Microalga Chlorella Pyrenoidosa Research Articles

Sodium selenite enhances the production of functional proteins and biomass in Chlorella pyrenoidosa 038F by promoting acetate assimilation under heterotrophic cultivation

Unicellular microalga Chlorella pyrenoidosa is an excellent source of protein, but its ability to produce functional proteins has received less attention. In this study, a strategy to enhance the levels of functional proteins and biomass, by adding sodium selenite under heterotrophic cultivation, is reported for C. pyrenoidosa 038F. Activities of catalase, superoxide dismutase, and glutathione peroxidase were significantly enhanced by 1.94-, 1.90- and 32.73-fold, respectively, in C. pyrenoidosa 038F exposed to 20 mg/L of sodium selenite. Further, western blot analysis confirmed that sodium selenite promoted the synthesis of glutathione peroxidase, which might be due to the up-regulation of peroxisome and selenocysteine-synthesis-related genes. Sodium selenite also increased biomass, the content of protein and soluble sugar by 1.32-, 1.29-, 1.46-fold, respectively. Subsequent transcriptomic analysis confirmed that cellular respiration and the gluconeogenesis pathway were enhanced. This study highlights the potential use of heterotrophic C. pyrenoidosa 038F as a novel selenoprotein-rich carrier while simultaneously producing soluble sugar and biomass. These results might be helpful for increasing economic production of C. pyrenoidosa under heterotrophic cultivation.

Toxicity of urban stormwater on Chlorella pyrenoidosa: Implications for reuse safety

Urban stormwater is an alternative water source used to mitigate water resource shortages, and ensuring the safety of stormwater reuse is essential. An in-depth understanding of both individual pollutant concentrations/loads in stormwater and holistic stormwater quality can be used to comprehensively evaluate how safely stormwater can be reused. The toxicity test takes all pollutants present in water samples into account, and the results reflect the integrated effect of these pollutants. In this study, the influence of urban stormwater sourced from different land uses on microalgae (Chlorella pyrenoidosa) and the possible toxicity mechanisms were investigated. The results showed that urban stormwater, particularly residential road stormwater, significantly inhibited microalgal growth. The chlorophyll contents of microalgae exposed to residential road stormwater were relatively lower, while the corresponding values were relatively higher for microalgae exposed to grassland road stormwater. Additionally, the antioxidant-related metabolism of microalgae could be dysregulated due to exposure to urban stormwater. A possible toxicity mechanism is that urban stormwater influences metabolic pathways related to chlorophyll synthesis and further hinders photosynthesis and hence microalgal growth. To resist oxidative stress and maintain regular microalgal cell activities, the ribosome metabolism pathway was upregulated. The research results contribute to elucidating the toxicity effects of urban stormwater and hence provide useful insight for ensuring the safety of stormwater reuse. It is also worth noting that the study outcomes can only represent the influence of land use on stormwater toxicity, while the impacts of other factors (particularly rainfall-runoff characteristics) have not been considered. Therefore, the consideration of all influential factors of stormwater is strongly recommended to generate more robust results in the future and provide more effective guidance for real practices related to stormwater reuse safety.

Exogenous 24-epibrassinolide (EBL) facilitates cell growth of Chlorella pyrenoidosa under high temperatures by enhancing the photosynthetic energy utilization and alleviating oxidative damage.

The microalga Chlorella pyrenoidosa is cultivated extensively for its constituents, which are of significant economic worth. Large-scale growth of C. pyrenoidosa in outdoor environments is subject to various stressors such as elevated temperature. The purpose of this study was to assess the protective effects of exogenous 24-epibrassinolide (EBL) on C. pyrenoidosa under high-temperature conditions. Compared to a temperature of 30°C, increasing the temperature to 43°C reduced the enzymatic capacity for carbon assimilation and resulted in the buildup of reactive oxygen species (ROS), thus reducing photosynthesis and proliferation. It was observed that exogenous EBL protected C. pyrenoidosa cells against high temperatures, with an optimal EBL concentration of 100 nM, resulting in enhanced capacity for photosynthetic carbon assimilation with a notable reduction in the imbalance between the absorption of light and energy used under high-temperature conditions. The addition of 100 nM EBL resulted in a 25.4% increase in cell density when exposed to elevated temperatures for 7 days. In addition, exogenous EBL reduced ROS production and increased the activities of critical antioxidant enzymes. This, in turn, mitigated heat-induced oxidative damage, resulting in advantageous outcomes in terms of cellular development and maintenance.

