Wael A. Fathy

Fenoxaprop‐p‐ethyl is a widely employed aryloxyphenoxypropionate herbicide that inhibits acetyl‐CoA carboxylase (ACCase), thus interfering with fatty acid biosynthesis in target organisms. While its effects on terrestrial plants are well‐documented, its impact on nontarget aquatic microorganisms, particularly cyanobacteria, which serve as the foundation of many aquatic ecosystems, remains inadequately characterized. Consequently, this study was undertaken to evaluate the differential uptake and metabolic responses of two cyanobacterial species, Anabaena laxa and Nostoc muscorum , upon exposure to fenoxaprop‐p‐ethyl. Cyanobacterial cultures were subjected to 200 mg/L of fenoxaprop‐p‐ethyl under controlled experimental conditions. Bioaccumulation was quantified, and a comprehensive analysis of photosynthetic parameters was conducted, including chlorophyll‐a, carotenoids, CO₂ fixation, Rubisco, and PEPC activity. Additional biochemical profiling encompassed carbohydrates, organic acids, amino acids, and fatty acid composition. Anabaena exhibited a 26.3% higher accumulation of the herbicide compared to Nostoc (4.70 vs. 3.72 μg/g). Both species demonstrated substantial reductions in chlorophyll‐a (57.4% in Anabaena , 47.2% in Nostoc ) along with increased carotenoid production, with Nostoc displaying superior defensive capabilities (67.4% vs. 37.6% increase). Carboxylation enzyme activities were more severely inhibited in Anabaena . Despite ACCase inhibition, both species exhibited notable increases in total fatty acids, with distinct species‐specific patterns in the accumulation of saturated, monounsaturated, and polyunsaturated fatty acids. Metabolic reconfiguration was further evidenced by significant accumulations of carbohydrates, organic acids, and selective amino acids, particularly branched‐chain amino acids. The results highlight distinct species‐specific metabolic adaptations to herbicide‐induced stress, with Nostoc displaying more robust stress response mechanisms despite lower herbicide uptake. These findings provide valuable insights into the resilience of cyanobacteria to agrochemical exposure and underscore the potential ecological implications for aquatic microbial communities in agricultural watersheds.

Rac‐metalaxyl is a widely used fungicide for managing plant diseases; however, its environmental persistence and potential toxicity to aquatic microorganisms raise significant ecological concerns. Despite its widespread application, there is limited understanding of how cyanobacteria, which play vital ecological roles in aquatic systems, respond to such chemical stressors. This study addresses this gap by investigating the physiological and metabolic responses of the cyanobacterium Anabaena laxa to rac‐metalaxyl exposure. Cultures were treated with 100 mg/L and 200 mg/L concentrations of the fungicide. Results showed increased intracellular accumulation of rac‐metalaxyl at 200 mg/L, leading to significant reductions in cell growth, photosynthetic pigments, and the activities of key enzymes such as phosphoenolpyruvate carboxylase and ribulose‐1,5‐bisphosphate carboxylase/oxygenase. Further elevated lipid peroxidation levels indicated oxidative damage. Consequently, rac‐metalaxyl triggered substantial metabolic shifts, total soluble sugars increased by 7.66% at 100 mg/L and 67.48% at 200 mg/L; malic acid rose to 76.23% at 200 mg/L; amino acids increased by 27.14% at 100 mg/L and 48.8% at 200 mg/L; total fatty acids rose by 10.11% at 100 mg/L and 35.06% at 200 mg/L. These findings suggest that Anabaena laxa exhibits coordinated oxidative and metabolic responses to mitigate rac‐metalaxyl toxicity, highlighting its potential resilience and role in the bioremediation of contaminated aquatic environments.

