title: Cost-effective production of 13C, 15N stable isotope-labelled biomass from phototrophic microalgae for various biotechnological applications.
abstract: The present study outlines a process for the cost-effective production of 13C/15N-labelled biomass of microalgae on a commercial scale. The core of the process is a bubble column photobioreactor with exhaust gas recirculation by means of a low-pressure compressor. To avoid accumulation of dissolved oxygen in the culture, the exhaust gas is bubbled through a sodium sulphite solution prior to its return to the reactor. The engineered system can be used for the production of 13C, 15N, and 13C-15N stable isotope-labelled biomass as required. To produce 13C-labelled biomass, 13CO2 is injected on demand for pH control and carbon supply, whereas for 15N-labelled biomass Na15NO3 is supplied as nitrogen source at the stochiometric concentration. The reactor is operated in semicontinuous mode at different biomass concentrations, yielding a maximum mean biomass productivity of 0.3 gL(-1) day(-1). In order to maximize the uptake efficiency of the labelled substrates, the inorganic carbon is recovered from the supernatant by acidification/desorption processes, while the nitrate is delivered at stochiometric concentration and the harvesting of biomass is performed when the 15NO3- is depleted. In these conditions, elemental analysis of both biomass and supernatant shows that 89.2% of the injected carbon is assimilated into the biomass and 6.9% remains in the supernatant. Based on elemental analysis, 97.8% of the supplied nitrogen is assimilated into the biomass and 1.3% remains in the supernatant. Stable isotope-labelling enrichment has been analysed by GC-MS results showing that the biomass is highly labelled. All the fatty acids are labelled; more than 96% of the carbon present in these fatty acids is 13C. The engineered system was stably operated for 3 months, producing over 160 g of 13C and/or 15N-labelled biomass. The engineered bioreactor can be applied for the labelling of various microalgae.
authors.affiliation: Department of Chemical Engineering, University of Almería, E-04071 Almería, Spain.
authors.forename: F G
authors.initials: FG
authors.lastname: Acién Fernández
authors.forename: J M
authors.initials: JM
authors.lastname: Fernández Sevilla
authors.forename: T A
authors.initials: TA
authors.lastname: Egorova-Zachernyuk
authors.forename: E
authors.initials: E
authors.lastname: Molina Grima
mesh_terms: D018533:Biomass; D019149:Bioreactors / Q000191:economics; D002247:Carbon Isotopes / Q000378:metabolism; D017377:Diatoms / Q000254:growth & development*; D007553:Isotope Labeling / Q000191:economics / Q000379:methods; D009587:Nitrogen Isotopes / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes