Ankistrodesmus Falcatus Research Articles

Performance Characteristics of Ankistrodesmus falcatus in Different Culture Media and Concentration.

This study determined the effect of growth media and culture concentration on the growth, proximate, and microelement composition of Ankistrodesmus falcatus. The culture of A. falcatus was done using three media, namely Modified COMBO Medium (COMBO), Bold’s Basal Medium (BBM), and Bristol, at two concentrations (50% and 100%). The results obtained show that the cell density (>3.5 × 107 cells/mL), optical density (>0.24), and specific growth rate (>0.429%/day) were significantly higher (p ≤ 0.05) in BBM and COMBO than in Bristol (<3.1 × 107 cells/mL; <0.23; <0.416%/day, respectively) at both concentrations. However, biomass was higher in BBM (>2.20 g/L) than in COMBO (1.87–2.13 g/L), while Bristol had the lowest value observed (1.70–1.73 g/L). Biochemical and microelement composition showed variations between media and at the different concentrations, with higher values observed in BBM and COMBO. Based on the growth parameters and nutritional composition, it was concluded that BBM and COMBO were better media for the propagation of A. falcatus growth than Bristol. The study also demonstrated that the microalgae can be cultured using half of the media’s concentration to lower production costs.

The impact of abiotic factors on the growth and lipid accumulation of some green microalgae for sustainable biodiesel production.

Three species of freshwater planktonic green microalgae: Ankistrodesmus braunii, Ankistrodesmus falcatus, and Scenedesmus incrassatulus, were isolated from the Nile water in Upper Egypt. These microalgae were exposed to nutritional (nitrogen, phosphorus, and iron) limitations and salinity stress to study their effects on the algal growth and to elevate the lipid content within their cells. The results indicated that exposure to these conditions had a significant impact on the algal growth. The lipid content of the studied algae increased as a result of the salinity stress. The highest lipid content was recorded in A. braunii culture treated with 50 mM NaCl (34.4% of dry weight) and S. incrassatulus cultures treated with 100 mM NaCl (37.7% of dry weight) on the 6th day of cultivation, while the culture of A. falcatus treated with 100 mM NaCl recorded the maximum lipid content (53% of dry weight) on the 10th day of the experiment. The biodiesel quality parameters of the fatty acid methyl ester profile of S. incrassatulus appeared to be in agreement with the international criteria. S. incrassatulus could be regarded as a quite promising feedstock for the biodiesel production.

The complete mitochondrial genome of the oleaginous microalgae Ankistrodesmus falcatus strain UCP001 from the Peruvian Amazon

Ankistrodesmus falcatus strain UCP001 is a native oleaginous microalgae isolated from the Peruvian Amazon basin. In this study we sequenced, de novo assembled, and functionally annotated the complete mitochondrial genome of the native oleaginous microalgae Ankistrodesmus falcatus strain UCP001 (Accesion number MT701044). This mitogenome is a typical circular double stranded DNA molecule of 41,048 bp in total length with G + C content of 37.4%. The mitogenome contains 49 genes, including 18 protein coding genes, 5 ribosomal (rRNA) genes and 26 transfer RNA (tRNA) genes. A phylogenetic analysis of 18 microalgae species indicated that Ankistrodesmus falcatus strain UCP001 was closely related to Ourococcus multisporus and Raphidocelis subcapitata. The complete mitochondrial genome sequence of Ankistrodesmus falcatus strain UCP001 enriches genomic resources of oleaginous native microalgae from the Peruvian Amazon for further basic and applied research.

Species Diversity of selected Flora and Fauna in the river Yamuna at Kalpi (U.P.) India

