Algae-inspired chitosan-pullulan-based multifunctional hydrogel for enhanced wound healing.

Chronic wounds caused by hyperglycaemia, hypoxia and bacterial infections are common complications in diabetic patients and chronic wound repair is extremely challenging in clinical practice. A series of hydrogels QPMP with good antioxidant and antimicrobial functions were prepared based on quaternized chitosan (QCS), oxidized pullulan polysaccharide (OP), dopamine-coated polypyrrole (PPY@PDA), and Chlorella vulgaris. The Schiff base cross-linking between the quaternized chitosan (QCS) and oxidized pullulan polysaccharide (OP) constitutes the basic skeleton of the hydrogel, and imparts a certain antimicrobial ability to the hydrogel. Chlorella vulgaris continuously produced oxygen under light conditions to relieve wound hypoxia and promote wound healing. The incorporation of PPY@PDA gave the hydrogel near-infrared (NIR) irradiation-assisted bactericidal activity and antioxidant activity, and as a conductive hydrogel, the hydrogel can be used to sense wound exudate and temperature changes, which can help to achieve the integration of diagnosis and treatment of wound healing. Most importantly, in a chronic wound model, the QPMP hydrogel was more effective in controlling the level of wound inflammation and promoting collagen deposition, angiogenesis, and early wound closure compared to the HeraDerm dressing. Therefore, this conductive oxygen-producing hydrogel is extremely beneficial for chronic wound healing in diabetes.

Visible-light-activated Fe2O3-TiO2 nanoparticles enhance biofouling resistance of polyethersulfone ultrafiltration membranes against marine algae Chlorella vulgaris.

This study investigated the modification of polyethersulfone (PES) ultrafiltration membranes with TiO2 and Fe2O3-TiO2 nanoparticles to enhance their hydrophilicity and biofouling resistance against the marine microalgae Chlorella vulgaris. It is a common freshwater and marine microalga that readily forms biofilms on membrane surfaces, leading to significant flux decline and increased operational costs in ultrafiltration processes. The microalgae cells and their extracellular polymeric substances (EPS) adhere to the membrane surface, creating a dense fouling layer that impedes water permeation. The modified membranes were characterized using contact angle measurements, scanning electron microscopy, and pure water flux/resistance tests. Short-term ultrafiltration experiments evaluated the membranes' antifouling performance by measuring flux decline, flux recovery ratio, and relative flux reduction during C. vulgaris filtration. The TiO2 membrane showed improved hydrophilicity and antifouling over the pristine PES membrane, while the Fe2O3-TiO2 nanocomposite membrane exhibited the best performance. It reduced the water contact angle and showed only a 5% relative flux reduction compared to 60% for the pristine membrane. SEM images confirmed reduced microalgal deposition on the nanocomposite surface. Long-term tests with microalgal cells under dark and visible light conditions in saline water further assessed the membranes' biofouling resistance. The Fe2O3-TiO2 membrane maintained 59 L/m2 h water flux under visible light after immersion in the microalgal solution, outperforming the pristine (38 L/m2 h) and TiO2 (52 L/m2 h) membranes. This superior antifouling was attributed to photocatalytic generation of reactive oxygen species inhibiting microalgal adhesion. This study demonstrates a promising strategy for mitigating biofouling in membrane-based water treatment and desalination processes.

Strain selection and adaptation of a fungal-yeast-microalgae consortium for sustainable bioethanol production and wastewater treatment from livestock wastewater.

