Cyanobacteria having improved photosynthetic activity
Inventors
Roberts, James • Carleton, Michael • CARRIERI, Damian • Hickman, Jason W.
Assignees
Publication Number
US-10563168-B2
Publication Date
2020-02-18
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
The invention demonstrates that photosynthetic microorganisms, specifically Cyanobacteria, can be genetically modified to reduce expression or accumulation of light harvesting proteins (LHP), resulting in unexpectedly increased photosynthetic activity. This modification is achieved through disrupting or deleting one or more genes associated with LHP biosynthesis, storage, or transport, such as nblA, rpaB, pbsB, pbsC, or phycobiliprotein genes, either individually or in combination.
The problem addressed is the low efficiency and manipulability of existing oil-producing organisms, such as algae, which are difficult to genetically modify and yield lower amounts of desirable oils like triglycerides in culture compared to their natural environments. In contrast, Cyanobacteria are genetically tractable and can be engineered to overcome these limitations, but their photosynthetic capacity is easily saturated due to excessive LHPs.
Through genetic modifications that reduce LHPs, including approaches like gene deletions, promoter replacements, or introduction of antisense sequences, the modified Cyanobacteria exhibit enhanced growth rates, biomass accumulation, and oxygen evolution compared to wild-type strains. The invention also encompasses methods of generating such Cyanobacteria using stress conditions (e.g., high light or metronidazole), and further includes modifications for production of carbon-containing compounds such as fatty acids and triglycerides by introducing or overexpressing genes encoding lipid biosynthesis enzymes.
Claims Coverage
The patent claims cover two primary inventive features relating to genetically modifying Cyanobacteria for increased biomass and photosynthetic activity.
Genetic disruption or deletion of light harvesting protein genes in Cyanobacteria to enhance photosynthetic activity and biomass
This feature claims a method that includes: - Providing a Cyanobacteria population genetically modified by mutating to disrupt or delete one or more genes encoding light harvesting proteins. - Growing the modified Cyanobacteria to obtain a culture. - Culturing the Cyanobacteria culture under light intensities between about 200 micromol photons per square meter per second and about 1000 micromol photons per square meter per second. - The result is a Cyanobacteria culture with increased photosynthetic activity and enhanced biomass accumulation compared to an unmodified control population.
Genetic deletion of phycobilisome or phycobiliprotein genes in Cyanobacteria to increase biomass under specified light conditions
This feature claims a method involving: - Providing a Cyanobacteria population genetically modified to delete a phycobilisome gene, which may specifically be a phycobiliprotein gene such as a phycocyanin gene. - Growing the modified population to obtain a culture. - Culturing under light intensities between about 200 and 1000 micromol photons per square meter per second. - The genetically modified Cyanobacteria demonstrates increased photosynthetic activity and biomass in comparison to unmodified Cyanobacteria.
The claims establish methods for increasing Cyanobacterial biomass and photosynthetic activity through targeted genetic modifications that reduce or delete light harvesting proteins, focusing especially on disruption of phycobilisome genes and application of specified light conditions.
Stated Advantages
The modified Cyanobacteria exhibit increased photosynthetic activity compared to wild type, resulting in improved growth rates, greater oxygen evolution, and higher biomass accumulation.
Genetic modification enables more efficient and flexible manipulation of Cyanobacteria for oil (e.g., triglyceride) production relative to algae, overcoming limitations of genetic intractability and low yield in traditional organisms.
Enhanced production of carbon-containing compounds, such as fatty acids and triglycerides, from minimal inputs (sunlight, water, CO2, simple nutrients) using modified Cyanobacteria.
Documented Applications
Use of modified Cyanobacteria as a feedstock in the production of biofuels, including biodiesel derived from triglycerides produced by the microorganisms.
Production of specialty chemicals, such as glycerin, from carbon-containing compounds synthesized by the modified Cyanobacteria.
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