Algal Medium Research Articles

Cultivation of Limnospira maxima under extreme environmental conditions in Saudi Arabia: Salinity adaptation and scaling-up from laboratory culture to large-scale production

Limnospira maxima has been adapted to grow in high salinity and in an economically alternative medium using industrial-grade fertilizers under harsh environmental conditions in Saudi Arabia. A sequence of scaling-up processes, from the laboratory to large-scale open raceways, was conducted along with gradual adaptation to environmental stress (salinity, light, temperature, pH). High biomass concentration at harvest point and areal productivity were achieved during the harsh summer season (1.122 g L−1 and 60.35 g m−2 day−1, respectively). The average protein content was found to be above 40 % of dry weight. Changes in the color and morphological appearance of the L. maxima culture were observed after direct exposure to sunlight in the outdoor raceways. These results demonstrate a successful and robust adaptation method for algal cultivation at outdoor large-scale in harsh environment (desert conditions) and also prove the feasibility of using hypersaline seawater (42 g kg−1) as an algal growth medium.

Development of SPEEK-Coated IrOx Sensor for High-Biomass Aquatic pH Monitoring.

Instability is a key challenge for current pH sensors in practical applications, especially in aquatic environments with high biomass and redox substances. Herein, we present a novel approach that uses a highly stable IrOx sensing layer enveloped in a composite film of SPEEK doped with a silicon-stabilized ionic liquid (SP-IrOx). This design mitigates drift due to sensitive layer variations and minimizes interference from complex external conditions. After exhibiting robustness under moderately reducing conditions caused by S2-, I-, and ascorbic acid, the SP-IrOx sensor's efficacy was validated through real-time pH measurements in demanding aquatic settings. These included laboratory algal culture medium, sediment substrates, and mussel aquaculture areas. The sensor sustained accuracy and stability over extended periods of 6-8 days when compared to calibrated commercial electrodes. The deviations from reference samples were minimal, with a variance of no more than 0.03 pH units in mussel aquaculture areas (n = 17) and 0.07 pH units in an algal culture medium (n = 37). As a potentiometric, this solid-state electrode features a compact structure and low energy consumption, making it an economical and low-maintenance solution for precise pH monitoring in diverse challenging environments with high biomass and turbidity.

Enhanced carotenoid production, biodiesel quality, and harvesting efficiency in microalga Graesiella emersonii via heterotrophic cultivation strategy

The aim of this study was to evaluate the potential industrial applicability of the green microalga Graesiella emersonii GEGS21 by comparing its biomass, photosynthetic pigments, and biodiesel properties under photoautotrophic (PA) and heterotrophic (HT) cultivation. Four agricultural soluble fertilizers (SFs) were tested as substitute medium for algal growth. Of these, three were not only cost-effective but also more efficient in promoting growth compared to the BG-11 algal medium. Supplementing the SF medium with 12 g/L of glucose significantly improved algal biomass productivity under HT condition, and the optimal conditions were identified as 0 M NaCl, a temperature of 30 °C, and a pH of 8. Subsequent supplementation with yeast extract led to a notable enhancement in algal growth, resulting in approximately 18.6-times higher biomass productivity compared to the PA condition. Under HT cultivation, the productivities of the photosynthetic pigments including lutein and zeaxanthin were significantly increased approximately by 3.6-fold and 3.5-fold, respectively compared to the PA condition (p < 0.05). Moreover, HT cultivation led to improved biodiesel properties, such as iodine value, cetane number, oxidative stability, and kinematic viscosity. These enhancements, achieved through altered fatty acid methyl ester composition, align with the ASTM D6751 and EN14214 biodiesel standards. Interestingly, when cultivated under HT conditions, algal strain exhibited higher sedimentation efficiency, accompanied by an enhanced cellular starch content, compared to both PA and mixotrophic conditions. This suggests a promising strategy for economically viable harvesting by altering the specific gravity of algal cells. In conclusion, our findings suggest that HT cultivation of Graesiella emersonii GEGS21 may serve as an effective approach to produce value-added compounds and bioenergy, offering potential for economical harvesting.