This study explores the potential of strain selection and adaptation for developing a fungi-yeast-microalgae consortium capable of integrated bioethanol production and livestock wastewater treatment. We employed a multi-stage approach involving isolation and strain selection/adaptation of these consortiums. The study started with screening some isolated fungi to grow on the cellulosic biomass of the livestock wastewater (saccharification) followed by a fermentation process using yeast for bioethanol production. The results revealed that Penicillium chrysogenum (Cla) and Saccharomyces cerevisiae (Sc) produced a remarkable 99.32 ppm of bioethanol and a concentration of glucose measuring 0.56 mg ml- 1. Following the impact of fungi and yeast, we diluted the livestock wastewater using distilled water and subsequently inoculated Nile River microalgae into the wastewater. The findings demonstrated that Chlorella vulgaris emerged as the dominant species in the microalgal community. Particularly, the growth rate reached its peak at a 5% organic load (0.105385), indicating that this concentration provided the most favorable conditions for the flourishing of microalgae. The results demonstrated the effectiveness of the microalgal treatment in removing the remaining nutrients and organic load, achieving a 92.5% reduction in ammonia, a 94.1% reduction in nitrate, and complete removal of phosphate (100%). The algal treatment also showed remarkable reductions in COD (96.5%) and BOD (96.1%). These findings underscore the potential of fungi, yeast, and Nile River microalgae in the growth and impact on livestock wastewater, with the additional benefit of bioethanol production.

Assessment of endogenous and exogenous silver nanoparticles effects on the microalgae Chlorella vulgaris.

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.

Dietary Chlorella vulgaris supplementation modulates health, microbiota and the response to oxidative stress of Atlantic salmon.

Microalgae are emerging as functional feed ingredients in aquaculture due to their immune-stimulating and stress-modulating properties. We investigated the potential of the microalgae Chlorella vulgaris as a feed supplement to improve the health and modulate microbiota and stress responses of Atlantic salmon. Triplicate groups of Atlantic salmon (~ 126 g) were reared in a recirculating aquaculture system (RAS) at 15 °C and received diets supplemented with 2% (CV2) or 14% (CV14) spray-dried C. vulgaris daily, 14% once weekly (CV14w), or a control diet (CD) for 8 weeks. Subsequently, all groups were exposed to an acute one-hour peracetic acid (CH3CO3H; PAA) treatment, a commonly used disinfectant in RAS. While CV14 increased feed conversion (FCR) significantly, feeding the diets CV2 and CV14w improved protein retention efficiency. CV14 significantly modulated beta-diversity in the intestinal digesta and mucosa, but this effect was already visible in fish fed CV2. Feeding CV14 and, to a lesser degree, CV2 increased the relative abundances of Paenarthrobacter and Trichococcus in the digesta and mucosa, which are able to metabolize complex carbohydrates. However, the same diets reduced the abundance of the lactic acid bacteria Lactobacillus and Weissella in the digesta and Floricoccus in the mucosa. Peracetic acid exposure induced systemic stress (increase in plasma glucose and cortisol) and a local immune response in the gill, with the most prominent upregulation of several immune- and stress-regulated genes (clra, cebpb, marco, tnfrsf14, ikba, c1ql2, drtp1) 18 h after exposure in fish fed the control diet. Fish receiving CV14 once a week showed a reduced transcriptional response to PAA exposure. Catalase protein abundance in the liver increased following exposure to PAA, while superoxide dismutase abundance in the gill and liver was increased in response to C. vulgaris inclusion before stress. Overall, the results highlight that a high (14%) inclusion rate of C. vulgaris in feed for Atlantic salmon impairs feed conversion and shifts the intestinal microbiota composition in digesta and mucosa. Weekly feeding of C. vulgaris proves a viable approach in improving protein retention and improving transcriptional resilience towards oxidative stress in increasingly intensive production systems. Thereby this study may motivate future studies on optimizing temporal feeding schedules for health-promoting aquafeeds.

Effects of coexisting nanomaterials on the photodegradation behavior and ecotoxicity of antibiotics in the aqueous.