Kinetics of pulsed electric fields assisted pigment extraction from Chlorella pyrenoidosa

Kinetics οf chlorophyll extraction from the microalga Chlorella pyrenoidosa, assisted by Pulsed Electric Fields (PEF), were studied. Treated (4.6 kV/cm, 0–179.2 kJ/kg) and untreated biomass was suspended in ethanolic solutions (75–95% v/v) and incubated at 30–60 °C for up to 6 h. Higher PEF treatment specific energy, ethanolic content of extraction solvent and extraction temperature led to higher recovery of pigments and antioxidants (chlorophyll and lutein, respectively). Chlorophyll characteristic extraction time depended only on extraction temperature (2.16 h at 30 °C vs. 0.61 h at 40 °C). A treatment of 179.2 kJ/kg before extraction with 95% ethanol at 60 °C for 4 h led to maximum recovery of both chlorophyll and lutein (18.2 and 1.17 mg/g dry biomass, respectively). Lutein was extracted more selectively at 30 °C which led to extracts with higher concentration in antioxidants (28.83 mg Trolox/g dry extract from treated samples with 179.2 kJ/kg and a four-hour extraction with 95% ethanol). Industrial relevanceChlorophylls and carotenoids from C. pyrenoidosa have garnered significant interest by the food industry for application as natural colorants and strong antioxidants in food products. Low energy requirements, short treatment times and selectivity establish Pulsed Electric Fields as a suitable technology to improve the extraction of these ingredients. An overall mathematical model of chlorophyll extraction, incorporating all process parameters, is a useful industrial tool for reliable predictions and the estimation of extraction efficiency under different process conditions.

Physiological and transcriptomic analysis reveals the toxic and protective mechanisms of marine microalga Chlorella pyrenoidosa in response to TiO2 nanoparticles and UV-B radiation

Concerns have been raised regarding the adverse effects of nanoparticles (NPs) on marine organisms, as an increasing number of NPs inevitably enter the marine environment with the development of nanotechnology. Owing to the photocatalytic properties, TiO2 NPs' toxicity may be aggravated by enhanced UV-B resulting from stratospheric ozone depletion. However, the molecular mechanisms of phytoplankton in response to TiO2 NPs under UV-B remains poorly understood. In this study, we integrated whole transcriptome analysis with physiological data to provide understanding on the toxic and protective mechanisms of marine Chlorella pyrenoidosa in response to TiO2 NPs under UV-B. The results indicated that the changes in gene expression could be related to the growth inhibition and TiO2 NP internalization in C. pyrenoidosa, and several molecular mechanisms were identified as toxicity response to TiO2 NPs and UV-B. Differential expression of genes involved in glycerophospholipids metabolism indicated that cell membrane disruption allowed TiO2 NPs to enter the algal cell under UV-B exposure, although the up-regulation of genes involved in the general secretory dependent pathway and the ATP-binding cassette transporter family drove cellular secretion of extracellular polymeric substances, acting as a barrier that prevent TiO2 NP internalization. The absence of changes in gene expression related to the antioxidant system may be responsible for the severe oxidative stress observed in algal cells following exposure to TiO2 NPs under UV-B irradiation. Moreover, differential expression of genes involved in pathways such as photosynthesis and energy metabolism were up-regulated, including the light-harvesting, photosynthetic electron transport coupled to photophosphorylation, carbon fixation, glycolysis, pentose phosphate pathway, tricarboxylic acid cycle, and oxidative phosphorylation, indicating that more energy and metabolites were supplied to cope with the toxicity of TiO2 NPs and UV-B. The obtained results provide valuable information on the molecular mechanisms of response of marine phytoplankton exposed to TiO2 NPs and UV-B.

