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Sulfadiazine (SD), sulfamerazine (SM1), and sulfamethazine (SM2) are widely used and disorderly discharged into surface water, causing contamination of lakes and rivers. However, microalgae are regard as a potential resource to alleviate and degrade antibiotic pollution. The physiological changes of Chlorella vulgaris in the presence of three sulfonamides (SAs) with varying numbers of –CH 3 groups and its SA-removal efficiency were investigated following a 7-day exposure experiment. Our results showed that the growth inhibitory effect of SD (7.9–22.6%), SM1 (7.2–45.9%), and SM2 (10.3–44%) resulted in increased proteins and decreased soluble sugars. Oxidative stress caused an increase in superoxide dismutase and glutathione reductase levels but decreased catalase level. The antioxidant responses were insufficient to cope-up with reactive oxygen species (hydrogen peroxide and superoxide anion) levels and prevent oxidative damage (malondialdehyde level). The ultrastructure and DNA of SA-treated algal cells were affected, as evident from the considerable changes in the cell wall, chloroplast, and mitochondrion, and DNA migration. C. vulgaris -mediated was able to remove up to 29% of SD, 16% of SM1, and 15% of SM2. Our results suggest that certain concentrations of specific antibiotics may induce algal growth, and algal-mediated biodegradation process can accelerate the removal of antibiotic contamination.

Background Low concentration NaHCO 3 (ca. 12 mM) had been demonstrated to be an excellent carbon source for industrially important green alga Chlorella vulgaris and high concentration NaHCO 3 (e.g. 160 mM) had been shown to be capable of controlling protozoa and stimulating lipid accumulation of another green alga, i.e., Neochloris oleoabundans . Furthermore, little was known about the mechanisms of the effects of NaHCO 3 on microalgae. Thorough studies on the effects of high NaHCO 3 on C. vulgaris and their mechanisms were therefore warranted. Methods We systematically compared the cell growth, lipid production, and cell morphology of the industrially important C. vulgaris in 160 mM NaHCO 3 or 160 mM NaCl media at different pH levels. These data allowed us to analyze the effects of total dissolved inorganic carbon (DIC) and individual DIC species on C. vulgaris . Cell growth of C. vulgaris at a range of concentrations at 160 mM or lower was also studied. Results Cellular lipid cell content of 494 mg g −1 and lipid productivity of 44.5 mg L −1 day −1 were obtained at 160 mM NaHCO 3 and pH 9.5. High concentration NaHCO 3 (e.g. 160 mM) was inhibitive to cell growth but stimulating to lipid accumulation and caused unicellular C. vulgaris to transfer to colonial cells. Increasing pH in the range of 7.5–9.5 caused increasing inhibition to cell growth in 160 mM NaCl. Whereas the optimal pH for cell growth was 8.5 for 160 mM NaHCO 3 cultures. Comparative experiments with 0–160 mM NaHCO 3 indicate that 10 mM was the optimal concentration and increasing NaHCO 3 from 10 to 160 mM caused increasing inhibition to cell growth. Conclusions High concentration DIC was inhibitor to cell growth but stimulator to lipid accumulation of C. vulgaris . It caused unicellular C. vulgaris to transform to colonial cells. Results suggest that high concentration of a particular DIC species, i.e., dCO 2 , was the primary stress responsible for cell growth inhibition. Where CO 3 2− was likely the DIC species responsible for lipid stimulation of C. vulgaris . Furthermore, we propose that the colony formation at high DIC conditions was employed by C. vulgaris to mitigate the stress by minimizing cell exposure to unfavorable environment.

The impact of high salinity stress on the growth and nutrient uptake of Chlorella vulgaris was investigated using a two-stage cultivation approach. Changes in the biochemical composition of the biomass were statistically evaluated through principal component analysis (PCA) and multiple linear regression (MLR). The presence of 150 mM NaCl promoted higher biomass accumulation (978 ± 11 mg L −1 ) and did not affect the nutrient removal rates. Elevated concentrations (> 300 mM) induced negative effects, resulting in microalgae mortality. The highest lipid (24% ± 1% DCW) and carbohydrate (32.3% ± 0.6% DCW) contents were achieved with 300 mM NaCl on days 7 and 4, respectively. Moreover, 150 mM NaCl led to the highest lipid productivity (23.4 mg L −1 d −1 ) only in 2 days of stress. PCA and MLR confirmed that the lipid content was positively associated with salinity and time of exposure and that the pigments were strongly affected by the exposure time.