Nanomaterials (NPs) and antibiotics, as two emergent pollutants, forms a complex contamination through their interaction, potentially causing adverse effects on the organism. This study systematically examined the influence of two NPs (CuO NPs and carbon nanotubes, CNTs) on the photodegradation behavior of tetracycline (TC) and their combined toxic effects on Chlorella vulgaris. The results showed that CuO NPs significantly accelerated TC photodegradation compared to CNTs, increasing the TC photodegradation rate constant by187.6%. Electron spin resonance (ESR) indicated that under the coexistence of CuO NPs or CNTs, 1O2、O2•- and •OH were the main active species promoting TC photodegradation. Probe and quenching experiments confirmed the predominant role of O2•- and 1O2 in the presence of CuO NPs and CNTs. Additionally, three possible TC photodegradation pathways were proposed for the coexistence of CuO NPs and CNTs. In the Chlorella vulgaris growth inhibition experiment, the combined toxicity of CuO NPs or CNTs and TC was higher than that of individual substance, indicating significant synergistic effects, especially with the combination of CNTs and TC. This study provides a new perspective on accurately assessing the environmental behaviors and risks when NPs and antibiotics coexist.

Enhancing methane yield from microalgae: abiotic stress and cells disruption with quartz powder.

This study investigates the biochemical methane potential (BMP) of microalgal biomass, introducing a novel cells disruption method using quartz powder (SiO2). A two-phase algae cultivation, involving nitrogen deprivation and salinity shifts, was employed to biochemically modify the biomass of two brackish green algae strains, Chlorella vulgaris and Monoraphidium contortum, enhancing their methane (CH4) production potential. Mechanical disruption of the algal cells further increased BMP, with C. vulgaris yielding 305 mL CH4/g volatile solids (VS) and M. contortum reaching 324 mL CH4/g VS, reflecting respective increases of 51 % and 86 %. The integration of this efficient mechanical cell disruption method with a simple, stress-based cultivation strategy presents significant potential for enhancing the methane yield of microalgal biomass.

Optimization of Brilliant Blue R photocatalytic degradation by silver nanoparticles synthesized using Chlorella vulgaris.

Synthesis of silver nanoparticles (Ag NPs) using microalgae is gaining recognition for its environmentally friendly and cost-effective nature while maintaining high activity of NPs. In the present study, Ag NPs were synthesized using a methanolic extract of Chlorella vulgaris and subjected to calcination. The X-ray diffraction (XRD) analysis showed a crystalline nature of the products with Ag2O and Ag phases with an average crystalline size of 16.07 nm before calcination and an Ag phase with 24.61 nm crystalline size after calcination. Fourier transform infrared spectroscopy (FTIR) revealed the capping functional groups on Ag NPs, while scanning electron microscopy (SEM) displayed their irregular morphology and agglomeration after calcination. The organic coating was examined by energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric (TGA) analyses, confirming the involvement of the metabolites. The UV-Vis analysis showed a difference in optical properties due to calcination. Synthesized Ag NPs were applied for the photodegradation of hazardous dye Brilliant Blue R in visible light. Different values of light intensity, catalyst dose, initial dye concentration, and pH were tested to identify the optimal set of operating conditions. The highest degradation efficiency of 90.6% with an apparent rate constant of 0.04402 min-1 was achieved after 90 min of irradiation in the highest tested catalyst dosage.

Exopolysaccharides as bio-based rheology modifiers from microalgae produced on dairy industry waste: Towards a circular bioeconomy approach.

The feasibility of exopolysaccharides (EPS) production from cheese whey using Chlorella vulgaris was investigated as an example of circular bioeconomy application. The effects of dairy waste utilization in EPS biosynthesis and rheological properties were evaluated, comparing with both control conditions and commercial xanthan gum (CXG). A twofold increase in yield, up to 0.32 g L-1, was observed when Chlorella vulgaris was used for EPS production from whey rather than conventional fertilizers. Additionally, the EPS produced using cheese whey exhibited superior pseudoplasticity in the 0.4-1.0 (w/v) range compared to the control. The EPS from the whey wastewater contained functional groups similar to those of CXG (82.7 %). Moreover, the solutions containing 1 % biopolymer showed rheological profiles similar to those of the 0.4 % CXG. The molecular weight averages predominantly fell within the range of 284 to 324 kDa, as deduced using diffusion NMR, an innovative and rapid determination method for estimating EPS size. The potential applications of EPS notably extend beyond the dairy industry, reaching diverse market sectors, and thereby enhancing the competitiveness of microalgal biorefineries while contributing to the achievement of Sustainable Development Goals.

