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The increased input of nutrients into biological systems has been shown to result in altered biotic interactions through changes in food availability. The aim of this study was to test for an association between phytoplankton nutrient content and epibiont variables in natural zooplankton populations. Via a field survey, we studied how a gradient in food quantity and quality impacted host population density and epibiont variables in Daphnia pulex . We found a significant decrease in epibiont prevalence and infracommunity richness, which could mainly be attributed to a changing phytoplankton N : P ratio (caused by P‐limitation). We performed a lab experiment in which we exposed Daphnia magna to different algal nutrient ratios and the epibionts detected in the field study. P‐limitation in the algae affected D. magna performance and resulted in similar trends of food quality effects in the epibiont variables. The experiment, however, also reflected subtle differences between different epibiont species.

International audience; Microalgae are a promising resource for biofuel production, although their industrial use is limited by the lack of effective harvesting techniques. Flocculation consists in the aggregation and adhesion of cells into flocs that can be more easily removed from water than individual cells. Although it is an efficient harvesting technique, contamination is a major issue as chemical flocculants are often used. An alternative is to use natural biopolymers flocculants such as chitosan. Chitosan is a biobased nontoxic polymer that has been effectively used to harvest Chlorella vulgaris cells at a pH lower than its pKa (6.5). While the reported flocculation mechanism is said to rely on electrostatic interactions between chitosan and the negative cell surface, no molecular evidence has yet confirmed this mechanism. In this study, we performed force spectroscopy atomic force microscopy (AFM) experiments to probe the interactions between C. vulgaris cells and chitosan at the molecular scale to decipher its flocculation mechanism. Our results showed that at pH 6, chitosan interacts with C. vulgaris cell wall through biological interactions rather than electrostatic interactions. These observations were confirmed by comparing the data with cationically modified cellulose nanocrystals, for which the flocculation mechanism, relying on an electrostatic patch mechanism, has already been described for C. vulgaris. Further AFM experiments also showed that a different mechanism was at play at higher pH, based on chitosan precipitation. Thus, this AFM-based approach highlights the complexity of chitosan-induced flocculation mechanisms for C. vulgaris.

At this moment about 7.6 billion people inhabit the earth (Worldpopulation clock 2018). A sustainability revolution is necessary (WCED 1987, UNCED 1992, Rockström 2009) to avoid this huge population in striving for a luxury life depleting the resources of the planet. There are also important social issues that need to be resolved (Raworth 2017). It has been argued that even a real cultural shift is needed (Kagan 2010).This revolution can be started in education (UN 2003). The decade of education for sustainable development (UNESCO 2014a) ran from 2005 till 2014. It is being carried further in the Global Action Program (UNESCO 2014b). At the University of Leuven, the ‘Science and Sustainability’ course is a stand-alone elective course of 6 credits that specifically aims to provide master’s students in the natural sciences with education for (the benefit of) sustainability action (Ceulemans & Severijns 2018a and 2018b). Last year (2016‐2017), the course ran for the first time and insight was gained in the competences that master’s level students hold for sustainability. Based on this experience, stronger emphasis was placed in the second year (2017‐2018) on providing, and making students use, tools to approach sustainability issues. Specific attention was directed toward allowing students to get acquainted with systems thinking and deal with inter- and transdisciplinary issues by approaching problems from a multi-stakeholder point of view. The sustainability reports the student teams compiled therefore necessarily included a representation of the system map they compiled to get a grip on the sustainability issue. Also a stakeholder map needed to be drawn.Near the end of the course it became apparent that students had difficulty in deviating from the Western interpretation of sustainability, where ecological criteria strongly dominate and ecological responsible behavior is pretended to be adequate to drive the transformation for true sustainability. However, it is in the socio-political and socio-cultural dimensions that the value-laden component of sustainability is really found. Several team-tailored feedback and discussion sessions were therefore organized to make students at least consider a slightly broader view on sustainability.Three student reports of projects that were carried out within this framework are presented in the appendices to this abstract. Students were asked to focus in their reports specifically on the broader sustainability related issues. Technical and exact-scientific information related to their project topic was preferably included in an addendum. Sustainability dimensions on which a focus was laid (e.g. Social, Cultural, Politics, Economics, Communications) varied among the projects, being largely dependent on the topic addressed and in part also on the major stakeholders.

Submerged macrophytes promote water clarity in shallow lakes in temperate regions via zooplankton refuge, allelopathy, and nutrient competition with phytoplankton, thereby increasing zooplankton grazing. However, in high-altitude Andean ecosystems, these interactions in shallow lakes have received far less attention. To understand the role of submerged plants in a relatively cold ecosystem (typical for the Andean region), two 100 L experiments were conducted in Yahuarcocha Lake, which has a permanent cyanobacterial bloom. In our first experiment, we evaluated the response of the cyanobacteria bloom to different concentrations of Egeria densa (15%, 35%, and 45% PVI). In the second experiment, we investigated the interactions between E. densa (35% PVI), zooplankton, and the small-sized fish Poecilia reticulata as well as their impacts on phytoplankton. We found a strong reduction in cyanobacteria in the presence of E. densa, whereas P. reticulata promoted cyanobacteria dominance and zooplankton had a null effect on phytoplankton. Remarkably, the combination of E. densa, fish, and zooplankton substantially reduced the algae. Our findings showed that the cyanobacteria bloom decreased in the presence of E. densa, thereby increasing the water clarity in the high-elevation eutrophic ecosystem in the Andes. This effect depended on the plant volume inhabited and the small-sized fish biomass.

Flocculation could offer a low-cost and straightforward solution to harvest microalgae in an economic and energy-efficient way. Cationically modified cellulose nanocrystals (CNCs) have been propose...

