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).

A regular Chlorella mannogalactan and its sulfated derivative as a promising anticoagulant: Structural characterization and anticoagulant activity.

Chlorella is one of the most widely cultivated species of microalgae and has been consumed as a "green healthy food". In this study, a novel polysaccharide (CPP-1) was isolated from Chlorella pyrenoidosa, structurally analyzed, and sulfated as a promising anticoagulant. Structural analyses by chemical and instrumental methods such as monosaccharide composition, methylation-GC-MS and 1D/2D NMR spectroscopy analysis revealed that CPP-1 had a molecular weight of ~13.6 kDa, and mainly consisted of d-mannopyranose (d-Manp), 3-O-methylated d-Manp (3-O-Me-d-Manp), and d-galactopyranose (d-Galp). The molar ratio of d-Manp and d-Galp was 1.0:2.3. CPP-1 consisted of a (1→6)-linked ß-d-Galp backbone substituted at C-3 by the d-Manp and 3-O-Me-d-Manp residues in a molar ratio of 1:1, which was a regular mannogalactan. The sulfated Chlorella mannogalactan (SCM) with sulfated group content of 40.2 % equivalent to that of unfractionated heparin was prepared and analyzed. NMR analysis confirmed its structure, indicating that most free hydroxyl groups in the side chains and partial hydroxyl groups in the backbone were sulfated. Anticoagulant activity assays indicated that SCM exhibited strong anticoagulant activity by inhibiting intrinsic tenase (FXase) with IC50 of 13.65 ng/mL, which may be a safer anticoagulant as an alternative to heparin-like drugs.

Living microecological hydrogels for wound healing.

Chronic hard-to-heal wounds draw great attention worldwide, as their treatments are limited by infections and hypoxia. Inspired by the natural oxygen production capacity of algae and the competitive advantage of beneficial bacteria over other microbes, we presented a living microecological hydrogel (LMH) with functionalized Chlorella and Bacillus subtilis encapsulation to realize continuous oxygen delivery and anti-infections for promoting chronic wound healing. As the hydrogel consisted of thermosensitive Pluronic F-127 and wet-adhesive polydopamine, the LMH could keep liquid at a low temperature while quickly solidifying and tightly adhering to the wound bed. It was demonstrated that by optimizing the proportion of the encapsulated microorganism, the Chlorella could continuously produce oxygen to relieve hypoxia and support the proliferation of B. subtilis, while B. subtilis could eliminate the colonized pathogenic bacteria. Thus, the LMH substantially promoted the healing of infected diabetic wounds. These features make the LMH valuable for practical clinical applications.

Impact of wastewater characteristics on the removal of organic micropollutants by Chlorella sorokiniana.

Microalgae-based technologies can be used for the removal of organic micropollutants (OMPs) from different types of wastewater. However, the effect of wastewater characteristics on the removal is still poorly understood. In this study, the removal of sixteen OMPs by Chlorella sorokiniana, cultivated in three types of wastewater (anaerobically digested black water (AnBW), municipal wastewater (MW), and secondary clarified effluent (SCE)), were assessed. During batch operational mode, eleven OMPs were removed from AnBW and MW. When switching from batch to continuous mode (0.8 d HRT), the removal of most OMPs from AnBW and MW decreased, suggesting that a longer retention time enhances the removal of some OMPs. Most OMPs were not removed from SCE since poor nutrient availability limited C. sorokiniana growth. Further correlation analyses between wastewater characteristics, biomass and OMPs removal indicated that the wastewater soluble COD and biomass concentration predominantly affected the removal of OMPs. Lastly, carbon uptake rate had a higher effect on the removal of OMPs than nitrogen and phosphate uptake rate. These data will give an insight on the implementation of microalgae-based technologies for the removal of OMPs in wastewater with varying strengths and nutrient availability.

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.

Early-Phase Drive to the Precursor Pool: Chloroviruses Dive into the Deep End of Nucleotide Metabolism.

