Scenedesmus Acuminatus Research Articles

Scenedesmus acuminatus as a potential phycoremediator: Enrichment and detoxification of cadmium/lead

Heavy metal pollution in water can cause severe environmental problems, harm the ecosystem, and ultimately threaten human health. The traditional methods used to remove heavy metals from water are expensive, inefficient, and can cause secondary pollution. However, microalgae have potential applications in the removal of toxic heavy metal pollutants from water. In this study, six green algae were screened in terms of their ability to adsorb cadmium (Cd) and lead (Pb) from a liquid medium. Ion content analyses confirmed that Scenedesmus acuminatus had the strongest Cd- and Pb-absorption ability. S. acuminatus was subjected to Cd and Pb treatments, and then transcriptome sequencing analysis was conducted. The results of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that the “proteasome” pathway was enriched with differentially expressed genes (DEGs) under Cd treatment, and the “photosynthesis” pathway was enriched with DEGs under Pb treatment. These results imply that the proteasome pathway maintained protein homeostasis and cellular activity by degrading damaged proteins under Cd toxicity, and that photosynthesis was affected by Pb toxicity in S. acuminatus. In conclusion, S. acuminatus showed a strong ability to accumulate Cd/Pb and might alleviate heavy metal toxicity and reduce heavy metal efflux using the ubiquitin-proteasome system. The results of this study identify a novel microalgal strain with potential applications in phytoextraction and phytoremediation, and provide information about the molecular mechanisms of Cd/Pb accumulation in this alga. These data provide a theoretical basis for reducing Cd/Pb toxicity and will be useful for devising strategies to protect aquatic animals and plants.

Systematic study of microzooplankton in mass culture of the green microalga Scenedesmus acuminatus and quantitative assessment of its impact on biomass productivity throughout a year

The green microalgae Scenedesmus spp. can grow rapidly and produce significant amounts of protein or lipid. However, frequent microzooplankton contamination leading to reduced biomass productivity has hindered the microalgae commercialization. Here, a comprehensive investigation into harmful microzooplankton species in mass cultures of a commercially promising species Scenedesmus acuminatus were conducted throughout the year. Twenty-five microzooplankton species were identified, with the amoeba Vannella sp. and the ciliate Vorticella convallaria being the most harmful to algal cells. The results indicated that it was the harmful grazers, rather than the overall microzooplankton diversity, led to culture deterioration and reduced biomass yield. Increasing the concentration of algal inoculants or reducing culture temperature during hot summer days were found to be effective in mitigating the impact of these harmful grazers. The findings will contribute to the best management protocol for monitoring and controlling the harmful microzooplankton in mass cultures of S. acuminatus.

Carbon-negative and high-rate nutrient recovery from municipal wastewater using mixotrophic Scenedesmus acuminatus

The efficiency of mixotrophic microalgae in enhancing the recovery of waste nutrients has been well established; however, the recovery rate is crucial in meeting the needs of field applications. This study evaluated the impact of media characteristics on nutrient recovery under mixotrophic conditions. The mixotrophic N recovery rate with S. acuminatus in modified BG-11 reached 2.59 mg L−1h−1. A mixotrophic growth optimization strategy was applied to achieve a high-rate nutrient recovery from municipal wastewater treatment plant effluents. The contribution of waste chemical oxygen demand (COD) to nutrient recovery was assessed using secondary effluent (SE) under heterotrophy. The results highlighted a significant increase in total nitrogen (TN) and total phosphorus (TP) recovery rates when glucose was supplied, indicating the additional carbon requirements for efficient nutrient recovery. The TN and TP recovery rates under mixotrophic conditions with the addition of trace metals and high cell density were enhanced by 91.94% and 92.53%, respectively, resulting in recovery rates of 3.43 mg L−1h−1 and 0.30 mg L−1h−1. The same conditions were used for nutrient recovery from primary effluent (PE), and the results were more satisfactory as the TN and TP recovery rates reached 4.79 and 0.55 mg L−1h−1, respectively. Additionally, the study estimated the carbon footprints (C-footprints) and areal footprints of mixotrophy-based nitrogen recovery. The findings revealed carbon footprints and areal footprints of −15.93 ± 4.57 tCO2e t−1 N recovery and 0.53 ± 0.19 m3 m−2d−1 wastewater, respectively. This high-rate nutrient recovery, achieved under a carbon-negative (C-negative) budget through mixotrophy, presents a novel strategy for efficiently recovering resources from municipal wastewater, thus facilitating resource recycling and ensuring environmental sustainability.

