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Growth and accumulation dynamics of poly(3‐hydroxyalkanoate) (PHA) in Pseudomonas putida GPo1 cultivated in continuous culture under transient feed conditions
Author(s) -
Zinn Manfred,
Durner Roland,
Zinn Hanspeter,
Ren Qun,
Egli Thomas,
Witholt Bernard
Publication year - 2011
Publication title -
biotechnology journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.144
H-Index - 84
eISSN - 1860-7314
pISSN - 1860-6768
DOI - 10.1002/biot.201100219
Subject(s) - pseudomonas putida , transient (computer programming) , dynamics (music) , chemistry , fed batch culture , biochemical engineering , chemical engineering , food science , physics , computer science , biochemistry , engineering , enzyme , acoustics , fermentation , operating system
It has been shown that Pseudomonas putida GPo1 is able to grow in continuous culture simultaneously limited by ammonium (N source) and octanoate (C source), and concomitantly accumulate poly([ R ]‐3‐hydroxyalkanoate) (PHA). Under such growth conditions the material properties of PHA can be fine‐tuned if a second PHA precursor substrate is supplied. To determine the range of dual carbon and nitrogen (C, N)‐limited growth conditions, tedious chemostat experiments need to be carried out for each carbon source separately. To determine the growth regime, the C/N ratio of the feed (f) to a chemostat was changed in a stepwise manner at a constant dilution rate of 0.3/h. Dual‐(C, N)‐limited growth was observed between C f /N f ≤ 6.4 g/g and C f /N f >9.5 g/g. In the following, we analyzed alternative approaches, using continuous medium gradients at the same dilution rate, that do not require time consuming establishments of steady states. Different dynamic approaches were selected in which the C f /N f ratio was changed continuously through a convex increase of C f , a convex increase of N f , or a linear decrease of C f (gradients 1, 2, and 3, respectively). In these experiments, the dual‐(C, N)‐limited growth regime was between 7.2 and 11.0 g/g · for gradient 1, 4.3 and 6.9 g/g for gradient 2, and 5.1 and 8.9 g/g for gradient 3. A mathematical equation was developed that compensated a time delay of the gradient that was caused by the wash‐in/wash‐out effects of the medium feed.