Anticancer Activity of Lectin Extracted from the Saltpan Microalga, Navicula sp.

Haemagglutinins are carbohydrates binding protein applied as tools in cell biology and immunology. In the present study, lectin from selected microalgae Navicula sp. was isolated and characterized for biomedical applications. The microalgae were collected from the saltpan water sample. A total of six species were isolated including Amphora sp., Nitzschia sp., Navicula sp., Scendesmus sp., Chlorella sp. and Nanochloropsis sp. by direct plating method using algal isolation medium and characterized. The crude microalgal extracts were screened for the presence of lectin and it was confirmed by haemagglution assay. Among the strains, Navicula sp. showed potent haemagglutinin activity. Heamagglutinin from Navicula sp. was further partially characterized using chromatography methods. Navicula lectin agglutinated animal and human erythrocytes. It showed high specificity for human “O” erythrocytes with the titre value of 32 HA units. The HA activity was stable between pH 7and 8 and showed thermal stability between 30 ºC and 40 ºC (p&lt;0.01). The isolated lectin was calcium dependent and HA activity was reduced when exposed to chelators such as EDTA (p&lt;0.01). Hemagglutination inhibition assay exhibited the strongest binding specificity towards glucose, sucrose and galactose. The cross-adsorption assay revealed that the Navicula sp. Possesses single agglutinin. The purified lectin showed anticancer activity against cervical cancer cell lines.

Computational fluid dynamics coupled to biokinetic models: Numerical methodology for microalgae cultivation optimization

Mixing of the algal culture medium in a photobioreactor (PBR) is a crucial factor to enhance microalgae cultivation and production, since it ensures microalgae cells can homogeneously access nutrients and light radiation. Hydrodynamic conditions in an industrially applicable PBR cannot be tested in laboratory cultivation systems since the scale-up methodology is not specified; hence requiring complex tests at a demonstrative scale or the application of mathematical models. In this study, a three-dimensional numerical model of the hydrodynamic conditions in a hybrid horizontal tubular PBR was developed to investigate the mixing of the culture medium under various operating conditions, in order to optimize biomass production in this type of system. The PBR consists of two open tanks connected through sixteen polyethylene transparent tubes, at a demonstrative scale (total volume 11.7 m3). Microalgae cells movement inside the tubes was simulated. Cell trajectory prediction allows to simulate the intensity of mixing of the culture medium. Subsequent coupling with the biokinetic BIO_ALGAE model allows to monitor the influence of hydrodynamic conditions on the distribution of light in the culture medium and the yield of microalgae. The simulations were experimentally validated. The more intense mixing of the culture medium caused by increasing flow rate (Re = 23,700–46,200) allows more frequent exposure of the microalgae cells to the light source, which according to the results obtained can increase the microalgal yield by 14% in the summer cultivation period and by 151% in the winter period.

Analysis of the growth profile, biochemical composition and nutrient removal efficacy of Spirulina sp. NCIM 5143

In the present manuscript, the growth profile of the microalgae Spirulina sp. NCIM 5143 was studied. Screening was performed on four commercial media, i.e., blue‒green-11 (BG-11), Bold’s basal medium (BBM), algal culture medium (ACM), Zarrouk’s medium (ZM), and different concentrations (20%, 40%, 60%, 80%, and 100%) of unsterilized dairy effluent (UDE). Characterization of biomass was performed to assess its biochemical composition through various assays. Elemental composition and bioactive compound analysis were accomplished by inductively coupled plasma-atomic emission spectroscopy (ICP‒AES) and gas chromatography‒mass spectrometry (GC‒MS), respectively. The results revealed that maximum values of most of the parameters, i.e., optical density (0.21), chlorophyll (2.00 mg/l), proteins (119.17 mg/l), and wet (4.06 g/l) and dry biomass weight (0.28 g/l), were found on ZM. For UDE, maximum growth parameters and the highest nutrient removal efficiency were obtained at 100% concentration. Biochemical analysis revealed that total Kjeldahl nitrogen (7.14±0.49%), crude protein (48.23± 3.34%), total antioxidant activity (3.07±0.03 mg AAE/g), and total phenols (8.88±1.93 mg GAE/g) were present in the biomass. Elemental and GC‒MS analysis detected essential micronutrients and many bioactive compounds, respectively. Hence, this study proved that Spirulina sp. NCIM 5143 has the potential for the management of waste dairy effluent. This study also showed its cost-effectiveness, as the dairy effluent analyzed is used without any kind of sterilization. In addition, its biomass is rich in several essential elements, antioxidants, and bioactive compounds of therapeutic and nutraceutical importance.

