33 research outputs found
Light regime characterization in an airlift photobioreactor for production of microalgae with high starch content
The slow development of microalgal biotechnology is due to the failure in the
design of large-scale photobioreactors (PBRs) where light energy is efficiently utilized. In
this work, both the quality and the amount of light reaching a given point of the PBR were
determined and correlated with cell density, light path length, and PBR geometry. This was
made for two different geometries of the downcomer of an airlift PBR using optical fiber
technology that allows to obtain information about quantitative and qualitative aspects of
light patterns. This is important since the ability of microalgae to use the energy of photons
is different, depending on the wavelength of the radiation. The results show that the circular
geometry allows a more efficient light penetration, especially in the locations with a higher
radial coordinate (r) when compared to the plane geometry; these observations were
confirmed by the occurrence of a higher fraction of illuminated volume of the PBR for this
geometry. An equation is proposed to correlate the relative light intensity with the
penetration distance for both geometries and different microalgae cell concentrations. It was
shown that the attenuation of light intensity is dependent on its wavelength, cell
concentration, geometry of PBR, and the penetration distance of light.Fundação para a Ciência e a Tecnologia (FCT
Integration of aqueous (micellar) two-phase systems on the proteins separation
A two-step approach combining an aqueous two-phase system (ATPS) and an aqueous micellar two-phase system
(AMTPS), both based on the thermo-responsive copolymer Pluronic L-35, is here proposed for the purification of
proteins and tested on the sequential separation of three model proteins, cytochrome c, ovalbumin and azocasein.
Phase diagrams were established for the ATPS, as well as co-existence curves for the AMTPS. Then, by scanning and
choosing the most promising systems, the separation of the three model proteins was performed. The aqueous
systems based on Pluronic L-35 and potassium phosphate buffer (pH = 6.6) proved to be the most selective platform
to separate the proteins (SAzo/Cyt = 1667; SOva/Cyt = 5.33 e SAzo/Ova = 1676). The consecutive fractionation of these
proteins as well as their isolation from the aqueous phases was proposed, envisaging the industrial application of this
downstream strategy. The environmental impact of this downstream process was studied, considering the carbon
footprint as the final output. The main contribution to the total carbon footprint comes from the ultrafiltration (~ 49%)
and the acid precipitation (~ 33%) due to the energy consumption in the centrifugation. The ATPS step contributes to
~ 17% while the AMTPS only accounts for 0.30% of the total carbon footprint.publishe
Thermoreversible (Ionic-Liquid-Based) Aqueous Biphasic Systems
The ability to induce reversible phase transitions between homogeneous solutions and biphasic liquid-liquid systems, at pre-defined and suitable operating temperatures, is of crucial relevance in the design of separation processes. Ionic-liquid-based aqueous biphasic systems (IL-based ABS) have demonstrated superior performance as alternative extraction platforms, and their thermoreversible behaviour is here disclosed by the use of protic ILs. The applicability of the temperature-induced phase switching is further demonstrated with the complete extraction of two value-added proteins, achieved in a single-step. It is shown that these temperature-induced mono(bi)phasic systems are significantly more versatile than classical liquid-liquid systems which are constrained by their critical temperatures. IL-based ABS allow to work in a wide range of temperatures and compositions which can be tailored to fit the requirements of a given separation process