Photosynthetic Activity Of Microalgae Research Articles

Transcriptomic characterization of the response to a microalgae extract in Arabidopsis thaliana and Solanum lycopersicum.

The steady world population growth and the current climate emergency crisis demand the development of sustainable methods to increase crop performance and resilience to the abiotic and biotic stresses produced by global warming. Microalgal extracts are being established as sustainable sources to produce compounds that improve agricultural yield, concurrently contributing during their production process to atmospheric CO2 abatement through the photosynthetic activity of microalgae. In the present study, we characterize the transcriptomic response in the model plant Arabidopsis thaliana and the plant of horticultural interest Solanum lycopersicum to the foliar application of a microalgae-based commercial preparation LRM™ (AlgaEnergy, Madrid, Spain). The foliar spray of LRM™ has a substantial effect over both transcriptomes potentially mediated by various compounds within LRM™, including its phytohormone content, activating systemic acquired resistance, possibly mediated by salicylic acid biosynthetic processes, and drought/heat acclimatization, induced by stomatal control and wax accumulation during cuticle development. Specifically, the agronomic improvements observed in treated S. lycopersicum (tomato) plants include an increase in the number of fruits, an acceleration in flowering time and the provision of higher drought resistance. The effect of LRM™ foliar spray in juvenile and adult plants was similar, producing a fast response detectable 2 h from its application that was also maintained 24 h later. The present study improves our knowledge on the transcriptomic effect of a novel microalgal extract on crops and provides the first step towards a full understanding of the yield and resistance improvement of crops. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Biomonitoring of the surface waters of the Volyntsevo reservoir using the fluorimetry method

The article examines the state of the drinking Volyntsevo reservoir and its tributaries in conditions of significant changes in the hydraulic regime and pollution by waste mine waters. The state of algoflora of a water body is considered, the results of studying the species composition of phytoplankton, the content of basic photopigments and photosynthetic activity of microalgae are presented. The study presents the results of the application of the method of fluorimetric assessment of the state of phytoplankton cells as the main bioindicator of the state of the aquatic environment. The research was conducted in the vicinity of Yenakievo for the Volyntsevo reservoir and the Bulavin river. These water bodies are subject to significant man-made impacts: as a result of intensive water use of reservoir resources, there has been a significant decrease in water levels and, as a result, a deterioration in water quality. The conducted studies have shown a significant excess of the permissible standards for the content of magnesium ions, sulfates, total hardness and alkalinity in water samples. The negative impact of surface water pollution on the species composition of algoflora, as well as the photosynthetic activity of phytoplankton cells, has been shown. The obtained materials can serve as a basis for further monitoring of drinking reservoirs in the region. The current situation requires constant monitoring observations aimed at identifying and eliminating all sources of pollution of the studied water bodies.

Photosynthetic Efficiency of Microalgae and Cyanobacteria on Reduced Graphene Oxide (RGO) Anode Surface for Utilization in Bio-Photovoltaics (BPV)

Bio-photovoltaics (BPV) is sustainable energy production technology that utilize photosynthetic organisms and convert it into electricity. This Study has been carried out to study the photosynthetic efficiency of three microalgae on a Reduced Graphene Oxide (RGO) anode surface. RGO, with its exceptional electrical conductivity and large surface area, presents an attractive platform for enhancing the performance of BPV systems. The work aims to investigate the combined effect of microalgae and RGO anodes for use in BPV technology. RGO was synthesized and characterized on which Chlorella vulgaris, Gloeocapsa and Synechocystis were allowed to grow. A model BPV system was assembled, incorporating the microalgae and cyanobacteria as photoactive agents and RGO as the anode surface. The system was subjected to different experimental condition and photosynthetic efficiency, current generation, and power output were collected and analysed. Results demonstrated a significant improvement in the photosynthetic activity of microalgae when cultured on the RGO anode surface. Chlorella Shows maximum Efficiency in terms of growth and current generation. Statistical analysis confirmed the reliability and significance of these findings. Our finding bridges a crucial knowledge gap in the field of BPV, highlighting the potential of microalgae-RGO systems for cleaner energy production.