High-temperature stress induces bacteria-specific adverse and reversible effects on Ulva (Chlorophyta) growth and its chemosphere in a reductionist model system

Abstract Axenic cultures of the green seaweed Ulva mutabilis were inoculated with bacteria providing essential algal growth and morphogenesis-promoting factors (AGMPFs) and were exposed to temperature shifts from 18 °C to 30 °C. The temperature-dependent effect of bacteria on longitudinal algal growth and the molecular composition of the chemosphere in the algal culture medium was explored. The reductionist tripartite model system of U. mutabilis, Roseovarius sp. MS2, and Maribacter sp. MS6 was applied as a reference and has been changed by substituting Roseovarius with isolates that phenocopy this strain. Rathayibacter festucae IH2 and Roseovarius aestuarii G8 boosted growth at 18 °C but slowed it down at 30 °C. Additional inoculation of Roseovarius sp. MS2 mitigated these adverse bacterial effects partially. At 30 °C, the molecular profile of the chemosphere differed dramatically between all tested tripartite communities, indicating different traits of the same bacterium with changing temperatures. Functional examinations should, therefore, accompany microbiome analysis to detect changing traits with the same microbiome composition.

Enhancing carotenoid production and exploring the potential use of microalga Desmodesmus cf. pleiomorphus DSHM22 as a biodiesel feedstock through photoheterotrophic cultivation

Improving biomass and value-added compound production is crucial for the industrial application of microalgae, achieved through the utilization of low-cost nutrients and various cultivation modes. This study aimed to enhance the biomass and biochemical production of the indigenous microalgae by comparing different cultivation modes. Among six algal strains obtained from the East Sea in South Korea, Desmodesmus cf. pleiomorphus DSHM22 exhibited the highest biomass productivity (0.0118 g L−1 d−1) and was selected for optimization. Algal growth responses were assessed under four commercially available soluble fertilizer media to identify a cost-effective nutrient substrate. The most effective fertilizer demonstrated 2.2-fold higher growth compared to the BG-11 algal medium after 14 days. Glucose was supplemented in the culture medium to evaluate organic carbon availability under light and dark conditions. While no growth responses were observed under glucose-supplemented dark condition, the highest biomass production (approximately 1.22 g L−1) was achieved under glucose-supplemented light condition. The algal strain showed growth under both photoautotrophic (PA) and photoheterotrophic (PH) conditions, excluding the heterotrophic mode. Biochemical accumulations were compared by analyzing photosynthetic pigments and fatty acids under both PA and PH modes. The algal strain effectively produced lutein, neoxanthin, and omega-3, 6, and 9 fatty acids. Although PH condition yielded significantly higher biochemicals and lipid production compared to PA condition, both culture conditions exhibited similar fatty acid compositions and biodiesel properties. This study suggests that PH cultivation is an effective approach for producing value-added biochemicals and biodiesel using microalga D. cf. pleiomorphus DSHM22.

Phycoremediation of crude oil polluted water from selected water sources in Ogoniland, Rivers State, Nigeria.

