Structural characterization of a Chlorella heteropolysaccharide by analyzing its depolymerized product and finding an inducer of human dendritic cell maturation

Chlorella polysaccharides have been gaining increasing attention because of their high yield from dried Chlorella powder and their remarkable immunomodulatory activity. In this study, the major polysaccharide fraction, CPP-3a, in Chlorella pyrenoidosa, was isolated, and its detailed structure was investigated by analyzing the low-molecular-weight product prepared via free radical depolymerization. The results indicated that CPP-3a with a molecular weight of 195.2 kDa was formed by →2)-α-L-Araf-(1→, →2)-α-D-Rhap-(1→, →5)-α-L-Araf-(1→, →3)-β-D-Glcp-(1→, →4)-α-D-Glcp-(1→, →4)-α-D-GlcpA-(1→, →2,3)-α-D-Manp-(1→, →3,4)-α-D-Manp-(1→, →3,4)-β-D-Galp-(1→, →3,6)-β-D-Galp-(1→, and →2,3,6)-α-D-Galp-(1→ residues, branched at C2, C3, C4, or C6 of α/β-D-Galp and α-D-Manp, and terminated by α/β-L-Araf, α-L-Arap, α-D-Galp, and β-D-Glcp. Biological assays showed that CPP-3a significantly altered the dendritic morphology of immature dendritic cells (DCs). Enhanced CD80, CD86, and MHC I expression on the cell surface and decreased phagocytic ability indicated that CPP-3a could induce the maturation of DCs. Furthermore, CPP-3a-stimulated DCs not only stimulated the proliferation of allogeneic naïve CD4+ T cells and the secretion of IFN-γ, but also directly stimulated the activation and proliferation of CD8+ T cells through cross-antigen presentation. These findings indicate that CPP-3a can promote human DC maturation and T-cell stimulation and may be a novel DC maturation inducer with potential developmental value in DC immunotherapy.

Physiological and molecular mechanisms of the inhibitory effects of artemisinin on Microcystis aeruginosa and Chlorella pyrenoidosa

Artemisinin, a novel plant allelochemical, has attracted attention for its potential selective inhibitory effects on algae, yet to be fully explored. This study compares the sensitivity and action targets of Microcystis aeruginosa (M. aeruginosa) and Chlorella pyrenoidosa (C. pyrenoidosa) to artemisinin algaecide (AMA), highlighting their differences. Results indicate that at high concentrations, AMA displaces the natural PQ at the QB binding site within M. aeruginosa photosynthetic system, impairing the D1 protein repair function. Furthermore, AMA disrupts electron transfer from reduced ferredoxin (Fd) to NADP+ by interfering with the iron-sulfur clusters in the ferredoxin-NADP+ reductases (FNR) domain of Fd. Moreover, significant reactive oxygen species (ROS) accumulation triggers oxidative stress and interrupts the tricarboxylic acid cycle, hindering energy acquisition. Notably, AMA suppresses arginine synthesis in M. aeruginosa, leading to reduced microcystins (MCs) release. Conversely, C. pyrenoidosa counters ROS accumulation via photosynthesis protection, antioxidant defenses, and by regulating intracellular osmotic pressure, accelerating damaged protein degradation, and effectively repairing DNA for cellular detoxification. Additionally, AMA stimulates the expression of DNA replication-related genes, facilitating cell proliferation. Our finding offer a unique approach for selectively eradicating cyanobacteria while preserving beneficial algae, and shed new light on employing eco-friendly algicides with high specificity.

XQZ3, a Chlorella pyrenoidosa polysaccharide suppresses cancer progression by restraining mitochondrial bioenergetics via HSP90/AKT signaling pathway

The mitochondria are known to exert significant influence on various aspects of cancer cell physiology. The suppression of mitochondrial function represents a novel avenue for the advancement of anti-cancer pharmaceuticals. The heat shock protein HSP90 functions as a versatile regulator of mitochondrial metabolism in cancer cells, rendering as a promising target for anticancer interventions. In this work, a novel acid polysaccharide named as XQZ3 was extracted from Chlorella pyrenoidosa and purified by DEAE-cellulose and gel-filtration chromatography. The structural characteristic of XQZ3 was evaluated by monosaccharides composition, methylation analysis, TEM, FT-IR, and 2D-NMR. It was found that XQZ3 with a molecular weight of 29.13 kDa was a complex branched polysaccharide with a backbone mainly composed of galactose and mannose. It exhibited good antitumor activity in vitro and in vivo by patient-derived 3D organoid models and patient-derived xenografts models. The mechanistic investigations revealed that XQZ3 specifically interacted with HSP90, impeding the activation of the HSP90/AKT/mTOR signaling cascade. This, in turn, led to the induction of mitochondrial dysfunction, autophagy, and apoptosis, ultimately resulting in the demise of cancer cells due to nutrient deprivation. This study offers a comprehensive theoretical foundation for the advancement of XQZ3, a novel polysaccharide inhibitor targeting HSP90, with potential as an effective therapeutic agent against cancer.

Phosphorus-supplemented seawater-wastewater cyclic system for microalgal cultivation: Production of high-lipid and high-protein algae

The reuse of wastewater after seawater cultivation is critically important. In this study, a phosphorus-supplemented seawater-wastewater cyclic system (PSSWCS) based on Chlorella pyrenoidosa SDEC-35 was developed. With the addition of phosphorus, the algal biomass and the ability to assimilate nitrogen and carbon were improved. At the nitrogen to phosphorus ratio of 20:1, the biomass productivity per mass of nitrogen reached 3.6 g g-1 (N) day-1 in the second cycle. After the third cycle the protein content reached 35.7% of dry mass, and the major metabolic substances in PSSWCS reached the highest content level of 89.5% (35.7% protein, 38.3% lipid, and 15.5% carbohydrate). After the fourth cycle the lipid content maintained at 40.1%. Furthermore, 100.0% recovery of wastewater in PSSWCS increased the nitrogen and carbon absorption to 15.0 and 396.8 g per tonne of seawater. This study achieved seawater-wastewater recycle and produced high-lipid and high-protein algae by phosphorus addition.

The interfacial interaction between typical microplastics and Pb2+ and their combined toxicity to Chlorella pyrenoidosa

Microplastics (MPs), a new type of pollutant, have attracted much attention worldwide. MPs are often complexed with other pollutants such as heavy metals, resulting in combined toxicity to organisms in the environment. Studies on the combined toxicity of MPs and heavy metals have usually focused on the marine, while on the freshwater are lacking. In order to understand the combined toxic effects of MPs and heavy metals in the freshwater, five typical MPs (PVC, PE, PP, PS, PET) were selected to investigate the adsorption characteristics of MPs to Pb2+ before and after the MPs aging by ultraviolet (UV) irradiation through static adsorption tests. The results showed that UV aging enhanced adsorption of Pb2+ by MPs. It is noteworthy that MPs-PET had the highest adsorption capacity for Pb2+, and the interaction between MPs-PET and Pb2+ was the strongest. We specifically selected MPs-PET to study its combined toxicity with Pb2+ to Chlorella pyrenoidosa. In the combined toxicity test, MPs-PET and Pb2+ had significant toxic effects on Chlorella pyrenoidosa in the individual exposure, and the toxicity of individual Pb2+ exposure was greater than that of individual MPs-PET exposure. In the combined exposure, when MPs-PET and Pb2+ without adsorption (MPs-PET/Pb2+), MPs-PET and Pb2+ had a synergistic effect, which would produce strong physical and chemical stress on Chlorella pyrenoidosa simultaneously, and the toxic effect was the most significant. After the adsorption of MPs-PET and Pb2+ (MPs-PET@Pb2+), the concentration and activity of Pb2+ decreased due to the adsorption and fixation of MPs-PET, and the chemical stress on Chlorella pyrenoidosa was reduced, but the physical stress of MPs-PET still existed and posed a serious threat to the survival of Chlorella pyrenoidosa. This study has provided a theoretical basis for further assessment of the potential environmental risks of MPs in combination with other pollutants such as heavy metals.

Integrating transcriptomics and biochemical analysis to understand the interactive mechanisms of the coexisting exposure of nanoplastics and erythromycin on Chlorella pyrenoidosa

Nanoplastics and antibiotics frequently co-exist in water polluted by algal blooms, but little information is available about interaction between substances. Erythromycin, as a representative of antibiotics, has been frequently detected in aquatic environments. This investigation attempted to reveal the interaction mechanism of nanoplastics and erythromycin on Chlorella pyrenoidosa. Results demonstrated that the joint toxicity of erythromycin and nanoplastics was dynamic and depended on nanoplastics concentration. Antagonistic effects of 1/2 or 1 EC50 erythromycin and nanoplastic concentration (10 mg/L) on the growth of C. pyrenoidosa was observed. The joint toxicity of 1/2 or 1 EC50 erythromycin and nanoplastic concentration (50 mg/L) was initially synergistic during 24-48 h and then turned to antagonistic during 72-96 h. Consequently, antagonistic effect was the endpoint for joint toxicity. Integration of transcriptomics and physiological biochemical analysis indicated that the co-existence of nanoplastics and erythromycin affected the signal transduction and molecular transport of algal cell membrane, induced intracellular oxidative stress, and hindered photosynthetic efficiency. Overall, this study provided a theoretical basis for evaluating the interactive mechanisms of nanoplastics and antibiotics.