To evaluate the pollution status species diversity of selected flora and fauna of the Yamuna river at Kalpi stretch was studied for a period of one year. Four sampling stations were selected for sampling purpose. Collected samples are evaluated for flora and fauna specially phytoplankton, aquatic macrophytes, zooplankton and fishes. Selected flora and fauna of studied water are presented by phytoplankton members of Chlorophyceae, Euglenophyceae, Bacillariophyceae and Cyanophyceae, aquatic macrophytes of 8 families, zooplankton members of Protozoa, Rotifera, Cladocera and Copepoda and fishes of 10 families. In these recorded species of different groups of flora and fauna, some pollution indicator species like Scenedesmus quadricauda, Stigeoclonium tenue,Ankistrodesmus falcatus, Chlorella vulgaris, Euglena viridis, Synedra ulna, Cyclotella meneghiniana, Navicula viridula, Nitzschia, Oscillatoria limosa, O. tenuis, O. chlorina, Phormidium uncinatum,Microcystis aeruginosa of phytoplanton, Eichhornea, Potamogeton and Cyperus species of aquatic macrophytes, Brachionus species and Keratella species of zooplankton and Clarias batrachus fish are also presented along with clean water species. Presence of both pollution indicator and clean water species show that water of Yamuna river at Kalpi stretch is moderately polluted. Sustaining the diversity of flora and fauna it is necessary to maintain living status of this river.

Epilithic Microalgae Isolated from Biofilm on Borobudur Temple Stone

Borobudur Temple is a historical heritage building located in an open area and made of porous building materials (stone materials). This condition makes the Borobudur Temple susceptible to various problems related to degradation and weathering. Biodeterioration of Borobudur Temple may be caused by activities of living organisms present in the biofilm of stone. Continuous monitoring and evaluation need to be carried out by observing and isolating the growth of micro-organisms, including epilithic microalgae. Therefore, this study aims to isolate and identify epilithic microalgae from the biofilm on Borobudur Temple stones. Epilithic microalgae were isolated to obtain a uni-algae and maintained under culture conditions. The morphological of microalgae were observed using light microscopy, while the 18S rRNA gene sequence determined the molecular identification of microalgae for eukaryotic and 16S rRNA sequence for prokaryotic. A total of nine epilithic microalgae were successfully isolated from the biofilm of Borobudur Temple stones. The isolated were identified as Ankistrodesmus falcatus, Tetraselmis cordiformis, Pseudendoclonium arthropyreniae, Anabaena cylindrica, Nostoc gelatinosum, Oscillatoria limnetica, Messastrum gracile, Stigeoclonium aestivale, and Scenedesmus acuminatus. This is the first study for the identification of microalgae from Borobudur temple stones. The isolates will be collected and will be used as a source for further study.

Effect of auxin and its synthetic analogues on the biomass production and biochemical composition of freshwater microalga Ankistrodesmus falcatus CMSACR1001

Exogenous supplementation of phytohormones to promote the selective enrichment of biomolecules without hampering biomass production is regarded as a promising approach to improve the techno-economic feasibility of biofuels and other value-added products derived from microalgae. The present work outlines the influence of natural auxin, indole-3-acetic acid (IAA) and two synthetic analogues, 1-naphthalene acetic acid (NAA), and 2,4-dichlorophenoxyacetic acetic acid (2,4-D) on the growth pattern and biochemical productivity of the green alga Ankistrodesmus falcatus CMSACR1001. A maximum biomass production of 431 mg L−1 with a concomitant increase in the protein and carbohydrate content (20.2% and 49.6% DCW respectively) was achieved under supplementation of 10 μM IAA. Biomass productivity at 1 μM concentration was found to be comparable for both IAA and NAA (32.8 mg L−1 day−1 and 32.4 mg L−1 day−1). At higher supplemented concentrations 2,4-D induced a 30–40% increase in carotenoid production and exhibited an increased lipid content of 41–47% DCW as compared with control (34.2% DCW). The current study also reports a substantial increase in the neutral lipid proportion as much as 73.9% and 79% under supplementation of NAA and 2,4-D respectively at 100 μM. The results indicate that the auxin and its analogues under the study could increase the biomass production and favourably modulate the biochemical composition of A. falcatus.

Fast cultivation and harvesting of oil-producing microalgae Ankistrodesmus falcatus var. acicularis fed with anaerobic digestion liquor via biogranulation in addition to nutrients removal

