Catalytic degradation mechanism of sulfamethazine via photosynergy of monoclinic BiVO4and microalgae under visible-light irradiation

Insights into the removal of antibiotics from livestock and aquaculture wastewater by algae-bacteria symbiosis systems

With the burgeoning growth of the livestock and aquaculture industries, antibiotic residues in treated wastewater have become a serious ecological threat. Traditional biological wastewater treatment technologies-while effective for removing conventional pollutants, such as organic carbon, ammonia and phosphate-struggle to eliminate emerging contaminants, notably antibiotics. Recently, the use of microalgae has emerged as a sustainable and promising approach for the removal of antibiotics due to their non-target status, rapid growth and carbon recovery capabilities. This review aims to analyse the current state of antibiotic removal from wastewater using algae-bacteria symbiosis systems and provide valuable recommendations for the development of livestock/aquaculture wastewater treatment technologies. It (1) summarises the biological removal mechanisms of typical antibiotics, including bioadsorption, bioaccumulation, biodegradation and co-metabolism; (2) discusses the roles of intracellular regulation, involving extracellular polymeric substances, pigments, antioxidant enzyme systems, signalling molecules and metabolic pathways; (3) analyses the role of treatment facilities in facilitating algae-bacteria symbiosis, such as sequencing batch reactors, stabilisation ponds, membrane bioreactors and bioelectrochemical systems; and (4) provides insights into bottlenecks and potential solutions. This review offers valuable information on the mechanisms and strategies involved in the removal of antibiotics from livestock/aquaculture wastewater through the symbiosis of microalgae and bacteria.

General performance, kinetic modification, and key regulating factor recognition of microalgae-based sulfonamide removal

Sulfonamides have been widely detected in water treatment plants. Advanced wastewater treatment for sulfonamide removal based on microalgal cultivation can reduce the ecological risk after discharge, achieve carbon fixation, and simultaneously recover bioresource. However, the general removal performance, key factors and their impacts, degradation kinetics, and potential coupling technologies have not been systematically summarized. To guide the construction and enhance the efficient performance of the purification system, this study summarizes the quantified characteristics of sulfonamide removal based on more than 100 groups of data from the literature. The biodegradation potential of sulfonamides from different subclasses and their toxicity to microalgae were statistically analyzed; therefore, a preferred option for further application was proposed. The mechanisms by which the properties of both sulfonamides and microalgae affect sulfonamide removal were comprehensively summarized. Thereafter, multiple principles for choosing optimal microalgae were proposed from the perspective of engineering applications. Considering the microalgal density and growth status, a modified antibiotic removal kinetic model was proposed with significant physical meaning, thereby resulting in an optimal fit. Based on the mechanism and regulating effect of key factors on sulfonamide removal, sensitive and feasible factors (e.g., water quality regulation, other than initial algal density) and system coupling were screened to guide engineering applications. Finally, we suggested studying the long-term removal performance of antibiotics at environmentally relevant concentrations and toxicity interactions for further research.

Effective photocatalytic inactivation of Microcystis aeruginosa by Ag3VO4/BiVO4 heterojunction under visible light

In recent years, photocatalytic technology has been increasingly used for the treatment of algal blooms in water bodies due to its high efficiency and environmental advantages. However, conventional semiconductor materials suffer from high electron-hole recombination rate, low carrier mobility and weak surface adsorption ability, which made their photocatalytic performance limited. Therefore, the photocatalytic performance of the composites can be improved by coupling another semiconductor material to form a heterojunction to accelerate electron transfer. In this study, a novel composite Ag3VO4/BiVO4 (ABV) photocatalyst was successfully prepared by in-situ deposition method for the photocatalytic inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. The photocatalyst showed excellent photocatalytic activity, and the degradation rate of M. aeruginosa chlorophyll a was up to 99.8% within 4 h under visible light. During the photocatalytic degradation, the morphology of algae cells, the permeability of cell membrane, the organic matter inside and outside the cells, the antioxidant system and the soluble protein were seriously damaged. Moreover, three cycle experiments showed that the prepared ABV photocatalyst had high reusability. Finally, a possible mechanism of M. aeruginosa inactivation was proposed. In general, the synthesized ABV photocatalyst can effectively inactivate cyanobacteria under visible light and provided a new method for M. aeruginosa removal in water.

