Title Participants Abstract "Towards a general kinetic microalgae model : extending a semi-deterministic green microalgae model for the cyanobacterium Arthrospira platensis and red alga Porphyridium purpureum" "Dave Manhaeghe, Larissa Terumi Arashiro, Stijn Van Hulle, Diederik Rousseau" "Mathematical models for microalgae and cyanobacteria are seldomly validated for different algal species, as such limiting their applicability. Therefore, in this research, a previously developed kinetic model describing the growth of the green microalgae species Chlorella vulgaris was used to simulate the growth of the cyanobacterium Arthrospira platensis and the red alga Porphyridium purpureum. Based on a global sensitivity analysis, the model parameter mu max,A was calibrated using respirometric-titrimetric data. Calibration yielded values of 5.76 +/- 0.17 d1, 2.06 +/- 0.16 d-1 and 1.06 +/- 0.09 d-1 for Chlorella vulgaris, Arthrospira platensis and Porphyridium purpureum, respectively. Model simulations revealed that the biological growth equations in this model are adequate. However, increased light intensities triggered a survival mechanism for Arthrospira platensis, which is currently not taken into account by the model, leading to bad model accuracy under these circumstances. Future work should address the most important survival mechanisms and include those in the model to widen its applicability." "Cultivation of Chlorella vulgaris and Arthrospira platensis with recovered phosphorus from wastewater by means of zeolite sorption" "Orily Depraetere, Dries Vandamme, Koenraad Muylaert" "In this study, zeolite was employed for the separation and recovery of P from synthetic wastewater and its use as phosphorus (P) source for the cultivation of the green microalga Chlorella vulgaris and the cyanobacterium Arthrospira (Spirulina) platensis. At P-loaded zeolite concentration of 0.15–1 g/L, in which P was limited, the two species displayed quite different behavior regarding their growth and biomass composition. C. vulgaris preferred to increase the intracellular P and did not synthesize biomass, while A. platensis synthesized biomass keeping the intracellular P as low as possible. In addition under P limitation, C. vulgaris did display some little alteration of the biomass composition, while A. platensis did it significantly, accumulating carbohydrates around 70% from about 15%–20% (control). Both species could desorb P from zeolite biologically. A. platensis could recover over 65% and C. vulgaris 25% of the P bounded onto zeolite. When P-loaded zeolite concentration increased to 5 g/L, P was adequate to support growth for both species. Especially in the case of C. vulgaris, growth was stimulated from the presence of P-loaded zeolite and produced more biomass compared to the control." "Influence of repeated medium recycling on the performance of an Arthrospira platensis culture" "Orily Depraetere, Dries Vandamme, Imogen Foubert, Koenraad Muylaert" "© 2015 Elsevier B.V.. To reduce the water footprint of microalgae biomass production, it is essential to recycle the culture medium. The influence of medium recycling on the performance of the cyanobacterium Arthrospira platensis, the most widely cultivated microalgae, was investigated. Arthrospira was harvested with a 20μmmesh size microstrainer, which is the benchmark harvesting technology for Arthrospira production. Repeated recycling of the culture medium resulted in a decline in growth rate and the maximum quantum yield of photosynthesis (Fv/Fm) when compared to a control culture in fresh medium. This decline was accompanied by accumulation of organic matter in the culture medium (up to 104mgCL-1). This organic matter consists of 70% of sugars, mostly rhamnose-rich polysaccharides with uronic acids. Accumulation of polysaccharides resulted in a decrease in the filtration rate through the microstrainer used for harvesting. Part of the biomass escaped harvesting and was returned to the culture with the recycled medium. This resulted in a change in the Arthrospira population and reduction in the harvesting efficiency, but this change in population had no effect on the growth rate. The growth rate of Arthrospira in the recycled