Unraveling the combined toxicity and removal mechanisms of fluoxetine and sertraline co-contaminants by the freshwater microalga Chlorella pyrenoidosa

Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (FLX) and sertraline (SER), are among the most widely detected pharmaceuticals in aquatic environments, and they usually occur as mixtures. However, little is known about the combined toxicity of SSRI mixtures to microalgae and the associated removal mechanisms. This study investigated the combined toxicity of FLX and SER to the growth, photosynthetic activity, and antioxidant system of Chlorella pyrenoidosa and their removal mechanisms. The results showed that FLX and SER strongly inhibited microalgal growth with 96 h EC50 values of 493 and 61.1 μg/L, respectively. Additionally, the combined toxicity of FLX and SER towards microalgal growth exhibited an additive effect. After 4 days of short-term exposure, FLX, SER, and their mixtures caused photosynthetic damage and oxidative stress in microalgae, and the mixture's toxicity was stronger than those of individuals. However, the adverse effects on microalgal growth, photosynthetic activity, and antioxidant system were alleviated with increasing exposure time. Meanwhile, C. pyrenoidosa efficiently removed FLX (67.59%–99.08%) and SER (94.92%–99.11%) individually after 11 days of cultivation. Biodegradation (59.25%–86.21%) was the prominent removal mechanism of FLX, while both biodegradation (48.08%–88.17%) and bioaccumulation (4.74%–43.38%) contributed significantly to SER removal. The co-existence of FLX and SER lowered the removal rate and biodegradation amount of both compounds. Besides, SER inhibited C. pyrenoidosa's N-demethylation and O-dealkylation of FLX, while co-existing with FLX inhibited the excretion of the N-deamination product of SER from microalgal cells. Furthermore, the principal component analysis indicated that the removal performance of FLX, SER, and their mixtures correlated strongly to the microalgae's physiological and biochemical states. These results highlighted the significance of co-contamination during ecological risk assessments and microalgae-based bioremediation of SSRIs.

Kinetics of high pressure homogenization assisted protein extraction from Chlorella pyrenoidosa

Protein extraction kinetics from microalga Chlorella pyrenoidosa by applying High Pressure Homogenization pretreatment was studied. Untreated and treated (400–800 bar, 1 and 4 passes) aqueous microalgal suspensions were incubated at 20–40 °C for up to 24 h. A four-pass treatment at 800 bar caused maximization of carbohydrate (103 mg carbohydrates/g dry biomass immediately after treatment) and protein recovery (382.0 mg proteins/g dry biomass after extraction at 40 °C for 24 h). Protein characteristic extraction time was significantly dependent on pretreatment conditions and extraction temperature (5.16 h for untreated sample at 20 °C vs. 1.34 h for 800 bar/4 passes treated biomass at 40 °C). A combination of a two-hour ethanolic extraction at 60 °C prior to a six-hour aqueous extraction from biomass treated at 800 bar/4 passes maximized chlorophyll separation (16.3 mg chlorophylls/g dry biomass) and led to aqueous extracts of high protein content (764.7 mg proteins/g dry extract).

Keystone microalgae species determine the removal efficiency of sulfamethoxazole: a case study of Chlorella pyrenoidosa and microalgae consortia.

In recent years, antibiotics pollution has caused serious harm to the aquatic environment, and microalgae mediated degradation of antibiotics has attracted increasing attention. However, the potential toxicity of antibiotics to keystone microalgae species or their microalgae consortia, and the impact of microalgal diversity on antibiotic removal need to be further studied. In this study, we investigated the removal efficiency and tolerance of five freshwater microalgae (Chlorella pyrenoidosa, Scenedesmus quadricauda, Dictyosphaerium sp., Haematoccocus pluvialis, and Botryococcus braunii) and their microalgae consortia to sulfamethoxazole (SMX). We found that the removal efficiency of SMX by C. pyrenoidosa reached 49%, while the other four microalgae ranged between 9% and 16%. In addition, C. pyrenoidosa, S. quadricauda, and Dictyosphaerium sp. had better tolerance to SMX than H. pluvialis, and their growth and photosynthesis were less affected. At 10 and 50 mg/L SMX, the removal capacity of SMX by mixed microalgae consortia was lower than that of C. pyrenoidos except for the consortium with C. pyrenoidos and S. quadricauda. The consortia generally showed higher sensitivity towards SMX than the individual species, and the biochemical characteristics (photosynthetic pigment, chlorophyll fluorescence parameters, superoxide anion (O2 -), superoxide dismutase activity (SOD), malondialdehyde (MDA) and extracellular enzymes) were significantly influenced by SMX stress. Therefore, the removal of antibiotics by microalgae consortia did not increase with the number of microalgae species. Our study provides a new perspective for the selection of microalgal consortia to degrade antibiotics.