Copper regulates degradation of typical antibiotics by microalgal-fungal consortium in simulated swine wastewater: insights into metabolic routes and dissolved organic matters

Microalgae-based biotechnology for antibiotics biodegradation in swine wastewater has been receiving an increasing attention. In this study, microalgae and fungi co-cultivation system, regulated by copper (Cu(II)), was investigated in terms of nutrients and sulfonamides degradation in simulated swine wastewater. Results showed that the removal of ammonium nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) by microalgal-fungal consortium increased under 0.1-0.5 mg/L Cu(II) with the highest removal efficiency of 79.19%, 76.18%, 93.93% and 93.46%, respectively. The addition of Cu(II) (0-0.5 mg/L) enhanced the removal of sulfamonomethoxine (SMM), sulfamethoxazole (SMX) and sulfamethazine (SMZ) from 49.05% to 58.76%, from 59.31% to 63.51%, and from 37.51% to 63.9%, respectively, and the main removal mechanism was found to be biodegradation. Biodegradation followed a pseudo-first-order model with variable half-lives (10.12 to 15.51 days for SMM, 9.01 to 10.88 days for SMX, and 8.74 to 12.85 days for SMZ). Through mass spectrometry analysis, metabolites and intermediates of sulfonamides were accordingly identified, suggesting that the degradation routes were involved with hydroxylation, deamination, oxidation, de-sulfonation and bond cleavage. Dissolved organic matters released by microalgal-fungal consortium were induced by Cu(II). Fulvic acid-like and protein-like substances were bound to Cu(II), reducing its concentration and thus mitigating the organismal damage to microorganisms. These findings drew an insightful understanding of microalgal-fungal consortium for sulfonamides remediation by Cu(II) regulation in simulated swine wastewater.

Amoxicillin degradation and high-value extracellular polymer recovery by algal-bacterial symbiosis systems

Algal-bacterial symbiosis systems have emerged as sustainable methods for the treatment of new pollutants and the recovery of resources. However, the bio-refinery of biomass derived from microalgae is inefficient and expensive. In order to simultaneously degrade antibiotic and recover resources efficiently, two algal-bacterial symbiosis systems were constructed using Pseudomonas aeruginosa (alginate overproduction) and Bacillus subtilis (poly-γ-glutamic acid overproduction) with amoxicillin-degrading-microalga Prototheca zopfii W1. The optimal conditions for W1 to degrade amoxicillin are 35 °C, pH 7, and 180 rpm. In the presence of 5-50 mg/L of amoxicillin, W1-P. aeruginosa and W1-B. subtilis exhibit higher amoxicillin degradation and produce more extracellular polymers than W1 or bacteria alone. The metabolomic analysis demonstrates that the algal-bacterial symbiosis enhances the tolerance of W1 to amoxicillin by altering carbohydrate metabolism and promotes the production of biopolymers by upregulating the precursors synthesis. Moreover, the removal of amoxicillin (10 mg/L) from livestock effluent by W1-P. aeruginosa and W1-B. subtilis is greater than 90 % in 3 days, and the maximum yields of alginate and poly-γ-glutamate are 446.1 and 254.3 mg/g dry cell weight, respectively. These outcomes provide theoretical support for the application of algal-bacterial symbiosis systems to treatment of amoxicillin wastewater and efficient production of biopolymers.

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.

Mechanisms for the increase in lipid production in cyanobacteria during the degradation of antibiotics

This study evaluated the responses of cell density, photosynthesis activity, dry cell weight, lipid productivity, proteome and metabolome in two non-toxic cyanobacterial species (Synechococcus sp. and Chroococcus sp.) exposed to two frequently detected antibiotics (sulfamethoxazole and ofloxacin) at test concentrations of 0.2-20.0 μg L^-1 in a 4-day culture period. Upregulated antioxidant enzymes and oxidoreductases contributed to antibiotic biodegradation in Synechococcus sp.; whereas, upregulated carotenoid protein contributed to antibiotic biodegradation in Chroococcus sp. The 4-day removal efficiencies of sulfamethoxazole and ofloxacin by cyanobacteria were 35.98-66.23% and 33.01-61.92%, respectively. In cyanobacteria, each antibiotic induced hormetic responses, such as increase in cell density, dry cell weight, and photosynthetic activity; upregulation of photosynthesis-related proteins; and elevation of lipid expression by up to 2.05-fold. Under antibiotic stress, the two cyanobacterial species preferred to store energy in the form of lipids rather than ATP, with fructose-bisphosphate aldolase playing an essential role in lipid synthesis. The downregulation of lipid transporters also facilitated lipid accumulation in Synechococcus sp. In general, the two non-toxic cyanobacterial species achieved a good combination of lipid deposition and antibiotic treatment performance, especially in Chroococcus sp. exposed to sulfamethoxazole.