Length-dependent toxic effects of microplastic fibers on Chlorella pyrenoidosa

Microplastics (MPs), a pervasive pollutant in aquatic environments, are increasingly recognized for their detrimental effects on aquatic organisms. However, the present understanding of their impact on phytoplankton, particularly freshwater microalgae, remains limited. Furthermore, previous studies have predominantly focused on MP particles, largely overlooking the most prevalent form of MPs in aquatic settings-fibers. In this study, we scrutinized the toxicological implications of microplastic fibers (MFs) spanning four distinct lengths (50 μm, 100 μm, 150 μm, and 200 μm) on the protein-nucleated algae Chlorella pyrenoidosa over a six-day period. The study unequivocally demonstrated that MFs markedly impeded C. pyrenoidosa growth, diminished photosynthetic pigment content, and induced oxidative stress, with all observed effects exhibiting a length-dependent correlation. Electron microscopy further revealed notable damage to algal cell membranes. Cell membrane shrinkage, cytoplasm outflow, and abnormalities in cell division were observed in the 150 μm and 200 μm groups. Furthermore, C. pyrenoidosa clustered around the 200 μm MF were notably denser compared to other groups. The present study demonstrated that MFs had length-dependent toxic effects on C. pyrenoidosa. These findings offer novel insights into the deleterious impact of MFs on aquatic organisms, underscoring the pivotal role of length in influencing their toxicity.

Differences in the response of Chlorella pyrenoidosa to three antidepressants and their mixtures in different light-dark start cycles

The use of antidepressants is increasing along with the continuing spike in the prevalence of depression worldwide. As a result, more and more antidepressants are entering the water and probably does harm to the aquatic organisms and even human health. Therefore, three antidepressants, including fluoxetine (FLU), citalopram (CIT), and aspirin (APC), were selected to investigate the toxic risks of antidepressants and their mixtures to a freshwater green alga Chlorella pyrenoidosa (C. pyrenoidosa). Due light is critical for the growth of green algae, six different light-dark cycle experiments were constructed to investigate the differences in toxicity and interaction responses of C. pyrenoidosa to antidepressants and their ternary mixture designed by the uniform design ray method. The toxic effects of individual antidepressants and their mixtures on C. pyrenoidosa were systematically investigated by the time-dependent microplate toxicity analysis (t-MTA) method. Toxicity interactions (synergism or antagonism) within mixtures were analyzed by the concentration addition (CA) and the deviation from the CA model (dCA) models. The results showed that the toxicities of the three antidepressants were different, and the order was FLU > APC > CIT. Light-dark cycles obviously affect the toxicity of three antidepressants and their combined toxicity interaction. Toxicity of the three antidepressants increases with the duration of light but decreases with the duration of darkness. The ternary antidepressant mixture exhibits antagonism, and the longer the initial lighting is, the stronger the antagonism. The antagonism of the ternary mixture is also affected by exposure time and mixture components' pi as well as exposure concentration.

Optimization of Protease Treatment Conditions for Chlorella pyrenoidosa Protein Extraction and Investigation of Its Potential as an Alternative Protein Source

This study aimed to determine enzymes that effectively extract Chlorella pyrenoidosa proteins and optimize the processing conditions using response surface methods. Furthermore, the potential of enzymatically hydrolyzed C. pyrenoidosa protein extract (CPE) as a substitute protein source was investigated. The enzymatic hydrolysis conditions for protein extraction were optimized using single-factor analysis and a response surface methodology-Box-Behnken design. The R2 value of the optimized model was 0.9270, indicating the reliability of the model, and the optimal conditions were as follows: a hydrolysis temperature of 45.56 °C, pH 9.1, and a hydrolysis time of 49.85 min. The amino acid composition of CPE was compared to that of C. pyrenoidosa powder (CP), which was found to have a higher content of essential amino acids (EAA). The electrophoretic profiles of CP and CPE confirmed that CPE has a low molecular weight. Furthermore, CPE showed higher antioxidant activity and phenol content than CP, with ABTS and DPPH radical scavenging abilities of 69.40 ± 1.61% and 19.27 ± 3.16%, respectively. CPE had high EAA content, antioxidant activity, and phenol content, indicating its potential as an alternative protein source. Overall, in this study, we developed an innovative, ecofriendly, and gentle enzymatic hydrolysis strategy for the extraction and refinement of Chlorella proteins.

Extraction, functionality, and applications of Chlorella pyrenoidosa protein/peptide

Chlorella pyrenoidosa (C. pyrenoidosa) has been widely used in commercial food and feed production for numerous years. Its high protein content and cost-effectiveness make it an attractive source of novel protein. With a focus on sustainable development and the search for green natural products, current research is dedicated to maximizing the utilization of C. pyrenoidosa protein (CPP) and peptide. Various techniques, such as the use of ionic liquids, freeze-thawing, ultrasonication, enzyme digest, microwaving are employed in the extraction of CPP. The extracted CPP has demonstrated antioxidant, anti-inflammatory, and bacteriostatic properties. It can also stimulate immune regulation, prevent cardiovascular disease, protect red blood cells, and even be used in wastewater treatment. Furthermore, CPP has shown some potential in combating obesity. Additionally, CPP is being explored in three-dimensional (3D) printing applications, particularly for the creation of biological scaffolds. It is also anticipated to play a role in 3D food printing. This review aimed to supply a comprehensive summary of CPP and C. pyrenoidosa peptide extraction methods, their functions, and practical applications in various industries. By doing so, it seeks to underpin subsequent research efforts, highlight current research limitations, and identify future research directions in this field.

Synergism of antiproliferative effects of young green barley and chlorella water extracts against human breast cancer cells

INTRODUCTION AND OBJECTIVE

Breast cancer is the most common type of tumour in terms of incidence and mortality among women. In the light of recent data that has revealed the beneficial impact of increasing plant-based food consumption on the risk of breast cancer, the use of young green barley and chlorella, the chemopreventive properties of which have been previously reported, seems to be a reasonable therapeutic strategy in this type of cancer. Nevertheless, there are only a few scientific reports focused on the influence of the mentioned products on breast cancer development; thus, the aim of the study was to enrich knowledge resources in this area.

MATERIAL AND METHODS

The chemopreventive effect of water extracts of chlorella (CH) and young green barley (YGB) and their mixture (MIX) was investigated in human breast adenocarcinoma T47D cells and human skin fibroblasts HSF by LDH, MTT and BrdU assays. Changes in cell morphology in response to tested extracts were examined in light microscopy.

RESULTS

Tested extracts were not toxic against HSF and did not affect their proliferation and morphology. Simultaneously, extracts increased the permeability of T47D cell membranes and inhibited their proliferation. Microscopic observation confirmed the results of biochemical assays and additionally suggested necrosis induction in T47D cells in response to tested compounds. Obtained results demonstrated that MIX induced stronger beneficial changes than their components.

CONCLUSIONS

The study revealed the chemopreventive properties of the investigated green food products against breast cancer cells, without any side-effects in human skin fibroblasts. The beneficial properties discovered of the tested extracts on cancer cells enhanced by their concomitant administration, and in the case of antiproliferative effects YGB and CH, revealed synergism of action.

Stimulating carbon and nitrogen metabolism of Chlorella pyrenoidosa to treat aquaculture wastewater and produce high-quality protein in plate photobioreactors

Wastewater treatment by microalgae is the economical and environmentally friendly strategy, but is still challenged with the strict discharge standards and valuable biomass exploitations. The carbon and nitrogen metabolism of Chlorella pyrenoidosa was improved by the red LED light and starch addition to treat Tilapia aquaculture wastewater (T-AW) and produce protein simultaneously in a plate photobioreactor. The red LED light was applied to improve the nutrient removals at an outdoor temperature, but the concentrations except total nitrogen did not satisfy the discharge standards. After starch addition, the removal efficiencies of total phosphorus, total nitrogen, chemical oxygen demand, and total ammonia nitrogen were 85.15, 96.96, 88.53, and 98.01 % in a flat-plate photobioreactor, respectively, which met the discharge standards and the protein production reached 0.60 g/L. At a molecular level, the metabolic flux and transcriptome analyses showed that red light promoted carbon flux of the Embden-Meyerhof-Pranas pathway and tricarboxylic cycle, and upregulated the levels of genes encoding α-amylase, glutamine synthetase, glutamate dehydrogenase, nitrate transporter, and ammonium transporter, which facilitated nutrients removal and provided nitrogen sources for protein biosynthesis. The harvesting C. pyrenoidosa possessed the 62 % essential amino acids and great lipid composition for biofuels. This study provided a new orientation for outdoor wastewater treatment and protein production by collaboratively regulating the carbon and nitrogen metabolism of microalgae.