Impacts of graphene oxide contamination on a food web: Threats to somatic and reproductive health of organisms.

Contamination of aquatic food webs with nanomaterials poses a significant ecological and human health challenge. Ingestion of nanomaterials alongside food disrupts digestion and impairs physiological processes, with potential consequences for organism fitness and survival. Complex interactions between nanomaterials and biota further exacerbate the issue, influencing life-history strategies and ecosystem dynamics. Accumulation of nanomaterials within autotrophic and detritus-based food webs raises concerns about biomagnification, especially for top-level consumers and seafood-dependent human populations. Understanding the extent and impact of nanomaterial contamination on aquatic biota is crucial for effective mitigation strategies. To address this challenge, we conducted a comprehensive study evaluating the bioaccumulation effects of graphene oxide (GO), a commonly used nanomaterial, within an aquatic food chain. Using a gnotobiotic freshwater microcosm, we investigated the effects of micro- and nano-scale GO sheets on key organisms: green algae (Chlorella vulgaris), brine shrimp (Artemia salina), and zebrafish (Danio rerio). Two feeding regimes, direct ingestion and trophic transfer, were employed to assess GO uptake and transfer within the food web. Direct exposure involved individual organisms being exposed to either nano- or micro-scale GO sheets, while trophic transfer involved a sequential exposure pathway: algae exposed to GO sheets, artemias feeding on the algae, and zebrafish consuming the artemias. Our study provides critical insights into nanomaterial contamination in aquatic ecosystems. Physicochemical properties of GO sheets, including ζ-potential and dispersion, were influenced by salt culture media, resulting in aggregation under salt conditions. Microscopic imaging confirmed the bioaccumulation of GO sheets within organisms, indicating prolonged exposure and potential long-term effects. Notably, biodistribution analysis in zebrafish demonstrated the penetration of nano-sized GO into the intestinal wall, signifying direct interaction with vital organs. Exposure to GO resulted in increased zebrafish mortality and impaired reproductive performance, particularly through trophic transfer. These findings emphasize the urgent need to address nanomaterial contamination in aquatic food webs to protect ecosystem components and human consumers. Our study highlights the importance of developing effective mitigation strategies to preserve the integrity of aquatic ecosystems, ensure resource sustainability, and safeguard human well-being. In conclusion, our study provides crucial insights into the impact of nanomaterial pollution on aquatic biota. By recognizing the challenges posed by nanomaterial contamination and implementing targeted interventions, we can mitigate the adverse effects, preserving the integrity of aquatic ecosystems and safeguarding human health.

Integrated transcriptomics and proteomics analyses reveal the ameliorative effect of hepatic damage in tilapia caused by polystyrene microplastics with chlorella addition.

