title: Dynamic behavior of Yarrowia lipolytica in response to pH perturbations: dependence of the stress response on the culture mode.
abstract: Yarrowia lipolytica, a non-conventional yeast with a promising biotechnological potential, is able to undergo metabolic and morphological changes in response to environmental conditions. The effect of pH perturbations of different types (pulses, Heaviside) on the dynamic behavior of Y. lipolytica W29 strain was characterized under two modes of culture: batch and continuous. In batch cultures, different pH (4.5, 5.6 (optimal condition), and 7) were investigated in order to identify the pH inducing a stress response (metabolic and/or morphologic) in Y. lipolytica. Macroscopic behavior (kinetic parameters, yields, viability) of the yeast was slightly affected by pH. However, contrary to the culture at pH 5.6, a filamentous growth was induced in batch experiments at pH 4.5 and 7. Proportions of the filamentous subpopulation reached 84 and 93 % (v/v) under acidic and neutral conditions, respectively. Given the significant impact of neutral pH on morphology, pH perturbations from 5.6 to 7 were subsequently assayed in batch and continuous bioreactors. For both process modes, the growth dynamics remained fundamentally unaltered during exposure to stress. Nevertheless, morphological behavior of the yeast was dependent on the culture mode. Specifically, in batch bioreactors where cells proliferated at their maximum growth rate, mycelia were mainly formed. Whereas, in continuous cultures at controlled growth rates (from 0.03 to 0.20 h-1) even closed to the maximum growth rate of the stain (0.24 h-1), yeast-like forms predominated. This pointed out differences in the kinetic behavior of filamentous and yeast subpopulations, cell age distribution, and pH adaptive mechanisms between both modes of culture.
authors.affiliation: LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France.
authors.forename: Asma
authors.initials: A
authors.lastname: Timoumi
authors.affiliation: LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France.
authors.forename: Mégane
authors.initials: M
authors.lastname: Cléret
authors.affiliation: LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France.
authors.forename: Carine
authors.initials: C
authors.lastname: Bideaux
authors.affiliation: LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France.
authors.forename: Stéphane E
authors.initials: SE
authors.lastname: Guillouet
authors.affiliation: Airbus Operations S.A.S, 316 Route de Bayonne, 31060, Toulouse, France.
authors.forename: Yohan
authors.initials: Y
authors.lastname: Allouche
authors.affiliation: LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Molina-Jouve
authors.affiliation: LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France.
authors.forename: Luc
authors.initials: L
authors.lastname: Fillaudeau
authors.affiliation: LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France. nathalie.gorret@insa-toulouse.fr.
authors.forename: Nathalie
authors.identifier: http://orcid.org/0000-0002-5290-1316
authors.initials: N
authors.lastname: Gorret
mesh_terms: D019149:Bioreactors / Q000382:microbiology; D003470:Culture Media / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D025282:Mycelium / Q000254:growth & development; D013312:Stress, Physiological; D025062:Yarrowia / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology*
chemical_list: D003470:Culture Media
keywords: Batch; Chemostat; Dynamic response; Morphology; Yarrowia lipolytica; pH stress