Viruses face many challenges on their road to successful replication, and they meet those challenges by reprogramming the intracellular environment. Two major issues challenging Paramecium bursaria chlorella virus 1 (PBCV-1, genus Chlorovirus, family Phycodnaviridae) at the level of DNA replication are (i) the host cell has a DNA G+C content of 66%, while the virus is 40%; and (ii) the initial quantity of DNA in the haploid host cell is approximately 50 fg, yet the virus will make approximately 350 fg of DNA within hours of infection to produce approximately 1000 virions per cell. Thus, the quality and quantity of DNA (and RNA) would seem to restrict replication efficiency, with the looming problem of viral DNA synthesis beginning in only 60-90 min. Our analysis includes (i) genomics and functional annotation to determine gene augmentation and complementation of the nucleotide biosynthesis pathway by the virus, (ii) transcriptional profiling of these genes, and (iii) metabolomics of nucleotide intermediates. The studies indicate that PBCV-1 reprograms the pyrimidine biosynthesis pathway to rebalance the intracellular nucleotide pools both qualitatively and quantitatively, prior to viral DNA amplification, and reflects the genomes of the progeny virus, providing a successful road to virus infection.

Multilayer adsorption of lead (Pb) and fulvic acid by Chlorella pyrenoidosa: Mechanism and impact of environmental factors.

When the multilayer adsorption of lead (Pb) and fulvic acid (FA) occurs on algal surface, the adsorption capacity of Pb on the algae will increase dramatically, thus increasing the environmental risk of Pb. However, the corresponding mechanism and the influence of environmental factors on the multilayer adsorption remain unclear. Here, microscopic observation methods and batch adsorption experiments were exactly designed to investigate the adsorption behavior of multilayer adsorption of Pb and FA on algal surface. The results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that carboxyl groups were the major functional groups responsible for the binding of Pb ions in multilayer adsorption, and its number was more than that in monolayer adsorption. The solution pH, with an optimal pH of 7, was a critical factor influencing the occurrence of multilayer adsorption because it influences the protonation of the involved functional groups and determines the concentration of Pb2+ and Pb-FA in the solution. Increasing the temperature was beneficial for multilayer adsorption, with ΔH for Pb and FA varied from +17.12 to +47.68 kJ/mol and +16.19 to +57.74 kJ/mol, respectively. The multilayer adsorption of Pb and FA onto algal surface also followed the pseudo-second order kinetic model, but was extremely slower than the monolayer adsorption of Pb and FA by 30 times and 15 orders of magnitude, respectively. Therefore, the adsorption of Pb and FA in the ternary system had a different adsorption behavior than that in the binary system, which verified the presence of multilayer adsorption of Pb and FA and further support the multilayer adsorption mechanism. This work is important to provide data support for water ecological risk prevention and control of heavy metals.

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.

Assessment of combined algal toxicity of TiO2 nanoparticles and organochlorines in karst surface waters.

The widespread use of nanoparticles (NPs) and organic pollutants increases the risk of their coexistence in the aquatic environments. It is uncertain how the combined toxicities of NPs and OCs affect aquatic organisms in surface waters. In this study, the binary combined toxicities of TiO2 NPs with three different organochlorines (OCs)-pentachlorobenzene (PeCB), 3,3,4,4-tetrachlorobiphenyl (PCB-77), and atrazine on Chlorella pyrenoidosa in three karst surface water bodies were investigated. The correlation analysis results indicated that the toxicities of TiO2 NPs and OCs to algae were mainly related to the total organic carbon (TOC) and ionic strength of surface water. Surface water relieved the growth inhibition of the pollutants on algae as compared with ultrapure water (UW). The combined toxic effect caused by the co-exposure of TiO2 NPs-atrazine was synergistic and had an antagonistic effect for TiO2 NPs-PCB-77 in four types of water bodies. However, the co-exposure of TiO2 NPs-PeCB had an additive effect in the Huaxi Reservoir (HX) and synergistic effects in Baihua Lake (BH), Hongfeng Lake (HF), and UW. TiO2 NPs increased the bioaccumulation of OCs by algae. Both PeCB and atrazine significantly increased the bioaccumulation of TiO2 NPs by algae, except for PeCB in HX; however, PCB-77 reduced the bioaccumulation of TiO2 NPs by algae. The toxic effects of TiO2 NPs and OCs on algae in different water bodies were the result of the nature of the pollutants, bioaccumulation, hydrochemical properties, and other factors.