Utilização de microalgas na biorremediação de águas eutrofizadas por efluente doméstico em um lago urbano na Amazônia

ABSTRACT The disposal of domestic effluents without an adequate treatment may increase nitrogen and phosphorus levels in natural water bodies. Bioremediation using microalgae is one of the solutions for treating effluents before disposal. We tested the effect of Scenedesmus acuminatus, Chlorella vulgaris and Planktothrix isothrix, as well as the effect of water dilution, on the nutrient concentration in water eutrophicated by domestic effluent in an urban lake in the Brazilian Amazon. We inoculated the three species in monoculture in undiluted water (PW0), and 50% (PW50) and 90% (PW90) diluted water. The experiment lasted 10 days and every 24 hours we removed a bottle of each treatment for nutrient analysis. The three species were equally efficient in removing ammonia in PW0. Nitrate removal rate was highest for Chlorella vulgaris in PW0, and higher for C. vulgaris and P. isothrix in PW50 and PW90. Orthophosphate removal efficiency was higher for S. acuminatus and C. vulgaris in PW0, equally efficient for the three species in PW50, and higher for C. vulgaris and P. isothrix in PW90. We concluded that the three species of microalgae tested are efficient in removing ammonia. Scenedesmus acuminatus was not an ideal species for nitrate removal. Planktothrix isothrix was efficient in removing nutrients when domestic wastewater is diluted. Chlorella vulgaris was efficient in removing nutrients from domestic wastewater whether diluted or not.

Application of microalgae Scenedesmus acuminatus enhances water quality in rice-crayfish culture.

Improper management of aquatic environments substantially restricts the development of the aquaculture industry. The industrialisation of the crayfish Procambarus clarkii, for example, is currently being limited by poor water quality. Research suggests that microalgal biotechnology has a great potential for water quality regulation. However, the ecological effects of microalgal applications on aquatic communities in aquaculture systems remain largely unknown. In the present study, 5L Scenedesmus acuminatus GT-2 culture (biomass 120gL-1) was added to an approximately 1,000m2 rice-crayfish culture to examine the response of aquatic ecosystems to microalgal application. The total nitrogen content decreased significantly as a result of microalgal addition. Moreover, the microalgal addition changed the bacterial community structure directionally and produced more nitrate reducing and aerobic bacteria. The effect of microalgal addition on plankton community structure was not obvious, except for a significant difference in Spirogyra growth which was inhibited by 81.0% under microalgal addition. Furthermore, the network of microorganisms in culture systems with the added microalga had higher interconnectivity and was more complex, which indicating microalgal application enhance the stability of aquaculture systems. The application of microalgae was found to have the greatest effect on the 6th day of the experiment, as supported by both environmental and biological evidence. These findings can provide valuable guidance for the practical application of microalgae in aquaculture systems.

Two types of growth pattern of the five microalgal species under different nitrogen supplies

Manipulation of nitrogen levels is a viable strategy to improve microalgal biomass production. Here, nitrogen uptake and biochemical characteristics of the five microalgal strains were studied with high and low nitrogen concentrations. Two types of growth pattern were observed, non-influencing growth (type Ⅰ, Nannochloropsis gaditana and Kirchneriella sp.) and inhibitory growth (type Ⅱ, Scenedesmus acuminatus, Scenedesmus obliquus and Chlorella vulgaris). The highest biomass of the type Ⅰ microalgae was obtained with higher nitrogen supply (≥18 mM), whereas type Ⅱ microalgae reached highest biomass under nitrogen-limited conditions (7.2–10.8mM). Type Ⅰ microalgae had the highest nitrogen uptake capacity (N. gaditana) and nitrate reductase (NR) activity (Kirchneriella sp. 3.67 U g−1, 10.8 mM). The lower the nitrogen concentration, the higher the NR activity measured in type Ⅱ microalgae on day 1. The nitrogen replete group (21.6mM) of the type Ⅱ microalgae decreased the nitrogen uptake. The NR activity of S. acuminatus was positively associated with the initial nitrogen supply, and an NR activity threshold effect was observed in S. obliquus and C. vulgaris. The amount of nitrite released by the type Ⅱ microalgae was one order magnitude higher than those released by the type Ⅰ microalgae. In nitrogen-limited conditions, the five microalgae species shifted the photosynthetic carbon partitioning into lipid accumulation. The difference in growth patterns was mainly due to nitrogen uptake capacity, activity of nitrate reductase and the amount of nitrite released.