The aroma and taste of eight different phototrophic microalgae species were investigated and compared with five seaweeds to evaluate their potential as flavor ingredients in plant-based seafood alternatives. To assess their performance, commercial seafood flavoring products were used as a reference during the sensory evaluation and their chemical odor-active and taste-active profiles were compared with those of the algae. Stronger seafood odor and taste were observed in microalgae Rhodomonas salina, Tetraselmis chui and Phaeodactylum tricornutum compared to seaweeds which could be explained by the presence of important seafood aroma compounds (dimethylsulfide, fatty acids-derived compounds and trimethylamine) and taste compounds (glutamic acid, alanine, arginine and 5′-ribonucleotides). R. salina has potential as a plant-based seafood flavoring because of its crab aroma. P. tricornutum possess a high umami taste and shellfish flavor, however, its bitterness could be undesirable. T. chui is less bitter and characterized by high umami and seafood (crab, fishy) flavor, however, it possesses a slightly higher grassy odor.

Flocculation of marine microalgae is challenging because of the high ionic strength of the culture medium. We investigated cationic cellulose nanocrystals (CNCs) as biobased flocculants for the marine microalgae Nannochloropsis oculata, and compared its performance to chitosan. Cationic CNCs induced flocculation at a low dose of 11 mg.L-1 while chitosan required a dose of 35 mg.L-1. Our cationic CNCs possess a permanent positive charge, allowing flocculation over a wide pH-range (4 to 10). The CNC maximum flocculation efficiency was 90 %, while chitosan achieved > 95 %, attributed to small flocs remaining in suspension for CNCs. However, centrifugation for 1 min at 180 g or gravity filtration using a 30 µm nylon filter after CNC flocculation resulted in the removal of these small, stable flocs (∼150 µm diam) and > 95% harvesting efficiency. Cationic CNCs can serve as a sustainable alternative natural flocculant for harvesting both freshwater and marine microalgae. ispartof: Carbohydrate Polymers vol:240 ispartof: location:England status: Published online

The assembly of host-associated bacterial communities is influenced by a multitude of biotic and abiotic factors. It is essential to gain insight in the impact and relative strength of these factors if we want to be able to predict the effects of environmental change on the assembly of host-associated bacterial communities, or deliberately modify them. The environmental pool of bacteria, from which the host is colonized, and the genetic background of the host are both considered to be important in determining the composition of host-associated bacterial communities. We experimentally assessed the relative importance of these two factors and their interaction on the composition of Daphnia magna gut bacterial communities. Bacterioplankton originating from natural ponds or a laboratory culture were used to inoculate germ-free Daphnia of different genotypes. We found that the composition of the environmental bacterial community has a major influence on the Daphnia gut bacterial community, both reflected by the presence or absence of specific taxa as well as by a correlation between abundances in the environment and on the host. Our data also indicate a consistent effect of host genotype on the occurrence of specific bacterial taxa in the gut of Daphnia over different environments., The assembly of the Daphnia magna gut microbiota is strongly influenced by the composition of the environmental bacterioplankton community, and additionally structured by the host genetic background.

Producción Científica, Microalgal-bacterial consortium can be used to upgrade biogas by removing CO2 and H2S. Photosynthetic biogas upgrading requires harvesting microalgal-bacterial biomass in order to use the biomass-free cultivation medium as scrubbing liquid in the absorption column. In this study, the efficiency of different flocculants (Zetag 8125, cationically modified cellulose nanocrystals, Tanfloc, chitosan, and FeCl3) to harvest microalgal-bacterial biomass used for biogas upgrading in alkaline medium (inorganic carbon concentration up to 1800 mg L−1 and a pH ~10) was evaluated. Zetag and cationic cellulose nanocrystals resulted in maximum flocculation efficiencies of 95% (optimal dose 30 mg g−1) and 93% (optimal dose 20 mg g−1), respectively. Low flocculation was observed with other flocculants at doses as high as 200 mg g−1, which can be ascribed to the high pH of the alkaline medium. Zetag and cationic cellulose nanocrystals were selected for harvesting the biomass during semi-continuous cultivation of the microalgal consortium. Both Zetag and cationic cellulose nanocrystals were effective in flocculating the biomass with efficiencies of over 90% during five successive harvesting cycles. Gravity settling of the flocs formed by Zetag and cationic cellulose nanocrystals resulted in low biomass concentration factors of 7.7 and 2.0, respectively. Screening of flocs using a nylon mesh screen (pore size of 180 μm) resulted in a biomass concentration factor as high as 19.8. Zetag and cationic cellulose nanocrystals could be useful in harvesting biomass under high alkaline conditions without detrimental effects on biomass growth., Junta de Castilla y León y programa EU-FEDER (CLU 2017-09) y (UIC 071), FWO-NRF cooperation project (VS00218N), European Union's Horizon 2020 research and innovation programme under grant agreement no 751637

Temperate and tropical shallow lakes differ in several fundamental aspects with respect to management of eutrophication. High altitude tropical shallow lakes are a special case, showing similarities with temperate and tropical lakes. We studied the ecology of the eutrophic high-altitude tropical lake Yahuarcocha in the Ecuadorian Andes and evaluated the potential of biomanipulation to control eutrophication. With a toxin-producing Cylindrospermopsis bloom, low Secchi depth and low submerged macrophyte cover, Yahuarcocha is clearly in a turbid ecosystem state. Relatively low nutrient concentrations should theoretically allow for a shift to a clear water state through biomanipulation. Top-down control of phytoplankton by zooplankton, however, is complicated by the (1) absence of predatory fish, (2) fish community dominated by small poecelid species, (3) lack of a refuge for zooplankton from fish predation within the macrophytes, and (4) persistent, grazing resistant bloom of the cyanobacterium Cylindrospermopsis. In these aspects, lake Yahuarcocha is more similar to tropical shallow lakes, probably because water temperature is high relative to the mean air temperature and because of the absence of a cold season. The fish and macrophyte communities consisted almost entirely of exotic species. The exotic fish species probably stabilized the turbid state in the lake.