A Sensitive Response Index Selection for Rapid Assessment of Heavy Metals Toxicity to the Photosynthesis of Chlorella pyrenoidosa Based on Rapid Chlorophyll Fluorescence Induction Kinetics.

Heavy metals as toxic pollutants have important impacts on the photosynthesis of microalgae, thus seriously threatening the normal material circulation and energy flow of the aquatic ecosystem. In order to rapidly and sensitively detect the toxicity of heavy metals to microalgal photosynthesis, in this study, the effects of four typical toxic heavy metals, chromium (Cr(VI)), cadmium (Cd), mercury (Hg), and copper (Cu), on nine photosynthetic fluorescence parameters (φPo, ΨEo, φEo, δRo, ΨRo, φRo, FV/FO, PIABS, and Sm) derived from the chlorophyll fluorescence rise kinetics (OJIP) curve of microalga Chlorella pyrenoidosa, were investigated based on the chlorophyll fluorescence induction kinetics technique. By analyzing the change trends of each parameter with the concentrations of the four heavy metals, we found that compared with other parameters, φPo (maximum photochemical quantum yield of photosystem II), FV/FO (photochemical parameter of photosystem II), PIABS (photosynthetic performance index), and Sm (normalized area of the OJIP curve) demonstrated the same monotonic change characteristics with an increase in concentration of each heavy metal, indicating that these four parameters could be used as response indexes to quantitatively detect the toxicity of heavy metals. By further comparing the response performances of φPo, FV/FO, PIABS, and Sm to Cr(VI), Cd, Hg, and Cu, the results indicated that whether it was analyzed from the lowest observed effect concentration (LOEC), the influence degree by equal concentration of heavy metal, the 10% effective concentration (EC10), or the median effective concentration (EC50), the response sensitivities of PIABS to each heavy metal were all significantly superior to those of φRo, FV/FO, and Sm. Thus, PIABS was the most suitable response index for sensitive detection of heavy metals toxicity. Using PIABS as a response index to compare the toxicity of Cr(VI), Cd, Hg, and Cu to C. pyrenoidosa photosynthesis within 4 h by EC50 values, the results indicated that Hg was the most toxic, while Cr(VI) toxicity was the lowest. This study provides a sensitive response index for rapidly detecting the toxicity of heavy metals to microalgae based on the chlorophyll fluorescence induction kinetics technique.

Utilization of Palm Oil Mill Effluent (POME) Liquid Waste to Increase Density and Growth Rate of Microalgae Chlorella Pyrenoidosa

Microalgae Chlorella pyrenoidosa is a microalgae that has the potential to have various roles, especially as a bioabsorbant for organic waste. The growth of the oil palm plantation industry is also directly proportional to the increase in waste generated from the CPO production process, namely POME Waste (Palm Oil Mill Effluent). POME waste has a high nutrient content so that it can be utilized by the microalgae Chlorella pyrenoidosa. This study aims to utilize POME waste to increase the growth of Chlorella pyrenoidosa. Microalgae cultivation had a significant effect on the 1:2 treatment and 1:3 treatment when compared to the control cultivation medium with the highest cell density values ​​of 263(106cells/ml) and 279(106cells/ml) respectively. Injection of POME waste into microalgae rearing media will have an impact on increasing the growth of Chlorella pyrenoidosa microalgae.

