title: Transient self-inhibition of the growth of Lactobacillus delbrueckii subsp. bulgaricus in a pH-regulated fermentor.
abstract: An industrial strain of Lactobacillus delbrueckii subsp. bulgaricus was grown in a synthetic medium on lactose as carbon substrate, in a pH-regulated fermentor. Growth proceeded in two distinct phases separated by a transient stationary phase. Various experimental approaches were used to identify the cause of this growth arrest. Growth experiments in L. bulgaricus culture supernatant fluids collected at different cultivation times in fermentor, and supplemented or not with various nutritional solutions, enabled us to discard the possibility of a nutritional limitation. Tube cultures of L. bulgaricus in medium supplemented with various lactic acid concentrations showed a potential inhibition by this metabolic end product but confirmed that this inhibition was not responsible for the cessation of growth. It was concluded that at least one inhibitory compound was produced during the growth phase of the strain, and this compound disappeared from the medium in the transient stationary phase, enabling the growth to start again later in the culture. Indeed, the stoichiometric analysis of the culture showed, firstly, that unidentified carbon compounds were produced from lactose during growth, which were probably converted in lactic acid during the transient stationary phase and, secondly, that part of the amino acids consumed gave catabolic end products. Finally, bacteriocin-like compounds were not considered to be responsible for this growth arrest.
authors.affiliation: Centre de Bioingénierie Gilbert Durand, UMR CNRS 5504, UMR INRA 792, Institut National des Sciences Appliquées, 135 Avenue de Rangueil, 31077 Toulouse Cedex 4, France.
authors.forename: Myriam
authors.initials: M
authors.lastname: Mercade
authors.forename: Florence
authors.initials: F
authors.lastname: Duperray
authors.forename: Pascal
authors.initials: P
authors.lastname: Loubière
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D001430:Bacteriocins / Q000378:metabolism; D019149:Bioreactors; D018929:Cell Culture Techniques / Q000379:methods*; D002455:Cell Division / Q000502:physiology; D005246:Feedback; D006706:Homeostasis / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism*; D007778:Lactobacillus / Q000737:chemistry / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism*; D008954:Models, Biological; D013045:Species Specificity
chemical_list: D001430:Bacteriocins; D019344:Lactic Acid; D007785:Lactose