Nitrogen (N) limitation is considered as the most efficient strategy to induce the accumulation of lipids, carbohydrates or other target compounds in microalgal biomass. However, along with biomass biochemical composition, alterations in N limitation affect the photosynthetic apparatus and result in decreased growth. In this study, Chlorella vulgaris was cultivated in semi-continuous mode with different degrees of N limitation and chlorophyll (Chl) fluorescence analyses were used to investigate the effect of N limitation on photosystem II (PSII) performance, in terms of structural and functional heterogeneity. As expected, N limitation resulted in the decrease of quantum yield and calculated OJIP parameters related to PSII performance. N limitation resulted in a significant increase of trapped energy per reaction center (RC) and subsequently to higher dissipation of excess energy. However, despite the negative effect of N limitation on the number of RCs, the electron transport beyond QA as well the capacity of reducing/re-oxidation of plastiquinone were not negatively affected, implying that performance of RCs was not affected by N limitation. Photochemical quenching (qp) increased of as N limitation increased while the curve of non-photochemical quenching (NPQ) was unimodal, i.e. increased up to a level of N limitation and then decreased as N limitation degree increased further. The overall results of the present study suggest that the decrease of PSII performance was due to a reduction of the number of RCs accompanied with higher energy dissipation a probable outcome of the decreased need for reductant by cells due to lower metabolic activity under N limitation.

The aim of the present study was to evaluate the effects of varying concentrations of different nitrogen sources (individually or in combination) on the biochemical, transcriptomic and proteomic profiles of Arthrospira sp. PCC 8005 under batch and continuous modes. In batch mode, while ammonium showed a repressive effect on nitrate-assimilation pathway of the cyanobacteria; better growth and nutrient uptake rate were observed in presence of urea than nitrate. The inhibitory effect of ammonium was further confirmed by the continuous photobioreactor study wherein the nutrient feed was transiently replaced from nitrate to ammonium (28mM turbiostat regime). The changes in lipid, exopolysaccharide, transcriptomic and proteomic profiles of cyanobacteria on transition from nitrate to ammonium indicated at an onset of nutrient stress.

Microalgae are promising sources of lipids for applications in food, fuel, pharmaceutics and cosmetics. However, these lipids are also subject to lipolysis reactions during processing and storage. Especially during wet biomass storage, substantial amounts of free fatty acids (FFA) are formed, which has negative effects on flavor and nutritional value and can cause downstream processing problems in biodiesel production. This study contributes to a better understanding of the underlying processes leading to lipolysis by focusing on cell wall differences between species. Therefore, in a first phase, a comparison was made between the lipolytic stability of Nannochloropsis oculata and T-Isochrysis lutea , two species reported to have substantial differences in cell wall structure and strength. Nannochloropsis appeared to be stable during the first days of wet storage, while in T-Isochrysis , lipolysis started immediately after harvest. In a second experiment, the influence of cell disruption by high pressure homogenization (HPH) on lipolytic stability during wet storage of Nannochloropsis was investigated. It was observed that the HPH treatment induced lipolysis, as the FFA content was rapidly increasing immediately after the treatment, in contrast to the control sample, in which the FFA content was constant during the first days of storage. The integrity of the microalgal cell was thus found to play a crucial role in lipid stability during short-term post-harvest wet storage.

Given the importance of A. platensis as a potential food protein source, we describe an affordable deodorization process that does not significantly affect the nutritional value of algae biomass.; Results: Ethanol, acetone or hexane were used to deodorize algae biomass and then to identify the profile of volatile compounds associated with its distinctive odor. Sensorial characteristics were improved in the biomass cake after the proposed solvent extraction. Panelists identified the ethanolic extract with the most pronounced algae-related odor. Gas chromatography-mass spectrometry analysis showed that a mixture of 20 different compounds derived from fatty acids and amino acids contributed to the characteristic smell of A. platensis biomass. The results of the present study show that the ethanol solvent-free A. platensis biomass contained > 600 g kg-1 protein, 65% in vitro protein digestibility, similar to the original biomass. The Fourier transform infrared spectroscopy secondary protein structure was comparable among samples, indicating that the only change after ethanol extraction was a reduction of the algae smell.; Conclusion: The various extraction procedures investigated in the present study were effective in deodorizing the algae biomass. The most effective protocol was the removal of odoriferous compounds with ethanol. This particular procedure yielded an algae biomass with an improved sensorial traits. The results of the present study should help with the identification of odoriferous compounds derived from fatty acids, pigments and proteins associated with A. platensis. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.

The detection of new pollutants, stricter environmental regulations, and advancements in treatment technologies are driving improvements in bioprocesses for treating wastewater. Specifically, special concern is being placed on phosphorus and nitrogen forms, which spur eutrophication of water bodies, and emerging micropollutants such as pharmaceuticals and person-care products. Algae and cyanobacteria cultivation requirements include water and nutrient sources that currently are supplied by fertilizers, which provide poor sustainability and economics. Using wastewater as a source of nitrogen and phosphorus represents an attractive option to cultivate microalgae simultaneous with contaminant removal. Phycoremediation refers to the assimilation or disintegration of organic and inorganic compounds (carbon, nitrogen, or phosphorus), metals, and emerging contaminants in wastewater by microalgae – algae and cyanobacteria. In addition, added value comes when the microalgae are harvested to become feedstock for biofuels such as biogas. Although promising studies have been published for algal growth in wastewater while simultaneously removing contaminants, limitations in the scale-up process still have to be addressed. In this work, we summarize biological mechanisms by which nutrients and contaminants are removed by microalgae. We specifically address the interactions that the microalgae have with other microorganisms and the production of extracellular polymeric substances, a mechanism well known in the literature, but hardly studied in microalgae. Finally, we discuss different strategies reported to improve the scale up of microalgae cultivation in wastewater.