Deciphering the toxicity mechanism of haloquinolines on Chlorella pyrenoidosa using QSAR and metabolomics approaches

The hazardous potential of haloquinolines (HQLs) is becoming an issue of great concern due to its wide and long-term usage in many personal care products. We examined the growth inhibition, structure-activity relationship, and toxicity mechanism of 33 HQLs on Chlorella pyrenoidosa using the 72-h algal growth inhibition assay, three-dimensional quantitative structure-activity relationship (3D-QSAR), and metabolomics. We found that the IC₅₀ (half maximal inhibitory concentration) values for 33 compounds ranged from 4.52 to > 150 mg·L^-1, most tested compounds were toxic (1 mg·L^-1 < IC₅₀ < 10 mg·L^-1) or harmful (10 mg·L^-1 < IC₅₀ < 100 mg·L^-1) for the aquatic ecosystem. Hydrophobic properties of HQLs dominate their toxicity. Halogen atoms with large volume appear at the 2, 3, 4, 5, 6, and 7-positions of the quinoline ring to significantly increase the toxicity. In algal cells, HQLs can block diverse carbohydrates, lipids, and amino acid metabolism pathways, thereby resulting in energy usage, osmotic pressure regulation, membrane integrity, oxidative stress disorder, thus fatally damaging algal cells. Therefore, our results provide insight into the toxicity mechanism and ecological risk of HQLs.

FIB-SEM combined with proteomics and modification omics clarified mechanisms of lipids synthesis in organelles of Chlorella pyrenoidosa cells with high CO2 concentration

In order to explain reasons why flue-gas CO₂ (normally containing high CO₂) enhanced carbon fixation and lipids synthesis with increased photochemical electron production in microalgae cells. Focused ion beam scanning electron microscopy (FIB-SEM) was combined with proteomics and phosphorylation modification mics to clarify mechanisms of lipids synthesis at protein and organelle levels in Chlorella pyrenoidosa cells cultivated with high CO₂ concentration (15 % v/v). The volumes of chloroplast and endoplasmic reticulum in subcellular organelles increased by 47 % and 306 %, respectively, compared with the control, which improved conversion efficiency of starch grains to lipids (lipid content increased by 57 %). Proteomics and modifications omics revealed that protein translation and ribosome structure and biogenesis-related enzymes were significantly modified by phosphorylation, which regulated protein biological functions. Glycolysis, pentose phosphate pathway and other carbohydrate metabolic pathways were markedly enriched and promoted the expression of lipid synthase, which was consistent with enhanced carbon fixation in photosynthesis, expansion of subcellular organelles and improved lipids synthesis.

Biomass production of Chlorella pyrenoidosa by filled sphere carrier reactor: Performance and mechanism

Microalgae-based Carbon Capture, Utilization and Storage is vital for mitigating global climate change. A filled sphere carrier reactor was developed to achieve high biomass production and carbon sequestration rate of Chlorella pyrenoidosa. By introducing air (0.04% CO₂) into the reactor, the dry biomass production achieved 8.26 g/L with the optimized parameters of polyester carrier, 80% packing density, 5-fold concentrated nutrient combining 0.2 mol/L phosphate buffer. At simulated flue gas CO₂ concentration of 7%, the dry biomass yield and carbon sequestration rate reached up to 9.98 g/L and 18.32 g/L/d in one day, which were as high as 249.5 and 79.65 times comparing with those of suspension culture at day 1, respectively. The mechanism was mainly attributed to the obvious intensification of electron transfer rate and remarkable increase of RuBisCO enzyme activity in the photosynthetic chloroplast matrix. This work provided a novel approach for potential microalgae-based carbon capture and storage.

Proteomic analysis reveals mechanisms of mixed wastewater with different N/P ratios affecting the growth and biochemical characteristics of Chlorella pyrenoidosa

Effects of different nutrient ratios on the biochemical compositions of microalgae and the changes were rarely studied at the molecular level. In this study, the impacts of various nitrogen to phosphorus (N/P) ratios on growing of C. pyrenoidosa, as well as biochemical compositions and the metabolic regulation mechanism in mixed sewage, were investigated. The results suggested that 18 was optimal N/P ratio, while the dry weight (1.0 g/L), chlorophyll-a (Chla) (3.63 mg/L), and lipid production (0.28 g/L) were all the highest comparing with other groups. In contrast, the protein production (0.37 g/L) was the least. The nature of the regulatory mechanisms inthe metabolic pathways of these biochemical compositions was revealed by proteomic results, and there were 62 different expression proteins (DEPs) taken part in fatty acid and lipid biosynthesis metabolism (FA), amino acid biosynthesis metabolism (AA), photosynthesis (PHO), carbon fixation in photosynthetic organisms (CFP), and central carbon metabolism (CCM).

FIB-SEM analysis on three-dimensional structures of growing organelles in wild Chlorella pyrenoidosa cells

To clarify dynamic changes of organelle microstructures in Chlorella pyrenoidosa cells during photosynthetic growth with CO₂ fixation, three-dimensional (3D) organelle microstructures in three growth periods of meristem, elongation, and maturity were quantitatively determined and comprehensively reconstructed with focused ion beam scanning electron microscopy (FIB-SEM). The single round-pancake mitochondria in each cell split into a dumbbell and then into a circular ring, while the barycenter distance of mitochondria to chloroplast and nucleus was reduced to 45.5% and 88.3% to strengthen energy transfer, respectively. The single pyrenoid consisting of a large part and another small part in each chloroplast gradually developed to a mature state in which the two parts were nearly equal in size. The nucleolus progressively became larger with euchromatin replication. The number of starch grains gradually increased, but the mean grain volume remained nearly unchanged.

Ultrasound-induced cell disintegration and its ultrastructure characterization for the valorisation of Chlorella pyrenoidosa protein

Chlorella pyrenoidosa (CP) has great potential for feeding future demands in food, environment, energy, and pharmaceuticals. To achieve this goal, the exploitation of emerging efficient technique such as ultrasound-assisted extraction (UAE) for CP nutrient enrichment is crucial. Here, UAE is deployed for high-efficient CP protein (CPP) valorisation. Compared to conventional solvent extraction (CSE), remarkable mass transfer enhancements with 9-time protein yields and 3-time extraction rate are achieved by ultrasonic cavitation in UAE, indicating UAE can drastically shift intracellular nutrients including proteins and pigments to solvent. Cell morphology and ultrastructure show the different responses of cell wall and membrane, indicating that the cell membrane may play a role in the extraction process, based on which the extremely-low efficiency of CSE and high efficiency of UAE are highlighted. This study provides a solution for future food crisis by extracting CPP and may open a new discussion field in ultrasonic extraction.

Toxicity interactions of azole fungicide mixtures on Chlorella pyrenoidosa

It is acknowledged that azole fungicides may release into the environment and pose potential toxic risks. The combined toxicity interactions of azole fungicide mixtures, however, are still not fully understood. The combined toxicities and its toxic interactions of 225 binary mixtures and 126 multi-component mixtures on Chlorella pyrenoidosa were performed in this study. The results demonstrated that the negative logarithm 50% effect concentration (pEC₅₀ ) of 10 azole fungicides to Chlorella pyrenoidosa at 96 h ranged from 4.23 (triadimefon) to 7.22 (ketoconazole), while the pEC₅₀ values of the 351 mixtures ranged from 3.91 to 7.44. The high toxicities were found for the mixtures containing epoxiconazole. According to the results of the model deviation ratio (MDR) calculated from the concentration addition (MDR_CA ), 243 out of 351 (69.23%) mixtures presented additive effect at the 10% effect, while the 23.08% and 7.69% of mixtures presented synergistic and antagonistic effects, respectively. At the 30% effect, 47.29%, 29.34%, and 23.36% of mixtures presented additive effects, synergism, and antagonism, respectively. At the 50% effect, 44.16%, 34.76%, and 21.08% of mixtures presented additive effects, synergism, and antagonism, respectively. Thus, the toxicity interactions at low concentration (10% effect) were dominated by additive effect (69.23%), whereas 55.84% of mixtures induced synergism and antagonism at high concentration (50% effect). Climbazole and imazalil were the most frequency of components presented in the additive mixtures. Epoxiconazole was the key component induced the synergistic effects, while clotrimazole was the key component in the antagonistic mixtures.