Role of Microalgae in the Recovery of Nutrients from Pig Manure

Animal production inevitably causes the emission of greenhouse gases and the generation of large amounts of slurry, both representing a serious environmental problem. Photosynthetic microorganisms such as microalgae and cyanobacteria have been proposed as alternative strategies to bioremediate agricultural waste while consuming carbon dioxide and producing valuable biomass. The current study assessed the potential of the microalga Scenedesmus sp. to remove nutrients from piggery wastewater (PWW) and the influence of the microalga on the microbial consortia. Maximum N-NH4+ consumption was 55.3 ± 3.7 mg·L−1·day−1 while P-PO43− removal rates were in the range 0.1–1.9 mg·L−1·day−1. N-NH4+ removal was partially caused by the action of nitrifying bacteria, which led to the production of N-NO3−. N-NO3− production values where lower when microalgae were more active. This work demonstrated that the photosynthetic activity of microalgae allows us to increase nutrient removal rates from PWW and to reduce the coliform bacterial load of the effluent, minimising both their environmental impact and health risks. Microalgae assimilated part of the N-NH4+ present in the media to produce biomass and did not to convert it into N-NO3− as in traditional processes.

Potential of Chlorella vulgaris and Nannochloropsis salina for nutrient and organic matter removal from municipal wastewater reverse osmosis concentrate.

Municipal wastewater reverse osmosis concentrate (ROC) poses health and environmental risks on its disposal as it contains nutrients and harmful organic compounds at elevated concentrations. This study compared a freshwater microalga Chlorella vulgaris and a marine microalga Nannochloropsis salina in suspended and alginate-immobilised cultures for batch and semi-continuous treatment of the ROC. The immobilised algae gave comparable nutrient removal rates to the suspended cells, demonstrating immobilisation had no apparent negative impact on the photosynthetic activity of microalgae. Semi-continuous algal treatment illustrated that the microalgae could remove significant amounts of nutrients (> 50% and > 80% for TN and TP, respectively), predominantly through algal uptake (> 90%), within a short period (48 h) and generate 335-360 mg DCW L-1 d-1 of algal biomass. The treatment also removed a significant amount of organic matter (12.7-13.3 mg DOC L-1 d-1), primarily (> 65%) through the biotic pathway.

Toxic effects of terpinolene on Microcystis aeruginosa: Physiological, metabolism, gene transcription, and growth effects

Bioherbicide terpinolene is widely employed in the agricultural field because of its unique phytotoxic properties. However, little is known about the toxicity of bioherbicide on harmful algal blooms (HABs) and its mechanisms. Therefore, in this study, the inhibiting effect of bioherbicide terpinolene on the growth and physiological change of Microcystis aeruginosa was determined. Results showed that the cell density and photosynthetic activity of microalgae were significantly inhibited by terpinolene. Activities of nitrate reductase (NR) and glutamine synthetase (GS) were decreased separately by 25.38% and 42.75% after 4 d of exposure to 1.47 mM terpinolene, suggesting the inhibiting effect of terpinolene on algal nitrogen metabolism. However, the transcript abundance of genes related to membrane protein cytochrome c oxidase subunit II (COX II) and ATP-binding cassette transporters (ABC transporter) were enhanced separately by 3.15 and 1.69-fold compared with control, suggesting the resistance response of cells to terpinolene stress. Additionally, terpinolene not only increased the content of endogenous phytohormones including indole-3-acetic acid (IAA), zeatin, and brassinolide, but also inhibited the expression of genes related to calcium-binding protein (CaBPs), one kind of calcium (Ca2+) sensors, suggesting its regulation on algal signal molecules. These findings helped to understand the ecotoxicity of terpinolene and guide the rational use of bioherbicide in agriculture.