The contamination resulting from heavy metals present in industrial effluents represents a critical global challenge, posing profound risks to aquatic ecosystems and human health. Industrial activities worldwide release wastewater laden with toxic metals, prominently cadmium (Cd), into rivers, lakes, and oceans, frequently surpassing permissible limits. Current treatment technologies are costly and may produce secondary pollutants, thereby necessitating the urgent development of sustainable and cost-effective alternatives. This study investigates the efficacy of the microalga Chlamydomonas sp. as a natural biosorbent for the phycoremediation of cadmium from industrial effluent. Critical parameters affecting cadmium biosorption, including pH, contact time, Cd concentration, and biomass dosage, were optimized. Under optimal conditions of 25°C, pH 4, Cd concentration of 50 mg/L, a contact time of 60 min, and a biomass dosage of 0.8 g/L, Chlamydomonas demonstrated a cadmium adsorption capacity of 44.75 mg/g, achieving a removal efficiency of 95.6%. Analytical techniques such as SEM, XRD, FTIR, DLS, and zeta potential analysis confirmed cadmium binding to the algal biomass. Kinetic modeling suggested a pseudo-second-order process, while isotherm analysis adhered to the Langmuir model, indicating considerable adsorption capacity and efficiency under optimal conditions. These results support using Chlamydomonas as an effective biosorbent for integration into global industrial wastewater treatment systems. This biological approach offers a sustainable and cost-efficient method for heavy metal removal, reducing secondary pollution and aligning with international efforts to mitigate water contamination. Implementing bioremediation strategies could greatly decrease the release of toxic metals into aquatic ecosystems, providing a scalable and environmentally friendly solution for industrial applications globally.

In the realm of applied phycology, algal physiology, and biochemistry publications, the absence of proper identification and documentation of microalgae is a common concern. This poses a significant challenge for non-specialists who struggle to identify numerous eukaryotic microalgae. However, a promising solution lies in employing an appropriate DNA barcoding technique and establishing comprehensive databases of reference sequences. To address this issue, we conducted a study focusing on the molecular characterization and strain identification of Tetraselmis and Chlorella species, utilizing the internal transcribed spacer (ITS) barcode approach. By analyzing the full nuclear ITS region through the Sanger sequencing approach, we obtained ITS barcodes that were subsequently compared with other ITS sequences of various Tetraselmis and Chlorella species. To ensure the reliability of our identification procedure, we conducted a meticulous comparison of the DNA alignment, constructed a phylogenetic tree, and determined the percentage of identical nucleotides. The findings of our study reveal the significant value of the ITS genomic region as a tool for distinguishing and identifying morphologically similar chlorophyta. Moreover, our results demonstrate that both the ITS1 and ITS2 regions are capable of effectively discriminating isolates from one another; however, ITS2 is preferred due to its greater intraspecific variation. These results underscore the indispensability of employing ITS barcoding in microalgae identification, highlighting the limitations of relying solely on morphological characterization.

Microalgae have garnered scientific interest for their potential to produce bioactive compounds. However, the large-scale industrial utilization of microalgae faces challenges related to production costs and achieving optimal growth conditions. Thus, this study aimed to investigate the potential role of exogenous indole-3-acetic acid (IAA) application in improving the growth and production of bioactive metabolites in microalgae. To this end, the study employed different concentrations of exogenously administered IAA ranging from 0.36 µM to 5.69 µM to assess its influence on the growth and biochemical composition of Synechocystis and Chlorella. IAA exposure significantly increased IAA levels in both strains. Consequentially, improved biomass accumulation in parallel with increased total pigment content by approximately eleven-fold in both strains was observed. Furthermore, the application of IAA stimulated the accumulation of primary metabolites. Sugar levels were augmented, providing a carbon source that facilitated amino acid and fatty acid biosynthesis. As a result, amino acid levels were enhanced as well, leading to a 1.55-fold increase in total amino acid content in Synechocystis and a 1.42-fold increase in Chlorella. Total fatty acids content increased by 1.92-fold in Synechocystis and by 2.16-fold in Chlorella. Overall, the study demonstrated the effectiveness of exogenously adding IAA as a strategy for enhancing the accumulation of microalgae biomass and biomolecules. These findings contribute to the advancement of microalgae-based technologies, opening new avenues to produce economically important compounds derived from microalgae.