Fish exhibit varying responses to polystyrene microplastics (MPs) depending on particle size. Previous studies suggested that microorganisms adhering to the surface of MPs can induce toxic effects. In this study, Tilapia were exposed to MPs of control (group A), 75 nm (B), 7.5 µm (C), 750 µm (D), as well as combinations of all sizes (E) and 75 nm MPs with Chlorella vulgaris addition (F) for 7, 10 and 14 days. Histopathological changes in liver of tilapia were assessed using enzyme activities, transcriptomics and proteomics. The results showed that in groups combined MPs of different particle sizes and those supplemented with chlorella, MPs were localized on the surface of goblet cells, leading to vacuoles, constricted hepatic sinuses and nuclei displacement. Exposure to 7.5 and 750 µm MPs significantly increased the contents of fatty acid synthase (FAS), adenosine triphosphate (ATP), acetyl-CoA carboxylase (ACC), lipoprotein lipase (LPL), total cholesterol (TC), total triglyceride (TG) contents at 7 and 10 days. In particular, cytochrome p450 1a1 (EROD), reactive oxygen species (ROS) and superoxide dismutase (SOD) were markedly elevated following exposure to MPs. Apoptotic markers caspase-3, and inflammatory markers, including tumor necrosis factor α (TNF-α) and interleukin-1ß (IL-1ß), had a similar upward trend in comparisons of group C vs A at 7 d, group D vs A at 14 d. The peroxisome proliferator activated receptor (PPAR) signaling pathway, spliceosome, was highly enriched during the 7-day exposure of medium sized MPs, while largest MPs in the comparison of group D vs A at 14 d activated pathways such as phagosome, apoptosis, salmonella infection. Transcriptomic analysis revealed that after 14 days, the kyoto encyclopedia of genes and genomes (KEGG) pathways associated with protein processing in endoplasmic reticulum and the PPAR signaling has been significantly enriched in the Chlorella-supplemented group, which was further confirmed via the proteomic analysis. Overall, the findings highlight the size-dependent effects of MPs on histopathological changes, gene and protein expression in the liver of tilapia, and C. vulgaris effectively attenuated liver damages, likely through modulation of endoplasmic reticulum protein processing and PPAR signaling pathways.

Enhanced biochemical, microbial, and ultrastructural attributes of reduced-fat labneh through innovative microalgae integration.

Reduced-fat labneh, while offering health benefits, often presents a challenge due to its diminished nutritional profile compared to full-fat varieties. Microalgae, such as Spirulina platensis and Chlorella vulgaris, are increasingly explored for their potential to fortify foods with essential nutrients. This study innovatively investigates the use of these microalgae to enhance the quality of reduced-fat labneh. The effect of incorporating different concentrations of both microalgae was investigated at different concentrations (0.25, 0.5, and 1%) on nutritional profile (including total solids, fat, protein, carbohydrates, essential amino acids, unsaturated fatty acids, pigments, and phenolic compounds), antioxidant activity, texture, sensory attributes, and viability of the starter culture. The findings revealed that 0.25 and 0.5% concentrations of both microalgae positively influenced the sensory characteristics of the labneh and significantly enhanced its nutritional profile. However, a 1% concentration negatively impacted sensory qualities. Chlorella vulgaris enrichment resulted in higher pH values but compromised texture attributes. Importantly, both microalgae varieties enhanced the viability of the starter culture during 21 days of refrigerated storage. The scanning electron microscope images provide visual evidence of the microstructural changes in labneh with varying concentrations of microalgae and over different storage periods. This research establishes the optimal concentrations for individual microalgae enrichment in reduced-fat labneh, offering valuable insights into their potential to improve both nutritional and sensory aspects. However, it's important to mention that while both microalgae have similar effects, they might differ in their specific impacts due to their unique nutritional profiles and physical properties. Therefore, further investigations could explore optimizing a microalgae mixture and its potential application in functional food development.

Biosorption of thorium onto Chlorella Vulgaris microalgae in aqueous media.

