including Cyanobacteria, that have a reduced amount of a light harvesting protein (LHP) and contain one or more introduced or overexpressed polynucleotides encoding one or more enzymes associated with lipid biosynthesis, and which are capable of producing increased amounts of fatty acids and/or synthesizing triglycerides.
Core Innovation
Embodiments of the invention are directed to genetically modified photosynthetic microorganisms, including Cyanobacteria, that have reduced levels of light harvesting proteins (LHP) and contain one or more introduced or overexpressed polynucleotides encoding enzymes associated with lipid biosynthesis. These modified Cyanobacteria are capable of producing increased amounts of fatty acids and/or synthesizing triglycerides compared to wild-type Cyanobacteria.
The patent addresses the problem that while certain photosynthetic microorganisms like algae can produce triglycerides for biofuel feedstocks, algae are difficult to genetically manipulate and tend to produce less oil under culture conditions than in the wild. In contrast, Cyanobacteria are genetically manipulable but naturally accumulate only modest levels of fatty acids. Additionally, the light harvesting proteins in Cyanobacteria are efficient but quickly become saturated, which limits photosynthetic efficiency and cell productivity under high light conditions.
The core of the invention involves mutating, disrupting, or deleting one or more genes encoding light harvesting proteins and introducing exogenous genes encoding desired polypeptides, such as enzymes for enhanced lipid biosynthesis. Methods further specify culturing these modified Cyanobacteria under specified light intensities, particularly between about 200 and 1000 micromol photons per square meter per second, leading to increased photosynthetic activity, improved growth, and increased biomass yield relative to unmodified cells. The modifications include, for example, reduction in phycobilisome- or phycobiliprotein-related genes and addition of nucleic acids for production of target polypeptides, enabling improved efficiency in the production of valuable bioproducts.
Claims Coverage
There are two independent claims in this patent, each introducing distinct inventive features covering genetically modified Cyanobacteria cultures and an associated production method.
Genetically modified Cyanobacteria population with LHP gene disruption and exogenous gene expression
A Cyanobacteria cell culture comprising a population of Cyanobacteria cells that: - Are genetically modified by mutation to disrupt or delete one or more genes encoding one or more light harvesting proteins. - Comprise a nucleic acid sequence that includes an exogenous gene encoding an exogenous polypeptide. - When cultured under light intensities between about 200 micromol photons per square meter per second and about 1000 micromol photons per square meter per second, the cell population expresses the exogenous polypeptide.
Method of producing exogenous polypeptides in genetically modified Cyanobacteria with LHP gene disruption
A method for producing an exogenous polypeptide in a Cyanobacteria culture, comprising: 1. Providing a modified Cyanobacteria cell population where cells are: - Mutated to disrupt or delete one or more genes encoding one or more light harvesting proteins. - Comprising a nucleic acid sequence with an exogenous gene encoding an exogenous polypeptide. 2. Growing the modified Cyanobacteria cell population under light intensities between about 200 and about 1000 micromol photons per square meter per second to obtain a Cyanobacteria culture. 3. Wherein the Cyanobacteria population expresses the exogenous polypeptide.
The inventive features center on Cyanobacteria modified by disruption of light harvesting protein genes and engineered to express exogenous polypeptides, along with methods for culturing such cells under specified light intensities to produce these polypeptides.
Stated Advantages
The modified Cyanobacteria have increased photosynthetic activity compared to wild-type Cyanobacteria.
The modified Cyanobacteria can be cultured to produce increased biomass and yield of carbon-containing compounds such as lipids and triglycerides.
The genetically manipulable Cyanobacteria overcome the limitation of low oil production observed with algae under culture conditions.
The invention enables efficient production of exogenous polypeptides in Cyanobacteria under specified light conditions.
The modified strains are capable of faster growth and division compared to corresponding wild-type strains.
Documented Applications
Production of increased amounts of fatty acids and/or synthesis of triglycerides using modified Cyanobacteria as feedstock for biofuels.
Production of exogenous polypeptides, including therapeutic polypeptides, in genetically modified Cyanobacteria.
Use of modified Cyanobacteria in cultures grown under light intensities between about 200 and 1000 micromol photons per square meter per second for large-scale biomass generation.
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