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Rhythm of Carbon and Nitrogen Fixation in Unicellular Cyanobacteria Under Turbulent and Highly Aerobic Conditions

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Title Rhythm of Carbon and Nitrogen Fixation in Unicellular Cyanobacteria Under Turbulent and Highly Aerobic Conditions
 
Creator KRISHNAKUMAR, S
GAUDANA, SB
VISWANATHAN, GA
PAKRASI, HB
WANGIKAR, PP
 
Subject cyanobacteria
nitrogen fixation
Cyanothece
flashing light
K(L)a
Reynolds number
RIFAMYCIN-B FERMENTATION
LIGHT-GROWN CULTURES
SP STRAIN ATCC-51142
TRANSLATIONAL REGULATION
BATCH FERMENTATION
FLASHING LIGHT
PHASE-SHIFTS
ATCC 51142
CYANOTHECE
ONLINE
 
Description Nitrogen fixing cyanobacteria are being increasingly explored for nitrogenase-dependent hydrogen production. Commercial success however will depend on the ability to grow these cultures at high cell densities. Photo-limitation at high cell densities leads to hindered photoautotrophic growth while turbulent conditions, which simulate flashing light effect, can lead to oxygen toxicity to the nitrogenase enzyme. Cyanothece sp. strain ATCC 51142, a known hydrogen producer, is reported to grow and fix nitrogen under moderately oxic conditions in shake flasks. In this study, we explore the growth and nitrogen fixing potential of this organism under turbulent conditions with volumetric oxygen mass transfer coefficient (K(L)a) values that are up to 20-times greater than in shake flasks. In a stirred vessel, the organism grows well in turbulent regime possibly due to a simulated flashing light effect with optimal growth at Reynolds number of approximately 35,000. A respiratory burst lasting for about 4h creates anoxic conditions intracellularly with near saturating levels of dissolved oxygen in the extracellular medium. This is concomitant with complete exhaustion of intracellular glycogen storage and upregulation of nifH and nifX, the genes encoding proteins of the nitrogenase complex. Further, the rhythmic oscillations in exhaust gas CO2 and O-2 profiles synchronize faithfully with those in biochemical parameters and gene expression thereby serving as an effective online monitoring tool. These results will have important implications in potential commercial success of nitrogenase-dependent hydrogen production by cyanobacteria. Biotechnol. Bioeng. 2013; 110:2371-2379. (c) 2013 Wiley Periodicals, Inc.
 
Publisher WILEY-BLACKWELL
 
Date 2014-10-16T06:00:38Z
2014-10-16T06:00:38Z
2013
 
Type Article
 
Identifier BIOTECHNOLOGY AND BIOENGINEERING, 110(9)2371-2379
0006-3592
1097-0290
http://dx.doi.org/10.1002/bit.24882
http://dspace.library.iitb.ac.in/jspui/handle/100/15401
 
Language en