Measuring the effects of diethyl phthalate microplastics on marine algae growth using dielectric spectroscopy

This paper presents the development of a dielectric spectroscopy-based method using a customized, transmission line probe, fabricated on a printed circuit board (PCB), for monitoring the effect of diethyl phthalate (DEP) microplastics on marine algae growth. Experiments were performed by exposing marine algae (Chlorella pyrenoidosa) to DEP (0-50 mg) for up to 6 days. In order to amplify the electrophysiological effects and improve the sensing, a glutaraldehyde crosslinking agent was used and encapsulated on the surface of the probe. The reflection coefficient (S₁₁) and the complex permittivity (ɛ' & ɛ″) of the Medium Under Test (MUT) were investigated in the frequency range of 30 kHz-800 MHz. Without the presence of DEP, the number of algae (10⁴ cells/mL) and chlorophyll content (mg/L) increased at the rates of 207.73 × 10⁴ cells/mL and 148.1 mg/L per day, respectively. After 6 days of exposing Chlorella pyrenoidosa (C. pyrenoidosa) algae to different DEP concentrations, the growth rate decreased down to -11.92 × 10⁴ cells/mL and -19.19 mg/L (50 mg DEP), respectively. Additionally, the linearity of the relationship kept decreasing as the DEP content increased from R² = 0.9716 to R² = 0.1050 and from R² = 0.9293 to R² = 0.4961, respectively. Dielectric spectroscopy using the custom, transmission line probe, at 740 MHz, showed linear relationship (-1.22 dB/day) between the reflection coefficient (S₁₁) and hence complex permittivity (ɛ' & ɛ″) without the presence of DEP. However, as the DEP content increased, algae growth was prohibited more intensely, shown both from the number of algae and the chlorophyll content. This trend was reflected on S₁₁ and subsequently on the complex permittivity. This relationship confirms the capability of this method to monitor the growth of marine algae in almost real-time. This dielectric spectroscopy method could be a potential, low-cost tool to examine the impact of microplastic pollutants on marine microorganisms.

Toxicity of Tetracycline and Metronidazole in Chlorella pyrenoidosa

Antibiotics have become a new kind of organic pollutant as they are widely used in the water environment of China. Tetracycline (TC) is a class of broad-spectrum antibiotics produced or semi-synthesized by actinomycetes. Metronidazole (MTZ) is the first generation of typical nitroimidazoles. The content of nitroimidazoles is relatively high in medical wastewater, and their ecotoxicity is worthy of attention because they are difficult to completely eliminate. In this paper, the effects of TC and MTZ on the growth, cell morphology, extracellular polymer and oxidative stress of Chlorella pyrenoidosa (C. pyrenoidosa) were studied, and the toxic interactions between TC and MTZ mixture components were analyzed. The results showed that the 96h-EC50 of TC and MTZ was 8.72 mg/L and 45.125 mg/L, respectively. The toxicity of TC to C. pyrenoidosa was higher than that of MTZ, and the combined toxicity effect of TC and MTZ was synergistic after the combined action of a 1:1 toxicity ratio. In addition, the algal cells of C. pyrenoidosa died to varying degrees, the membrane permeability of algal cells was increased, the membrane was damaged, the surface of algal cells exposed to higher concentration of pollutants was wrinkled, and their morphology was changed. The extracellular polymer of C. pyrenoidosa was affected by a change in concentration. The effect of pollutants on the reactive oxygen species (ROS) level and malondialdehyde (MDA) content of C. pyrenoidosa also had an obvious dose-effect relationship. This study contributes to the assessment of the possible ecological risks to green algae due to the presence of TC and MTZ in aquatic environments.

Single and combined toxicity assessment of primary or UV-aged microplastics and adsorbed organic pollutants on microalga Chlorella pyrenoidosa

Microplastics (MPs), an emerging pollutant, have been increasingly raising concern due to the potential impacts on aquatic organisms. Moreover, the environmental aged MPs always exhibit different environmental behavior and interaction effect with organic pollutants from virgin MPs. In this work, the single and combined toxicity impact on Chlorella pyrenoidosa, a symbiont representative, has been investigated between MPs (e.g., polyamide microplastic (PA6), 75 μm) and organic pollutants (e.g., sulfamethoxazole (SMX) and dicamba (DCB)). Growth inhibition, chlorophyll accumulation, superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT) were investigated with the primary or UV-aged PA6. Above 0.5 g/L PA6 (primary or UV-aged) inhibited cell growth and chlorophyll accumulation after 96 h cultivation as compared with the control. Besides, the inhibition impacts have enhanced as the UV-aging time extending in the single PA6 systems. The algae growth inhibition rate after 96 h cultivation in both the system i.e., single (PA6: 6.9%) and combined (PA6-SMX: 14.2%, PA6-DCB: 14.9%) was slightly lower than that of exposing in organic pollutants alone (SMX: 23.9%, DCB: 25.0%), while the chl. b concentration in 60 days UV-aged PA6 combined with SMX (1.19 mg/L) or DCB (1.40 mg/L) systems were higher than in single SMX (1.04 mg/L) or DCB (1.33 mg/L) system. In addition, there were several differences of the cellular oxidative stress in the combined system of SMX and DCB. Specially, it was not noticeable of three enzymatic activities for SMX exposing in the presence of primary or UV-aged PA6. While SOD, CAT, and MDA activities was obviously increasing after exposing in PA6 and DCB combined system, indicating the significant synergistic effect on algae cells damage. This research verified the remarkable combined toxicity between UV-aged MPs and organic pollutants on microalgae.

Improved effects of combined application of nitrogen-fixing bacteria Azotobacter beijerinckii and microalgae Chlorella pyrenoidosa on wheat growth and saline-alkali soil quality

Soil salinization seriously affects crop yield and soil productivity. The application of bacteria and microalgae has been considered as a promising strategy to alleviate soil salinization. However, the effect of bacteria-microalgae symbiosis on saline-alkali land is still unclear. This study evaluated the effects of Azotobacter beijerinckii, Chlorella pyrenoidosa, and their combined application on the wheat growth and saline-alkali soil improvement. The results showed that, among all the treatments, A. beijerinckii + live C. pyrenoidosa combined inoculation group (BA) had the best effect on increasing wheat plant biomass, improving salt tolerance, and improving soil fertility. The dry weight of wheat plant in the BA group increased by 66.7%, 17.4%, and 35.0%, respectively, compared with the control group (CK), A. beijerinckii inoculation group (B), and live C. pyrenoidosa inoculation group (A). The total nitrogen content of wheat plant in the BA group increased by 69.5%, 76.7%, and 71.1%, compared with the CK, B, and A group. The proline content of wheat plant in the BA group was 100% higher than that in the CK group. The N/P ratio and K/Na ratio of wheat plant increased by 157% and 12.9% in the BA group compared with the CK group, respectively, which was more conducive to alleviating nitrogen limitation and salt stress. The A. beijerinckii + live C. pyrenoidosa inoculation treatment better reduced soil pH and improved the availability of phosphorus in soil. This study illustrated the comprehensive application prospects of bacteria-microalgae interactions on wheat growth promotion and soil improvement in saline-alkali land, and provided a new effective strategy for improving saline-alkali soil quality and increasing crop productivity.

Interspecific competition between the bloom-causing dinoflagellates Hetrocapsa bohaiensis and the local species Chlorella pyrenoidosa

Harmful algal blooms caused by Heterocapsa bohaiensis have broken out in aquaculture areas near Liaodong Bay, China, since 2012, resulting in mass mortality of Eriocheir sinensis larvae and substantial economic loss. Chlorella pyrenoidosa is a local phytoplankton species that is found in aquaculture ponds. However, the reason why H. bohaiensis dominated and proliferated in the phytoplankton community remains unknown. Previous studies have revealed the toxicity and hemolytic activity of H. bohaiensis. It is suspected that the out-competition of H. bohaiensis to C. pyrenoidosa was associated with toxicity. Filtrate and bi-algal cultures were investigated to determine the interspecific competition between H. bohaiensis and C. pyrenoidosa in this study. Filtrate experiments revealed that H. bohaiensis showed no toxin allelopathy in C. pyrenoidosa. However, the C. pyrenoidosa filtrates had significant allelopathic effects on the growth of H. bohaiensis. The bi-algal culture experiments and the simulation showed that the dominant species were dependent on the initial cell density ratios of the species and nutrient ratios. Therefore, H. bohaiensis achieved competitive advantage through exploitation competition but not allelopathy. The results contribute to the reasons for the occurrence of H. bohaiensis blooms in a further study.

