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Title: Enhancing photo-catalytic production of organic acids in the cyanobacterium S ynechocystis sp. PCC 6803 Δ glg C , a strain incapable of glycogen storage

We describe how a key objective in microbial biofuels strain development is to maximize carbon flux to target products while minimizing cell biomass accumulation, such that ideally the algae and bacteria would operate in a photo-catalytic state. A brief period of such a physiological state has recently been demonstrated in the cyanobacterium Synechocystis sp. PCC 6803 ΔglgC strain incapable of glycogen storage. When deprived of nitrogen, the ΔglgC excretes the organic acids alpha-ketoglutarate and pyruvate for a number of days without increasing cell biomass. This study examines the relationship between the growth state and the photo-catalytic state, and characterizes the metabolic adaptability of the photo-catalytic state to increasing light intensity. It is found that the culture can transition naturally from the growth state into the photo-catalytic state when provided with limited nitrogen supply during the growth phase. Photosynthetic capacity and pigments are lost over time in the photo-catalytic state. Reversal to growth state is observed with re-addition of nitrogen nutrient, accompanied by restoration of photosynthetic capacity and pigment levels in the cells. While the overall productivity increased under high light conditions, the ratio of alpha-ketoglutarate/pyruvate is altered, suggesting that carbon partition between the two products is adaptable to environmental conditions.
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  1. National Renewable Energy Lab. (NREL), Golden, CO (United States). Biosciences Center
Publication Date:
Report Number(s):
Journal ID: ISSN 1751-7915
Grant/Contract Number:
Published Article
Journal Name:
Microbial Biotechnology (Online)
Additional Journal Information:
Journal Name: Microbial Biotechnology (Online); Journal Volume: 8; Journal Issue: 2; Journal ID: ISSN 1751-7915
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F)
Country of Publication:
United States
09 BIOMASS FUELS; Synechocystis sp.; photo-catalysis, organic acids
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1220612; OSTI ID: 1345699