Chlorella sorokiniana FK-montmorillonite interaction enhanced remediation of heavy metals in tailings.

Non-ferrous metal mining activities are known to cause ecological irreversible damage in the tailings and surrounding areas as well as heavy metal (HM) contamination. The enhancement of Chlorella-montmorillonite interaction on the remediation of HM contaminated tailings was verified from the lab to the tailings in Daye City, Hubei Province, China. The results showed a positive correlation between the quantity of montmorillonite and the transformation of Pb and Cu into residual and carbonate-binding states, which resulted in a considerable decrease in the leaching ratio. The buildup of tailings fertility throughout this process benefited from montmorillonite's ability to buffer environmental changes and store water. This further offers a required environmental foundation for the rebuilding of microbial community and the growth of herbaceous plants. The structural equation model demonstrated that the interaction between Chlorella and montmorillonite directly affected the stability of HM, and that this interaction also had an impact on the accumulation of organic carbon, total nitrogen, and available phosphorus, which improved the immobilization of Pb, Cu, Cd, and Zn. This work made the first attempt to apply Chlorella-montmorillonite composite to in-situ tailings remediation, and proposed that the combination of inorganic clay minerals and organic microorganisms was an eco-friendly, long-lasting, and efficient method for immobilizing multiple-HMs in mining areas.

Biomass, photosynthetic activity, and biomolecule composition in Chlorella fusca (Chlorophyta) cultured in a raceway pond operated under greenhouse conditions.

Raceways are widely used as microalgae culture systems due to their low cost, but they are not the best option for biomass yield. Understanding in situ photosynthetic performance can be a first step to increase their biomass productivity. This study aimed at comparing the real time photosynthetic activity in a greenhouse raceway culture (250 L) with discrete measurements under laboratory conditions. We evaluated the photophysiology and biochemical composition of Chlorella fusca culture up to 120 h. In situ photosynthetic activity was continuously monitored and compared to discrete ex situ measurements; biochemical compounds were measured daily. The results showed a final biomass density of 0.45 g L-1 (5 days - 120 h) and an increase of the electron transport rate (ETR) up to 48 h but decreased thereafter. When the relative ETR was estimated considering the absorption coefficient (a) positive correlations of this parameter with photosynthetic capacity, cell density, biomass, biocompounds and antioxidant activity were obtained, whereas no correlation was detected without considering a. In situ photosynthesis monitoring showed higher absolute maximal ETR (10 - 160 µmol m-3s-1) than discrete ex situ measurements. We demonstrated the importance of considering the light absorption coefficient for expressing photosynthetic capacity and showed that C. fusca can produce, in the short-term, bioactive compounds that are correlated to photosynthetic conditions.

The microalgae-based wastewater treatment system coupled with Cerium: A potential way for energy saving and microalgae boost.

The microalgae-based system attracts more attention in wastewater treatment for high quality effluent, low carbon emission, and resource utilization. Light is the key factor for algae growth, but the light masking in sewage will cause low efficiency of the system. This study designed laboratory scale experiments with Chlorella to investigate the influence of cerium on the nutrient removal by algae wastewater treatment system under different light intensities. The best removal rates of NH4-N, TP, and COD were 72.43%, 88.87%, and 68.08% under 50 µmol/(m 2·s) light intensity and 1 mg/L Ce. Low concentration of Ce could activate protein synthesis, electron transfer, and antioxidase, while excessive Ce might cause toxicity which could be relieved by strong light for energy supply and further activating superoxide dismutase (SOD) and catalase (CAT). Comparing to other similar experiences, this system reached an equal or greater performance on nutrients removal with better efficiency in light utilization. It might provide a new idea for microalgae-based system development.