Microbiologically influenced corrosion (MIC) poses a significant threat to carbon steel facilities in marine environments. Due to its environmental friendliness and excellent bactericidal effect, NaClO has been widely applied in the marine industry to inhibit MIC. In fact, algae can also cause severe biocorrosion to carbon steels. However, there are very few studies on the biocorrosion induced by algae, and thus the algicidal effect of bactericide NaClO is still unclear. In this study, the biocorrosion of 45# mild steel induced by Chlorella vulgaris (C. vulgaris) and the effect of NaClO on the biocorrosion were systematically investigated. The results showed that the corrosion rate of the steel in C. vulgaris-containing biotic artificial seawater was significantly higher than that in the abiotic solution. An increase in NaClO concentration resulted in a higher corrosion rate of the steel in general but relatively mild local corrosion penetration. The overall corrosion damage of the steel in the biofilm-covered areas was alleviated, while the corrosion penetration in the biofilm-discontinuous area became deeper after NaClO addition. The addition of 1 ppm NaClO into the biotic artificial seawater could not significantly inhibit the growth of C. vulgaris. When NaClO concentration increased to 10 ppm, the growth of C. vulgaris was markedly suppressed, resulting in a lower corrosion rate than that at 0 ppm and 1 ppm NaClO. At 100 ppm of NaClO, C. vulgaris cells were completely killed, and the overall corrosion rate in the biotic solution was close to that in the abiotic solution. Based on the experimental observations, algae-induced corrosion and its inhibition by NaClO were finally analyzed.

At present, the realm of nanobionics has garnered significant attention for its potential applications in microalgal systems, offering innovative strategies to augment growth, productivity, and metabolic performance. Present study influences nanotechnology to explore the multifaceted effects of novel biocompatible nanocomposite Ag–ZnO–PEEK (silver-zinc oxide- Polyether Ether Ketone) on isolated microalgae Chlorella vulgaris_ AK, with a focus on improving the biomass production, mitigating oxidative stress, and enhancing the lipid biosynthesis. The morphometric demonstrations of Ag–ZnO–PEEK nanocomposite were characterized by Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. Different concentrations of Ag–ZnO–PEEK (10, 20, 40, 80, and 160 ppm) were applied to the microalgae for observing the biomass enhancement and lipid yield. Among all the applied concentrations, 40 ppm exhibited the suitable one for high biomass and lipid yield of 4.25 g/L and 3.31 g/L respectively. Machine learning integrating forward prediction and E-UCB-based inverse design was employed to optimize microalgal growth conditions. Gradient boosting achieved the highest R 2 of 0.9794, while ensemble uncertainty enabled reliable identification of high-performing unsampled conditions. Additionally, the effect of the as synthesized nanocomposite was also investigated as a potential antibacterial candidate against Bacillus sp. Hence, these advancements not only elevate the microalgae biomass production but also support the sustainable generation of biofuels and bioproducts from microalgae. Therefore, this study provides a scalable framework for integrating nanotechnology into renewable energy by maintaining circular bio-economy.

The green microalga Chlorella vulgaris was used as a test organism during this study for evaluation of the impact of different heavy metal stress, Mn 2+ , Co 2+ , and Zn 2+ , on enhancing the biodiesel production. The algal cultures were grown for 13 days under heavy metal stress after which were subjected to estimation of growth, some primary metabolites, lipid, and fatty acid profiles. The maximum lipid accumulation (283.30 mg/g CDW) was recorded in the algal culture treated with 3 µM cobalt nitrate. Application of 2 mM manganese chloride; 1, 2, and 3 μM cobalt nitrate; and 0.2, 0.4, and 0.6 mM zinc sulfate caused highly significant increases in the lipid contents amounting to 183.8, 191.4, 230.6, 283.3, 176.3, 226.0, and 212.1 mg/g CDW, respectively, in comparison to control (153.4 mg/g CDW). The maximum proportion of saturated fatty acids (SFA) (64.44%) was noted in the culture treated with 6 mM MnCl 2 due to the existence of palmitic acid (C16:0), stearic acid (C18:0), and pentadecylic acid (C15:0) which are represented by 53.59%, 5.96%, and 1.37%, respectively, of the total FAs. Relative increase in energy compound (REEC) showed that 1, 2, and 3 µM Co 2+ lead to the highest stimulation in lipid and carbohydrate contents to 0.207, 0.352, and 0.329 × 10 3 %, respectively. Empirical formulas were used for the assessment of biodiesel fuel properties based on FAME composition. The estimated properties met the prescribed international standard criteria.

