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Response coefficient analysis of a fed-batch bioreactor to dissolved oxygen perturbation in complementary cultures during PHB production

DIR@IMTECH: CSIR-Institute of Microbial Technology

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Title Response coefficient analysis of a fed-batch bioreactor to dissolved oxygen perturbation in complementary cultures during PHB production
 
Creator Patnaik, Pratap R
 
Subject QD Chemistry
 
Description Background: Although the production of poly-β-hydroxybutyrate (PHB) has many biological,
energetic and environmental advantages over chemically synthesized polymers, synthetic polymers
continue to be produced industrially since the productivities of fermentation processes fr PHB are
not yet economically competitive. Improvement of a PHB fermentation requires good
understanding and optimization under the realistic conditions of large bioreactors.
Laboratory-scale studies have shown that co-cultures of Ralstonia eutropha and Lactobacillus
delbrueckii generate better fermentation efficiencies than R. eutropha alone. In large bioreactors,
incomplete dispersioin and perturbations in the dissolved oxygen (DO) concentration, both of
which affect the fermentation, have to be considered. This study analyzes the effect of DO
fluctuations on bioreactor performance for both ideal and optimally dispersed broths.
Results: Response coefficient analysis was employed to obtain quantitative information on the
effect of DO perturbations on different variables. Three values of the Peclet number (Pe)
cheracterized three levels of dispersion: Pe = 0.01 for nearly complete dispersion, Pe = 20 for
optimum dispersion and Pe = 60 for insufficient dispersion. The response coefficients (RCs) of the
pairs of bacterial concentrations and the main substrates, glucose and ammonium chloride, showed
contrasting variations with time. Lactate, a critical intermediate, and PHB had similar RC profiles
but those of lactate were one to two orders of magnitude larger than other RCs. Significantly, the
optimum Pe also resulted in the largest RCs, suggesting a balance between productivity and reactor
stability.
Conclusion: Since R. eutropha requires oxygen for its growth whereas L. delbrueckii does not,
fluctuations in the DO concentartion have a strong influence on the fermentation. Apart from this,
the mechanism of PHB biosynthesis indicates that control of lactate is a critical determinant of
fermentation efficiency. The RC profiles indicate that, under non-ideal conditions, a compromise
may be required between PHB formation and reactor stability, especially in the latter half of the
process.
 
Publisher Biomedcentral
 
Date 2008
 
Type Article
PeerReviewed
 
Format application/pdf
 
Identifier http://crdd.osdd.net/open/1069/1/patnaik2008.pdf
Patnaik, Pratap R (2008) Response coefficient analysis of a fed-batch bioreactor to dissolved oxygen perturbation in complementary cultures during PHB production. Journal of Biological Engineering, 2 (1). p. 4. ISSN 1754-1611
 
Relation http://dx.doi.org/10.1186/1754-1611-2-4
http://crdd.osdd.net/open/1069/