Enhancement of carbon sequestration via MIL-100(Fe)@PUS in bacterial-algal symbiosis treating municipal wastewater.

Bacterial-algal symbiosis (BAS) is a promising carbon neutrality technology to treat municipal wastewater. However, there are still non-trivial CO2 emissions in BAS due to the slow diffusion and biosorption of CO2. Aiming to reduce CO2 emissions, the inoculation ratio of aerobic sludge to algae was further optimized at 4:1 on the base of favorable carbon conversion. MIL-100(Fe) served as CO2 adsorbents was immobilized on polyurethane sponge (PUS) to increase the interaction with microbes. When MIL-100(Fe)@PUS was added to BAS in the treatment of municipal wastewater, zero CO2 emission was achieved and the carbon sequestration efficiency was increased from 79.9% to 89.0%. Most genes related to metabolic function were derived from Proteobacteria and Chlorophyta. The mechanism of enhanced carbon sequestration in BAS could be attributed to both enrichment of algae (Chlorella and Micractinium) and increased abundance of functional genes related to PS I, PS II and Calvin cycle in photosynthesis.

Genomic insights into the coupling of a Chlorella-like microeukaryote and sulfur bacteria in the chemocline of permanently stratified Lake Cadagno.

Meromictic Lake Cadagno is a permanently stratified system with a persistent microbial bloom within the oxic-anoxic boundary called the chemocline. The association between oxygenic and anoxygenic photosynthesis within the chemocline has been known for at least two decades. Although anoxygenic purple and green sulfur bacteria have been well studied, reports on oxygenic phytoplankton have remained sparse since their discovery in the 1920s. Nearly a century later, this study presents the first near-complete genome of a photosynthetic microbial eukaryote from the chemocline of Lake Cadagno, provisionally named Chlorella-like MAG. The 18.9 Mbp nuclear genome displays a high GC content (71.5%), and the phylogenetic placement suggests that it is a novel species of the genus Chlorella of Chlorophytes. Functional annotation of the Chlorella-like metagenome-assembled genome predicted 10,732 protein-coding genes, with an approximate 0.6% proportion potentially involved in carbon, sulfur, and nitrogen (C, N, and S) metabolism. In addition to C4 photosynthesis, this study detected genes for heat shock proteins (HSPs) in the Chlorella-like algae, consistent with the other Chlorella species. Altogether, the genomic insights in this study suggest the cooperation of photosynthetic algae with phototrophic sulfur bacteria via C, N, and S metabolism, which may aid their collective persistence in the Lake Cadagno chemocline. Furthermore, this work additionally presents the chloroplast genome of Cryptomonas-like species, which was likely to be presumed as cyanobacteria in previous studies because of the presence of phycobilisomes.

Combined toxicity of erythromycin and roxithromycin and their removal by Chlorella pyrenoidosa.

