title: Growth inhibition by ammonia and use of a pH-controlled feeding strategy for the effective cultivation of Mycobacterium chlorophenolicum.
abstract: The inhibitory effect of ammonia on the growth of the polychlorinated xenobiotic-degrading bacterium Mycobacterium chlorophenolicum was examined. The strain is inhibited by both the ionized and nonionized forms of ammonia, At pH 6.9, 50% reduction of the growth rate was observed at 6.8 g/l total ammonium. For 23 experiments performed in shake-flask culture at different pH values, and ammonium concentrations a growth model based on the extended Monod kinetic fits the data with a deviation of 5.3%. To overcome growth inhibition in bioreactors, a pH- controlled feeding strategy was developed for effective cultivation of M. chlorophenolicum at an ammonium level below 0.3 g/l. The ammonium addition was controlled online by the stoichiometric interdependence of ammonium consumption and pH decline. With this online control strategy, a biomass concentration as high as 26.2 g/l can be achieved within less than a week of cultivation. The yield is also increased from 0.32 g to 0.43 g biomass (per gram glucose). The strategy developed provides an effective method for the production of biomass o M. chlorophenolicum serving as the inoculum in remediation technologies.
authors.affiliation: GBF-Gesellschaft für Biotechnologie Forschung mbH, Biochemical Engineering Division, Braunschweig, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Wittmann
authors.forename: A P
authors.initials: AP
authors.lastname: Zeng
authors.forename: W D
authors.initials: WD
authors.lastname: Deckwer
mesh_terms: D001331:Automation / Q000295:instrumentation; D001431:Bacteriological Techniques / Q000295:instrumentation; D001673:Biodegradation, Environmental; D003470:Culture Media; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology / Q000295:instrumentation / Q000379:methods; D007700:Kinetics; D009161:Mycobacterium / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D009862:Online Systems; D010416:Pentachlorophenol / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*
chemical_list: D003470:Culture Media; D000644:Quaternary Ammonium Compounds; D010416:Pentachlorophenol; D005947:Glucose