A novel integrated system for heavy metals removal and biodiesel production via green microalgae: A techno-economic feasibility assessment

The removal of heavy metals combined with biodiesel production by microalgae in a cost-effective way is a promising approach. Herein, we grew two green microalgal species, Chlorella sorokiniana and Scenedesmus acuminatus, in media contaminated with Cu2+ (3.2 ppm) or Zn2+ (65.4 ppm) to investigate their growth and full metabolic profile. Furthermore, to integrate the potential economic impact of biodiesel production with heavy metals removal efficiencies. Although acute exposure to heavy metals, on the other hand, reduced growth and increased removal efficiencies of Cu2+ (59.4, 98.1%) and Zn2+ (72.4, 98.2%) in C. sorokiniana and S. acuminatus, respectively. Besides, Cu2+ and Zn2+ increased primary metabolites, particularly lipids (49, 47% in S. acuminatus, 27, 26% in C. sorokiniana), with a significant induction in the unsaturation levels. Indicating that C. sorokiniana and S. acuminatus are excellent phycoremediators for industrial drainage and future sustainable algal-biofuels platform. Economic assessment of daily 1000-tonne biodiesel production from S. acuminatus grown on highly polluted wastewater via Na4SiO4 transesterification catalysis has all been assessed with an accuracy of ± 10% for the price of the diesel of US$ 1000/tonne and for the cost of the evaluated algal biomass of US$ 430/tonne. The daily 1000 T algal diesel business was viable, with a return on high investment (16.4%) and a payback period of 5 years. According to break-even and sensitivity analyses, the algal diesel cost that makes this business viable should be greater than US$ 147/barrel, while the biomass cost should not exceed US$ 462/tonne. Brent Crude Oil Spot exceeds US$ 95/barrel indicating promising prospects for algal fuel industrialization. Furthermore, the protein and amino acids-based waste biomass may serve as a sustainable biorefienry platform for various biofuel industries through biomass conversion technologies.

Production and use of Scenedesmus acuminatus biomass in synthetic municipal wastewater for integrated biorefineries.

Bioethanol production from algal biomass is a promising alternative for sustainable biofuel production. Algae possess a high photosynthetic capacity and an adaptive ability to thrive under harsh environmental conditions. The potential properties of Scenedesmus acuminatus CCALA 436 were assessed in this research for its bioethanol efficiency, and the effects of growing the algae in wastewater and at different concentrations of mepiquat chloride were studied. Also, pre-treatment efficiencies of different concentrations of calcium oxide were carried out on microalgae biomass. Superoxide dismutase, catalase activity, glutathione, and malondialdehyde contents of microalgae were examined, and the changes in chlorophyll, photoprotective carotenoid contents, and protein concentrations were determined. The results revealed that the maximum sugar and ethanol contents of Scenedesmus acuminatus CCALA 436 were 44.7 ± 1.5% and 20.32 g/L, respectively, for 50% wastewater and mepiquat chloride (2.5 mg/L) after pre-treatment with calcium oxide (0.08%). Additionally, the levels of oxidative enzymes varied depending on the wastewater concentrations. These findings indicate Scenedesmus acuminatus CCALA 436 grown in wastewater and mepiquat chloride can be used for the treatment of wastewater and the production of ethanol and high-value products such as carotenoid.