Enhanced degradation of bisphenol A: Influence of optimization of removal, kinetic model studies, application of machine learning and microalgae-bacteria consortia

Bisphenol A (BPA), a typical endocrine disruptor and a contaminant of emerging concern (CECs), has detrimental impacts not only on the environment and ecosystems, but also on human health. Therefore, it is essential to investigate the degrading processes of BPA in order to diminish its persistent effects on ecological environmental safety. With this objective, the present study reports on the effectiveness of biotic/abiotic factors in optimizing BPA removal and evaluates the kinetic models of the biodegradation processes. The results showed that BPA affected chlorophyll a, superoxide dismutase (SOD) and peroxidase (POD) activities, malondialdehyde (MDA) content, and photosystem intrinsic PSII efficiency (Fv/Fm) in the microalga Chlorella pyrenoidosa, which degraded 43.0 % of BPA (8.0 mg L^-1) under general experimental conditions. The bacteria consortium AEF21 could remove 55.4 % of BPA (20 mg L^-1) under orthogonal test optimization (temperature was 32 °C, pH was 8.0, inoculum was 6.0 %) and the prediction of artificial neural network (ANN) of machine learning (R² equal to 0.99 in training, test, and validation phase). The microalgae-bacteria consortia have a high removal rate of 57.5 % of BPA (20.0 mg L^-1). The kinetic study revealed that the removal processes of BPA by microalgae, bacteria, and microalgae-bacteria consortia all followed the Monod's kinetic model. This work provided a new perspective to apply artificial intelligence to predict the degradation of BPA and to understand the kinetic processes of BPA biodegradation by integrated biological approaches, as well as a novel research strategy to achieve environmental CECs elimination for long-term ecosystem health.

Alkyl carbamate ionic liquids for permeabilization of microalgae biomass to enhance lipid recovery for biodiesel production

Microalgae are potential biomass source for biodiesel production. However, their strong cell walls make efficient lipid extraction problematic. Disrupting the cell wall is a key point in enhancing lipid yield from microalgae biomass. A new type of ionic liquid (IL) has been suggested in this work as a potentially viable solvent to permeabilize the strong microalgae cell structure for the efficient extraction of lipids. Morphological changes in microalgae cells were studied before and after ionic liquid permeabilization to understand the mechanism of ionic liquid treatment. Among the three selected CO₂-based alkyl carbamate ionic liquids, DIMCARP performed with the best extraction efficiency. The effects of extraction variables (temperature, time, ratio ionic liquid/Methanol, and solvent to biomass) on lipid extraction were examined via single-factor experiments coupled with response surface methodology (RSM) using a Box-Behnken design (BBD). The highest lipid yield (16.40%) was obtained after 45 min of extraction at 45 °C using a 9:1 ionic liquid to methanol and 7 mL of solvent to biomass ratio. Transesterification of lipids to make fatty acid methyl esters found that the most common fatty acids were C16:0, C18:2, and C18:3 (19.50%). The quality of the biodiesel made meets European and US standards.

Evaluation of acute toxicity response to the algae Chlorella pyrenoidosa of biosynthetic silver nanoparticles catalysts

Biosynthetic of silver nanoparticles (AgNPs) by using fungi has attracted much attention due to its high catalytic efficiency and environmentally friendly characteristic. However, a few studies have focused on the ecological toxicity effects of biogenic AgNPs on algae. Here, we first investigated the catalytic reduction of 4-nitrophenol (4-NP) by WZ07-AgNPs biosynthesized by Letendraea sp. WZ07. WZ07-AgNPs had significant catalytic activity with 97.08% degradation of 4-NP in 3.5 min. Then, the toxic effects of WZ07-AgNPs and commercial-AgNPs were compared by Chlorella pyrenoidosa growth, chlorophyll content, protein content, physiological, and biochemical indexes. The results demonstrated that the algal cell biomass of C. pyrenoidosa was differentially inhibited after exposure to different concentrations of AgNPs, which showed concentration dependence and time dependence. The 96h-EC₅₀ values of WZ07-AgNPs and commercial-AgNPs on C. pyrenoidosa were 15.99 mg/mL and 12.69 mg/mL, respectively. With the increase concentration of AgNPs, the chlorophyll content was gradually decreased, the protein content was first increased and then decreased, the activities of superoxide dismutase (SOD) and catalase (CAT) were decreased, and the level of malondialdehyde (MDA) was increased significantly of C. pyrenoidosa. In general, AgNPs affect the growth of algae to some extent. However, compared with commercial-AgNPs, WZ07-AgNPs is less toxic to C. pyrenoidosa, which could be used as a potential and an eco-friendly catalyst. This study provides a basis for the safe application of biosynthetic AgNPs.

Effects of environmental factors on selenite volatilization by freshwater microalgae

The accumulation and volatilization of Se by algae in surface water are important parts of the biogeochemical cycle of selenium but are also variable and complex. Experiments with 5-8 day of exposure under various temperatures, solution pH values, lighting regimes, and different initial Se concentrations were carried out to study the change in Se accumulation and volatilization behavior of algae. The study showed that algae accumulated and volatilized more Se under harsher environments, such as a lower pH, a shorter lighting time, and a higher Se load. The maximum average daily volatilization rate of Se was 234 ± 23 μg Se (g algae·d)-1, much greater than the values of previous studies. Therefore, in some Se-polluted water environments, when the pH of lakes is acidic, Se emissions to the atmosphere are much higher than currently estimated. Both the accumulation rate (Raccu) and volatilization rate (Rvol) of Se by algae were significantly negatively correlated with final pH, final OD, and residual Se in solution (Cres). Moreover, multiple linear regression equations were used to estimate the rates of Se accumulation and volatilization. This study provides theoretical basis data to quantify the contribution of selenium metabolism by algae to selenium biogeochemistry and a technical reference for the treatment of Se-containing wastewater.

Begonia-Inspired Slow Photon Effect of a Photonic Crystal for Augmenting Algae Photosynthesis

Plant photosynthesis is considered to be an environmentally friendly and effective measure for reducing carbon dioxide levels to meet the global objective of carbon neutrality. However, the light energy utilization of photosynthetic pigments is insufficient. Begonia pavonine (B. pavonina) with blue leaves exhibits a photosynthetic quantum yield 10% higher than those of other plants by virtue of their photonic crystal (PC) thylakoids. Inspired by this property, we prepared non-angle-dependent PC hydrogels and assembled them with algae Chlorella pyrenoidosa (C. pyre). The band edge of PC hydrogels matched the absorption peaks of C. pyre, and the resulting slow photon effect increased the interaction time between incident light and photosynthetic pigments, which in turn induced the expression of light-harvesting proteins and the synthesis of pigments, thereby improving the light energy utilization. Further, we introduced an artificial antenna into the assembly, which assisted the slow photon effect in increasing the oxygen evolution and carbon sequestration rate by more than 200%. This method avoids the photobleaching problems faced by methods of synthesizing artificial antenna pigments and the biosafety problems faced by genetically engineered methods of editing pigments or proteins.

[Effects of directional adaptation on selenium tolerance and accumulation of heterotrophic Chlorella pyrenoidosa]

Selenium (Se) is an essential trace element for organisms. Se deficiency will cause diseases such as Keshan disease and Kashin-Beck in human being, and huge loss to animal husbandry. Currently available Se supplements have such problems as low Se content, poor bioavailability, and poor safety. Chlorella pyrenoidosa can produce bioavailable and safe organic Se under suitable conditions, which is thus a promising Se supplement. Therefore, in this study, we tried to improve the Se tolerance and accumulation of C. pyrenoidosa by directional adaptation. To be specific, we gradually increased the concentration of Na₂SeO₃ in medium to domesticate C. pyrenoidosa and optimized the adapting time and concentration gradient of Na₂SeO₃ during the adaptation. The results showed that the adapted C. pyrenoidosa was more tolerant to Se and had stronger Se enrichment ability. In 5 L fermenter, the adapted strains could tolerate 40 mg/L Na₂SeO₃ and the synthesis rate of organic Se was 175.6% higher. Then, Se addition method in the 5 L fermenter was optimized. The result demonstrated that addition of Na₂SeO₃ at 40 mg/L during heterotrophic culture achieved the final dry weight of C. pyrenoidosa cells at 106.4 g/L, content of organic Se at 1 227 mg/kg, and synthesis rate of organic Se at 1.36 mg/(L·h). Compared with the reported highest cell density of 75 g/L and the highest organic Se content of 560 mg/kg, the corresponding figures in this study were 41.9% and 119.1% higher, respectively. In conclusion, directional adaptation can remarkably improve the Se tolerance and enrichment of C. pyrenoidosa.