The ecological effects of antibiotics in surface water have attracted increasing research attention. In this study, we investigated the combined ecotoxicity of erythromycin (ERY) and roxithromycin (ROX) on the microalgae, Chlorella pyrenoidosa, and the removal of ERY and ROX during the exposure. The calculated 96-h median effect concentration (EC50) values of ERY, ROX, and their mixture (2:1 w/w) were 7.37, 3.54, and 7.91 mg∙L-1, respectively. However, the predicted EC50 values of ERY+ROX mixture were 5.42 and 1.51 mg∙L-1, based on the concentration addition and independent action models, respectively. This demonstrated the combined toxicity of ERY+ ROX mixture showed an antagonistic effect on Chlorella pyrenoidosa. During the 14-d culture, low-concentration (EC10) treatments with ERY, ROX, and their mixture caused the growth inhibition rate to decrease during the first 12 d and increase slightly at 14 d. In contrast, high-concentration (EC50) treatments significantly inhibited microalgae growth (p < 0.05). Changes in the total chlorophyll contents, SOD and CAT activities, and MDA contents of microalgae suggested that individual treatments with ERY and ROX induced higher oxidative stress than combined treatments. After the 14-d culture time, residual Ery in low and high concentration Ery treatments were 17.75% and 74.43%, and the residual Rox were 76.54% and 87.99%, but the residuals were 8.03% and 73.53% in ERY+ ROX combined treatment. These indicated that antibiotic removal efficiency was higher in combined treatments than that in individual treatments, especially at low concentrations (EC10). Correlation analysis suggested that there was a significant negative correlation between the antibiotic removal efficiency of C. pyrenoidosa and their SOD activity and MDA content, and the enhanced antibiotic removal ability of microalgae benefited from increased cell growth and chlorophyll content. Findings in this study contribute to predicting ecological risk of coexisting antibiotics in aquatic environment, and to improving biological treatment technology of antibiotics in wastewater.

Environmental pollution mitigation through utilization of carbon dioxide by microalgae.

Anthropogenic emissions of CO2 have reached a critical level and the global surface temperature is expected to rise by 1.5 °C between 2030 and 2050. To ameliorate the current global warming scenario, the research community has been struggling to find more economical and innovative solutions for carbon sequestration. Among such techniques, the use of microalgal species such as Chlorella sp., Dunaliella tertiolecta, Spirulina platensis, Desmodesmus sp., and Nannochloropsis sp., among others have shown high carbon tolerance capacity (10-100%) for establishing carbon capture, utilization and storage systems. To make microalgal-based carbon capture more economical, the microalgal biomass (∼2 g/L) can be converted biofuels, pharmaceuticals and nutraceuticals through biorefinery approach with product yield in the range of 60-99.5%. Further, CRISPR-Cas9 has enabled the knockout of specific genes in microalgal species that can be used to generate low pH tolerant strains with high lipid production. Inspite of the emerging developments in pollution control by microalgae, only limited investigations are available on its economic aspects which indicate a production cost of ∼$ 0.5-15/kg microalgal biomass. This review intends to summarize the advancements in different carbon sequestration techniques while highlighting their mechanisms and major research areas that need attention for economical microalgae-based carbon sequestration.

Elucidating microalgae-mediated metabolism for sulfadiazine removal mechanism and transformation pathways.

Sulfadiazine (SDZ) as a typical sulfonamide antibiotic is commonly detected in wastewater, and its removal mechanism and transformation pathways in microalgae-mediated system remain unclear. In this study, the SDZ removal through hydrolysis, photodegradation, and biodegradation by Chlorella pyrenoidosa was investigated. Higher superoxide dismutase activity and biochemical components accumulation were obtained under SDZ stress. The SDZ removal efficiencies at different initial concentrations were 65.9-67.6%, and the removal rate followed pseudo first-order kinetic model. Batch tests and HPLC-MS/MS analyses suggested that biodegradation and photodegradation through the reactions of amine group oxidation, ring opening, hydroxylation, and the cleavage of S-N, C-N, C-S bond were dominant removal mechanisms and pathways. Characteristics of transformation products were evaluated to analyze their environmental impacts. High-value products of lipid, carbohydrate, and protein in microalgae biomass presented economic potential of microalgae-mediated metabolism for SDZ removal. The findings of this study broadened the knowledge for the microalgae self-protection from SDZ stress and provided a deep insight into SDZ removal mechanism and transformation pathways.

Optimization of hydrolysis conditions of crop straw and its effect in Chlorella sorokiniana culture.