© 2016 John Wiley & Sons Ltd The tropical Andes has a high density of glacial lakes that are situated in the high-altitude páramo (3500–4500 m). Ecological information about such lakes is scant despite the fact that these lakes are an important source of water for drinking, irrigation and electricity generation and feed several major tributaries of the Amazon. In this study, we provide data on a survey of 31 lakes in Cajas National Park (Ecuador). Two of the lakes were monitored monthly during one year. In situ nutrient addition experiments were carried out in three of the lakes. Seasonal monitoring in two lakes revealed a thermal stratification of the water column between October and June, with a small temperature difference between epi- and hypolimnion (2–3 °C). Oxygen depletion of the hypolimnion towards the end of the stratification period indicated that no complete mixing of the water column occurred during stratification. There was no evidence of depletion of nutrients in the epilimnion or accumulation in the hypolimnion during stratification. There were also no clear seasonal changes in chlorophyll-a (Chl-a) concentration nor in phytoplankton community composition in the two lakes. Inputs of dissolved organic carbon (DOC) from the vegetated catchment resulted in high DOC concentrations (median 2.9 mg L−1) compared to temperate mountain lakes. Water transparency was relatively low, with a median extinction coefficient for photosynthetic active radiation of 0.50 m−1 and for UV-B radiation of 10.13 m−1. Although the thermocline was deep and water transparency was low, estimates of the critical depth for photosynthesis were deeper than the mean water depth in all lakes, suggesting that phytoplankton was not light limited. The phytoplankton community was dominated by chlorophytes (e.g. Oocystis), diatoms (small Cyclotella spp.) or small colonial cyanobacteria (Aphanocapsa, Merismopedia). The zooplankton community was either dominated by large cladocerans and cyclopoid copepods, or by the calanoid copepod Boeckella occidentalis. Total concentrations of phosphorus (P) and nitrogen (N) were comparable to those in temperate mountain lakes (4–35 μg P L−1 and 162–758 μg N L−1) while Chl-a concentrations were in the lower range (

© 2016, Springer Science+Business Media New York. This study investigated the effects of pH, salinity, biomass concentration, and algal organic matter (AOM) on the efficiency of four commercial cationic flocculants. The tannin-based biopolymers Tanfloc SG and SL and the polyacrylamide polymers Flopam FO 4800 SH and FO 4990 SH were tested for flocculation of two microalgae models, the freshwater Chlorella vulgaris and the marine Nannochloropsis oculata. Both biomass concentration and AOM presence affected all polymers evaluated, whereas salinity and pH affected only Flopam and Tanfloc, respectively. A restabilization effect due to overdosing was only observed for Flopam polymers and increasing Tanfloc dose resulted in improved efficiency. Flopam polymers showed a significant decrease in the maximum quantum yield of photosystem II as function of polymer dose for Chlorella, which supported the need for toxicological studies to assess the potential toxicity of Flopam. In overall, Tanfloc was not affected by salinity nor presented potential toxicity therefore being recommended for the flocculation of both freshwater and marine species. ispartof: BIOENERGY RESEARCH vol:10 issue:2 pages:427-437 status: published

© 2018 Elsevier B.V. Contamination of microalgal cultures by rotifers is known to cause large losses in productivity. The factors that control population dynamics of rotifers in microalgal cultures were studied in controlled contamination experiments in laboratory cultures. These experiments revealed that rotifer growth rates increase with microalgae biomass at low rotifer population densities and declines with rotifer biomass as the rotifer population approaches a carrying capacity. Experimental results were used to construct a model that describes the impact of rotifer contamination on three types of large-scale microalgal cultures. The results of this model indicate that rotifer contamination causes a complete loss in productivity in open pond and closed photobioreactor cultivation systems. In contrast, losses in productivity are limited in thin layer cascade reactors because the rotifer population cannot achieve a sufficiently high population density to cause a crash of the culture. These results suggest that different cultivation systems respond differently to rotifer contamination. ispartof: ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS vol:38 status: published

Ciliates are a common but less-explored group of contaminants in microalgal cultures that feed on microalgae and can cause severe losses in productivity of cultures. The aim of this study was to evaluate the potential of biological control to eradicate ciliates from microalgal cultures. In lab-scale experiments, we used the carni- vorous cyclopoid copepod Acanthocyclops robustus as a biological control agent to eliminate the ciliate Sterkiella from cultures of the microalga Chlamydomonas. Our experiments showed that the copepod Acanthocyclops ro- bustus can consume up to 400 ciliates individual−1 day−1. Addition of 0.07 copepods mL−1 to a culture that was contaminated with 10 ciliates mL−1 resulted in a complete elimination of ciliates from the culture within 1 day and restored the algal biomass production at the level of a non-contaminated culture. Addition of copepods to a fresh Chlamydomonas culture did not cause a reduction in the microalgal biomass concentration, indicating that this copepod does not feed on Chlamydomonas. These laboratory-scale experiments indicate that copepods have potential to be used as a biological control agent to address the problem of contamination of large-scale mi- croalgal cultures by ciliates. The authors are grateful to three anonymous reviewers for their constructive comments, which helped us improve the manuscript. The authors thank KU Leuven University for funding this research through grant OT/14/065. The first author would like to acknowledge the Ministry of Education and Training of Vietnam for funding the PhD program. D. Vandamme is a researcher funded by the Research Foundation - Flanders Belgium (FWO) (2016-2019 12D8917N).

Microalgae have a great commercial potential as a source of several compounds of interest to the food, pharmaceutical, and chemical industries. The market was estimated to be around US$1.25 billion per year with more than 20 different commercial products and the genera commercially produced are mainly Chlorella, Arthrospira (Spirulina), Dunaliella, and Haematococcus, with a production of 5.000 tons of dry matter in 2004, increasing to 9.000 tons in 2010. However, despite extensive research carried out to date, harvesting is still one of the most costly processes in microalgae production. Consequently, the microalgae that are currently produced commercially are mainly indented for high value products (>$10,000 t−1). The aim of this chapter is to give an overview of the major constraints and technologies available for harvesting microalgae.

Arthrospira is the most widely cultivated strain of all microalgae and cyanobacteria. Arthrospira forms helical trichomes that, under certain circumstances, can switch to a straight morphology. This study compared harvesting using filtration and centrifugation between helical and straight Arthrospira strains. Filtration using woven nylon membranes is the most commonly used harvesting method in the industry. Gravity filtration using nylon membranes resulted in a high retention efficiency for both strains, but the filtration flux was very low for the straight strain. Pumped filtration resulted in an increase in the filtration flux for both strains (12 to 20 m3 m−2 h−1) but in a strong decline in the retention efficiency for the straight Arthrospira strain. The nominal pore size of the woven nylon membranes had only a minor influence on the harvesting efficiency. Centrifugation yielded a high harvesting efficiency and a solid pellet at relatively low g forces (4000 g) for the straight strain, but efficiency was low even at high g forces for the helical strain. These results illustrate the importance of selecting the most appropriated harvesting methodology depending on Arthrospira strains’ morphology. While the helical strain could be easily harvested using filtration, it is preferably to use centrifugation at low g force for the straight strain.