This study examined the feasibility of cultivation and harvesting of oil-producing microalgae (i.e. Ankistrodesmus falcatus var. acicularis) via biogranulation in two identical sequencing batch reactors (SBRs) fed with synthetic anaerobic digestion liquor. Easily settled algae granules with compact structure appeared around day 90 and mature granules were obtained after 150 days' operation. The microalgae settleability was remarkably improved, signaling by the substantial decrease of sludge volume index (SVI30) from initially >3000 to 53.44 ± 3.31 mL/g, with settling velocity correspondingly increased from nearly 0 to 18.47 ± 0.23 m/h. Although the percentage of the target microalgae (Ankistrodesmus falcatus var. acicularis) decreased along with the granulation process, the biomass concentration (2–4 g/L) and biomass productivity (130–270 mg/L/d) using biogranulation were 10–20 times and 16–34 times that by the traditional suspension method. Compared to the seed microalgae cells, more extracellular polymeric substances (EPS) (162.54 ± 3.60 mg/g-mixed liquor volatile suspended solids (MLVSS)) with a higher proteins/polysaccharides ratio (7.62) were excreted from the mature algae granules. Moreover, the mature microalgae granules showed comparable nutrients removal, averagely 96% and 86% of dissolved organic carbon (DOC) and NH4+-N from the digestion liquor, respectively, reflecting its great potential for simultaneous microalgae cultivation, harvesting and wastewater treatment.

АНАЛІЗ ХІМІЧНИХ ЗАГРОЗ ЕКОЛОГІЧНІЙ БЕЗПЕЦІ ВІННИЦЬКОЇ ОБЛАСТІ

The main threats to the environmental safety of Vinnytsia and Vinnytsya oblast in the field of the use and storage of pesticide and chemical wastes are presented in this work. The analysis of threats to ecological safety from pesticides, which consist of pesticide-contaminated soils, compositions and places of storage of pesticides and contaminated groundwater. The data of the Department of Agricultural Development, Ecology, and Natural Resources of Vinnytsia Oblast State Administration is presented, and it was analyzed how effective the cleaning of the territory of Vinnytsia Oblast was from the non-standard CWCP, and which components of this problem remain relevant and dangerous. It was established that four districts can be considered as cleared from the remains of unsuitable pesticides, in particular, Vinnytsia, Lipovetsky, Nemyrivsky, and Khmelnytsky, while in the Teplitsky, Tyvrivsky and Shargorodsky districts the situation with unsuitable pesticides is critical. In recent years, the process of export of pesticides abroad has been stopped due to significant costs, but work on inventory and re-stocking is constantly taking place. During the inventory of pesticides, new places of storage of non-conforming pesticides are detected. In addition to pesticides, there are an industrial waste on the territory of the region, which also creates chemical threats to environmental safety. These include waste from the 45th experimental plant, Khimprom, Plant Oreol, Terminal Plant, and others. The chemical classification of pesticides is given and according to the statistics, the most widely used in Ukraine are chlorinated and phosphorous pesticides. Among the most chemically dominated regions, the leaders are Vinnytsya, Khmelnytsky and Kirovograd regions in 2018. The methods of penetration and penetration of pesticides into soils are given and the main ways of their restoration and reclamation are analyzed. Among the most optimal methods of restoration is the removal of heat treatment and biological reclamation with phytomelioration. It is suggested to use strains of microorganisms: Agrobacterium radiobacter, Pseudomonas sp., Bacillus sp., Pseudomonas sp., Micrococcus sp., Proteus sp., Xanthomonas sp., Ankistrodesmus falcatus, A. nannoselene, Selenastrum capricornutum, and plants are able to reduce the toxicity of pesticides: ordinary beans and one-year sunflower.

Bioindicational Potential of Biophysical and Hydrobiological Indicators of Phytoplankton in Experiments with Laboratory Algocenoses

Bioindication, a method for the assessment of the quality of the natural environment with allowance for the state of the biota, is widely used to assess the impact of various factors on an ecosystem. Two problems remain relevant: on the one hand, the adequate selection of biological indicators of the ecosystem state with the greatest bioindicative potential, and, on the other, the establishment of the numerical boundaries of the norm for the indicators. A laboratory algocenosis has been created to study the bioindicational potential of hydrobiological and biophysical indicators. It consists of representatives of various classes of microalgae and cyanobacteria: Anabaena variabilis, Pleurochloris magna, Ankistrodesmus falcatus, and Stichococcus bacillaris. Salts of copper and zinc and diuron were used as effective toxicants. The method of local ecological norms was used for the analysis of the experimental data. The method is based on a computer analysis of the interrelated distribution of biological and physicochemical characteristics, i.e., on the search for boundaries of the factor and indicator norms for which suitable values of the indicator correspond to acceptable values of the factor and unacceptable values of the factor correspond to unsuitable indicator values. The paper analyzes data on 27 bioindicators: various fluorescence indicators, spectral characteristics; number and average volumes of cells of each type; parameters of the rank distribution of the number of species in the sample; evenness indices; nonparametric indices of species diversity; and the phytoplankton saprobity index. The boundaries of each indicator norm have been calculated; the most significant factors, as well as the boundaries of those factors' norm, have been revealed and determined. The bioindicators were compared by the average strength of connection with factors, the number of found significant factors, and their geometric mean value.