Taking straws of corn, wheat, and millet as raw materials, we pretreated them with alkaline hydrogen peroxide, and then hydrolyzed by cellulase and xylanase. We selected the total sugar content in the hydrolysate as the indicator to evaluate the hydrolysis of the straws from three crop species, and further optimized the conditions. Then, the hydrolysates of three types of crop straws were used as carbon source for Chlorella sorokiniana culture to assess their effects on microalgal cultivation. The results showed that the optimal hydrolysis conditions for the three crop straws were identified as solid-liquid ratio of 1:15, temperature of 30 ℃, and treatment time of 12 h. Under such optimal condition, the total sugar contents increased up to 1.677, 1.412, and 1.211 g·L-1 in the corn, millet and wheat straw hydrolysate, respectively. The hydrolysates from the three crop straw could significantly increase both algal biomass and lipid content of C. sorokiniana. Corn straw hydrolysate had the best effect, with high levels of algal biomass (1.801 g·L-1) and lipid content (30.1%). Therefore, we concluded that crop straw hydrolysates as carbon source could significantly promote microalgal biomass and lipid enrichment. The results could lay the foundation for the efficient conversion and utilization of straw lignocellulose raw materials, provide new knowledge for the resource utilization of agricultural wastes, as well as the theoretical basis for the efficient cultivation of microalgae using crop straw hydrolysates.

Impact of Regular Intake of Microalgae on Nutrient Supply and Cardiovascular Risk Factors: Results from the NovAL Intervention Study.

A 14-day randomized controlled study with a parallel design was conducted with 80 healthy participants. Intervention groups I (IG1) and II (IG2) received a defined background diet and consumed a smoothie enriched with either 15 g of Chlorella dry weight (d.w.) or 15 g of Microchloropsis d.w. daily. Control group II (CG2) received a defined background diet without the smoothie. Control group I (CG1) received neither. Blood samples and 24-h urine were collected at the beginning and the end of the study. Serum concentrations of 25-hydroxyvitamin D3, vitamin D3, selenium, iron, ferritin, transferrin saturation, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, non-HDL cholesterol and the LDL-cholesterol/HDL cholesterol ratio decreased in IG1 (p < 0.05), while 25-hydroxyvitamin D2 increased (p < 0.05). In IG2, vitamin D3, 25-hydroxyvitamins D2 and D3 decreased (p < 0.05), while concentrations of fatty acids C20:5n3 and C22:5n3 increased. Serum and urine uric acid increased in IG1 and IG2 (p < 0.05). Microchloropsis is a valuable source of n3 fatty acids, as is Chlorella of vitamin D2. Regular consumption of Chlorella may affect the iron and selenium status negatively but may impact blood lipids positively. An elevated uric acid concentration in blood and urine following the regular consumption of microalgae poses potential risks for human health.

Unexpected growth promotion of Chlorella sacchrarophila triggered by herbicides DCMU.

The ecotoxicological effects of herbicide contamination on the autotrophic growth of microalgae in aquatic environments have been major concerns. However, little is known about the influence of herbicides on the mixotrophic growth of microalgae. This study investigated the ecotoxicological effect of 3-(3,4-dichlorophenyl)-1,1-dimethyl-urea (DCMU) on the mixotrophic growth of Chlorella sacchrarophila FACHB 4. Results showed that C. sacchrarophila in mixotrophy was more resistant to DCMU than in photoautotrophy. Moreover, a low content of DCMU (20-80 µg·L-1) promoted the mixotrophic growth of C. sacchrarophila, and the promotion effect was obviously enhanced with the increase in light intensity. The chlorophyll content and glucose absorption rate of C. sacchrarophila were found to increase after incubation with DCMU for 24 h. Transcriptome analyses revealed that the mechanism of DCMU to promote the mixotrophic growth of C. sacchrarophila was probably through accelerating glucose uptake and utilization, which was accomplished by reducing photodamage and increasing the chlorophyll content of C. sacchrarophila. This study not only revealed an unexpected bloom of mixotrophic microalgae triggered by herbicides, but it also shed new light on an effective and low-cost strategy to improve the microalgae productivity for utilization.