© 2018 John Wiley & Sons Australia, Ltd The high-altitude páramo grasslands of the Andes Mountains are rich in lakes that represent a source of high-quality water for the region. Páramo grasslands are mainly used for cattle grazing. The aim of this study was to investigate the influence of cattle on the trophic status of páramo lakes. In a survey of 30 lakes in Cajas National Park (NP), a semi-quantitative estimate for cattle abundance in the vicinity of the lakes was the best predictor of the chlorophyll-a concentrations in the lakes. Cattle abundance was also significantly related to phytoplankton community composition, being associated with a shift from chlorophytes to diatoms and dinoflagellates. Lake Culibrillas, a lake situated in the Sangay National Park (Sangay NP), a region with much more intensive cattle farming than Cajas NP exhibited a chlorophyll-a concentration greater than twice as much as the largest concentration measured in the Cajas NP lakes, being characterized by a dinoflagellate bloom. Although chlorophyll-a concentrations increased with cattle abundance, the concentrations in all the study lakes remained low (0.02–1.8 μg/L), indicating that extensive cattle farming does not cause severe eutrophication. The results of this study nevertheless indicate that intensification of livestock farming in páramo grasslands might result in a deterioration of water quality in the páramo lakes. ispartof: Lakes and Reservoirs: Research and Management vol:23 issue:4 pages:303-311 status: published

Key issues for membrane technology in harvesting microalgae are to reach high fluxes and to alleviate fouling by microalgal cells and extracellular organic matter. To achieve this goal, negatively charged patterned membranes were prepared from polysulfone/sulfonated polysulfone (PSf/sPSf) blends using a spray-modified phase inversion method, and the effect of sPSf on the membrane morphology and filtration performance was investigated. The patterned membrane with highest sPSf concentration exhibited the highest clean water permeance (2420 ± 260 L/m2 h bar), lowest membrane intrinsic resistance (6.1 m-1) and highest critical flux (55 L/m2 h) for harvesting microalgae. Membrane vibration could mitigate membrane fouling both for the patterned and flat membranes. The vibration system can easily achieve turbulent flow at frequencies higher than 7 Hz. The synergy between membrane vibration, surface pattern and charge thus resulted in a clearly enhanced membrane performance.

International audience; Membranes have a lot of potential for harvesting microalgae, but membrane fouling is hampering their breakthrough. In this study, the effects of charge and corrugated surface on membrane filtration performance were investigated. The clean water permeance (CWP), the microalgae harvesting efficiency and the membrane flux for a microalgal broth were determined using patterned polysulfone (PSf) membranes with different shapes of the surface patterns and containing different charge densities by blending sulfonated polysulfone (sPSf). The flow behavior near the patterned membrane surface, as well as the interaction energy between membrane and microalgae were investigated using computational fluid dynamics (CFD) simulation and the improved extended "Derjaguin, Landau, Verwey, Overbeek" (XDLVO) theory, respectively. Membrane charge and pattern shape significantly improve the membrane performance. The critical pressures of all sPSf blend patterned membranes were higher than 2.5 bar. A 4.5w% sPSf blend patterned membranes with wave patterns showed the highest CWP (2300 L/m(2) h bar) and membrane flux in the microalgal broth (1000 L/m(2) h bar) with 100% harvesting efficiency. XDLVO analysis showed that sPSf blend patterned membranes prepared obtained the lowest interaction energy and highest energy barrier for microalgal attachment. CFD simulation showed a higher velocity and wall shear on the pattern apexes.

Arthrospira platensis (A. platensis), one of the successfully commercialized microalgae, can generate abundant extracellular polysaccharides (EPS). Separating the EPS from the culture medium is important to recycle the medium and further process the polysaccharide resource. To separate EPS from spent Arthrospira platensis culture medium, a negatively charged polysulfone (PSf) membrane was prepared by lending PSf with sulfonated PSf (sPSf), and was optimized using the response surface methodology. The optimal preparation conditions were found to be a PSf concentration of 12.5 w%, sPSf of 1.9 w% and PEG of 5.5 w% in N,N-dimetylacetamide. The hydrophilicity, porosity, mean pore size, infrared absorption spectrum, water uptake (WU), thickness and clean water permeability (CWP) were determined to characterize the membrane, and critical pressure was used to evaluate the fouling resistance of the membrane. The results show that sPSf was successfully incorporated in the optimized PSf/sPSf, and it had higher hydrophilicity, porosity, larger mean pore size, WU, CWP, thickness and higher EPS retention and lower protein retention than the pristine PSf membrane. The final EPS retention of the optimized membrane was higher than 96%.

Flocculation holds great potential as a low-cost harvesting method for microalgae biomass production. Three flocculation methods (ferric chloride, chitosan, and alkaline flocculation) were compared in this study for the harvesting of 9 different freshwater and marine microalgae and one cyanobacterium species. Ferric chloride resulted in a separation efficiency greater than 90% with a concentration factor (CF) higher than 10 for all species. Chitosan flocculation worked generally very well for freshwater microalgae, but not for marine species. Alkaline flocculation was most efficient for harvesting of Nannochloropsis, Chlamydomonas and Chlorella sp. The concentration factor was highly variable between microalgae species. Generally, minimum flocculant dosages were highly variable across species, which shows that flocculation may be a good harvesting method for some species but not for others. This study shows that microalgae and cyanobacteria species should not be selected solely based on their productivity but also on their potential for low-cost separation. publisher: Elsevier articletitle: Flocculation properties of several microalgae and a cyanobacterium species during ferric chloride, chitosan and alkaline flocculation journaltitle: Bioresource Technology articlelink: http://dx.doi.org/10.1016/j.biortech.2016.08.080 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved. ispartof: Bioresource Technology vol:220 pages:464-470 ispartof: location:England status: published

