Open AccessEnhancing photo‐catalytic production of organic acids in the cyanobacterium S ynechocystis sp. PCC 6803 Δ glg C , a strain incapable of glycogen storage
Author(s) -
Carrieri Damian,
Broadbent Charlie,
Carruth David,
Paddock Troy,
Ungerer Justin,
Maness PinChing,
Ghirardi Maria,
Yu Jianping
Publication year - 2015
Publication title -
microbial biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.287
H-Index - 74
ISSN - 1751-7915
DOI - 10.1111/1751-7915.12243
Subject(s) - photosynthesis , chemistry , cyanobacteria , bacteria , biomass (ecology) , biochemistry , metabolism , yeast , catalysis , chlamydomonas reinhardtii , food science , biology , ecology , genetics , mutant , gene
Summary 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 S ynechocystis sp. PCC 6803 Δ glgC strain incapable of glycogen storage. When deprived of nitrogen, the Δ glgC 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.