Toxicity evaluation of chlorinated natural water using Photobacterium phosphoreum: Implications for ballast water management

Chlorination of ballast water could produce harmful disinfection by-products (DBPs) and total residual oxidants. The International Maritime Organization calls for toxicity testing of discharged ballast water with fish, crustacea and algae to reduce the risk, but it is difficult to evaluate the toxicity of treated ballast water in a short time. Therefore, the purpose of this study was to analyze the applicability of luminescent bacteria to the assessment of residual toxicity of chlorinated ballast water. The toxicity unit for all treated samples were higher for Photobacterium phosphoreum than for microalgae (Selenastrum capricornutum and Chlorella pyrenoidosa), after adding neutralizer, all samples showed little effect on the luminescent bacteria and microalgae. For the DBPs, except for 2,4,6-Tribromophenol, Photobacterium phosphoreum could produce more sensitive and rapid test results than other species, the results in Photobacterium phosphoreum showed that the toxicity of DBPs in order of: 2,4-Dibromophenol > 2,6-Dibromophenol > 2,4,6-Tribromophenol > Monobromoacetic acid > Dibromoacetic acid > Tribromoacetic acid, and most binary mixtures (aromatic DBPs and aliphatic DBPs) presented synergistic effects based on the CA model. The aromatic DBPs in ballast water deserve more attention. In general, for ballast water management, the use of luminescent bacteria to evaluate the toxicity of treated ballast water and DBPs is desirable, this study could provide beneficial information for enhancing ballast water management.

Investigating the effects of surfactants on Chlorella pyrenoidosa in the hydrolysis acidification liquor by integrated physiochemical and transcriptome analyses

In our two recently published articles, we investigated the effects of Tween 80, sodium lignosulfonate (LS), sodium dodecyl sulfate (SDS), and rhamnolipid (RL) on the co-conversion of endogenous carbon (C) and nitrogen (N) of dairy wastewater in the hydrolytic acidification coupled microalgae culture system. Although the effects of surfactants on the microalgae (Chlorella pyrenoidosa) growth from the perspective of enhancing the accumulation of the volatile fatty acids (VFAs) were investigated, the question regarding the effect of surfactants themselves on microalgae growth and mechanism remains to be addressed. In this work, we extend our discussion to clearly demonstrate the effects of these four surfactants on microalgae growth, nutrient removal, and the output of the culture system in artificial hydrolysis-acidification liquor (HAL). Furthermore, de novo transcriptome profiling and the metabolic pathway analysis of C. pyrenoidosa cells in response to these four surfactants were also performed. The results showed that SDS inhibited while the other three surfactants promoted microalgae growth (promotion order of dry weight: Tween 80 > RL > LS). The maximum ammonia nitrogen removal rate followed Tween 80 80.90 % > RL 78.32 % > LS 75.23 % > control 67.08 % > SDS 34.74 %. Surfactants enhanced the C assimilation followed Tween 80 > RL ≈ LS > control. Tween 80, RL, and LS treatment groups achieved higher yield of protein, carbohydrates, and lipid. The differential transcriptome analysis revealed that the number of down-regulated differential expression of unigenes (DEUs) more than that of up-regulated in SDS group, while the opposite was true for the other 3 surfactants. KEGG enrichment analysis revealed that Tween 80 mainly affects lipid metabolism in the early stage of microalgae growth, RL mainly affects lipid metabolism and membrane transport, SDS mainly affects energy metabolism, lipid metabolism, and transport and catabolism, while no DEUs significant enriched KEGG in LS group.

