title: Insights into pH-induced metabolic switch by flux balance analysis.
abstract: Lactate accumulation in mammalian cell culture is known to impede cellular growth and productivity. The control of lactate formation and consumption in a hybridoma cell line was achieved by pH alteration during the early exponential growth phase. In particular, lactate consumption was induced even at high glucose concentrations at pH 6.8, whereas highly increased production of lactate was obtained at pH 7.8. Consequently, constraint-based metabolic flux analysis was used to examine pH-induced metabolic states in the same growth state. We demonstrated that lactate influx at pH 6.8 led cells to maintain high fluxes in the TCA cycle and malate-aspartate shuttle resulting in a high ATP production rate. In contrast, under increased pH conditions, less ATP was generated and different ATP sources were utilized. Gene expression analysis led to the conclusion that lactate formation at high pH was enabled by gluconeogenic pathways in addition to facilitated glucose uptake. The obtained results provide new insights into the influence of pH on cellular metabolism, and are of importance when considering pH heterogeneities typically present in large scale industrial bioreactors.
authors.affiliation: Dept. of Chemistry and Applied Biosciences, Inst. for Chemical and Bioengineering, ETH Zurich, Zurich, Switzerland.
authors.forename: Marija
authors.initials: M
authors.lastname: Ivarsson
authors.forename: Heeju
authors.initials: H
authors.lastname: Noh
authors.forename: Massimo
authors.initials: M
authors.lastname: Morbidelli
authors.forename: Miroslav
authors.initials: M
authors.lastname: Soos
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000032:analysis / Q000378:metabolism; D002460:Cell Line; D015870:Gene Expression; D005947:Glucose / Q000032:analysis / Q000378:metabolism; D006801:Humans; D006825:Hybridomas; D006863:Hydrogen-Ion Concentration; D042541:Intracellular Space / Q000378:metabolism; D019344:Lactic Acid / Q000032:analysis / Q000378:metabolism*; D064688:Metabolic Flux Analysis / Q000379:methods*; D053858:Metabolic Networks and Pathways / Q000502:physiology*; D051379:Mice
chemical_list: D000911:Antibodies, Monoclonal; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D005947:Glucose
keywords: flux balance analysis; gene expression analysis; lactate metabolism; mammalian cell cultivation; pH