The potential of microalgae to produce valuable compounds has garnered considerable attention. However, there are various challenges that hinder their large-scale industrial utilization, such as high production costs and the complexities associated with achieving optimal growth conditions. Therefore, we investigated the effects of glycine at different concentrations on the growth and bioactive compounds production of Synechocystis sp. PAK13 and Chlorella variabilis cultivated under nitrogen availability. Glycine supplementation resulted in increased biomass and bioactive primary metabolites accumulation in both species. Sugar production, particularly glucose content, significantly improved in Synechocystis at 3.33 mM glycine (1.4 mg/g). This led to enhanced organic acid, particularly malic acid, and amino acids production. Glycine stress also influenced the concentration of indole-3-acetic acid, which was significantly higher in both species compared to the control. Furthermore, fatty acids content increased by 2.5-fold in Synechocystis and by 1.36-fold in Chlorella. Overall, the exogenous application of glycine is a cheap, safe, and effective approach to enhancing sustainable microalgal biomass and bioproducts production.

Microalgae have received continued attention as a potential source for biofuel production. However, the lack of suitable strains that provide a lipid‐rich biomass and tolerate harsh condition inhibits their industrial application. This report describes an effort to transform Synechocystis sp. with genes encoding acetyl‐CoA carboxylase (ACC), a key regulatory enzyme in the lipogenesis pathway, from the white mustard plant (Sinapis alba) and the bacterium Escherichia coli DH5α using chitosan nanoparticles. Although a recombinant plasmid encoding S. alba ACC failed to express, successful transformation was achieved with a recombinant plasmid encoding E. coli DH5α ACC. The successful transformant, Synechocystis sp. PAK13, exhibited increased ACC expression compared with its wild‐type parent (11.8 vs. 7.2 ng), which significantly increased its lipid content (by 3.6‐fold). Synechocystis sp. PAK13 also exhibited a significant (20%) reduction in photosynthetic pigments, a 1.52‐fold higher glucose content and a 3.5‐fold lower sucrose content than the wild‐type. In conclusion, this report introduces a useful strategy to overexpress the ACC gene in microalgae, creating strains with improved lipid production that are suited to industrial applications.

Background: Biofuels produced from trans-esterification of high lipid content in microalgae represent a promising alternative renewable source of energy to the limited and depleted global fossil fuel reservoir. The most critical step in such a process is the harvesting of algal cells. Objective: We aimed to improve the current methodology for microalgae harvesting via utilizing biosynthesized silver nanoparticles (AgNPs) from Synechocystis sp. ElfSCS31 as an eco-friendly, stable, and affordable flocculant agent. Methods: AgNPs were prepared by the green synthesis method using the alcoholic extract of Synechocystis sp. ElfSCS31. The synthesized nanoparticles were characterized by Zeta sizer, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and UV-Vis Spectroscopy. Biosynthesised AgNPs were applied for harvesting 20 microalgae strains, and then, harvesting efficiency was determined by UV Spectrophotometry. Results: Our results revealed an average size of polydispersed nanoparticles ranging from 10 to 100 nm for prepared AgNPs and the potential of 1.78 mV, with an average crystallite size of 22 nm. Biosynthesised AgNPs exhibited harvesting efficiency towards different strains of microalgae, which reached 97% in some strains as in Chlorella lobophora and Chlorococcum oleofaciens. Conclusion: The presented study introduces a feasible strategy using biosynthesized AgNPs as a flocculant agent to harvest different strains of microalgae at normal growth conditions of light and temperature. Our developed method could replace the classical high-cost step of harvesting that leads to unravelling the full potential of microalgae as a promising and fascinating source for biofuels production.