Thorium biosorption by a green microalga, Chlorella Vulgaris, was studied in a stirred batch reactor to investigate the effect of initial solution pH, metal ion concentration, biomass dosage, contact time, kinetics, equilibrium and thermodynamics of uptake. The green microalgae showed the highest Th adsorption capacity at 45 °C for the solution with a thorium concentration of 350 mg L-1 and initial pH of 4. The amount of uptake raised from 84 to 104 mg g-1 as the temperature increased from 15 to 45 °C for an initial metal concentration of 75 mg L-1 at pH 4. Transformation Infrared Spectroscopy (FTIR) was employed to characterize the vibrational frequency changes for peaks related to surface functional groups. Also, the scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to determine the morphological changes and elemental analysis of the biosorbent before and after the sorption process. The Langmuir isotherm was in perfect agreement with the equilibrium empirical data of thorium biosorption and the highest sorption capacity of the Chlorella Vulgaris microalgae was determined as 185.19 mg g-1. Also, the results of kinetic studies show that the thorium biosorption process follows a pseudo-second-order kinetic model. The negative value of ΔG0 indicates spontaneity and the positive values of ΔH0 indicate the endothermic nature of the adsorption process.

Ecotoxicological assessment of sanitary sewer overflows and rainfall dynamics offers insights into conditions for potential adverse ecological outcomes.

Sewer overflows are an environmental concern due to their potential to introduce contaminants that can adversely affect downstream aquatic ecosystems. As these overflows can occur during rainfall events, the influence of rainwater ingress from inflow and infiltration on raw untreated wastewater (influent) within the sewer is a critical factor influencing the dilution and toxicity of the contaminants. The Vineyard sewer carrier in the greater city of Sydney, Australia, was selected for an ecotoxicological investigation of a sanitary (separate from stormwater) sewerage system and a wet-weather overflow (WWO). Three influent samples were collected representing dry-weather (DW), intermediate wet-weather (IWW) and wet-weather (WW). In addition, a receiving water sample was also collected downstream in Vineyard Creek (WW-DS) coinciding with a WWO. We employed direct toxicity assessment (DTA) and toxicity identification evaluation (TIE) approaches to gain comprehensive insights into the nature and magnitude of the impact on influent from rainwater ingress into the sewer. Three standard ecotoxicological model species, a microalga, Chlorella vulgaris, the water flea, Ceriodaphnia dubia and the midge larva, Chironomus tepperi were used for both acute and chronic tests. The study revealed variable toxicity responses, with the sample of influent collected in wet-weather displaying lower toxicity compared to the dry-weather sample of influent. Ammonia, and metals, were identified in dry weather as contributors to the observed toxicity, however, this risk was alleviated through rainwater ingress in wet-weather with further dilution within the receiving water. Based on toxicity data, dilutions of influent to minimise effects on C. vulgaris and C. dubia ranged from 1 in 12 in DW to 1 in 2.8 in WW, and further diminished in the receiving water to 1 in 1.8. The successful application of ecotoxicological approaches enabled the assessment of cumulative effects of contaminants in influent, offering valuable insights into the sanitary sewer system under rainwater ingress.

Synergistic impact of Chlorella vulgaris, zinc oxide- and/or selenium nanoparticles dietary supplementation on broiler's growth performance, antioxidant and blood biochemistry.

The current study explored the influence of dietary supplementation of Chlorella vulgaris dried powder (CV) with zinc-oxide-nanoparticles (ZnO-NPs), and/or selenium-nanoparticles (Se-NPs) on broilers' growth, antioxidant capacity, immune status, histological responses, and gene expression of some related genes. Several 200 one-day-old Cobb-500 male chicks were distributed into 5 groups with four replicates each. In the 1st group, birds were fed the basal diet (BD). In the 2nd, 3rd, 4th, and 5th groups, birds received the BD supplemented with CV only, CV + ZnO-NPs, CV + Se-NPs, and CV + ZnO-NPs + Se-NPs, respectively. The CV dried powder, ZnO-NPs, and Se-NPs were added to the BD at a rate of 1 g, 40 mg, and 0.3 mg/kg diet, respectively. After 6 weeks of feeding, increases in final body weights (P < 0.05), body weight gain (P < 0.05), and feed intake (P < 0.05) were linked with improvements in FCR (P < 0.05) and intestinal morphometric indices (P < 0.05), and marked up-regulations of MYOS (P < 0.05), GHR (P < 0.05), and IGF (P < 0.05) genes were established. Additionally, distinct increases in antioxidant enzyme activities of SOD (P < 0.05), and GPX (P < 0.05) with increases in the mRNA copies of their genes were measured. Moreover, slight improvement in immunity indices, WBCs count (P > 0.05), and phagocytic and lysozyme activities (P > 0.05) were found. However, distinct increases in phagocytic index (P < 0.05) and up-regulations of IL-1ß and TNF, and down-regulation of IL-10 mRNA levels were reported (P < 0.05). These findings were prominent in the case of the separate supplementation of CV with ZnO-NPs or Se-NPs confirming the synergistic mechanisms of CV with ZnO-NPs or Se-NPs. Thus, the synergetic supplementation of CV with ZnO-NPs, or Se-NPs in the broiler's diet could augment their growth and antioxidant response.

