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Glembin P.,TU Hamburg - Harburg | Racheva R.,TU Hamburg - Harburg | Kerner M.,Strategic Science Consult SSC Ltd | Smirnova I.,TU Hamburg - Harburg
Separation and Purification Technology | Year: 2014

In this work micelle-mediated extraction was investigated in order to develop an alternative process for the in situ extraction of hydrophobic substances from microalgae cultures. The main requirements for an in situ extraction process such as biocompatibility, phase separation behavior and partitioning of the hydrophobic target substance between micellar- and aqueous phases were studied for a number of surfactants. The cloud point temperatures (CPT) as well as the biocompatibility of seven nonionic surfactants with the microalgae Scenedesmus obliquus were determined as a function of time. For the most biocompatible surfactant, Triton X-114 with a biocompatibility of 98%, the kinetics of phase separation in the temperature range between 30 and 40 °C have been investigated. The fastest phase separation (12 min) took place at a Triton X-114 concentration of 3 wt% at 40 °C, in contrast to the slowest (55 min) at a Triton X-114 concentration of 5 wt% at 30 °C. The partitioning of representative hydrophobic substances between the both phases was predicted using the model COSMO-RS, the results were compared to experimental data with satisfying accordance (LogPcalc. palmitic acid: 0.82; LogP exp. palmitic acid: 0.75). Based on these results the extraction of valuable compounds from the microalgae S. obliquus was realized on a pilot plant and compared to the lab scale experiments.© 2014 Elsevier B.V. All rights reserved.

Glembin P.,TU Hamburg - Harburg | Kerner M.,Strategic Science Consult SSC Ltd | Smirnova I.,TU Hamburg - Harburg
Separation and Purification Technology | Year: 2013

The micellar in situ extraction of hydrophobic compounds from microalgae cultures (Chlamydomonas reinhardtii, Chlorella vulgaris, Scenedesmus obliquus) using nonionic surfactants (Triton X-114, Tergitol TMN 6, Tergitol 15-s-7) was studied in lab- and pilot scale. Therefore, phase separation behavior of the cloud point systems as well as the biocompatibility of the surfactants was investigated. It was shown that algae cells are concentrated in the aqueous phase, whereas the hydrophobic compounds (fatty acids) are enriched in the micellar phase. The thermodynamic model COSMO-RS was used to calculate partitioning coefficients of fatty acids between the phases. The biocompatibility of the surfactants applied was studied by monitoring the photosynthetic activity of algae upon contact with surfactants using puls amplitude modulation. Significant differences in growth and the photosynthetic activity of different algae strains after exposure to surfactants were determined. Whereas the photosynthetic activity of C. reinhardtii decreased rapidly upon contact with surfactants, the photosynthetic activity of S. obliquus, was 90% in comparison to a control after exposure for 240 min to all tested surfactants. C. vulgaris showed an intermediate decrease. Thus, besides extraction, surfactants might be applied to control the growth of certain algae enabling the monoalgal culturing in outdoor cultivation of microalgae since the growth of the less surfactant-tolerant microalgae could be suppressed. Overall, the results indicate that a micellar extraction with nonionic surfactants offers the opportunity for an in situ extraction of hydrophobic substances directly from the culture medium and might be a promising alternative to a classic solvent extraction of dried algal biomass. © 2012 Published by Elsevier B.V. All rights reserved.

Patzelt D.J.,University of Hamburg | Patzelt D.J.,Strategic Science Consult SSC Ltd | Hindersin S.,Strategic Science Consult SSC Ltd | Elsayed S.,Karlsruhe Institute of Technology | And 3 more authors.
Journal of Applied Phycology | Year: 2015

