F.J. Valdés

Estimation of CO2 stripping/CO2 microalgae consumption ratios in a bubble column photobioreactor using the analysis of the pH profiles. Application to Nannochloropsis oculata microalgae culture.

Nannochloropsis oculata was grown in an outdoor bubble column photobioreactor. To obtain information about the behaviour of microalgae/photobioreactor system related to the CO(2) net balance, an analysis of the pH profiles during microalgae growth was carried out. The use of the carbonate equilibrium chemistry and the overall CO(2) volumetric mass transfer in the photobioreactor has permitted to obtain information of the CO(2) losses/CO(2) microalgae consumption ratios. The simplicity of the technique used (a pH probe) could extend the use of this methodology for the correct selection of the photobioreactor/microalgae parameters with the aim to maximize the [CO(2) uptaken/(CO(2) uptaken+CO(2) stripped)] ratios.

Thermogravimetry and Py–GC/MS techniques as fast qualitative methods for comparing the biochemical composition of Nannochloropsis oculata samples obtained under different culture conditions

Microalgae have many applications, such as biodiesel production or food supplement. Depending on the application, the optimization of certain fractions of the biochemical composition (proteins, carbohydrates and lipids) is required. Therefore, samples obtained in different culture conditions must be analyzed in order to compare the content of such fractions. Nevertheless, traditional methods necessitate lengthy analytical procedures with prolonged sample turn-around times. Results of the biochemical composition of Nannochloropsis oculata samples with different protein, carbohydrate and lipid contents obtained by conventional analytical methods have been compared to those obtained by thermogravimetry (TGA) and a Pyroprobe device connected to a gas chromatograph with mass spectrometer detector (Py-GC/MS), showing a clear correlation. These results suggest a potential applicability of these techniques as fast and easy methods to qualitatively compare the biochemical composition of microalgal samples.

Comments on the Methods of Characterization of Textural Properties of Solids from Gas Adsorption Data

Certain drawbacks of several of the conventional methods of analyzing Type I and II adsorption isotherms frequently used to characterize the structural properties of adsorbent materials have been demonstrated. A simple and flexible procedure, based on an equation combining the Dubinin equation to account for the micropore contribution and the BET equation to account for the non-porous contribution, has been proposed which is capable of simultaneously correlating the adsorption isotherm up to relative pressures of 0.4. Examples are presented showing that the suggested procedure provides a proper interpretation of the data coherent with the origin of the samples and avoids the misinterpretation that could arise from the application of the conventional methods.