Metabolites produced by microalgae from northeastern Brazil with potential food industry uses

The production potential of metabolites of interest to the food industry was evaluated in 17 microalgae species isolated from natural sources in northeastern Brazil. The species were cultivated to their stationary phase under controlled conditions, when the experiments were interrupted and the dry biomass harvested. We observed differences in their growth parameters, productivity, and the biochemical compositions of their biomasses, with high levels of protein productivity in Monoraphidium litorale D296WC (48.96%), Kirchneriella concorta D498WC (42.49%), Monoraphidium griffithi D499WC (48.37%), Chlamydomonas sp. D530WC (44.80%), and Cosmarium sp cf. depressum D578WC (49.32). The greatest carbohydrate productivities were observed in Xanthonema sp. D464WC (34.15%), K. concorta D498WC (38.95%), and Scenedesmus acuminatus D514WC (36.54%). The three different extraction techniques of microalgae lipids all gave slightly different results, with the method utilizing phospho-vanillin being considered the most rapid and it requires only small quantities of biomass. Unsaturated fatty acids (oleic, linoleic, and linolenic) were encountered at high levels in most of the species, especially α-linolenic acid (ω3), which reached concentrations above 30% in Golenkinia radiata (D325WC). Due to their high productivity, rapid growth, and the large numbers of important dietary metabolites they produce, the species Monoraphidium litorale (D296WC), Xanthonema sp. (D464WC) and Monoraphidium griffithi (D499WC) show significant potential for utilization by the food industry as sources of proteins, lipids, and carbohydrates.

Aquaculture waste nutrients removal using microalgae with floating permeable nutrient uptake system (FPNUS)

Large area requirements and huge energy consumption restrict the applications of microalgae in wastewater treatment. In this study, in-situ nutrient removal was tested using a floating permeable nutrients uptake system with pore sizes of 1, 5, 10, and 40 µm, and Chlorella sorokiniana and Scenedesmus acuminatus. Results showed that N transfer rate across FPNUS varied with membrane pore size and N-type. Average transfer rate of NH4+-N, NO3–-N, and NO2–-N across 1 µm membrane was 2.6, 14.6, and 2.3 mg m-2h−1, respectively, sufficient to support microalgal growth. The NH4+-N and NO3–-N removal rate in shrimp wastewater reached 1.32 and 1.88 mg L-1d-1, comparable to some BNR processes used in RAS. According to the developed area ratio prediction model, FPNUS to pond area ratio of 21% is sufficient to balance N loading of 0.05 mg L-1d-1. These results indicate extraordinary potential of in-situ nutrient removal from wastewaters using FPNUS.

Dietary supplementation of cattle manure in Scenedesmus acuminatus algae suspension in daphnia magna farming

The use of live food has been recommended in the larval stage of several species of fish, providing better survival and growth results when compared to those obtained with artificial diets. This study aims to evaluate the biomass and protein content of Daphnia magna submitted to three diets: Diet A (Scenedesmus acuminatus) at a concentration of 1.5x107 cells/mL per individual, diet B (cattle manure) at 6.5g/L, and diet C at the same diets and concentration as in diets A and B for a period of 21 days. The experiment was repeated three times, totaling 63 days of study with a completely randomized design, with three replicates in each treatment. The experimental unit consisted of polyethylene containers with 20L, containing 10 D. magna neonates. Every two days, temperature, pH, dissolved oxygen and saturation were measured. At the end of the experimental period, nutrient quantification of the culture water and diets (phosphorus, nitrate, ammoniacal nitrogen, total nitrogen, and organic nitrogen), determination of the final biomass and protein content of the individuals were performed. Diet C provided a higher mean biomass value, followed by diet A and B, with values ​​of 344.12 g, 157.71 g and 81.93 g, respectively. The D. magna fed with diet B had a higher protein content, with 2.56%, followed by those fed diets C and A, with 2.17 and 1.32%, respectively. At the end of the experiment, it was found that the organisms fed diet C had a larger reproduction rate when compared to the other diets.