Crude oil exploitation in the Niger Delta, particularly in Ogoniland, brought environmental devastation occasioned by petroleum pollution, as farmlands and water sources were destroyed. This study was designed to remediate crude oil contaminated water obtained from water sources in Ogoniland using two green algal species. Thirty water samples were collected from eight different water sources. The samples were analysed for total petroleum hydrocarbon (TPH) using gas chromatography/flame ionization detector (GC/FID). Algal samples were collected from Ogba River and at wetland in Military Hospital Benin, Edo State, Nigeria. The algal samples were identified, screened, optimized and grown in Bold basal medium. Results obtained from the determination of TPH showed that the infiltrated pond (Exc) sample site had the highest concentration among all the sites sampled with 198.8329 μg/L, R2 with 134.1296 μg/L, R1 with 108.9394 μg/L, R3 with 105.8011 μg/L, R4 with 98.442 8 μg/L, the hand-dug wells (Wll) had 9.6586 μg/L while the borehole (Bhl) had the lowest with 1.8310 μg/L. It was deduced that pollution of water sources was principally because of pollutants washed from the soil environment into the open surface water sources via run-off rather than through the seepage from the underground aquifers, incriminating illegal oil mining and artisanal refining. Results obtained from the analysis of algal growth medium indicated that the two algal species were able to absorb the hydrocarbon contaminants, albeit at different rates, corresponding with the algal growth rate. Analysis of algal biomass after 4 weeks of remediation showed that from the initial 10.27 μg/20 mL added to the growth medium, the highest TPH mean value of 0.490 μg/20 mL was extracted from Ulothrix zonata (F.Weber & Mohr) Kützing biomass grown in Exc compared to 0.344 μg/20 mL of TPH extracted from Chlorella sorokiniana Shihira & R.W.Krauss grown in the same sample site. Also, Ulothrix zonata had higher TPH yield 0.023 μg/20 mL in Bhl compared to Chlorella sorokiniana 0.021 μg/20 mL of TPH from the same water source. This result indicated Ulothrix zonata had superior TPH phycoremediation ability to Chlorella sorokiniana. While the present study calls for deployment of the algal species for field trial, it is strongly recommended that crude oil pollution should be discouraged.

Feasibility of growing microalgae on wastewaters collected from a vinegar plant for, concurrently, nutrient removal and biomass production

In this work, feasibility of using winemaking wastewater (WW), vinegar wastewater (VW), and pickle wastewater (PW) to cultivate microalgae was investigated. Results showed that the three wastewaters possessed different nutrient profiles due to their various sources, and VW was much richer in nutrients than WW and PW. The maximum biomass concentrations of 0.73, 2.45, and 0.64 g L−1 were observed when Chlorella vulgaris was cultivated in WW, VW, and PW, respectively, suggesting that VW was a potential algal culture medium. Moreover, four algal strains could grow well on VW, but biomass production and nutrient removal of C. vulgaris were significantly higher than that of the other three strains, indicating that this alga was a promising algal strain for VW treatment. Furtherly, initial cell density was optimized for improving nutrients removal and biomass production. The maximum biomass concentration and productivity of 2.83 g L−1 and 349.8 mg L−1 d−1, and TN, TP, and COD removal efficiencies of 80.02, 64.38, and 77.10 %, respectively, were obtained when initial cell density was 0.4 g L−1. Initial cell density had little impact on the algal chemical composition, but availability and concentration of nutrients and algal species exhibited remarkable influences on the chemical compositions of microalgae cultivated in these wastewaters. These findings not only verified the feasibility of using vinegar production wastewaters to cultivate microalgae, but also paved a way for large-scale microalgae cultivation using the wastewaters.

Effects of Hyphomonas Strains on the Growth of Red Algae Pyropia Species by Attaching Specifically to Their Rhizoids.