Applying mixotrophy strategy to enhance biomass production and nutrient recovery of Chlorella pyrenoidosa from biogas slurry: An assessment of the mixotrophic synergistic effect

Using biogas slurry to cultivate microalgae can simultaneously obtain microalgal biomass and allow nutrient recovery. Mixotrophic microalgae are widely recognized for their high biomass accumulation and low light dependence, making it possible to overcome the drawbacks of photoautotrophy. In this study, three complete metabolic modes of photoautotrophy, heterotrophy, mixotrophy and two incomplete metabolic modes with the addition of diuron and rotenone were applied to investigate Chlorella pyrenoidosa growth in biogas slurry. The results showed that the mixotrophic group obtained 1.15 g/L biomass, 30 % starch content, 99.40 % ammonium removal and 81.69 % total phosphorus removal, which were highly promoted compared to the others. The decline in chlorophyll, the simultaneous downregulation of Rubisco and citrate synthase and the increase in the actual quantum yield of PSII under mixotrophy revealed a synergistic effect: the complementation of photophosphorylation and oxidative phosphorylation greatly contributed to maximizing energy metabolism efficiency and minimizing energy dissipation loss.

Focus on the role of synthetic phytohormone for mixotrophic growth and lipid accumulation by Chlorella pyrenoidosa

Synthetic phytohormone (SP) is regarded as an attractive candidate for microalgae cultivation due to its potential for high-value microalgae biomass production. Herein, α-naphthylacetic acid (NAA), indomethacin (IN) and 2,4-dichlorophenoxyacetic acid (2,4-D) were used for the mixotrophic cultivation of Chlorella pyrenoidosa with mariculture wastewater (MW) acidogenic fermentation effluent. The growth and lipid accumulation of Chlorella pyrenoidosa added with SP were enhanced, given their high bioavailability of the nutrients. Among these three SPs, IN was optimal for Chlorella pyrenoidosa growth, with the maximum optical density of 1.81. NAA exhibited the best performance for lipid production and the proportion of lipid reached 50.24%. Furthermore, the energy of Chlorella pyrenoidosa cultured with SP preferentially allocated to lipogenesis. To understand the mechanism of lipid accumulation in Chlorella pyrenoidosa in response to SP, the enzyme activities involved in carbon metabolism were determined. The malic enzyme (ME) and acetyl-CoA carboxylase (ACCase) were positively correlated with lipid accumulation. Phosphoenolpyruvate carboxylase (PEPC) was the negative feedback enzyme for lipid synthesis. The findings could provide valuable information for regulation mechanism of lipid accumulation and value-added products recovery by microalgae.

The toxic effects of polystyrene microplastics on freshwater algae Chlorella pyrenoidosa depends on the different size of polystyrene microplastics

Microplastics (MPs) are persistent environmental contaminants. The toxic effects of MPs on aquatic organisms have raised increasing concerns, but their toxic effects on aquatic phytoplankton has not been thoroughly investigated. In the present study, the toxic effects of two sizes MPs (1 μm and 5 μm) on Chlorella pyrenoidosa at 2, 10, 50 mg/L were explored for 1, 5, 10 days. The growth ratio, photosynthetic pigments content, extracellular polymeric substances content, soluble protein content, MDA content and relative expression of genes related to photosynthesis and energy metabolism were measured. These results indicated that 1 μm MP could significantly inhibit the growth of C. pyrenoidosa. Compared with the control group, 1 μm MP significantly reduced the photosynthetic pigment content, induced oxidative stress and disrupted the cell membrane integrity of C. pyrenoidosa. At the molecular level, 1 μm MP altered the transcript levels of genes related to photosynthesis and energy metabolism. Scanning electron microscopy and fluorescent images showed that MPs aggregation with C. pyrenoidosa may be the main reason for the toxic effects of MPs. These results will provide new insight into the toxicity of different MPs on aquatic phytoplankton, and evaluate the risks caused by MPs in aquatic environments.

Rhizopus oryzae fermentation wastewater nutrient removal coupling protein fodder production by employing Chlorella pyrenoidosa

The scenario was to investigate feasibilities of employing Chlorella pyrenoidosa for Rhizopus oryzae fermentation wastewater nutrient removal coupling protein fodder production. Results stated that TN, TP, NH₃-N, COD, BOD removal reached 99.79%, 94.70%, 98.80%, 97.60%, 99.60% to acquire discharge permit under fed-batch manipulation, whilst the peaked protein yield (19.94 g/L) was 6.04-fold more than batch manipulation. Rhizopus oryzae fermentation wastewater feeding C. pyrenoidosa was praised as high-quality protein not only with 26.78% essential amino acids and essential amino acids/nonessential amino acids value of 0.84 but also pathogenic bacteria and heavy metal loads complying with fodder standards. In vitro digestibility of dry matter, protein, lipid, and starch achieving 80.07%, 92.13%, 95.93%, 91.9% and bioavailability of polypeptides, triglycerides, free fatty acids, and oligosaccharides displaying 98.67%, 87.12%, 93.86%, 30.21%, which were roughly-equivalent to corn/soybean fodder. The findings formed exemplifications in utilizing other microalgal systems for wastewater nutrient removal coupling chemicals production.

[Effects of ultrasound on the physiological characteristics and competitive growth between Microcystis aeruginosa and Chlorella pyrenoidosa]

Microcystis aeruginosa is a common bloom-forming cyanobacterium, which generally coexists and competes with Chlorella pyrenoidosa in lakes. Sonication can be used for emergency management of algal blooms. Ultrasound influences algal growth and physiological parameters, as well as interspecific competition in algal community. To explore the effects of ultrasonic stress (35 kHz, 0.035 W·cm^-3) on physiological characteristics and interspecific competition of algae, M. aeruginosa and C. pyrenoidosa were sonicated in mono- and co-cultures (1:1 mixture, according to cell concentration). Results showed that M. aeruginosa was more sensitive to ultrasonic stress. After the sonication for 600 s, both photosynthetic activity (F_v/F_m) and esterase activity of M. aeruginosa showed significant changes, with F_v/F_m values in mono- and co-cultures being decreased by 51.8% and 64.7%, respectively. In comparison, F_v/F_m values of C. pyrenoidosa changed slightly. M. aeruginosa released more chromophoric dissolved organic matter (CDOM, including tryptophan-, tyrosine-, and fulvic-like substances) than C. pyrenoidosa. The cell concentration of C. pyrenoidosa showed little changes regardless of sonication time, while the cell concentration of M. aeruginosa decreased at different degrees. The cell concentration of M. aeruginosa in co-cultures decreased by 42.6% after sonication for 600 s, which might be responsible for the dominance of C. pyrenoidosa during 8 days after sonication. M. aeruginosa inhibited C. pyrenoidosa in other treatments, but mutual inhibition appeared in the 600 s sonication treatment. After ultrasonic treatment, the activity of M. aeruginosa could recover gradually. The treatment should be conducted again within a week to improve the persistence of algal control.

Mechanism of enhanced production of triterpenoids in algal-fungal consortium

Chlorella pyrenoidosa-Ganoderma lucidum symbiotic systems were constructed. The mechanism of enhanced production of triterpenoids in algal-fungal consortium by comparing the contents of triterpenoids in individual fungal systems and algal-fungal consortium systems was investigated. The production of triterpenoids in C. pyrenoidosa-G. lucidum consortium increased significantly (P < 0.05). The categories and relative abundances of metabolites in the individual systems and algal-fungal systems were measured and analyzed by metabonomic tests. There were 57 significant different metabolites (VIP > 1 and P < 0.05) including 12 downregulated metabolites and 45 upregulated metabolites were obtained. The significant enriched metabolic pathways (VIP > 1 and P < 0.05) of citrate cycle (TCA cycle), tyrosine metabolism, glycolysis, and terpenoid backbone biosynthesis in algal-fungal consortium were obtained. The relative abundances of important precursors of triterpenoids including mevalonic acid, lanosterol, and hydroquinone were 1.4 times, 1.7 times, and 2 times, respectively, in algal-fungal consortium than that in the individual fungal systems. The presence of C. pyrenoidosa in algal-fungal consortium promoted the biosynthesis of triterpenoids in G. lucidum.

Anti-Diabetic Potential of Chlorella Pyrenoidosa-Based Mixture and its Regulation of Gut Microbiota

The aim of the present study was to investigate the anti-diabetic effect of CGSGCG and its beneficial effects on gut microbiota in type 2 diabetes (T2D) mice induced by streptozotocin and high sucrose and high fat diet. The results showed that treatment with CGSGCG reduced fasting blood glucose, improved oral glucose tolerance test, protected the liver from injury, and reduced inflammation in T2D mice. The contents of acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid and isovaleric acid in CGSGCG group were 2.49-, 1.74-, 3.31-, 1.93-, 1.36- and 1.30-fold than that of the model group. Moreover, administration of CGSGCG up-regulated the expression of INSR/IRS-1/PI3K/AKT/GLUT4 and mTOR but down-regulated the P38MAPK expression. Furthermore, the abundance of beneficial bacteria such as Verrucomicrobia, Proteobacteria, Osillibacter, Dubosiella and Lactococcus in intestinal tract increased, indicating that CGSCGG regulated and improved the bacterial community structure of T2D mice, which were closely related to glycometabolism.