Previously, it has been observed that lipolysis occurring during (even short term) wet storage of microalgal biomass causes high free fatty acid (FFA) concentrations in the biomass. These FFA have a negative impact for different applications of microalgal lipids, e.g. downstream processing problems in biodiesel production, off-flavors and loss of nutritional value for food applications. However, it is not clear which factors influence lipolysis in microalgal biomass and which lipid class are more susceptible to lipolysis. In this study, wet biomass of T-Isochrysis lutea was stored at 20°C, 4°C and -20°C during 3 weeks. The extent of lipolysis was followed by analyzing the lipid classes distribution by ultrahigh-performance liquid chromatography−accurate mass mass spectrometry (UHPLC-amMS) and the FFA content. It was observed that FFA were formed very rapidly during post-harvest storage of wet biomass at 20°C and 4°C, the rate of this process being faster at 20°C than at 4°C, while almost no lipolysis was observed at -20°C. However, the FFA content levelled off after several days of storage because FFA reacted with alcohols to form fatty acyl esters. publisher: Elsevier articletitle: Lipolysis in T-Isochrysis lutea during wet storage at different temperatures journaltitle: Algal Research articlelink: http://dx.doi.org/10.1016/j.algal.2016.07.003 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved. ispartof: Algal Research vol:18 pages:281-287 status: published

The biosorption of phosphorus in the form of orthophosphate (Po) from wastewater using biomass as the sorbent is of potential importance because the Po-loaded biomass could be applied in the agricultural sector as fertilizer and soil conditioner. However, biomass generally displays a very low affinity for Po sorption and therefore biomass surface modification is required. In the present study, the biomass (as model grinded leaves of Phragmites sp. were used) was pretreated with Ca(OH)2 to enhance Po biosorption capacity (qe). The results indicate that the alkaline pretreatment resulted in a modification of surface functional groups. It was concluded that the main sorption mechanisms were ligand exchange and electrostatic attraction. A series of experiments were conducted to investigate the performance of the pretreated biomass for Po uptake under various conditions. Isotherm and thermodynamic studies were also applied and analyzed. The biosorption process was best described by the pseudo-second order kinetic model and Langmuir isotherm, which gave a qmax of 12.27mgP/g at 25°C and pH7. The Ca(OH)2 treated Phragmites biomass applied in this study for Po recovery may present some potential advantages in terms of costs and environmental impact.

Although ammoniacal nitrogen is the preferred nitrogen source for microalgae/cyanobacteria, at elevated concentrations and high pH values it may negatively impact photosynthesis and growth. Chlorophyll (Chl) fluorescence analysis is a useful tool to monitor the influence of various stress conditions on the photosynthetic activity of plants or microalgae/cyanobacteria. In this study, we investigated the effect of ammoniacal nitrogen on Chl fluorescence in microalgae/cyanobacteria. Chl fluorescence analysis revealed that the parameters related to flux ratios and specific energy fluxes of photochemistry were gradually inhibited as the free ammonia (FA) concentration increased. Photosynthetic electron transport activity was measured using artificial electron acceptors, donors or inhibitors. These analyses suggest that ammonia has multiple impacts on the photosynthetic apparatus; photosystems I (PSI) and II (PSII), the electron transport chain, the oxygen-evolution complex (OEC) as well the dark respiration were gradually inhibited by increasing FA concentration. At high FA concentration, the PSI/PSII activity increased, suggesting that PSI was more tolerant to FA than PSII. Non-photochemical quenching (NPQ) decreased to zero at elevated FA concentrations. The Chl fluorescence data obtained in the presence of DCMU (diuron) suggest that the decrease of NPQ under ammonia inhibition/toxicity is due to the increase of PSI/PSII activity. The rapid response of Chl fluorescence transients to increases in FA may allow one to use pulse amplitude modulation (PAM) fluorescence as a tool to monitor ammonia inhibition/toxicity in cultures of microalgae/cyanobacteria.

Bentonite was chemically pretreated with Ca(OH)2 to enhance orthophosphate phosphorus (OPP) sorption capacity (qe). The pretreatment resulted in an increase of qe from about 0.3 mg P per g to about 8 mg P per g at pH 7 and 25 °C, and of OPP concentration 100 mg P per L. The effects of solution pH, OPP concentration, sorbent dosage, and temperature on OPP sorption onto pretreated bentonite were investigated. The variation of initial pH (4–9) did not affect qe, however, re-adjustment of the final pH showed that the variation of the final pH had a significant positive effect on qe. The sorption kinetics showed a low rate, reaching half of qe in the first 4 h and equilibrium after 96 h. The calculated Langmuir qmax was 11.68 mg P per g. Thermodynamic analysis suggests that the sorption process is spontaneous and endothermic. Desorption of OPP was high in solutions of 0.1 M HCl and 0.01 EDTA-Na2 and reached 83% and 98%, respectively. We conclude that the predominant sorption mechanism for OPP uptake is inner-sphere surface complexation (ligand exchange). Other less important mechanisms such as surface precipitation and replacement of P5+ for Si4+ on the tetrahedral sites of montmorillonite may operate during the OPP uptake process by pretreated bentonite with Ca(OH)2.

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 H 2 SO 4 ) 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 medium for the cultivation of A. platensis and C. vulgaris . A. platensis could not survive in 15 × and 10 × diluted leachate and while 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-based media had lower protein content and higher carbohydrate and lipid content than in the control medium. The overall process for producing microalgal biomass from PL that we propose includes: (i) acid extraction of nutrients through the generation of PL leachate (PLL), (ii) indoor PL composting and recovery of stripped ammonia and CO 2 , and (iii) use of recovered ammonia and CO 2 along with the PLL for the cultivation of microalgae and cyanobacteria for the production of biomass.