Phytoplankton communities of eutrophic freshwater bodies (Kerala, India) in relation to the physicochemical water quality parameters

Algal bloom of eutrophic freshwaters is important from different aspects of sustainable developmental perspectives. Apart from the identification of the algal species which multiply fast in response to eutrophication, phytoplankton studies concerning water quality parameters of eutrophic waters help environment inventory of such fast-growing algal species. The knowledge of specific environment requirements of fast-growing algae is highly significant in the control of toxic algal blooming and industrial utilization of non-toxic species in phycoremediation or as new bioresources for fuel, food or feeds. In this context, seasonal dynamics of the phytoplankton community in seven different kinds of eutrophic waters from 66 representative locations of Kerala, South India, was measured in two seasons. Altogether, 297 algal species belonging to 8 phyla, 11 classes and 26 orders were observed in the waters. Ecology and diversity of algal communities concerning physicochemical water quality parameters were compared, which enabled assessment of the ecological amplitude of several specific dominant species common to eutrophic waters in Kerala. The crucial roles of dissolved oxygen (p < 0.05), total Kjeldahl nitrogen (p < 0.01), and ammoniacal nitrogen (p < 0.05) in causing algal blooms are assessed using correlation analysis. The principal component analysis extracted the entire water quality parameters into five groups of components acting towards the cause of algal blooms. Overall, the investigation has generated relevant new information of several hitherto uninvestigated fast-growing non-toxic algal species such as Kirchneriella lunaris, Ankistrodesmus falcatus, Radiococcus nimbatus, Coelastrum microporum and Scenedesmus dimorphus, which are industrially useful and can contribute to ecotechnological innovations essential for sustainable development.

Comparative characteristics of species diversity of the algal flora of lakes in the Almaty region

The species diversity of the algoflora of five lakes, with different types of landscapes, located in the territory of the Almaty region was studied. The study covered five freshwater bodies includin: Balkhash, Alakol, Kolsay, Issyk and Big Almaty lake. Phytoplankton was studied for the first time in two lakes (Issyk and Big Almaty lake). The aim was to study the biodiversity of algoflora in lakes that are subject to various degrees of anthropogenic impact during recreational use. These water bodies are of great economic importance populations of the region, so the biological assessment of the water of these lakes is the most relevant. Analysis of the floral composition of the algoflora of lakes revealed a high species diversity of microalgae in all the studied objects. The highest quantitative and qualitative diversity in the lakes is represented by diatoms and green algae. The assessment of the ecological state of the water using microalgae as an indicator revealed that lake Balkhash is relatively dirty of all the studied lakes. Big Almaty lake,&nbsp;a high-altitude reservoir located in the reserve zone of the Trans-ili Alatau, was identified as the cleanest by saprobity. The scientific significance is to study the species diversity of microalgae and cyanobacteria of these objects. The practical significance is that the results obtained are necessary for forecasting and making recommendations for the conservation and normal functioning of natural complexes. Based on the results of the work of allocating pure cultures from samples taken from the lakes of the Almaty region received 5 algal pure cultures: Nephrochlamys sp., Ankistrodesmus falcatus, Monoraphidium griffthii, Parachlorella sp. и Monoraphidium sp. Key words: bioindication, algal flora, lakes Almaty region, microalgae, saprobity, algal pure cultures.