Effects of three surfactants on co-conversion of endogenous carbon and nitrogen of dairy wastewater in mesophilic hydrolytic acidification coupled microalgae culture system

To determine the feasibility of enhancing co-conversion of endogenous C and N in dairy wastewater by surfactants, the effects of varying dosages of sodium lignosulfonate (LS), sodium dodecyl sulfate (SDS), and Tween-80 on mesophilic hydrolytic acidification coupled microalgae culture system were investigated. Tween-80 had a positive effect on hydrolytic acidification, while LS had no clear effect and SDS had a negative effect. Tween-80 significantly increased the C/N ratio in hydrolytic acidification liquor (HAL) (maximum HAc/NH₄⁺-N rate reached 7.90 in 2.9% Tween-80 test). Pyrosequencing analysis demonstrated that community richness and diversity decreased and the proportion of acidobacteria increased with increasing Tween-80 dosage. Furthermore, the effect of Tween-80-enhanced HAL on microalgae (Chlorella pyrenoidosa) growth and nitrogen removal and the assimilation of C and N on the microalgae culture system were investigated. The biomass concentration and a C and N assimilation yield of 4.8% Tween-80 test (1.75 g/L, 825.01 mg/L, 126.68 mg/L) were significantly higher than those of both the low-concentration Tween-80 tests and control. The yield of protein and carbohydrates and higher heating value in the microalgae culture system were also promoted by Tween-80.

Food abundance mediates the harmful effects of ZnO nanoparticles on development and early reproductive performance of Daphnia magna

Most aquatic ecosystems are at risk of being polluted by new environmental pollutant nanoparticles. As the main food source of zooplankton, the biomass of algae always fluctuates. Cladocerans, an important part of zooplankton, are usually be simultaneously exposed to different abundance of algae and nanoparticles in aquatic environment. To evaluate the combined effects of food abundance and ZnO nanoparticles concentration on the development and early reproductive performance of cladocerans, we exposed Daphnia magna, a common and representative model organism in cladocerans, to the combinations of different abundances of Chlorella pyrenoidosa and different concentrations of ZnO nanoparticles, recorded the key life-history traits, and used multiple models to fit the data. Results showed that high level of ZnO nanoparticles and low abundance Chlorella had an interactively negative effect on the life history of D. magna. When D. magna was exposed to ZnO nanoparticles, some life history traits, such as survival time, body length at maturation, and offspring per female, increased exponentially with the increase of food abundance, and then reached a theoretical maximum value, whereas some other life history traits, such as time to maturation and time to first brood, showed an opposite trend. However, higher Chlorella abundance reduced the negative effect of ZnO nanoparticles on D. magna, but the negative effect could not be eliminated with the increase of food abundance. Below Chlorella 0.30 mg C L^-1, food plays a decisive role, while at or above this threshold, ZnO nanoparticles play a decisive role. Therefore, the effect of different ZnO nanoparticles concentrations can be fully reflected only when food is sufficient, and the negative effects of food shortages may mask the toxic effects of ZnO nanoparticles on D. magna. The findings indicated that the effects of food abundance should be considered in evaluating the realistic impact of pollutants on zooplankton.

Evaluation of the acute toxic response induced by triazophos to the non-target green algae Chlorella pyrenoidosa

Residues of triazophos in aquatic ecosystems due to extensive use for controlling pests in agriculture has became worldwide concern, while the toxic response of triazophos on the non-target green algae in aquatic environment is not well studied. Therefore, the acute (96 h) toxic effects of 1 and 10 mg/L triazophos on green algae Chlorella pyrenoidosa were evaluated in present study. The results showed that the growth was notably inhibited when treated with triazophos and the 96 h-EC₅₀ (median inhibition concentration) were 12.79 mg/L. The content of photosynthetic pigments (including chl a, chl b, total-chl and carotinoids) clearly decreased under two treatments after 48 h and 96 h with exception for the values at 48 h exposure in 1 mg/L treatment. In addition, the transcript abundance of photosynthesis-related genes (psbA, psbC and rbcL) showed obvious decrease in above two treatments after exposure 96 h to triazophos. In response to 10 mg/L triazophos treatment, the morphology of thylakoid chloroplast of algal cells were obviously damaged. It was also found that starch granules increased with down-regulation of atpB gene expression in 10 mg/L treatment, which suggests that triazophos may inhibit the energy metabolism of C. pyrenoidosa. Moreover, the algal growth inhibition was along with the increase of intracellular reactive oxygen species (ROS), activity of antioxidant enzymes and malondialdehyde content indicating oxidative damage and lipid peroxidation in the algal cells. Our findings reveal that triazophos has potential toxicity and environmental risks to one of the primary producers green algae.

Ultrahigh recovery rate of nitrate from synthetic wastewater by Chlorella-based photo-fermentation with optimal light-emitting diode illumination: From laboratory to pilot plant

To achieve ultrahigh recovery rate of nitrate from synthetic wastewater by Chlorella pyrenoidosa-based photo-fermentation, light-emitting diode (LED) spectrum was firstly evaluated in 5-L glass photo-fermenter with surrounding LED panels. Results showed that warm white LED was favorable to improve biomass yield and recovery rate of nutrients than mixed white LED. When scaling up from laboratory (50-L, 500-L) to pilot scale photo-fermenter with inner LED panels, the maximum recovery rates of NO₃^- (5.77 g L^-1 d^-1) and PO₄^3- (0.44 g L^-1 d^-1) were achieved in 10,000-L photo-fermenter, along with high productivity of biomass (11.06 g L^-1 d^-1), protein (3.95 g L^-1 d^-1) and lipids (3.79 g L^-1 d^-1), respectively. This study demonstrated that photo-fermenter with inner warm white LED illumination is a superhigh-efficient system for nitrate and phosphate recovery with algal biomass coproduction, providing a promising application in pilot demonstration of wastewater bioremediation and facilitating novel facility development for green manufacturing.

Use of reverse osmosis reject from drinking water plant for microalgal biomass production

The present study evaluates the use of reverse osmosis (RO) reject, termed as ROR, for microalgal biomass production. The supplementation of ROR from two different sources, namely domestic RO unit (ROR1) and commercial-scale RO plant (ROR2), showed a synergistic effect on the growth and biochemical composition of Chlorella pyrenoidosa. Among the tested ROR1 doses, the highest biomass production (1.27±0.06 g L^-1) was observed with 25% ROR1 supplemented growth media. In contrast, the lipid content (28.85±3.13% of TS) in C. pyrenoidosa at 50% ROR1 dose was almost twice that in BG11 (positive control). Interestingly, the microalgae showed relatively higher biomass production (1.37±0.07 g L^-1) and higher lipid content (33.23±3.92% of TS) when 50% ROR2 was used in growth media. At the same time, the estimated carbohydrate and protein contents were 28.41±0.73 and 29.75±0.31% of TS, respectively. Furthermore, the lipid productivity (28.98±2.79 mg L^-1 d^-1) was relatively higher than the nutrient media (12.35±1.34 mg L^-1 d^-1). The present findings revealed that the RO reject from drinking water purifiers can efficiently be utilized for lipid-rich microalgal biomass production. Hence, the dependency on freshwater resources for mass scale microalgae cultivation through recycling of RO reject can be reduced.

Enhancing microalgae production by installing concave walls in plate photobioreactors

In order to optimize light distribution for promoting biomass growth rate of Chlorella pyrenoidosa, concave walls were installed in plate photobioreactors (PBR) to generate rotational flow field of microalgal solution circulated from top inlets to bottom outlets. Flow vortices in four corners of concave-wall PBR resulted in decreased mixing time and increased mass transfer coefficient. The CO₂ bio-fixation by C. pyrenoidosa increased by 27% and chlorophyll-a concentration enhanced by 18.5% in concave-wall PBR compared to those in control (flat-wall) PBR. The concave walls diverge light rays to enhance frontal light exposure and supply more light photons into interior regions of PBRs. The promotion in light distribution and vortex flow field with concave walls enhanced light and nutrients utilization by microalgal cells, leading to an increased biomass growth rate by 21%.

Adsorption of uranium by chitosan/Chlorella pyrenoidosa composite adsorbent bearing phosphate ligand

In order to remove and recover uranium from acidic uranium-bearing wastewater in uranium mining and metallurgy. Herein, a novel chitosan/Chlorella pyrenoidosa composite adsorbent bearing phosphate ligand (CSP/CP) was designed and synthesized, demonstrating a high uranium adsorption capacity at a pH of 5 and excellent selectivity in an aqueous solution with eight coexisting ions. The CSP/CP exhibits a maximum adsorption capacity (1393.338 mg g^-1) and selectivity (Su = 80.53%) for uranium, which is higher than many reported adsorbents. Mechanism analysis shows that the surface of CSP/CP is rich in hydroxyl, amino, phosphate and carboxyl groups, resulting in an excellent three-dimensional structure with active sites for high-performance uranium adsorption; U(VI) is selectively bound via ion exchanges with -COOH and -OH and through surface complexation with NH₂ and PO. Furthermore, by desorption with 0.1 M Na₂CO₃ + 2% H₂O₂ at 318 K, CSP/CP can be recycled more than five times. It provides a new scientific basis for the preparation of high selectivity composite adsorbent by chitosan.