Alkaline flocculation is a promising strategy for the concentration of microalgae for bulk biomass production. However, previous studies have shown that biological changes during the cultivation negatively affect flocculation efficiency. The influence of changes in cell properties and in the quality and composition of algal organic matter (AOM) were studied using Chlorella vulgaris as a model species. In batch cultivation, flocculation was increasingly inhibited over time and mainly influenced by changes in medium composition, rather than biological changes at the cell surface. Total carbohydrate content of the organic matter fraction sized bigger than 3 kDa increased over time and this fraction was shown to be mainly responsible for the inhibition of alkaline flocculation. The monosaccharide identification of this fraction mainly showed the presence of neutral and anionic monosaccharides. The addition of 30-50 mg L(-1) alginic acid, as a model for anionic carbohydrate polymers containing uronic acids, resulted in a complete inhibition of flocculation. These results suggest that inhibition of alkaline flocculation was caused by interaction of anionic polysaccharides leading to an increased flocculant demand over time.

Ciliates are a common but understudied group of grazers that can invade microalgal cultures. To estimate the potential impact of ciliates on microalgal culture productivity, the identification of species that can invade these cultures is essential. Furthermore, isolation of these herbivorous ciliates allows to use them in experiments that investigate the impact of ciliate grazing on the productivity of microalgal cultures. The main aims of this study were to isolate and identify ciliates that invade cultures of the freshwater microalgae Chlorella and Chlamydomonas, and to establish a live collection of these ciliates for usage in future experiments. To this end, we optimized a method for isolating ciliates from contaminated microalgal cultures and we developed a new PCR primer set for amplifying the partial 18S rDNA of ciliates belonging to the classes Spirotrichea, Oligohymenophorea and Colpodea. As a result, we isolated 11 ciliates from microalgal enrichment cultures inoculated with non-sterile dust and various freshwater sources. Of these 11 species, 7 were found to be feeding on Chlamydomonas. Ciliate species that fed on Chlorella could not be isolated in this study. Ciliate species feeding on Chlamydomonas were identified based on a combination of morphological observations and molecular analyses of partial 18S rDNA sequences. ispartof: EUROPEAN JOURNAL OF PROTISTOLOGY vol:76 ispartof: location:Germany status: published

Membranes with a wave pattern on the membrane surface are now proposed for the first time to alleviate microalgal fouling and increase the membrane flux. The membrane morphology was observed via scanning electron microscope, and the clean water permeance, microalgae harvesting efficiency and membrane flux in a real broth were determined to investigate the effects of polysulfone (PSF) and polyethylene glycol (PEG) concentrations in the membrane casting solution. Furthermore, the influence of the height of the patterned waves and the inter-pattern distance on the fouling prevention were investigated. Higher PSF and PEG concentrations resulted in better pronounced patterns. Patterned membrane showed higher fluxes and critical pressures than the corresponding flat membranes. Larger patterns gave higher membrane fluxes and less fouling. Computational fluid dynamics simulation showed a higher velocity and shear on the pattern apexes.

Flocculation of two different fresh-water green microalgae, Chlorella vulgaris and Dictyosphaerium sp., was explored using chitosan, FeCl3 and NaOH as flocculants. The most optimal dosage of each flocculant under certain pH was determined. Both chitosan and FeCl3 gave a higher flocculation efficiency then flocculation induced by pH increase. Flocculation induced by chitosan could be achieved with lower dosage. The optimal dosages of chitosan for Chlorella vulgaris and Dictyosphaerium sp. were 10 mg/L and 5 mg/L, respectively. Furthermore, the synergy between membrane filtration and flocculation was investigated and showed a higher membrane filtration performance and harvesting efficiency compared with the filtration without flocculation in both dead-end filtration and filtration with vibration. The filtration under sub-optimal flocculation conditions also showed significant potential. Introducing such flocculation into the membrane filtration process prominently reduced both energy input and required membrane area.

The optimal operational parameters of a second generation magnetically induced membrane vibration (MMV) system were determined using the response surface methodology (RSM) combined with single-factor experiments. The membrane surfaces were characterized by scanning electron microscopy (SEM) and algae cell states by inverted microscopy. The effect of an intermittent vibration strategy on filtration performance and energy consumption was studied. The results showed that the responses could be fitted by RSM models. High membrane flux, low energy consumption, efficient fouling control and no damage to the microalgae could thus be realized. The filtration strategy tests suggested that an intermittent cycle time of 4 min with 50% vibration rate could be the best vibration strategy for harvesting the microalgae under investigation.

This work mainly studied B. braunii adapted to different CO2 concentrations with cobalt enrichment, and developed a process for CO2 capture, hydrocarbon production and cobalt removal. The results showed that B. braunii favored rapid growth at 5.0% (v/v) CO2, and the highest biomass was 1.89 g.L−1 with 4.5 mg.L−1 of cobalt. Hydrocarbon productivity in high concentration CO2 (5.0% and 10.0%) with cobalt enrichment was higher than that in Chu 13 medium. The change in cobalt removal efficiency mainly corresponded to the growth of B. braunii. The LCE of B. braunii in cobalt-rich with high CO2 concentration (5.0% and 10.0%) was 15.7%, and 14.9%, respectively, which was higher than that in normal medium. CO2 fixation rates were also higher in cobalt enrichment coupled with high CO2 concentration. This study not only provides ideas for the removal of toxic metal cobalt, but also has great potential for CO2 biofixation.

© 2018 American Chemical Society. Chitosan is a nontoxic biobased polymer, attractive for the flocculation-based harvesting of microalgae. While it is generally effective to harvest algae in freshwater medium, its performance in seawater has been unpredictable. This study determined the optimal conditions for flocculation of the marine microalgae Nannochloropsis oculata using chitosan. Whereas in freshwater a low pH (7.5). The dosage of chitosan required for flocculation of Nannochloropsis in seawater (75 mg/L) was higher than the reported dose to flocculate the freshwater microalgae (±10 mg/L) reported in the literature. Experiments carried out in synthetic seawater with modified magnesium concentration indicated that flocculation induced by chitosan at varying pH was not related to precipitation of magnesium hydroxides (so-called "autoflocculation"). Chitosan flocculation at high pH in seawater medium was found to be caused by precipitation of chitosan due to (partial) deprotonation of the amine groups, resulting in a sudden network formation that induces flocculation by a sweeping mechanism. Visual observations and viscosity measurements indeed confirmed the occurrence of precipitation of chitosan at pH > 7.5. ispartof: Acs Sustainable Chemistry & Engineering vol:6 issue:9 pages:11273-11279 status: published

