title: High cell density cultivation of the chemolithoautotrophic bacterium Nitrosomonas europaea.
abstract: Nitrosomonas europaea is a chemolithoautotrophic nitrifier, a gram-negative bacterium that can obtain all energy required for growth from the oxidation of ammonia to nitrite, and this may be beneficial for various biotechnological and environmental applications. However, compared to other bacteria, growth of ammonia oxidizing bacteria is very slow. A prerequisite to produce high cell density N. europaea cultures is to minimize the concentrations of inhibitory metabolic by-products. During growth on ammonia nitrite accumulates, as a consequence, N. europaea cannot grow to high cell concentrations under conventional batch conditions. Here, we show that single-vessel dialysis membrane bioreactors can be used to obtain substantially increased N. europaea biomasses and substantially reduced nitrite levels in media initially containing high amounts of the substrate. Dialysis membrane bioreactor fermentations were run in batch as well as in continuous mode. Growth was monitored with cell concentration determinations, by assessing dry cell mass and by monitoring ammonium consumption as well as nitrite formation. In addition, metabolic activity was probed with in vivo acridine orange staining. Under continuous substrate feed, the maximal cell concentration (2.79 × 10(12)/L) and maximal dry cell mass (0.895 g/L) achieved more than doubled the highest values reported for N. europaea cultivations to date.
authors.affiliation: Department of Biochemical Engineering, Faculty of Science and Technology, University of Debrecen, H-4032, Egyetem tér 1, Debrecen, Hungary.
authors.forename: Benedek
authors.initials: B
authors.lastname: Papp
authors.affiliation: Safety and Environmental Department, TEVA Pharmaceutical Ltd., H-4032, Pallagi u. 13, Debrecen, Hungary.
authors.forename: Tibor
authors.initials: T
authors.lastname: Török
authors.affiliation: Institute of Food Science, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, H-4032, Böszörményi út 138, Debrecen, Hungary.
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Sándor
authors.affiliation: Department of Biochemical Engineering, Faculty of Science and Technology, University of Debrecen, H-4032, Egyetem tér 1, Debrecen, Hungary.
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Fekete
authors.affiliation: Department of Biochemical Engineering, Faculty of Science and Technology, University of Debrecen, H-4032, Egyetem tér 1, Debrecen, Hungary.
authors.forename: Michel
authors.initials: M
authors.lastname: Flipphi
authors.affiliation: Department of Biochemical Engineering, Faculty of Science and Technology, University of Debrecen, H-4032, Egyetem tér 1, Debrecen, Hungary. karaffa.levente@science.unideb.hu.
authors.forename: Levente
authors.initials: L
authors.lastname: Karaffa
mesh_terms: D061249:Batch Cell Culture Techniques; D018533:Biomass; D019149:Bioreactors; D052837:Chemoautotrophic Growth; D005285:Fermentation; D007700:Kinetics; D009573:Nitrites / Q000378:metabolism; D043370:Nitrosomonas europaea / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D009573:Nitrites