Hydrothermal gasification is a process which uses any biomass or carbon-containing source as substrate to generate biogas of regenerative energy production. We used microalgae as biomass source and evaluated the potential of using the residual water of the conversion process as recycled nutrient source for cultivation of microalgae. Nutrient recycling was tested by monitoring growth of Acutodesmus obliquus and Chlorella vulgaris on residual water from hydrothermal gasification of A. obliquus. Four different gasification set ups were tested. After the procedure, all obtained liquid nutrient phases contained, beside nutrients, growth-inhibiting substances affecting photosynthetic activity and biomass yield of the two algal species. At least 28 potential toxic substances were found within one of the batches. Phytotoxicity on cellular structure was verified by electron microscopy. The cell form remained intact but cell compartments vanished. C. vulgaris was not able to recover to a vital growing organism during cultivation, whereas A. obliquus was able to restore cell compartments, photosynthetic activity and growth after 3 days of cultivation. A 355-fold dilution, UV treatment for 4 h and activated carbon filtration of the residual water from gasification finally enabled the discharge to support microalgal growth. UV treatment eliminated 23 substances but generated 4 new substances that were not detected before treatment. Activated carbon filtration eliminated 26 substances. Growth of microalgae obtained in the treated residual water was comparable with that in control medium. This study demonstrated the possibility to recover nutrients after the hydrothermal gasification process when the discharge got remediated to restart the value adding chain of microalgae and lower additional nutrient supply for microalgal cultivation. © 2015, Springer Science+Business Media Dordrecht.

Patzelt D.J.,University of Hamburg | Patzelt D.J.,Strategic Science Consult SSC Ltd | Hindersin S.,Strategic Science Consult SSC Ltd | Kerner M.,Strategic Science Consult SSC Ltd | Hanelt D.,University of Hamburg
Applied Microbiology and Biotechnology | Year: 2016

Nutrients derived from hydrothermal gasification of Acutodesmus obliquus were tested on its biological compatibility to support growth of the same microalgae. Photosynthetic parameters of photosystems I and II (PS I and PS II) were investigated to study physiological effects on the microalgal cell. The nutrients were collected as liquid residues. Dilutions of 1:500 showed no effect on both photosystems. Lower dilutions affected PS II initially and later also PS I. Cyclic electron flow around PS I compensated for loss of electrons due to partially inhibited PS II. The highest tested concentration of liquid residue erased any photosynthetic activity of PS II after 28 min and onwards. In contrast, PS I remained active. The results suggest that PS I is less susceptible than PS II and that the mixture of chemicals in the liquid residue did not directly affect PS I but PS II. The toxicants in the residues seemed to interfere with linear electron flow of PS II even though light-driven formation of radicals and subsequent damage to one of the photosystems can be excluded as demonstrated in darkness. Lowered photosynthetic activity of PS I during actinic irradiation was caused due to lack of supply of electrons from PS II. The cyclic electron flow might play a key role in delivering the energy needed to restore PS II activity and to biodegrade the toxicants when linear electron flow failed. These negative effects of liquid residue towards microalgal cells require a remediation step for direct application of the liquid residue to substitute commercial fertilizers in microalgal mass cultures. © 2015, Springer-Verlag Berlin Heidelberg.

Leupold M.,University of Hamburg | Leupold M.,Strategic Science Consult SSC Ltd | Hindersin S.,University of Hamburg | Hindersin S.,Strategic Science Consult SSC Ltd | And 3 more authors.
Journal of Applied Phycology | Year: 2013

Photosynthetic activity (PA) and growth of different microalgae species (Chlorella vulgaris, Scenedesmus obliquus, and Chlamydomonas reinhardtii) depends in addition to other factors on mixing (tip speed) and shear stress (friction velocity) and was studied in a stirring tank (microcosm). In order to detect cause-effect relationships for an increase in photosynthetic activity, experiments were conducted under different pH values (6. 0-8. 5) and CO2 concentrations (0. 038 and 4 % (v/v)). The PA was determined as the effective quantum yield by pulse amplitude modulation during a stepwise increase of the tip speed from 0 to 589 cm s-1 (friction velocity: 0-6. 05 cm s-1) in short-term experiments. The increase caused a distinctive pattern of PA of each species. Compared to 0 cm s-1, C. vulgaris and S. obliquus showed a 4. 0 and 4. 8 % higher PA at the optimum tip speed of 126 cm s-1 (friction velocity of 2. 09 cm s-1) and a 48 and 71 % higher growth, respectively. At 203 cm s-1, the PA dropped to the value of the unstirred control, while at 589 cm s-1, the PA decreased of up to 7 and 8 %. In contrast, C. reinhardtii showed 7 % stronger growth at 126 cm s-1, while the PA decreased about 15 % at an increase of tip speed to 589 cm s-1. For all investigated microalgae, the pattern of PA and higher growth was not only explained by the main contributing factors like light supply, nutrient supply, and overcoming diffusion gradients. The results indicate that hydrodynamic forces have a stimulating effect on the physiological processes within the cells. © 2012 Springer Science+Business Media B.V.

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