Low-carbon wastewater treatment and resource recovery of recirculating aquaculture system by immobilized chlorella vulgaris based on machine learning optimization.

Immobilized microalgae biotechnologies can conserve water and space by low-carbon wastewater treatment and resource recovery in a recirculating aquaculture system (RAS). However, technical process parameters have been unoptimized considering the mutual interaction between factors. In this study, machine learning optimized the parameters of alginate-immobilized Chlorella vulgaris (C. vulgaris), that is, 474 µmol/(m2·s) of light intensity, 23 × 106 cells/mL for initial cell number, and 2.07 mm particle size. Importantly, under continuous illumination, the immobilized C. vulgaris and microalgal-bacterial consortium improved water purification and biomass reutilization. Transcriptomics of C. vulgaris showed enhanced nitrogen removal by increasing pyridine nucleotide and lipid accumulation via enhanced triacylglycerol synthesis. Symbiotic bacteria upregulated genes for nitrate reduction and organic matter degradation, which stimulated biomass accumulation through CO2 fixation and starch synthesis. The recoverable microalgae (1.94 g/L biomass, 47 % protein, 26.23 % lipids), struvite (64.79 % phosphorus), and alginate (79.52 %) every two weeks demonstrates a low-carbon resource recovery in RAS.

Influence of growth medium on the species-specific interactions between algae and bacteria.

In this study, we investigated a species-specific algal-bacterial co-culture that has recently attracted worldwide scientific attention as a novel approach to enhancing algal growth rate. We report that the type of interaction between Chlorella vulgaris and bacteria of the genus Delftia is not solely determined by species specificity. Rather, it is a dynamic process of adaptation to the surrounding conditions, where one or the other microorganism dominates (temporally) depending on the growth conditions, in particular the medium. Under laboratory conditions, we found that Delftia sp. had a negative effect on C. vulgaris growth when co-cultured in a TAP medium. However, the co-culture of algae and bacteria under BG-11 and BG-11 + acetic acid resulted in an increase in algal concentration compared to algal cultures without bacteria under the same conditions. Additional chemical analysis revealed that the presence of different carbon (the main organic carbon source-acetic acid in TAP or BG-11 + acetic acid medium and inorganic carbon source-Na2CO3 in BG-11 or BG-11 + acetic acid medium) and nitrogen (NH4Cl in TAP medium and NaNO3 in BG-11 or BG-11 + acetic acid medium) species in the growth medium was one of the main factors driving the shift in interaction type.

Comparative toxic effect of tire wear particle-derived compounds 6PPD and 6PPD-quinone to Chlorella vulgaris.