Bacteria and marine macroalgae form close associations, while various bacteria affect the morphogenesis and growth of macroalgae. Hyphomonas strains exhibit normal morphogenetic activity in protoplasts of the red alga Pyropia yezoensis (nori). However, the effects of the bacteria on the growth of Pyropia from protoplast cells to regenerated thalli remain unknown. Here, we assessed the growth of P. yezoensis and Pyropia tenera using combined cultures of three Hyphomonas strains (LNM10-16, SCM-2, and LNM-9) and three algal media (artificial seawater with vitamins, artificial seawater, and natural seawater) over 7weeks. Third week after culture, the three Hyphomonas strains showed almost similar levels of normal growth activity for both Pyropia species. However, at 7weeks, significant differences were observed among the three Hyphomonas strains in terms of length, length-to-width ratio, and normal morphology of Pyropia thalli. LNM10-16 significantly promoted the thalli length and length-to-width ratios of both Pyropia species in artificial seawater without vitamins and natural seawater, compared with the other two Hyphomonas strains. P. yezoensis cultured in artificial seawater with vitamins showed a much higher demand for LNM10-16 in development of the thalli length than P. tenera. These results may be explained by differences in the growth activities of Hyphomonas strains and the nutrient requirements of Pyropia species. Furthermore, the bacteria were more specifically attached to the rhizoid surfaces of both species. This study is the first to reveal that Hyphomonas strains affect the growth of Pyropia species by attaching to their rhizoids.

Comparing the Ability of Secretory Signal Peptides for Heterologous Expression of Anti-Lipopolysaccharide Factor 3 in Chlamydomonas reinhardtii

Anti-lipopolysaccharide factor 3 (ALFPm3) possesses a wide antimicrobial spectrum and high antibacterial and viral activities for broad application prospects in the aquaculture industry. However, the application of ALFPm3 is limited by its low production in nature, as well as its low activity when expressed in Escherichia coli and yeast. Although it has been proven that its secretory expression can be used to produce antimicrobial peptides with strong antimicrobial activity, there is no study on the high-efficiency secretory expression of ALFPm3 in Chlamydomonas reinhardtii. In this study, signal peptides ARS1 and CAH1 were fused with ALFPm3 and inserted into the pESVH vector to construct pH-aALF and pH-cALF plasmids, respectively, that were transformed to C. reinhardtii JUV using the glass bead method. Subsequently, through antibiotic screening, DNA-PCR, and RT-PCR, transformants expressing ALFPm3 were confirmed and named T-JaA and T-JcA, respectively. The peptide ALFPm3 could be detected in algal cells and culture medium by immunoblot, meaning that ALFPm3 was successfully expressed in C. reinhardtii and secreted into the extracellular environment. Moreover, ALFPm3 extracts from the culture media of T-JaA and T-JcA showed significant inhibitory effects on the growth of V. harveyi, V. alginolyticus, V. anguillarum, and V. parahaemolyticus within 24 h. Interestingly, the inhibitory rate of c-ALFPm3 from T-JcA against four Vibrio was 2.77 to 6.23 times greater than that of a-ALFPm3 from T-JaA, indicating that the CAH1 signal peptide was more helpful in enhancing the secreted expression of the ALFPm3 peptide. Our results provided a new strategy for the secretory production of ALFPm3 with high antibacterial activity in C. reinhardtii, which could improve the application potentiality of ALFPm3 in the aquaculture industry.

Removal of ciprofloxacin from aqueous media by Chlorella pyrenoidosa, Scenedesmus obliquus, and isolated Stichococcus bacillaris: A comparative study on toxicity, removal mechanism and biochemical composition

This study investigates the acute toxicity and removal capacity of the native isolated species Stichococcus bacillaris towards Ciprofloxacin (CIP) and compared its efficiency with the most explored algal species Chlorella pyrenoidosa and Scenedesmus obliquus in antibiotic removal. The toxicity assessment revealed that 24 hr EC50 values are in the order of Stichococcus bacillaris (64 mg/L) > Chlorella pyrenoidosa (52 mg/L) > Scenedesmus obliquus (42 mg/L) and 24 hr LC50 values are in the order of Stichococcus bacillaris (313 mg/L) > Chlorella pyrenoidosa (228 mg/L) > Scenedesmus obliquus (197 mg/L). Furthermore, CIP (5 mg/L) was spiked into the algal medium to study their removal potential for 7 days. Stichococcus bacillaris and Scenedesmus obliquus reported higher removal efficiency (40%) compared to Chlorella pyrenoidosa (28%) with biodegradation as the major contributing removal mechanism in all the species with the order of Stichococcus bacillaris (84%) > Scenedesmus obliquus (80%) > Chlorella pyrenoidosa (59%). Biochemical characterization revealed that Scenedesmus obliquus is a suitable candidate for biodiesel production as the lipid production (830 mg/L) is higher in this species and Stichococcus bacillaris is suitable for bioethanol production as the carbohydrates production (609 mg/L) is substantial in this species.