An Insight into the Combined Toxicity of 3,4-Dichloroaniline with Two-Dimensional Nanomaterials: From Classical Mixture Theory to Structure-Activity Relationship

The assessment and prediction of the toxicity of engineered nanomaterials (NMs) present in mixtures is a challenging research issue. Herein, the toxicity of three advanced two-dimensional nanomaterials (TDNMs), in combination with an organic chemical (3,4-dichloroaniline, DCA) to two freshwater microalgae (Scenedesmus obliquus and Chlorella pyrenoidosa), was assessed and predicted not only from classical mixture theory but also from structure-activity relationships. The TDNMs included two layered double hydroxides (Mg-Al-LDH and Zn-Al-LDH) and a graphene nanoplatelet (GNP). The toxicity of DCA varied with the type and concentration of TDNMs, as well as the species. The combination of DCA and TDNMs exhibited additive, antagonistic, and synergistic effects. There is a linear relationship between the different levels (10, 50, and 90%) of effect concentrations and a Freundlich adsorption coefficient (KF) calculated by isotherm models and adsorption energy (Ea) obtained in molecular simulations, respectively. The prediction model incorporating both parameters KF and Ea had a higher predictive power for the combined toxicity than the classical mixture model. Our findings provide new insights for the development of strategies aimed at evaluating the ecotoxicological risk of NMs towards combined pollution situations.

ZnO-decorated green-synthesized multi-doped carbon dots from Chlorella pyrenoidosa for sustainable photocatalytic carbamazepine degradation.

The promising green synthesis of carbon dots (CDs) from microalga Chlorella pyrenoidosa was achieved using simple hydrothermal and microwave-assisted methods. Doping of nanomaterials by nonmetals (N, S, and P) was confirmed by X-ray photoelectron spectroscopy (XPS), while the existence of metals in the CDs was confirmed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and transmission electron microscopy (TEM), and Mg, Ca, K, and Na were found as the dominant doped metals. The novel nanomaterials with excellent photoluminescence (PL) properties were used for the modification of ZnO obtained by a simple hydrothermal process. In this regard, a series of ZnO decorated with multi-doped carbon dots (xCDs) was prepared and their photocatalytic properties were evaluated. The ZnO-xCD photocatalysts were characterized by various advanced techniques including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), XPS, Brunauer-Emmett-Teller (BET), PL, ultraviolet-visible (UV-vis) spectroscopy and electrochemical impedance spectroscopy (EIS) analysis. The photocatalytic behaviour of the obtained materials was investigated in the degradation of carbamazepine (CBZ). The influence of the synthesis method of xCDs and their content on the activity of the photocatalyst was examined. The photocatalyst ZnO modified with 3% xCDs obtained by the microwave-assisted method revealed the highest effectiveness for CBZ degradation and allowed for a first-order degradation rate of 2.85 times in comparison with non-modified ZnO. The improvement of the photocatalytic process was achieved by support with peroxymonosulphate resulting in up to 3.18 times a first order kinetic rate constant compared with that of simple photocatalysis in the presence of ZnO-xCDs. Taken together, our synthesized multi-doped CDs and their nanohybrids with ZnO, can be considered as promising candidates for photocatalytic applications.

Living Chinese Herbal Scaffolds from Microfluidic Bioprinting for Wound Healing

Biological scaffolds have been widely employed in wound healing applications, while their practical efficiency is compromised by insufficient oxygen delivery to the 3-dimensional constructs and inadequate nutrient supply for the long-term healing process. Here, we present an innovative living Chinese herbal scaffold to provide a sustainable oxygen and nutrient supply for promoting wound healing. Through a facile microfluidic bioprinting strategy, a traditional Chinese herbal medicine (Panax notoginseng saponins [PNS]) and a living autotrophic microorganism (microalgae Chlorella pyrenoidosa [MA]) were successfully encapsulated into the scaffolds. The encapsulated PNS could be gradually released from the scaffolds, which promoted cell adhesion, proliferation, migration, and tube formation invitro. In addition, benefiting from the photosynthetic oxygenation of the alive MA, the obtained scaffolds would produce sustainable oxygen under light illumination, exerting a protective effect against hypoxia-induced cell death. Based on these features, we have demonstrated through invivo experiments that these living Chinese herbal scaffolds could efficiently alleviate local hypoxia, enhance angiogenesis, and thereby accelerate wound closure in diabetic mice, indicating their great potential in wound healing and other tissue repair applications.

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.

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.