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), a widely used antioxidant in rubber products, and its corresponding ozone photolysis product N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q), have raised public concerns due to their environmental toxicity. However, there is an existing knowledge gap on the toxicity of 6PPD and 6PPD-Q to aquatic plants. A model aquatic plant, Chlorella vulgaris (C. vulgaris), was subjected to 6PPD and 6PPD-Q at concentrations of 50, 100, 200, and 400 µg/L to investigate their effects on plant growth, photosynthetic, antioxidant system, and metabolic behavior. The results showed that 6PPD-Q enhanced the photosynthetic efficiency of C. vulgaris, promoting growth of C. vulgaris at low concentrations (50, 100, and 200 µg/L) while inhibiting growth at high concentration (400 µg/L). 6PPD-Q induced more oxidative stress than 6PPD, disrupting cell permeability and mitochondrial membrane potential stability. C. vulgaris responded to contaminant-induced oxidative stress by altering antioxidant enzyme activities and active substance levels. Metabolomics further identified fatty acids as the most significantly altered metabolites following exposure to both contaminants. In conclusion, this study compares the toxicity of 6PPD and 6PPD-Q to C. vulgaris, with 6PPD-Q demonstrating higher toxicity. This study provides valuable insight into the risk assessment of tire wear particles (TWPs) derived chemicals in aquatic habitats and plants.

Polyethylene terephthalate nanoparticles induce oxidative damage in Chlorella vulgaris.

Polyethylene Terephthalate (PET) is a type of plastic largely used for packing food and beverages. Unfortunately, it includes a major portion of the plastic distributed through aquatic systems wherever systematic collection and recycling are lacking. Although PET is known to be non-toxic, it is not obvious whether the nanoparticles (NPs) formed due to their degradation have any direct/indirect effect on aquatic organisms. In order to study the effects on aquatic environment, fresh water algae Chlorella vulgaris was subjected to incremental concentrations of the NPs. We observed a concentration and duration of exposure dependent decrease in algal growth rate along with reduced total chlorophyll content. Scanning electron microscopy revealed deformities in cell shape and the uptake of Propidium Iodide suggested membrane damage in response to NP exposure. Intracellular Reactive Oxygen Species level was also found significantly higher, evidenced by Dichlorodihydrofluorescein diacetate staining. Activity of antioxidant enzymes Superoxide dismutase (SOD), Peroxidase (POD) and Catalase (CAT) were significantly higher in the NP exposed groups suggesting the cellular response to regain homeostasis. Further, expression levels of the genes psaB, psbC, and rbcL associated with photosynthesis increased above two fold with respect to the control inferring the possibility of damage to photosynthesis and the initial molecular responses to circumvent the situation. In short, our studies provide evidence for oxidative stress mediated cellular damages in Chlorella vulgaris exposed to NPs of PET.

A newly identified algicidal bacterium of Pseudomonas fragi YB2: Algicidal compounds and effects.

Harmful algal bloom (HAB) is an unresolved existing problem worldwide. Here, we reported a novel algicidal bacterium, Pseudomonas fragi YB2, capable of lysing multiple algal species. To Chlorella vulgaris, YB2 exhibited a maximum algicidal rate of 95.02 % at 120 h. The uniqueness of YB2 lies in its ability to self-produce three algicidal compounds: 2-methyl-1, 3-cyclohexanedione (2-MECHD), N-phenyl-2-naphthylamine, and cyclo (Pro-Leu). The algicidal properties of 2-MECHD have not been previously reported. YB2 significantly affected the chloroplast and mitochondrion, thus decreasing in chlorophyll a by 4.74 times for 120 h and succinate dehydrogenase activity by 103 times for 36 h. These physiological damages disrupted reactive oxygen species and Ca2+ homeostasis at the cellular level, increasing cytosolic superoxide dismutase (23 %), catalase (35 %), and Ca2+ influx. Additionally, the disruption of Ca2+ homeostasis rarely reported in algicidal bacteria-algae interaction was observed using the non-invasive micro-test technology. We proposed a putative algicidal mechanism based on the algicidal outcomes and physiological algicidal effects and explored the potential of YB2 through an algicidal simulation test. Overall, this study is the first to report the algicidal bacterium P. fragi and identify a novel algicidal compound, 2-MECHD, providing new insights and a potent microbial resource for the biocontrol of HAB.