Potassium alleviating power overshoot and promoting carbon capture of bufferless algae microbial fuel cells

Power overshoot makes microbial fuel cell (MFC) unable to work normally under high current densities, limiting its application in carbon capture. Herein, effects of cations in medium on overshoot are compared using bufferless MFCs filled by saline or algae suspension containing Na+ or K+. Furthermore, the relationship between cation type and CO2 sequestration abilities of algae MFCs are analyzed under continuous flow mode. As a result, K+ helps to inhibit oxygen leakage while promote proton transport through Nafion separator. Transmembrane diffusion coefficient of oxygen in Na+ saline medium is 1.41 × 10−4 cm·s−1, which decreases to 0.91 × 10−4 cm·s−1 in K+ group. K+ as well as cathodic biofilms or algae cells attribute to overshoot alleviation. No matter saline or algal medium, MFCs containing K+ exhibit better electrochemical properties and achieve more than 40% and 20% increases in maximum power and current densities. Carbon capture capacities of algae MFCs are promoted over 40% in the presence of K+. Under the inlet CO2 concentration of 1% v/v, 5% v/v and 10% v/v, CO2 removal efficiencies of single-chamber algae MFCs containing K+ are 27.46 ± 1.07%, 35.51 ± 1.24% and 39.15 ± 1.35%. This work provides a new strategy for the optimization of MFC power generation and carbon capture by simply adjusting the cations in the solution matrix.

13CO2-labelling and Sampling in Algae for Flux Analysis of Photosynthetic and Central Carbon Metabolism.

The flux in photosynthesis can be studied by performing 13CO2 pulse labelling and analysing the temporal labelling kinetics of metabolic intermediates using gas or liquid chromatography linked to mass spectrometry. Metabolic flux analysis (MFA) is the primary approach for analysing metabolic network function and quantifying intracellular metabolic fluxes. Different MFA approaches differ based on the metabolic state (steady vs. non-steady state) and the use of stable isotope tracers. The main methodology used to investigate metabolic systems is metabolite steady state associated with stable isotope labelling experiments. Specifically, in biological systems like photoautotrophic organisms, isotopic non-stationary 113C metabolic flux analysis at metabolic steady state with transient isotopic labelling (13C-INST-MFA) is required. The common requirement for metabolic steady state, alongside its very short half-timed reactions, complicates robust MFA of photosynthetic metabolism. While custom gas chambers design has addressed these challenges in various model plants, no similar tools were developed for liquid photosynthetic cultures (e.g., algae, cyanobacteria), where diffusion and equilibration of inorganic carbon species in the medium entails a new dimension of complexity. Recently, a novel tailor-made microfluidics labelling system has been introduced, supplying short 13CO2 pulses at steady state, and resolving fluxes across most photosynthetic metabolic pathways in algae. The system involves injecting algal cultures and medium containing pre-equilibrated inorganic 13C into a microfluidic mixer, followed by rapid metabolic quenching, enabling precise seconds-level label pulses. This was complemented by a 13CO2-bubbling-based open labelling system (photobioreactor), allowing long pulses (minutes-hours) required for investigating fluxes into central C metabolism and major products. This combined labelling procedure provides a comprehensive fluxome cover for most algal photosynthetic and central C metabolism pathways, thus allowing comparative flux analyses across algae and plants.

