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Cultivation of Methylosinus trichosporium OB3b: III. Production of particulate methane monooxygenase in continuous culture
Author(s) -
Shah Nilesh N.,
Park Sunghoon,
Taylor Robert T.,
Droege Michael W.
Publication year - 1992
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260400609
Subject(s) - methane monooxygenase , chemistry , methanotroph , nitrate , dilution , methane , environmental chemistry , biochemistry , anaerobic oxidation of methane , enzyme , organic chemistry , physics , thermodynamics
Continous culture experiments with the obligatory methanotroph, Methylosinus trichosporium OB3b, were conducted to study the whole‐cell methane monooxygenase (MMO) and nitrogenase activities in a nitrate minimal salts medium under oxygen‐limited conditions with methane as the carbone source. The important variables investigated were the feed medium concentrations of copper and nitrate, CO 2 addition, the agitation speed, and the dilution rate. M. trichosporium OB3b required quantitative amounts of copper (2.6 × 10 −4 g Cu/g dry cell Wt) for the exclusive production of particulate MMo during continous culture growth. When the feed medium nitrate concentration was varied in the range of 5‐50 m M , the whole‐cell specific pMMO activity exhibited a maximum at 40 m M . The elimination of external CO 2 gassing decreased pMMO activity by more than 30%. The steady‐state cell density increased continuously over a 300‐700 rpm range of agitation speed, whereas, the pMMO activity became maximal at 400 rpm. Also, the pMMO activity increased with the dilution rate up to 0.06 h −1 and remained constant thereafter. Maximal continuous pMMO productivity was, thus, achieved in Higgin's medium containing 10 μ M Cu, 80 μ M Fe, and 40 m M nitrate with an agitation speed of 500 rpm and a dilution rate of 0.06 h −1 . Nitrogenase activity, on the other hand, increased over a feed medium copper concentration of 2‐15 μ M , falling sharply at 20 μ M , and it exhibited a minimum at 20 m M when the feed medium nitrate concentration was varied. © 1992 John Wiley & Sons, Inc.