Allelopathic effects of the aquatic macrophyte Ceratophyllum demersum L. on phytoplankton species: contrasting effects between cyanobacteria and chlorophytes

Abstract Aim To assess the allelopathic effects of the submerged macrophyte Ceratophyllum demersum on four strains of phytoplankton species: two cyanobacteria (Microcystis aeruginosa - microcystin producing and M. panniformis - non-microcystin producing), and two chlorophytes (Ankistrodesmus falcatus and Raphidocelis subcapitata). Methods A coexistence experiment between C. demersum and the four strains was carried out for six days, with eight treatments and three replicates. The strains were cultivated in ASM1 culture medium, under controlled laboratory conditions. Two treatments were assigned for each strain, one with 6 g.L-1 of the macrophyte, and the control without the plant. Biomasses and growth rates of the strains were evaluated every two days, which were compared through the T-test and two-way ANOVA, respectively. Results The results varied among the strains, with toxic M. aeruginosa being intensely inhibited by C. demersum, with a decrease of 99.5% in its biomass (p&lt;0.001), while non-toxic M. panniformis was less affected by the allelochemicals, with a reduction of 86.2% (p&lt;0.001). Ankistrodesmus falcatus delayed its growth when in coexistence with the macrophyte, decreasing its biomass in 50.4% (p&lt;0.01), while R. subcapitata was not altered (p&gt;0.05). In coexistence with C. demersum, M. aeruginosa exhibited the lowest growth rates (-0.65 d-1), followed by M. panniformis (-0.15 d-1), A. falcatus (0.19 d-1), and R. subcapitata (0.34 d-1), with significant differences between all strains (p&lt;0.001). Microcystis aeruginosa presented higher inhibition rates than M. panniformis (p&lt;0.001), as well as, A. falcatus was more inhibited than R. subcapitata (p&lt;0.05). Conclusions The presence of microcystins could influence the allelopathic responses of C. demersum, that may release more allelochemicals in coexistence with toxic strains of M. aeruginosa. Accordingly, C. demersum can be used in biomanipulation strategies to control toxic and non-toxic cyanobacterial blooms, without damaging other phytoplankton species, like chlorophytes.

Survivorship characteristics and adaptive mechanisms of phytoplankton assemblages in ballast water

Phytoplankton diversity and abundance were determined in ballast water from 26 vessels in the Shanghai Yangshan Deep-Water Port from April 2015 to January 2016. In total, 84 species of phytoplankton were identified, belonging to 43 genera and 5 phyla. Bacillariophyta (75.0%, including 30 genera and 63 species) were the dominant algae in the ballast water. Their density ranged from (5.55±9.62) SD to (1.878±0.872)×10 3 cells/L, with a mean of 410.1 cells/L. Nine potentially harmful phytoplankton taxa were detected: Ceratium furca, Ce. marcroceros, Leptocylindrus danicus, Coscinodiscus radiatus, Co. granii, Prorocentrum micans, Melosira sulcata, Meuniera membranacea and Skeletonema costatum. Our survey and identification results showed that Microcystis aeruginosa, Ankistrodesmus falcatus and Scenedesmus survived in the high-salinity ballast water, even though they are freshwater species. We identified the common features of surviving phytoplankton and impacts on the phytoplankton assemblage of ballast water age and source. Our goal was to understand the adaptative mechanisms of phytoplankton in ballast water, providing statistical and theoretical support for future ballast water research and suggesting a scientific basis of ballast water management and inspection of vessels entering the port.

Grazing of the copepod Cyclops vicinus on toxic Microcystis aeruginosa: potential for controlling cyanobacterial blooms and transfer of toxins

Abstract Grazing of zooplankton on phytoplankton may contribute to a reduction of harmful cyanobacteria in eutrophic waters. However, the feeding capacity and interaction between zooplankton and toxic cyanobacteria vary among grazer species. In this study, laboratory feeding experiments were designed to measure the grazing rate of the copepod Cyclops vicinus on Microcystis aeruginosa and the potential microcystin (MC) accumulation in the grazer. Copepods were fed a mixed diet of the edible green alga Ankistrodesmus falcatus and toxic M. aeruginosa for 10 days. The results showed that C. vicinus efficiently ingested toxic Microcystis cells with high grazing rates, varying during the feeding period (68.9–606.3 Microcystis cells animal-1 d-1) along with Microcystis cell density. Microcystis cells exhibited a remarkable induction in MC production under grazing conditions with concentrations 1.67–12.5 times higher than those in control cultures. Furthermore, C. vicinus was found to accumulate MCs in its body with concentrations increasing during the experiment (0.05–3.21 μg MC animal-1). Further in situ studies are needed to investigate the ability of Cyclops and other copepods to assimilate and detoxify MCs at environmentally relevant concentrations before deciding on the biocontrol of Microcystis blooms by copepods.