Statistical study of growth kinetics and lipid content of microalgae grown in brackish waters for bioenergetic purposes

This study aimed to statistically prove the influence of salinity on growth kinetics and intracellular lipid accumulation in microalgae. The species Chlorella sp., Scenedesmus acuminatus, Nannochloropsis sp., Monoraphidium contortum and Pediastrum tetras were studied, which were isolated in the Brazilian semi-arid region and cultivated in synthetic media with the addition of NaCl. From the crops, growth kinetics, dry biomass production and lipid content were analyzed, using the experimental planning for one factor as a tool, with the NaCl concentration as an independent variable. The kinetic parameters maximum growth speed (µmax) and generation time (tg), as well as lipid concentration were the response variables studied. The results showed that, in the species Scenedesmus acuminatus, Nannochloropsis sp. and Pediastrum tetras, salt stress contributed to the increase in µmax and the consequent decrease in tg. The highest levels of lipid accumulation were obtained in Nannochloropsis sp. (62.04%), in the medium with the highest salinity and Pediastrum tetras (54.04%) in the lowest. Dry biomass production was higher in Scenedesmus acuminatus (1,941.37 mg.L-1) and Nannochloropsis sp. (1237.05 mg.L-1), both at a concentration of 4.0 g.L-1. Therefore, saline stress acted directly on the cell growth and lipid content of the species, which can be used as a device to enhance lipid production for the purpose of producing biofuels.

Trophic Transition Enhanced Biomass and Lipid Production of the Unicellular Green Alga Scenedesmus acuminatus.

Microalgal heterotrophic cultivation is an emerging technology that can enable producing high cell-density algal cell cultures, which can be coupled with photoautotrophic cultivation for valuable chemicals such as lipids manufacturing. However, how the heterotrophically grown algal cells respond to the lipid-inducing conditions has not been fully elucidated so far. In this study, when the heterotrophically grown Scenedesmus acuminatus cells were subjected to the high light (HL) and nitrogen-limited (NL) conditions, both the biomass and lipid productivity were enhanced as compared to that of the photoautotrophically grown counterparts. The chlorophyll a fluorometry analysis showed that the Fv/Fm and Y(II) of the heterotrophically grown cells subjected to the HL and NL conditions was recovered to the maximum value of 0.75 and 0.43, respectively, much higher than those of the photoautotrophically grown cells under the same stress conditions. Transcriptomic analysis revealed that heterotrophically grown cells fully expressed the genes coding for the photosystems proteins, including the key photoprotective proteins D1, PsbS, light-harvesting-complex (LHC) I and LHC II. Meanwhile, downregulation of the carotenoid biosynthesis and upregulation of the glycolysis/gluconeogenesis, tricarboxylic acid (TCA) cycle and oxidative phosphorylation pathways were observed when the heterotrophically grown cells were subjected to the HL and N-limited conditions for lipid production. It was deduced that regulation of these pathways not only enhanced the light utilization but also provided the reducing power and ATP by which the biomass accumulation was significantly elevated. Besides, upregulation of the acetyl-CoA carboxylase/biotin carboxylase, digalactosyl diacylglycerol synthase and diacylglycerol acyltransferase 2 encoding genes may be attributable to the enhanced lipid production. Understanding the cellular responses during the trophic transition process could guide improvement of the strength of trophic transition enhancing microalgal biomass and lipid production.

Spatial diversity of microalgae in Simeulue Island, Indonesia

Microalgae naturally occur as valuable genetic resources for many industrial interests. However, the study on their diversity and potential as local strain resources, especially in Indonesia are limited. To assess the spatial diversity as basic information on exploring their further potential, we isolated microalgae from outer island-Simeulue, the Province of Aceh in four different habitats and locations. Seventeen cultures of microalgae were selected, purified, and maintained to the preferable conditions in IMK and AF6 media under light-based culture. Generally, the selected microalgae were referred to eukaryotic group based on morphological obsexrvation. BLASTn and phylogenetic analysis of 18S rRNA gene revealed 12 closely related species which are Chlorella kessleri, Chlorella sorokiniana, Oocystis heteromucosa, Stichococcus bacillaris, Coccomyxa melkonianii, Scenedesmus acuminatus, Scenedesmus bijugus, Coelastrella oocystiformis, Ankistrodesmus falcatus, Chlorococcum oleofaciens, Stigeoclonium tenue, and Planophila laetevirens. These species inhabit the spatial habitat and location of natural aquatic sources of Simeulue island. This study is expected to provide basic information for uncovering patterns of microalgae diversity and obtain new genetic resources for industrial uses as well as for taxonomic studies.

