title: Effect of Medium pH on Rhodosporidium toruloides NCYC 921 Carotenoid and Lipid Production Evaluated by Flow Cytometry.
abstract: The effect of the culture medium pH (3.5-6.0) on the carotenoid and lipid (as fatty acids) production by the yeast Rhodosporidium toruloides NCYC 921 was studied. Flow cytometry was used to evaluate the yeast's physiological response to different culture medium pH values. The yeast biomass concentration and lipid content were maxima at pH 4.0 (5.90 g/L and 21.85 % w/w, respectively), while the maximum carotenoid content (63.37 μg/g) was obtained at pH 5.0. At the exponential phase, the yeast cell size and internal complexity were similar, at different medium pH. At the stationary phase, the yeast cell size and internal complexity decreased as the medium pH increased. At the exponential phase, the proportion of cells with polarized membranes was always high (>80 %) but at the stationary phase, the proportion of yeast cells with depolarized membranes was dominant (>65 %) and increased with the medium pH increase. The results here reported may contribute for yeast bioprocesses optimization. For the first time, multiparameter flow cytometry was used to evaluate the impact of medium pH changes on the yeast cell physiological status, specifically on the yeast membrane potential, membrane integrity, cell size and internal complexity.
authors.affiliation: Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 22, 1649-038, Lisboa, Portugal.
authors.forename: Carla
authors.initials: C
authors.lastname: Dias
authors.affiliation: Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 22, 1649-038, Lisboa, Portugal.
authors.forename: Corália
authors.initials: C
authors.lastname: Silva
authors.affiliation: Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 22, 1649-038, Lisboa, Portugal.
authors.forename: Claudia
authors.initials: C
authors.lastname: Freitas
authors.affiliation: Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 22, 1649-038, Lisboa, Portugal.
authors.forename: Alberto
authors.initials: A
authors.lastname: Reis
authors.affiliation: Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 22, 1649-038, Lisboa, Portugal. teresa.lopessilva@lneg.pt.
authors.forename: Teresa Lopes
authors.initials: TL
authors.lastname: da Silva
mesh_terms: D001487:Basidiomycota / Q000187:drug effects / Q000254:growth & development*; D002338:Carotenoids / Q000096:biosynthesis* / Q000737:chemistry; D003470:Culture Media / Q000494:pharmacology; D005434:Flow Cytometry; D006863:Hydrogen-Ion Concentration; D008055:Lipids / Q000096:biosynthesis* / Q000737:chemistry
chemical_list: D003470:Culture Media; D008055:Lipids; D002338:Carotenoids
keywords: Carotenoids; Fatty acids; Flow cytometry; Lipids; Medium pH; Rhodosporidium toruloides; Yeast