Nitrite inhibition of microalgae induced by the competition between microalgae and nitrifying bacteria

Outdoor microalgae cultivation systems treating anaerobic membrane bioreactor (AnMBR) effluents usually present ammonium oxidising bacteria (AOB) competition with microalgae for ammonium uptake, which can cause nitrite accumulation. In literature, nitrite effects over microalgae have shown controversial results. The present study evaluates the nitrite inhibition role in a microalgae-nitrifying bacteria culture.For this purpose, pilot- and lab-scale assays were carried out. During the continuous outdoor operation of the membrane photobioreactor (MPBR) plant, biomass retention time (BRT) of 2 d favoured AOB activity, which caused nitrite accumulation. This nitrite was confirmed to inhibit microalgae performance. Specifically, continuous 5-d lab-scale assays showed a reduction in the nitrogen recovery efficiency by 32, 42 and 80% when nitrite concentration in the culture accounted for 5, 10 and 20 mg N·L−1, respectively. On the contrary, short 30-min exposure to nitrite showed no significant differences in the photosynthetic activity of microalgae under nitrite concentrations of 0, 5, 10 and 20 mg N·L−1.On the other hand, when the MPBR plant was operated at 2.5-d BRT, the nitrite concentration was reduced to negligible values due to increasing activity of microalgae and nitrite oxidising bacteria (NOB). This allowed obtaining maximum MPBR performance; i.e. nitrogen recovery rate (NRR) and biomass productivity of 19.7 ± 3.3 mg N·L−1·d−1 and 139 ± 35 mg VSS·L−1·d−1, respectively; while nitrification rate (NOxR) reached the lowest value (13.5 ± 3.4 mg N·L−1·d−1).Long BRT of 4.5 d favoured NOB growth, avoiding nitrite inhibition. However, it implied a decrease in microalgae growth and the accumulation of nitrate in the MPBR effluent. Hence, it seems that optimum BRT has to be within the range 2–4.5 d in order to favour microalgae growth with respect to AOB and NOB.

Comparison of different trophic cultivations in microalgal membrane bioreactor containing N-riched wastewater for simultaneous nutrient removal and biomass production

In this study, a submerged membrane was installed in a bioreactor to treat N-riched wastewater and obtain high biomass productivity. Chlorella vulgaris was cultivated under mixotrophic, heterotrophic, and photoautotrophic conditions in different kinds of nitrogen sources (nitrate and ammonium) to compare the microalgae growth and nutrient removal in a membrane bioreactor. Further, the respirometric and photosynthetic activities of microalgae were investigated to evaluate the viability of microalgae in different conditions. The highest biomass productivity was obtained under mixotrophic cultivation in ammonium source (0.230±0.009 gr/Ld). Moreover, with this type of cultivation and nitrogen source, specific oxygen uptake rate (SOUR) was higher than oxygen product rate (SOPR). However, SOPR improved in mixotrophic cultivation using nitrate source. In both nitrogen source types, the photosynthetic activity of mixotrophic microalgae was reduced at high cell density. Compared favorably with other cultivation types, mixotrophic microalgae could achieve high N and P removal rates (about 23.64–28.84 and 4.38–5.08mg/Ld, respectively). In all cultivation types (except photoautotrophic condition with nitrate source), N and P removal amounts were assimilated to biomass. Based on the obtained results, membrane bioreactor containing mixotrophic microalgae would be the most useful system for application in N-riched wastewater treatment systems.

Promising microbial consortia for producing biofertilizers for rice fields

Two cyanobacterial cultures from rice paddies of Kyzylorda region, Kazakhstan were isolated and characterized: Anabaena variabilis and Nostoc calsicola. Based on these cultures, new consortia ofcyanobacteria, microalgae and Azotobacter were developed: ZOB-1 (Anabaena variabilis, Chlorella vulgaris, and Azotobacter sp.) and ZBOB-2 (Nostoc calsicola, Chlorella vulgaris, and Azotobacter sp.). High growth rate and photosynthetic activity of microalgae were observed in these consortia. The active consotrium ZOB-1 was selected, which improvd germination and growth of rice plants. ZOB-1 was recommended as a biostimulator and biofertilizer for crops.