Synergistic integration of wastewaters from second generation ethanol plant for algal biofuel production: an industrially relevant option

The present study provides an integrated method for utilizing the wastewaters from second generation (2G) ethanol pretreatment plant for microalgal biomass and lipid production. The study was conducted using a mixture of wastewaters (referred as MW; pH 4.3) generated after washing of acidic and alkaline-soaked lignocellulosic biomass prior to pretreatment process. The growth studies indicated that the thermotolerant strain of Chlorella pyrenoidosa (C. pyrenoidosa) M18 exhibited higher cell proliferation in wastewater as compared to freshwater. About 20-25% enhancement in biomass (509 mg L^-1 d^-1 ± 3.09) and lipid productivity (146 mg L^-1 d^-1 ± 1.34) was observed in MW. The total chlorophyll content and variable fluorescence by maximum fluorescence (Fv/Fm) ratio of strain cultivated in MW were 10.32 µg mL^-1 and 0.75, respectively. The use of MW also enhanced the content of saturated and monounsaturated fatty acids in total lipid. The exhausted wastewater medium obtained after harvesting the auto-flocculated biomass was also reused up to three successive growth cycles. The recycled medium without any nutrient addition could be used for two subsequent rounds with enhanced biomass (520 mg L^-1 d^-1 ± 4.07) and lipid (157.71 mg L^-1 d^-1 ± 1.09) productivities. This synergistic approach of cultivating thermotolerant microalgae with wastewater from 2G pretreatment plant provides an economical setup for development of commercial algal biofuel technology.

Novel approach for harvesting of microalgal biomass using electric geyser waste material deposit as flocculant in coupling with poultry excreta leachate

The aim of this work was to study the flocculation efficiency of algal biomass (Chlorella pyrenoidosa) in coupling with waste materials i.e. poultry excreta leachate by using other waste material which was obtained from deposition of scaling in electric geyser. Utilization of electric geyser waste material deposit (EGWMD) for flocculation is a novel approach because of various elements which are replica of chemical flocculants responsible for flocculation mechanism in culture medium. Flocculation process was optimized by response surface methodology and 98.21% flocculation efficiency was achieved with designed process parameters as temperature 32.5 °C, flocculant dose 275 mgL^-1, pH 5 and time 30 min. The reusability of spent medium was also analyzed at 70.2% and 32.5% flocculation efficiency with two successive steps. The cellular morphology of pre-harvested and post-harvested Chlorella pyrenoidosa was also observed. EGWMD is abundant and freely available that has no application till now and can alternate of chemical flocculants.

Rapid and Sensitive Detection of Water Toxicity Based on Photosynthetic Inhibition Effect

To achieve rapid and sensitive detection of the toxicity of pollutants in the aquatic environment, a photosynthetic inhibition method with microalgae as the test organism and photosynthetic fluorescence parameters as the test endpoint was proposed. In this study, eight environmental pollutants were selected to act on the tested organism, Chlorella pyrenoidosa, including herbicides (diuron, atrazine), fungicides (fuberidazole), organic chemical raw materials (phenanthrene, phenol, p-benzoquinone), disinfectants (trichloroacetonitrile uric acid), and disinfection by-products (trichloroacetonitrile). The results showed that, in addition to specific PSII inhibitors (diuretic and atrazine), other types of pollutants could also quickly affect the photosynthetic system. The photosynthetic fluorescence parameters (Fv/Fm, Yield, α, and rP) could be used to detect the effects of pollutants on the photosynthetic system. Although the decay rate of the photosynthetic fluorescence parameters corresponding to the different pollutants was different, 1 h could be used as an appropriate toxicity exposure time. Moreover, the lowest respondent concentrations of photosynthetic fluorescence parameters to diuron, atrazine, fuberidazole, phenanthrene, P-benzoquinone, phenol, trichloroacetonitrile uric acid, and trichloroacetonitrile were 2 μg·L⁻¹, 5 μg·L⁻¹, 0.05 mg·L⁻¹, 2 μg·L⁻¹, 1.0 mg·L⁻¹, 0.4 g·L⁻¹, 0.1 mg·L⁻¹, and 2.0 mg·L⁻¹, respectively. Finally, diuron, atrazine, fuberidazole, and phenanthrene were selected for a comparison of their photosynthetic inhibition and growth inhibition. The results suggested that photosynthetic inhibition could overcome the time dependence of growth inhibition and shorten the toxic exposure time from more than 24 h to less than 1 h, or even a few minutes, while, the sensitivity of the toxicity test was not weakened. This study indicates that the photosynthetic inhibition method could be used for rapid detection of the toxicity of water pollutants and that algae fluorescence provides convenient access to toxicity data.

Growth of Chlorella pyrenoidosa on different septic tank effluents from rural areas for lipids production and pollutants removal

Septic tank effluent from rural areas was an ideal medium for cultivating oleaginous microalgae. However, the characteristics of septic tank effluents varied greatly due to the different incoming wastewater, and bring uncertain risks for algal growth. In this study, an oleaginous microalgae was cultivated in septic effluents from different mixed wastewater. The results showed that the effluent from pure toilet wastewater was the best medium to achieve the highest biomass yield (1.68 g·L^-1) and productivity (154.6 mg·L^-1·d^-1). In contrast, the discharge of kitchen or laundry wastewater reduced the biomass production by 50.5-79.1%. That caused much lower lipids production in effluents from mixed wastewater regardless of its high lipids content and saturation degree. The results suggest that the discharge of kitchen or laundry wastewater bring risks for biomass and lipids production, and should be separated from the toilet wastewater before entering into septic tank.

Mixotrophic Chlorella pyrenoidosa as cell factory for ultrahigh-efficient removal of ammonium from catalyzer wastewater with valuable algal biomass coproduction through short-time acclimation

To achieve ultrahigh-efficient ammonium removal and valuable biomass coproduction, Chlorella-mediated short-time acclimation was implemented in photo-fermentation. The results demonstrated short-time acclimation of mixotrophic Chlorella pyrenoidosa could significantly improve NH₄⁺ removal and biomass production in shake flasks. After acclimation through two batch cultures in 5-L photo-fermenter, the maximum NH₄⁺ removal rate (1,400 mg L^-1 d^-1) were achieved under high NH₄⁺ level (4,750 mg L^-1) in batch 3. In 50-L photo-fermenter, through one batch acclimated culture, the maximum NH₄⁺ removal rate (2,212 mg L^-1 d^-1) and biomass concentration (58.4 g L^-1) were achieved in batch 2, with the highest productivities of protein (5.56 g L^-1 d^-1) and total lipids (5.66 g L^-1 d^-1). The hypothetical pathway of nutrients assimilation in mixotrophic cells as cell factory was proposed with detailed discussion. This study provided a novel strategy for high-ammonium wastewater treatment without dilution, facilitating the algae-based "waste-to-treasure" bioconversion process for green manufacturing.

Investigation of Chlorella pyrenoidosa Protein as a Source of Novel Angiotensin I-Converting Enzyme (ACE) and Dipeptidyl Peptidase-IV (DPP-IV) Inhibitory Peptides

Chlorella pyrenoidosa (C. pyrenoidosa) is a microalgae species with a remarkably high protein content that may potentially become a source of hypotensive and hypoglycemic peptides. In this study, C. pyrenoidosa proteins were extracted and hydrolyzed overnight with pepsin and trypsin with final degrees of hydrolysis of 18.7% and 35.5%, respectively. By LC-MS/MS, 47 valid peptides were identified in the peptic hydrolysate (CP) and 66 in the tryptic one (CT). At the concentration of 1.0 mg/mL, CP and CT hydrolysates inhibit in vitro the angiotensin-converting enzyme (ACE) activity by 84.2 ± 0.37% and 78.6 ± 1.7%, respectively, whereas, tested at cellular level at the concentration of 5.0 mg/mL, they reduce the ACE activity by 61.5 ± 7.7% and 69.9 ± 0.8%, respectively. At the concentration of 5.0 mg/mL, they decrease in vitro the DPP-IV activity by 63.7% and 69.6% and in Caco-2 cells by 38.4% and 42.5%, respectively. Short peptides (≤10 amino acids) were selected for investigating the potential interaction with ACE and DPP-IV by using molecular modeling approaches and four peptides were predicted to block both enzymes. Finally, the stability of these peptides was investigated against gastrointestinal digestion.