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Bio-based photosynthetic conversion of CO2 and water to replace petroleum feedstock on an industrial scale

National Renewable Energy Laboratory

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Technology Marketing Summary

Alpha-ketoglutarate (AKG) is widely used as an organic synthesis intermediate, a medical and biochemical reagent, and as a nutritional additive in food and sports drinks.  Typically, it is produced from a derivative of petroleum and concentrated hydrochloric acid.  However, the rising cost of petroleum has led to the exploration and development of alternative, biological production systems for fuels and chemicals.  Recently, a number of organizations have successfully applied closed-loop photobioreactors to the production of hydrocarbon feedstocks.  One such system developed at NREL utilizes the freshwater photosynthetic cyanobacterium, Synechosystis, to produce AKG in an environmentally friendly and sustainable process on an industrial scale.


Through metabolic engineering of a strain of Synechocystis, a gene delete mutant was derived that shows robust growth similar to the wild-type under standard laboratory conditions.  However, metabolite distribution is altered in this mutant.  In addition to genetic modification, the distribution can be manipulated by changing growth conditions.  Under specific conditions the mutant produces high levels of the AKG, about 30% of cell dry weight, which is on the order of 10,000-fold increase from the wild type. The production of AKG has been identified and quantified by three independent techniques: GC/MS, H+-NMR, and HPLC.

The extrapolated photosynthetic production rate of the intermediate is at least 150 grams per day per 1,000L reactor at a cell density of 1 gram dry weight per liter. This genetically engineered cyanobacterial strain has potential application for the production of the AKG in a continuous "milking" (verses batch culture) process, which improves energy conversion efficiency and reduces operational cost.  The principle established in this innovation can be applied to other cyanobacteria and algae for similar production.

  • Environmentally friendly and sustainable process
  • Milking process reduces operation cost and increases energy conversion efficiency
Applications and Industries
  • Medical and biochemical reagents
  • Nutritional additives
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 9,309,541
Biological production of organic compounds
Strains of cyanobacteria that produce high levels of alpha ketoglutarate (AKG) and pyruvate are disclosed herein. Methods of culturing these cyanobacteria to produce AKG or pyruvate and recover AKG or pyruvate from the culture are also described herein. Nucleic acid sequences encoding polypeptides that function as ethylene-forming enzymes and their use in the production of ethylene are further disclosed herein. These nucleic acids may be expressed in hosts such as cyanobacteria, which in turn may be cultured to produce ethylene.
National Renewable Energy Laboratory 04/12/2016
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
11-18Development - Bench-scale production and testing of various growth conditions to improve production rates.Available - Available for licensing and currently seeking sponsored research opportunities.08/24/201108/24/2011

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To: Eric Payne<>