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Exploration of the hydrogen producing potential of Rhodobacter capsulatus chemostat cultures: The application of deceleration‐stat and gradient‐stat methodology
Author(s) -
Hoekema Sebastiaan,
van Breukelen Frank R.,
Janssen Marcel,
Tramper Johannes,
Wijffels René H.
Publication year - 2009
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1002/btpr.196
Subject(s) - chemostat , dilution , rhodobacter , biomass (ecology) , hydrogen production , hydrogen , light intensity , chemistry , reaction rate constant , analytical chemistry (journal) , chromatography , biochemistry , thermodynamics , biology , physics , kinetics , ecology , organic chemistry , optics , bacteria , genetics , quantum mechanics , mutant , gene
In this work, the dependency of the volumetric hydrogen production rate of ammonium‐limited Rhodobacter capsulatus chemostat cultures on their imposed biomass concentration and dilution rate was investigated. A deceleration‐stat experiment was performed by lowering the dilution rate from 1.0 d −1 to zero aimed at a constant biomass concentration of 4.0 g L −1 at constant incident light intensity. The results displayed a maximal volumetric hydrogen production rate of 0.6 mmol m −3 s −1 , well below model predictions. Possibly the high cell density limited the average light availability, resulting in a sub‐optimal specific hydrogen production rate. To investigate this hypothesis, a gradient‐stat experiment was conducted at constant dilution rate of 0.4 d −1 at constant incident light intensity. The biomass concentration was increased from 0.7 to 4.0 g L −1 by increasing the influent ammonium concentration. Up to a biomass concentration of 1.5 g L −1 , the volumetric hydrogen production rate of the system increased according to model predictions, after which it started to decline. The results obtained provide strong evidence that the observed decline in volumetric hydrogen production rate at higher biomass concentrations was at least partly caused by a decrease in light availability. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009