OPTIMIZATION OF CULTURE MEDIA FOR THE GROWTH OF ANABAENA PCC550, ANABAENA PCC 574, AND CYLINDROSPERMUM PCC518, CYLINDROSPERMUM PCC 567

In the present study, Anabaena PCC550, Anabaena PCC574 and Cylindrospermum PCC518, Cylindrospermum PCC 567 have been subjected to 7 different inorganic culture media. In order to identify the best growth medium i.e.; optimized medium, the nutrient requirement of these two algae have been evaluated as prime requisite. The present investigation analyzed the growth of wet biomass of the four microalgae. In order to attain optimal growth of Anabaena and Cylindrospermum species, the 7 culture media employed in the current study were (i) BG11 medium (ii) Knoops medium (iii) Cyanophycean agar medium (iv) Modified Bristols medium (v) Prigsheims Medium (vi) Foggs Medium and (vii) Algal culture medium. Highest growth on 60th day was seen in Cylindrospermum PCC 518 (0.134mg/100ml), Anabaena PCC 574 (0123mg/100ml), Cylindrospermum PCC 567 (0.098mg/100ml), Anabaena PCC 550 (0.094mg/100ml) in Algal culture media which shows luxurient growth when compared to BG11, Foggs Media, Modified Bristols media, Knoops media. While, Prigsheims medium did not show any growth of Anabaena PCC550, Anabaena PCC574 and Cylindrospermum PCC518, Cylindrospermum PCC 567.

Algae from Aiptasia egesta are robust representations of Symbiodiniaceae in the free-living state.

Many cnidarians rely on their dinoflagellate partners from the family Symbiodiniaceae for their ecological success. Symbiotic species of Symbiodiniaceae have two distinct life stages: inside the host, in hospite, and outside the host, ex hospite. Several aspects of cnidarian-algal symbiosis can be understood by comparing these two life stages. Most commonly, algae in culture are used in comparative studies to represent the ex hospite life stage, however, nutrition becomes a confounding variable for this comparison because algal culture media is nutrient rich, while algae in hospite are sampled from hosts maintained in oligotrophic seawater. In contrast to cultured algae, expelled algae may be a more robust representation of the ex hospite state, as the host and expelled algae are in the same seawater environment, removing differences in culture media as a confounding variable. Here, we studied the physiology of algae released from the sea anemone Exaiptasia diaphana (commonly called Aiptasia), a model system for the study of coral-algal symbiosis. In Aiptasia, algae are released in distinct pellets, referred to as egesta, and we explored its potential as an experimental system to represent Symbiodiniaceae in the ex hospite state. Observation under confocal and differential interference contrast microscopy revealed that egesta contained discharged nematocysts, host tissue, and were populated by a diversity of microbes, including protists and cyanobacteria. Further experiments revealed that egesta were released at night. In addition, algae in egesta had a higher mitotic index than algae in hospite, were photosynthetically viable for at least 48 hrs after expulsion, and could competently establish symbiosis with aposymbiotic Aiptasia. We then studied the gene expression of nutrient-related genes and studied their expression using qPCR. From the genes tested, we found that algae from egesta closely mirrored gene expression profiles of algae in hospite and were dissimilar to those of cultured algae, suggesting that algae from egesta are in a nutritional environment that is similar to their in hospite counterparts. Altogether, evidence is provided that algae from Aiptasia egesta are a robust representation of Symbiodiniaceae in the ex hospite state and their use in experiments can improve our understanding of cnidarian-algal symbiosis.

Ru/C-Catalyzed Hydrogenation of Aqueous Glycolic Acid from Microalgae - Influence of pH and Biologically Relevant Additives.

Ethylene glycol (EG) is obtained by a novel, two‐step approach combining a biotechnological and a heterogeneously catalyzed step. First, microalgae are cultivated to photobiocatalytically yield glycolic acid (GA) by means of photosynthesis from CO2 and water. GA is continuously excreted into the surrounding medium. In the second step, the GA‐containing algal medium is used as feedstock for catalytic reduction with H2 to EG over a Ru/C catalyst. The present study focuses on the conversion of an authentic algae‐derived GA solution. After identification of the key characteristics of the algal medium (compared to pure aqueous GA), the influence of pH, numerous salt additives, pH buffers and other relevant organic molecules on the catalytic GA reduction was investigated. Nitrogen‐ and sulfur‐containing organic molecules can strongly inhibit the reaction. Moreover, pH adjustment by acidification is required, for which H2SO4 is found most suitable. In combination with a modification of the biotechnological process to mitigate the use of inhibitory compounds, and after acidifying the algal medium, over Ru/C a EG yield of up to 21 % even at non‐optimized reaction conditions was achieved.

