Growth inhibition by ammonia and use of a pH-controlled feeding strategy for the effective cultivation of Mycobacterium chlorophenolicum

• Published in: Applied microbiology and biotechnology Vol. 44; no. 3-4; p. 519
• Main Authors: Wittmann, C, Zeng, A P, Deckwer, W D
• Format: Journal Article
• Language: English
• Published: Germany 01.12.1995
• Subjects: Automation - instrumentation; Bacteriological Techniques - instrumentation; Biodegradation, Environmental; Culture Media; Glucose - metabolism; Hydrogen-Ion Concentration; Industrial Microbiology - instrumentation; Industrial Microbiology - methods; Kinetics; Mycobacterium - drug effects; Mycobacterium - growth & development; Mycobacterium - metabolism; Online Systems; Pentachlorophenol - metabolism; Quaternary Ammonium Compounds - pharmacology
• ISSN: 0175-7598
• DOI: 10.1007/bf00169954

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.