Physico-Chemical Parameters and Diversity of Phytoplankton in Kirtankhola River, Bangladesh

The river Kirtankhola has great importance in southern part of Bangladesh due to its necessity in transportations, municipal and agricultural purposes. But the ecological status and impacts of water quality on phytoplankton diversity were undiscovered. To cover the maximum area of the river, water samples were collected from the 6 locations (ST) covering about 13 km. Some parameters were measured immediately after sampling by portable devices and others done in laboratory following standard methods. The overall quality of the water was found good according to water quality guidelines of World Health Organization, although the water of port area showed comparatively high SO42- and CO3- values which attracts attention for future monitoring. ST 6 showed comparatively more alkaline water (pH 8.45) along with highest EC, TDS, NO3-, NH4+ and DIP values. Besides, 53 phytoplankton taxa belonging to Cyanophyceae (6), Chlorophyceae (10), Euglenophyceae (12) and Bacillariophyceae (25) were identified from the river. Scenedesmus acuminatus was found commonly in five stations except ST 1, whereas Euglena chlamydophora (ST 1), Gomphonema olivaceum (ST 3) and Cymbella parva (ST 5) found rarely. Highest diversity was counted in ST 6. Moreover, Chlorophyceae and Bacillariophyceae have positive correlation with several physical parameters, whereas Cyanophyceae negatively correlated. Euglenophyceae has both negative and positive correlations with some physico-chemical parameters. However, this was first attempt to measure diversity of primary producers and their correlations with water quality of Kirtankhola River.

Effects of the induction of anoxia in photobioreactor on effective cultivation of Scenedesmus acuminatus under mixotrophic cultivation mode

ABSTRACT The purpose of this study was to investigate the optimum conditions of several factors (i.e. types and concentration of acetate, aeration rate, pH control) for maximizing the mixotrophic cultivation of Scenedesmus acuminatus using acetate as an organic carbon source. When acetate was used, dissolved oxygen (DO) was quickly consumed and resulted in an anoxic condition for 52 h. Then, DO increased quickly by photosynthetic reaction. Whenever we put acetate in a reactor after DO was recovered to higher than 7 mg/L, cells were quickly grown via cell respiration, which subsequently resulted in an anoxic condition. Compared to aeration, ammonium acetate, ammonium acetate with aeration tests, the highest maximum biomass productivity of 0.73 g/L/d was obtained for pH control test with ammonium acetate dosage. From this study, we found that DO was essential for the fast assimilation of acetate and depleted DO was quickly regenerated for pH control test. From this fact, we found that pH control test with ammonium acetate dosage was the best cultivation method for Scenedesmus acuminatus under mixotrophic condition. These findings could be a useful reference for maximizing the cultivation of S. acuminatus in industrial-scale applications.

Renewable source hydrocarbons obtaining from microalgae by catalytic deoxygenation

In line with global demand for greenhouse gas reduction, the aviation industry has invested in biofuels development. A source feedstock that deserves special mention for this process is microalgae, because of its cultivation of renewable biomass with high yields, low cost, and high CO2 sequestering potential. This research aimed the study of microalgae culture with hard potential for biofuel production and its obtaining through catalytic deoxygenation to renewable source hydrocarbons in C12–C18 range. Thus, the oils of the Scenedesmus acuminatus and Cosmarium sp. species were cultivated and identified. Scenedesmus acuminatus oil is the majority composition of palmitic acid (C16:0) and has a higher production and yield than Cosmarium sp. oil. Scenedesmus acuminatus oil was then submitted to catalytic deoxygenation by the semi-batch reaction using the 5% Pd/C catalyst. The obtained results showed a selectivity of 82.9% and n-alkane yielding of 36.6%, placing the specie as potential biojet fuel precursor.