Microalgae are a novel biomass feedstock for the production of biogas through anaerobic digestion. However, anaerobic digestion of microalgal biomass often suffers from low methane yields due to their rigid cell walls. In contrast to eukaryotic microalgae, prokaryotic cyanobacteria have a weaker cell wall and might be more attractive as feedstock for anaerobic digestion. Nevertheless, feedstock biomass composition influences the anaerobic digestion process. In cyanobacteria, nitrogen is a key nutrient for which availability induces changes in the biomass composition. In this study, the cyanobacterium Pseudanabaena sp. CY14-1 was cultivated at different nitrogen concentrations (14, 42 and 56 mg N L−1) to achieve biomass with a variable carbohydrate content (61, 38 and 23% dry weight, respectively). Anaerobic digestion of these three types of Pseudanabaena sp. CY14-1 biomass was performed in batch experiments to evaluate the effect of biomass composition on methane yields. During the first days of the experiment, the methane yield of the biomass was comparable irrespective of the carbohydrate content. The final methane yield, however, was higher for the biomass with 23% carbohydrate content (251 mL CH4 g-1 CODin) than for the biomass with 38 and 61% carbohydrates (226 and 215 mL CH4 g-1 CODin, respectively). In contrast, 61% carbohydrate-rich biomass showed the highest hydrolysis constant (0.21 day-1) among the three types of Pseudanabaena sp. CY14-1 biomass. Methane yields achieved with these three biomasses are higher than those reported for some eukaryotic microalgae species, highlighting the potential of cyanobacteria as biomass feedstock for anaerobic digestion.

ispartof: Freshwater Metadata Journal vol:29 pages:1-9 status: published

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 0.02mol-H(+)/g was required. The optimum mass of ash required was 0.07-0.08g/g dry biomass, while the addition of ammoniac nitrogen of 8-9mgN per g of dry biomass per day was adequate for a satisfactory production of A. platensis and C. vulgaris.

Twenty-five natural and synthetic cationic polymers of different molecular weights and charge densities were evaluated for microalgae flocculation. Tanfloc is a natural low molecular weight tannin polymer whereas Zetag and Flopam are both synthetic high molecular weight polyacrylamide polymers. Five exponential concentrations (0.55, 1.66, 5, 15 and 45 mg L− 1) were tested for freshwater Chlorella vulgaris and marine Nannochloropsis oculata. All polymers were efficient (> 90% at ≥ 1.66 mg L− 1) for C. vulgaris. However, for N. oculata, only Tanfloc was effective. Charge density positively influenced flocculation decreasing the required polymer dosage. Restabilization was observed only for synthetic polymers when overdosed. Natural polymers performed similarly for both species. Overall, Tanfloc SL and Flopam FO 4990 SH were the most efficient polymers for microalgae flocculation though Tanfloc is a more economical option (US$37 per ton− 1 of biomass) and environmentally friendly than Flopam (US$171 per ton− 1 of biomass). publisher: Elsevier articletitle: Screening of commercial natural and synthetic cationic polymers for flocculation of freshwater and marine microalgae and effects of molecular weight and charge density journaltitle: Algal Research articlelink: http://dx.doi.org/10.1016/j.algal.2015.05.008 content_type: article copyright: Copyright © 2015 Elsevier B.V. All rights reserved. ispartof: Algal Research vol:10 issue:1 pages:183-188 status: published

Four different microalgal species (Phaeodactylum tricornutum, Isochrysis galbana, Nannochloropsis oculata, and Chlorella fusca) in two doses (125 and 250 mg ALA + EPA + DHA per 100 g feed) were supplemented to the diet of laying hens to examine the impact on the dynamics of long chain omega-3 polyunsaturated fatty acid (n-3 LC-PUFA) incorporation in the egg and yolk color changes. However, no major differences in dynamics of these parameters were observed between the species and between the supplementation doses. The maximum n-3 LC-PUFA content was observed after 14 days supplementation, except for the highest supplementation doses of Phaeodactylum and Nannochloropsis. In this case, the maximal value was obtained after 10 days. After a few days of wash-out, still an enrichment of n-3 LC-PUFA was observed, except for the lowest dose of Chlorella. Due to the enrichment of carotenoids in the egg, originating from microalgae, the yolk color changed. Concomitant with the delay of n-3 LC-PUFA incorporation, also a delay of yolk color changes was observed. After 7 days of microalgal supplementation, again a stable yolk color was obtained and after 10 days of wash-out, the yolk color returned to the standard yolk color in most cases. Practical applications: Knowledge of the dynamics of n-3 LC-PUFA and carotenoid incorporation is very important to know how long the microalgae need to be supplemented in to the diet of the laying hens in order to find a compromise between omega-3 and pigment levels to be stated on eggs' labels and the cost of the treatment. From an economical viewpoint, it is interesting to evaluate the supplementation of different microalgal species and different doses, since this could lead to different impacts on the economical aspect of the use of microalgae in the diet of laying hens. Microalgae were supplemented into the diets of laying hens and the impact of this supplementation on long chain omega-3 polyunsaturated fatty acid incorporation into the egg and yolk color changes was examined.

Reservoirs associated with run-of-the-river type hydroelectrical power plants (i.e. pondages) have short water residence times. For this reason, pondages are thought to have a limited impact on the fluxes of particles and solutes transported by rivers. The Malause reservoir (South West France) is such a pondage. Fed by both the Garonne and Tarn rivers, it has a water residence time of only a few days. Incoming and outgoing fluxes of nutrients, suspended particulate matter (SPM) and phytoplankton were measured weekly over the course of 1 year. Mass balance calculations showed that Malause pondage retained 24% of soluble reactive phosphorus (SRP) supplied by both rivers on an annual basis. SRP retention occurred mostly in spring–summer,pointing to biological uptake. In addition, the pondage was a sink for SPM and phytoplankton, retaining 39% of SPM and 14% of chlorophyll a supplied by both rivers on an annual basis. The retention efficiency appeared to be constrained by water temperature and residence time. The pondage was a source of phytoplankton during summer, when temperature and water residence time was high. The pondage was a sink for SPM when water residence time was low (