Toxic Effects of Tetracycline and Its Removal by the Freshwater Microalga Chlorella pyrenoidosa

The prevalence of tetracycline (TC) in aquatic environments has raised increasing concern due to its high ecotoxicology risk. The application of microalgae in the removal of antibiotics is a competitive alternative technology. However, the removal mechanism of TC by microalgae and its correlation with the ecotoxic response of microalgae are still not clear. In this study, the ecotoxicity of TC (0.5–10 mg L−1) and its removal by the freshwater alga Chlorella pyrenoidosa were investigated. The results show that TC has significant inhibitory effects on microalgal growth, photosynthetic pigment, and photosynthetic efficiency, with maximum inhibition rates of 49.68%, 62.54%, and 48.08%, respectively. However, the growth inhibition and photosynthesis impairment caused by TC seems to be reversible, as reflected by the decreased inhibition rates with prolonged exposure time. The simultaneous increases in the activities of superoxide dismutase (9.69–23.53%) and peroxidase (15.15–110.92%) and the contents of glutathione (17.62–64.17%) and malondialdehyde (25.16–35.25%) suggest that TC causes moderate oxidative stress. C. pyrenoidosa exhibits high removal efficiency (91.44–95.14%) for TC after 48 h of exposure with short half-lives of 11.31–13.48 h. Biodegradation (56.86–64.62%) is the primary removal mechanism of TC, accompanied by the abiotic process (24.68–40.97%), bioaccumulation (1.95–10.97%), and bioadsorption (0.09–0.38%). These findings demonstrate the toxicity resistance and high removal capacity of C. pyrenoidosa to TC, highlighting its potential application in the remediation of TC-contaminated water.

A novel partial complete nitrification coupled microalgae assimilation system for resource utilization of high ammonia nitrogen wastewater

In order to evaluate the feasibility of the partial complete nitrification (PCN) in removing the ammonia inhibition during culturing microalgae with synthetic high ammonia nitrogen wastewater, biological aerated filters (BAFs) coupled microalgae culture system were constructed. Firstly, after the successful start-up of the biofilter, the controllable nitrate nitrogen conversion rate (NCR) (approximately 88%, 77%, and 48%) was realized through alkalinity/NH4+-N regulation (8:1, 5:1, and 3:1, respectively). Experiments revealed that under continuous operation mode, the proper control of the degree of PCN was more conducive to the microalgae (Chlorella pyrenoidosa) growth and biomass production (maximal accumulated harvested biomass of microalgae of 16.81 g was recorded when NCR was 77%). Furthermore, based on the comparison between the experimental data of day 5 and day 11, it was shown that the crude protein content in biomass on day 11 slightly increased while the carbohydrates content slightly decreased. More importantly, it was observed that the lipid content significantly increased (a maximum of 41.43% was recorded in 48% NCR coupled microalgae culture system), and the degree of increase was negatively correlated with the alkalinity of upstream BAFs influent.

Metabolomics and biochemical insights on the regulation of aging-related diabetes by a low-molecular-weight polysaccharide from green microalga Chlorella pyrenoidosa.

Globally, aging and diabetes are considered prevalent threats to human health. Chlorella pyrenoidosa polysaccharide (CPP) is a natural active ingredient with multiple health benefits including antioxidant and hypolipidemic activities. In this study, the aging-related diabetic (AD) mice model was established to investigate the underlying hypoglycemic and antioxidant mechanisms of CPP. It improved superoxide dismutase, catalase (CAT), glutathione peroxidase (GSH-px), and malondialdehyde activities in liver and insulin secretion. CAT and GSH-px activity in the brain increased after CPP administration. In addition, through histopathological examinations, it was evident that injuries in the liver, brain, jejunum, and pancreas were restored by CPP. This restoration was likely mediated via the activation of glucagon-like peptide-1 receptor/FOXO-1 (forkhead box O1) pathway concurrent with the inhibition of interleukin-6 receptor/FOXO-1 pathway. Furthermore, metabolomics and correlation analysis revealed that CPP possibly relived AD through changes in insulin levels and declined oxidative stress as regulated by phenylpyruvic acid. These findings suggested that CPP exerted antioxidant and hypoglycemic roles in an AD mice model, thereby providing a sound scientific foundation for further development and utilization of CPP.