A freshwater microalga strain of Chlorella vulgaris was used to investigate toxic effects induced by nickel oxide nanoparticles (NiO-NPs) in suspension. Algal cells were exposed during 96 h to 0–100 mg L−1 of NiO-NPs and analyzed by flow cytometry. Physicochemical characterization of nanoparticles in tested media showed a soluble fraction (free Ni2+) of only 6.42% for 100 mg L−1 of NiO-NPs, indicating the low solubility capacity of these NPs. Toxicity analysis showed cellular alterations which were related to NiO-NPs concentration, such as inhibition in cell division (relative cell size and granularity), deterioration of the photosynthetic apparatus (chlorophyll synthesis and photochemical reactions of photosynthesis), and oxidative stress (ROS production). The change in cellular viability demonstrated to be a very sensitive biomarker of NiO-NPs toxicity with EC50 of 13.7 mg L−1. Analysis by TEM and X-ray confirmed that NiO-NPs were able to cross biological membranes and to accumulate inside algal cells. Therefore, this study provides a characterization of both physicochemical and toxicological properties of NiO-NPs suspensions in tested media. The use of the freshwater strain of C. vulgaris demonstrated to be a sensitive bioindicator of NiO-NPs toxicity on the viability of green algae.

Microalgae are susceptible to most pollutants in aquatic ecosystems and can be potentially damaged by silver nanoparticles (AgNPs). This study aims to clarify the potential consequences of Chlorella vulgaris internalizing AgNPs. The exposure of C. vulgaris to AgNPs stabilized with citrate led to the accumulation of NPs in the cell wall, increasing permeability, which allowed the entry of AgNPs and Ag  +  ions resulting from the dissolution of AgNPs. Ag  +  accumulated inside the cell could be converted into AgNPs (endogenous) due to the reducing potential of the cytoplasm. Both exogenous and endogenous AgNPs caused damage to all biological structures of the algae, as demonstrated by TEM images. This damage included the disorganization of chloroplasts, deposition of AgNPs on starch granules, and increased amounts of lipids, starch granules, exopolysaccharides, plastoglobuli, and cell diameters. These changes caused cell death by altering cell viability and interfering with organelle functions, possibly due to reactive oxygen species generated by nanoparticles, as shown in a lipid bilayer model. These findings highlight the importance of considering the exposure risks of AgNPs in a worldwide distributed chlorophyte. Graphical Abstract Highlights Exposure to AgNPs increased the permeability of the cell wall to both AgNPs and Ag + . Cytoplasmic reducer potential can transform Ag  +  into endogenous AgNPs in the cell. FTIR spectra show AgNPs promote lipid oxidation, leading to membrane damage. TEM analysis shows exogenous and endogenous AgNPs damage all biological structures. AgNPs and Ag  +  produced cells death by altering membranes and organelles functions.

Iron and phosphorus (P) are the important micro- and macro-nutrient for microalgae growth, respectively. However, the effect of iron and P on microalgae growth in co-culture associating with the formation of dominate algae has not been investigated before. In the current study, Anabaene flos-aquae , Chlorella vulgaris and Melosira sp. were co-cultivated under the addition of different initial iron and P to reveal the effect of iron and phosphorus on the growth of microalgae. The results showed that the mean growth rate of A. flos-aquae , C. vulgaris and Melosira was 0.270, 0.261 and 0.062, respectively, indicating that the A. flos-aquae and C. vulgaris algae are liable to be the dominant algae while the growth of Melosira was restrained when co-cultured. The ratio of Fe to P has a significant impact on the growth of microalgae and could be regarded as an indicator of algae growth. Microalgae showed a much more obvious uptake of iron compared to that of P. The information obtained in the current study was useful for the forecast of water quality and the control of microalgae bloom.

Microalgae are increasingly recognized as promising organisms for bioremediation of organic pollutants. This study investigates the potential of enhancing the bioremediation efficiency of pyrene (PYR), a polycyclic aromatic hydrocarbon (PAH), through NaCl induced physiological and biochemical alterations in two microalgae species, Chlorella vulgaris and Scenedesmus acutus. Our findings reveal significant improvement in PYR removal when these microalgae were cultivated in the presence of 0.1% NaCl where PYR removal increased from 54 to 74% for C. vulgaris and from 26 to 75% for S. acutus. However, it was observed that NaCl induced stress had varying effects on the two species. While C. vulgaris exhibited increased PYR removal, it experienced reduced growth and biomass production, as well as lower photosynthetic efficiency when exposed to PYR and PYR + NaCl. In contrast, S. acutus displayed better growth and biomass accumulation under PYR + NaCl conditions, making it a more efficient candidate for enhancing PYR bioremediation in the presence of NaCl. In addition to assessing growth and biochemical content, we also investigated stress biomarkers, such as lipid peroxidation, polyphenol and proline contents. These findings suggest that S. acutus holds promise as an alternative microalgae species for PYR removal in the presence of NaCl, offering potential advantages in terms of bioremediation efficiency and ecological sustainability. This study highlights the importance of understanding the physiological and biochemical responses of microalgae to environmental stressors, which can be harnessed to optimize bioremediation strategies for the removal of organic pollutants like PYR.