culture medium was primarily influenced by organic matter that accumulated in the medium." "Applying raw poultry litter leachate for the cultivation of Arthrospira platensis and Chlorella vulgaris" "Koenraad Muylaert" "© 2015 Elsevier B.V. All rights reserved. In the present paper, the use of raw poultry litter (PL) as a nutrient source for the cultivation of Arthrospira platensis and Chlorella vulgaris was investigated. PL was added to acid solution (62.5 mM H2SO4) for the extraction of nutrients contained in PL. After settling, the supernatant, called PL leachate (PLL) was diluted 25×, 20×, 15×, and 10× and used as a mediumfor the cultivation of A. platensis and C. vulgaris. A. platensis could not survive in 15× and 10× diluted leachate andwhile in 20× and 25× dilutions the biomass production was only half of that in a control medium(Zarrouk). The biomass composition had a high carbohydrate content (37-44%),which suggests that A. platensis was stressed due to nutrient limitation. C. vulgaris grew well in PLL-based media and the biomass production was higher than in the control medium (BG-11). Biomass composition of C. vulgaris in PLL-basedmedia had lower protein content and higher carbohydrate and lipid content than in the control medium. The overall process for producing microalgal biomass fromPL thatwe propose includes: (i) acid extraction of nutrients through the generation of PL leachate (PLL), (ii) indoor PL composting and recovery of stripped ammonia and CO2, and (iii) use of recovered ammonia and CO2 along with the PLL for the cultivation of microalgae and cyanobacteria for the production of biomass." "Harvesting carbohydrate-rich Arthrospira platensis by spontaneous settling" "Orily Depraetere, Imogen Foubert, Koenraad Muylaert" "The filamentous cyanobacterium Arthrospira platensis is an attractive feedstock for carbohydrate-based biofuels because it accumulated up to 74% of carbohydrates when nitrogen stressed. Nitrogen stressed A. platensis also settled spontaneously, and this occurred simultaneously with carbohydrates accumulation, suggesting a link between both phenomena. The increased settling velocity was neither due to production of extracellular carbohydrates, nor due to degradation of gas vacuoles, but was caused by an increase in the specific density of the filaments as a result of accumulation of carbohydrates under the form of glycogen. Settling velocities of carbohydrate-rich A. platensis reached 0.64mh(-1), which allowed the biomass to be harvested using a lamella separator. The biomass could be concentrated at least 15 times, allowing removal of 94% of the water using gravity settling, thus offering a potential application as a low-cost and high-throughput method for primary dewatering of carbohydrate-rich A. platensis." "Quantum yield alterations due to the static magnetic fields action on Arthrospira platensis SAG 21.99: Evaluation of photosystem activity" "Koenraad Muylaert" "Static magnetic fields (SMF) influence the metabolism of microorganisms, however, there is no knowledge explaining how SMF act in cells. This study aimed at evaluating the SMF (30 mT) effect on photosynthetic performance, growth and biomass composition of the cyanobacterium Arthrospira platensis SAG 21.99. A. platensis was cultivated under 30 mT applied for 1 h d-1 and 24 h for 10 d in glass bottles. SMF in both conditions increased cellular growth, achieving a 30% higher biomass concentration. SMF applied for 1 h d-1 increased the pigments and carbohydrate content. The quantum yield was used as an indicator of the photosystem II (PSII) activity and was shown to have been positively affected. SMF for 1 h d-1 had a significant effect on the OJIP curves. This is the first study that evaluated the photosynthetic activity in cyanobacteria cultures under SMF action." "Advancement of green process through microwave-assisted extraction of bioactive metabolites from Arthrospira Platensis and bioactivity evaluation" "Sara Cuellar Bermudez" "Bioactivity and functional properties of cyanobacterial extract mostly depends on process of extraction, temperature and solvent used (polar or non-polar). To evaluate these parameters a design of experiment (DOE; using a 2k