Algal flora of Rajarani Lake, Dhankuta and their seasonal distribution

In this paper, a total 46 algae belonging to 34 genera and 3 classes (Chlorophyceae 54%, Bacillariophyceae 28%, Cyanophyceae 18%) have been reported from Rajarani Lake, Dhankuta, Nepal. Among these, 13 algae were reported as new to the country. Genera Ankistrodesmus, Closterium, and Desmodesmus had maximum number of species whereas 25 genera were represented by single species. Seasonal variation of algae showed that there was changing number and type of algae with physicochemical parameters in different seasons. Cyanophycean algae Microcystis flos-aque was dominant and observed in all sites in every collection of winter, summer and rainy seasons, and followed by bacillariophyceaean algae i.e., Aulacoseira granulata var. angustissima. The maximum number of algae was found in summer (59%) followed by winter (50%) and rainy (31%) seasons. There were 6 common algae found in all season’s viz. Ankistrodesmus falcatus, Aulacoseira granulata var. angustissima, Flagilaria tenera, Microcystis flos-aquae, Navicula radiosa and Oedogonium sp. Algae viz., Anabaena affinis, Cyclotella meneghiana, Pinnularia divergens, Pinnularia interrupta, Tetrastrum heteracanthum, and Ulothrix subtilissima were found only in winter season whereas, Aulacoseirsa granulata var. muzzanensis, Bolbochaete sp, Closterium striolatum, Cylindrospermum muscicola, Desmodesmus abundans, Desmodesmous quadricauda var.bicaudatus, Eunotia bilunaris, Gomphonema lacusrankaloides and Gomphonema pseudoaugur were observed only in summer. Similarly, Aphanocapsa pulchra, Oscillatoria sancta and Pediastrum duplex var. gracillimum were reported only in rainy season.

Exposure to the herbicide 2,4-D produces different toxic effects in two different phytoplankters: A green microalga (Ankistrodesmus falcatus) and a toxigenic cyanobacterium (Microcystis aeruginosa)

The extensive use of 2,4-dichlorophenoxiacetic acid (2,4-D) in agriculture is an important source of pollution to water and soil. Toxicity of commonly used herbicides to non-target, planktonic photosynthetic organisms has not been described completely yet. Therefore, we determined the effect of subinhibitory 2,4-D concentrations on the Chlorophycean alga Ankistrodesmus falcatus and on a toxigenic strain of the cyanobacterium Microcystis aeruginosa. Population growth, photosynthetic pigments, macromolecular biomarkers (carbohydrates, lipids, and protein), and antioxidant enzymes (catalase [CAT], glutathione peroxidase [GPx], and superoxide dismutase [SOD]) were quantified, and the integrated biomarker response (IBR) was calculated. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations were also performed. The 96-h median inhibitory concentration (IC50) for 2,4-D was 1353.80 and 71.20mgL−1 for the alga and the cyanobacterium, respectively. Under 2,4-D stress, both organisms increased pigments and macromolecules concentration, modified the activity of all the evaluated enzymes, and exhibited ultrastructural alterations. M. aeruginosa also increased microcystins production, and A. falcatus showed external morphological alterations. The green alga was tolerant to high concentrations of the herbicide, whereas the cyanobacterium exhibited sensitivity comparable to other phytoplankters. Both organisms were tolerant to comparatively high concentrations of the herbicide; however, negative effects on the assessed biomarkers and cell morphology were significant. Moreover, stimulation of the production of cyanotoxins under chemical stress could increase the risk for the biota in aquatic environments, related to herbicides pollution in eutrophic freshwater ecosystems.