Efficacy of Ciprofloxacin and Amoxicillin Removal and the Effect on the Biochemical Composition of Chlorella vulgaris.

Antibiotics are frequently detected in the aquatic environment due to their excessive usage and low-efficiency removal in wastewater treatment plants. This can provide the origin to the development of antibiotic-resistant genes in the microbial community, with considerable ecotoxicity to the environment. Among the antibiotics, the occurrence of ciprofloxacin (CIP) and amoxicillin (AMX) has been detected in various water matrices at different concentrations around the Earth. They are designated as emerging contaminants (ECs). Microalga Chlorella vulgaris (C. vulgaris) has been extensively employed in phycoremediation studies for its acclimatization property, non-target organisms for antibiotics, and the production of value-added bioproducts utilizing the nutrients from the wastewater. In this study, C. vulgaris medium was spiked with 5 mg/L of CIP and AMX, and investigated for its growth-stimulating effects, antibiotic removal capabilities, and its effects on the biochemical composition of algal cells compared to the control medium for 7 days. The results demonstrated that C. vulgaris adapted the antibiotic spiked medium and removed CIP (37 ± 2%) and AMX (25 ± 3%), respectively. The operating mechanisms were bioadsorption, followed by bioaccumulation, and biodegradation, with an increase in cell density up to 46 ± 3% (CIP) and 36 ± 4% (AMX), compared to the control medium. Further investigations revealed that, in the CIP stress-induced algal medium, an increase in major photosynthetic pigment chlorophyll-a (30%) and biochemical composition (lipids (50%), carbohydrates (32%), and proteins (65%)) was observed, respectively, compared to the control medium. In the AMX stress-induced algal medium, increases in chlorophyll-a (22%), lipids (46%), carbohydrates (45%), and proteins (49%) production were observed compared to the control medium. Comparing the two different stress conditions and considering that CIP is more toxic than AMX, this study provided insights on the photosynthetic activity and biochemical composition of C. vulgaris during the stress conditions and the response of algae towards the specific antibiotic stress. The current study confirmed the ability of C. vulgaris to adapt, bioadsorb, bioaccumulate, and biodegrade emerging contaminants. Moreover, the results showed that C. vulgaris is not only able to remove CIP and AMX from the medium but also can increase the production of valuable biomass usable in the production of various bioproducts.

Enhanced microalgae harvesting in a microfluidic centrifugal separator

Biofuel is a promising renewable energy source that has gained interest in recent years due to its viability and sustainability. Microalgae in particular have three orders of magnitude higher in oil-to-fuel yield when compared with other crop-based feedstocks, and therefore microalgal biofuels have the substantial potential to meet national energy demands. One challenge of the microalgae-derived biofuels is limited harvesting efficiency, prompting an urgent need for alternative harvesting methods that are cost-effective and viable. Centrifugation has been used as one such method of separation due to its simple principle and effectiveness. However, most centrifugation methods lie in the high operating costs as opposed to other mechanical or chemical methods. To maximize separation efficiency while also limiting costs, we hereby demonstrate a spiral microalgae separator consistent with the centrifugal method, along with manipulating selected parameters of the algal medium to achieve a degree of separation within a single experiment that yields significantly more concentrated algal slurry. Concentration, temperature, and pH manipulation were among the few selected parameters that we found to yield high concentrations within single, rapid separations in seconds. Initial concentration of algae solutions was found to relate proportionally to separation efficiency. Algae solutions at lower density experienced flocculation that aids in the separation and centrifugal effect whereas high density samples experienced flocculation of algal groups too large for efficient separation. Similarly, basic pH and higher temperature manipulations specifically targeted the flocculation of microalgae particles to form larger groups, with more efficient harvesting. These parameters enable the principle and benefits of microfluidic centrifugal separation to be demonstrated on the microalgae flow, with the ability to be scaled up using parallelization of multiple platforms: a viable alternative to the conventional centrifugal method.