design) was performed with Arthrospira platensis. Extraction process was optimized through microwave-assisted extraction considering solvent ratio, temperature and time of extraction with polar (PS) and non-polar (NPS). Maximum extract yield obtained was 4.32±0.25% and 5.26±0.11% (w/w) respectively for PS and NPS. Maximum content of bioactive metabolites in PS extracts were thiamine (846.57±14.12μg/g), riboflavin (101.09±1.63μg/g), C-phycocyanin (2.28±0.10μg/g) and A-phycocyanin (4.11±0.03μg/g), while for NPS extracts were α-tocopherol (37.86±0.78μg/g), β-carotene (123.64±1.45μg/g) and 19.44±0.21mg/g of fatty acids. A. platensis PS extracts showed high antimicrobial activity and PS extracts had antioxidant activity of 0.79±0.12μmolTE/g for FRAP assay, while for NPS extracts 1.03±0.08μmol α-TE/g for FRAP assay." "Exploration of using stripped ammonia and ash from poultry litter for the cultivation of the cyanobacterium Arthrospira platensis and the green microalga Chlorella vulgaris" "Giorgos Markou, Koenraad Muylaert" "Herein a new approach of exploiting poultry litter (PL) is demonstrated. The suggested method includes drying of PL with simultaneously striping and recovery of ammonia, followed by the direct combustion of dried PL. The generated ash after the combustion, and the striped ammonia consequently, could be used as nutrient source for the cultivation of microalgae or cyanobacteria to produce feed additives. The present study explored the application of PL ash and recovered ammonia for the cultivation of Arthrospira platensis and Chlorella vulgaris. For a simultaneously 90% dissolution of ash potassium and phosphorus, a ratio of acid to ash of 0.02 mol-H+/g was required. The optimum mass of ash required was 0.07–0.08 g/g dry biomass, while the addition of ammoniac nitrogen of 8–9 mg N per g of dry biomass per day was adequate for a satisfactory production of A. platensis and C. vulgaris." "Using natural zeolite for ammonia sorption from wastewater and as nitrogen releaser for the cultivation of Arthrospira platensis" "Dries Vandamme, Koenraad Muylaert" "Herein a new approach for the application of wastewater nutrients for the cultivation of cyanobacteria or microalgae is described. Natural zeolite was used as medium for the sorption of ammonia from wastewater and subsequently as nitrogen releaser in cultures of Arthrospira. platensis. The main scope of the present approach was to isolate ammonia from the wastewater and to transfer it into the culture medium excluding thus the suspended solids, the dissolved colored compounds or any other possible contaminant of the wastewater. The results demonstrate that the indirect use of ammonia derived from wastewater using zeolite as sorption and releasing medium for the cultivation of A. platensis is promising. This is the first time that a medium was used for indirect application of wastewater nutrient for the production of cyanobacterial or microalgal biomass." "Thermal and acidic denaturation of phycocyanin from Arthrospira platensis: Effects of complexation with λ-carrageenan on blue color stability" "Myriam Loeffler" "The pH and temperature sensitivity of the natural blue pigment phycocyanin from Arthrospira platensis limits its application as food colorant. This study examines the effect of protein stabilization by the anionic polysaccharide λ-carrageenan on phycocyanins color appearance at pH 2.5-6.0, unheated and after heat treatments (70/90 °C). Electrostatic interactions, hydrophobic interactions, hydrogen bonds and disulfide-bridges were assessed by adding NaCl, urea and dithiothreitol (DTT) to the samples. Measurements of the zeta potential, transmittance and two-dimensional gel electrophoresis coupled to mass spectrometry confirmed electrostatic interactions around the zero surface charge of phycocyanin over a broad pH range (∼4.1-6.4). Despite a color shift towards turquoise, the color remained stable during heating, especially below of pH 3.5. Precipitation was inhibited over the entire pH range. Overall, electrostatic complexation of phycocyanin and λ-carrageenan is a promising technique to stabilize proteinaceous colorants, helping to reduce food waste and foster a shift to renewable materials."