title: Kinetics of growth and leukotoxin production by Mannheimia haemolytica in continuous culture.
abstract: The growth and product formation kinetics of the bovine pathogen Mannheimia (Pasteurella) haemolytica strain OVI-1 in continuous culture were investigated. The leukotoxin (LKT) concentration and yield on biomass could substantially be enhanced by supplementation of a carbon-limited medium with an amino acid mixture or a mixture of cysteine and glutamine. Acetic acid was a major product, increasing to 1.66 g l(-1) in carbon-limited chemostat culture at intermediate dilution rates and accounting for more than 80% of the glucose carbon, whereas in amino acid-limited cultures high acetic acid concentrations were produced at low dilution rates, suggesting a carbon-overflow metabolism. The maintenance coefficients of carbon-limited and carbon-sufficient cultures were 0.07 and 0.88 mmol glucose g(-1) h(-1), respectively. LKT production was partially growth-associated and the LKT concentration was maximised to 0.15 g l(-1) and acetic acid production minimised by using a carbon-limited medium and a low dilution rate.
authors.affiliation: Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa. dpreezjc.sci@ufs.ac.za.
authors.forename: James C
authors.initials: JC
authors.lastname: du Preez
authors.forename: Eugéne
authors.initials: E
authors.lastname: van Rensburg
authors.forename: Stephanus G
authors.initials: SG
authors.lastname: Kilian
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D005098:Exotoxins / Q000096:biosynthesis*; D005947:Glucose / Q000378:metabolism; D007700:Kinetics; D016978:Mannheimia haemolytica / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D013447:Sulfites / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D003470:Culture Media; D005098:Exotoxins; D013447:Sulfites; C018579:leukotoxin; D002244:Carbon; D005947:Glucose; D019342:Acetic Acid; C025026:sodium sulfite