Effects of Light-emitting Diodes (LEDs) on the Accumulation of Lipid Content in Microalgae

Microalgae is a popular condidate for the sustainable biodiesel due to its high growth rate and lipid content. This paper reviewed the effects of light conditions, including light intensity, photoperiod and spectrum on the lipid accumulation in microalgae and selects the spectrum as the variable. In this paper, the effects of different light emitting diodes (LEDs) spectra such as red, blue and white on the lipid accumulation in two microalgae species were discussed. The results showed that the total lipid content was the highest (13.76% and 31.18% of dry cell weight) in the two microalgae species, Ankistrodesmus falcatus and Chlorella vulgaris, cultured under blue light. The fatty acid methyl esters (FAME) composition was significantly influenced by the light spectrum

Allelopathy prevents competitive exclusion and promotes phytoplankton biodiversity

It has been hypothesized that allelopathy can prevent competitive exclusion and promote phytoplankton diversity in aquatic ecosystems, where numerous species coexist on a limited number of resources. However, experimental proof‐of‐principle is not available to support this hypothesis. Here we present the first experimental evidence to support this hypothesis by demonstrating that allelopathy promotes the coexistence of two phytoplankton species, Ankistrodesmus falcatus and Oscillatoria sp., that compete for a single limiting nutrient. By performing long‐term competition experiments in nitrate‐limited continuous cultures, and by describing the population dynamics using a mechanistic model, we demonstrate that when allelopathy comes into play, one of the following outcomes is possible depending on the relative initial abundances of the species: dominance of the stronger competitor for nitrate (the non‐allelopathic species), oscillatory coexistence, or dominance of the weaker competitor (the allelopathic species). Our model analysis revealed that sustained oscillatory coexistence of the two species would be a common outcome of this experiment. Our study confirms for the first time, based on laboratory experiments combined with mechanistic models, that allelopathy can alter the predicted outcome of inter‐specific competition in a nutrient‐limited environment and increase the potential for the coexistence of more species than resources, thereby contributing to the identification of endogenous mechanisms that explain the extreme diversity of phytoplankton communities.

Demonstration of transgressive overyielding of algal mixed cultures in microdroplets.

Algae are ubiquitous in natural ecosystems and have been studied extensively for biofuel production due to their unique metabolic capabilities. Most studies to date have approached biofuel optimization through synthetic biology and process engineering with few industrial scale projects considering algal community interactions. Such interactions can potentially lead to increased productivity and reduced community invasability, both important characteristics for scalable algal biofuel production. It is estimated that over a million species of algae exist such that elucidating the interactions that might be beneficial for biofuel production remains extremely resource and time intensive. Here we describe a strategy for rapid, high-throughput screening of algal community combinations using a microfluidic platform to generate millions of parallel, nanoliter-scale algal mixed cultures for estimation of biomass accumulation. Model communities were first studied in a bench scale flask experiment and then examined using microfluidic droplets. These experiments showed consistent results for both positively interacting algal bicultures that increase biomass when together, and negatively interacting bicultures that decrease biomass. Specifically, these included enhanced performance of two bicultures, Ankistrodesmus falcatus and Chlorella sorokiniana, Chlorella sorokiniana and Selenastrum minutum, and reduced performance of a biculture consisting of Selenastrum capricornutum and Scenedesmus ecornis. While the ultimate techno-economic feasibility of algal bioproducts hinges on an amalgamation of scientific fields, rapid screening of algal communities will prove imperative for efficiently discovering community interactions.

Microalgal cultivation using aquaculture wastewater: Integrated biomass generation and nutrient remediation

Microalgal cultivation using aquaculture wastewater is a promising biorefinary concept for integrated biomass generation and subsequent nutrient removal. In this study, potential of aquaculture wastewater (AWW) as a nutrient substrate for cultivation of Scenedesmus obliquus, Chlorella sorokiniana and Ankistrodesmus falcatus was investigated. Nutrient removal efficiencies were also investigated for selected microalgal strains. Sodium nitrate supplementation strategy is applied to enhance the productivities of biomass, lipid, carbohydrate and protein. Biomass productivities of A. falcatus (198.46mgL−1d−1) with 400mgL−1 sodium nitrate supplementation and C. sorokiniana (157.04mgL−1d−1) with 600mgL−1 sodium nitrate supplementation in AWW were comparable to the synthetic medium. Comparable lipid, carbohydrates and proteins productivities were observed in microalgal biomass cultivated using AWW to the productivities in the synthetic medium. Microalgal cultivation in AWW showed removal efficiencies in the range of 86.45–98.21% for ammonia, 75.76–80.85% for nitrate, 98.52–100% for phosphate and 42–69% for COD.