The Community of Chlorophyta as Bioindicator of Water Pollution in Pandanduri Dam District of Terara East Lombok

The Pandanduri Dam has a function as a support for agricultural irrigation water and also supports community activities so that it will affect the quality of its waters. The quality of the water needs to be analyzed because it can affect the aquatic ecosystem. This study aims to determine the level of water pollution in the Pandanduri Dam based on the phytoplankton community from the Chlorophyta Division. This type of research is descriptive exploratory. Sampling was carried out at 5 stations that were haphazardly selected with ecological representativeness consideration. Phytoplankton data were analyzed using the abundance formula, Shannon-Wiener diversity index, PIELOU uniformity index, and Simpson dominance index. The phytoplankton from the Chlorophyta Division found in the Pandanduri Dam were 14 species that are Pediastrum duplex var. Gracillimum, Gonium sp. 1, Gonium sp. 2, Coelastrum reticulatum, Scenedesmus acuminatus, Cosmarium sp., Chlamydomonas nasuta, Chlamydomonas sp., Selenastrum capricornutum, Monoraphidium dybowskii, Monoraphidium contortum, Monoraphidium irregular, Westella botryoides, and Kirchneriella lunaris consisting of 4 orders (Sphaeropleales, Chlorococcales, Chlamydomonadales and Desmidiales) and 10 genera (Pediastrum, Coelastrum, Scenedesmus, Gonium, Cosmarium, Chlamydomonas, Selenastrum, Monoraphidium, Westella, and Kirchneriella). The species diversity index of 2.21 is classified as moderate diversity, the species uniformity index is 0.83 which indicates even species growth, and the species dominance index indicates that no species dominates with a value of 0.12. The level of water pollution in the Pandanduri Dam was found in the moderate pollution category (oligotrophic).

Effects of sulfur limitation on nitrogen and sulfur uptake and lipid accumulation in Scenedesmus acuminatus

Sulfur limitation is a frequently exploited method for inducing lipid accumulation in microalgae. However, there is little understanding of the underlying mechanism of this process. Hence, a study was conducted to determine the effects of sulfur limitation on nitrogen and sulfur uptake, lipid production strategies, and photosynthetic physiological characteristics of Scenedesmus acuminatus. A low sulfur concentration (0.076 mM; 0.25S group) decreased nitrate reductase activity and inhibited nitrogen absorption. The highest lipid productivity was obtained in the 0.75S (0.229 mM) group (221.93 mg L−1 day−1), significantly higher than that of the 0.5S (0.153 mM) and 0.25S groups (p < 0.05). Acetyl-coenzyme A carboxylase (ACCase) activity was upregulated in the 0.25S group to promote the accumulation of lipid and fatty acids, and generated the maximum lipid and fatty acid content (47.27% and 43.98% of dry weight, respectively). An important supplementation of energy for lipid accumulation under low-sulfur conditions is to drive a higher proportion of cyclic electron flow. Superoxide dismutase and peroxidase activities and malondialdehyde content increased at lower sulfur concentrations, indicating the elevated antioxidant activity of S. acuminatus.

Efeito do extrato de algas no desempenho germinativo e crescimento radicular em sementes de feijão BRS Estilo em resposta a diferentes métodos de aplicação

RESUMO The biostimulating potential of algae extracts represents an opportunity to increase efficiency in food production. Cultivable microalgae are viable candidates due to the high production capacity. In this work, the chemical composition and effect of the microalgae extract Scenedesmus acuminatus (Lagerh.) Chodat and commercial product AMPEP (Acadian Marine Plant Extract Powder) derived from the macroalgae Ascophyllum nodosum (L.) Le Jol. on the germination of BRS Estilo bean seeds were evaluated. The treatments analyzed the methodology of exposure of seeds to extracts: soaking for 5 hours (T1) and applications every 48 hours (T2). The parameters evaluated were: germination percentage (PG), speed index (IVG) and mean germination time (TMG). The values of PG and IVG were higher in T2, representing about 50% higher yield than T1. In relation to chemical composition, Scenedesmus acuminatus extract obtained higher levels of proteins and carbohydrates. Thus, S. acuminatus is a potential producer of biostimulant extracts, while beans obtained lower germinative performance when submitted to the soaking process.