Effect of live and inactivated Chlamydomonas reinhardtii on the removal of tetracycline in aquatic environments

With the development of medical drugs, the widely used tetracycline has brought many adverse effects on the ecosystem and human health. Tetracycline pollution of water environment is becoming more and more serious, and has become an emerging environmental problem. As single celled organisms, microalgae are not only model organisms for risk assessment of aquatic ecosystems, but also can efficiently purify sewage. Microalgae-mediated pollutant remediation has attracted more and more attention from researchers. In this paper, Chlamydomonas reinhardtii (C. reinhardtii) was used to remove tetracycline in aqueous solution, and the removal efficiency and mechanism of microalgae on tetracycline were studied. The results showed that the removal rates of tetracycline by active and inactivated microalgae at a density of 5 × 10⁶ cells·mL^-1 were 81.9% and 89.8%, respectively. C. reinhardtii removed tetracycline through biosorption and nonmetabolic processes. Microalgal cell supernatant and hydroxyl radicals could significantly promote the removal of tetracycline. The positively charged tetracycline was electrostatically adsorbed on the microalgae surface and extracellular polymeric substances. Microalgae biomass can promote the production of ROS and enhance the ability of microalgae to remove tetracycline.

Co-culturing fungus Penicillium citrinum and strain Citrobacter freundii improved nitrate removal and carbon utilization by promoting glyceride metabolism

Exploring the interaction between denitrifying microbial species is significant for improving denitrification performance. In this study, the effects of co-culturing fungus Penicillium citrinum and strain Citrobacter freundii on denitrification were investigated. Results showed that the maximum nitrate removal and carbon utilization in co-culture were 68.0 and 14.1 mg·L^-1·d^-1, respectively. The total adenosine triphosphatase activity was increased to 9.87 U‧mg^-1 protein in co-culture, and nicotinamide adenine dinucleotide production was 1.7-2.3 times that of monoculture, attributing to increased carbon utilization. Further metabolomics and membrane permeability assay revealed that co-culture increased the metabolism of glycerides, thereby enhancing the membrane permeability of strain Citrobacter freundii and promoting the transmembrane transport of nitrate and glucose, which boosted nitrate reductase activity and nicotinamide adenine dinucleotide production in turn. In summary, co-culturing promoted carbon utilization and enhanced substrate removal efficiency through the metabolism of glycerides, which provided a strategy to enhance denitrification performance in wastewater treatment.

Historical development and prospect of intimately coupling photocatalysis and biological technology for pollutant treatment in sewage: A review

Through the synergistic effect of photocatalysis and biodegradation, intimately coupling photocatalysis and biological (ICPB) technology could improve the removal rate and mineralization rate of refractory pollutants and reduce the toxicity of intermediate products. ICPB system was characterized with the advantages of simple operation, low energy consumption and high treatment efficiency. As a new sewage treatment technology, ICPB system has shown great potential in the treatment of refractory pollutants, and has been widely concerned. In this study, the research progress of photocatalyst, carrier and biofilm in ICPB system were discussed, and the degradation mechanism was introduced. The shortcomings of the current ICPB system were pointed out, and the possible research directions of ICPB in the future were proposed. This review aimed to deepen the understanding of ICPB technology and promoted the further development of ICPB technology in the treatment of refractory pollutants.

Protonated carbon nitride elicits microalgae for water decontamination

Comprehending the effects of synthetic nanomaterials on natural microorganisms is critical for the development of emerging nanotechnologies. Compared to artificial inactivation of microbes, the up-regulation of biological functions should be more attractive due to the possibility of discovering unexpected properties. Herein, a nanoengineering strategy was employed to tailor g-C₃N₄ for the metabolic regulation of algae. We found that surface protonated g-C₃N₄ (P-C₃N₄) as a nanopolymeric elicitor enabled the reinforced biological activity of Microcystis aeruginosa and Scenedesmus for harmful substances removal. Metabolomics analysis suggested that synthetic nanoarchitectures induced moderate oxidative stress of algae, with up-regulated biosynthesis of extracellular polymeric substances (EPS) for resisting the physiological damage caused by toxic substances in water. The formation of oxidative ^.O₂^- contributed to over five-fold enhancement in the biodecomposition of harmful aniline. Our study demonstrates a synergistic biotic-abiotic platform with valuable outcomes for various customized applications.

Micropollutant degradation by UV/H2O2 in drinking water: Facilitated prediction through combination of model simulation and portable measurement

Ultraviolet-based advanced oxidation processes (UV-AOPs) are highly effective for micropollutant degradation. However, it is considerably time and labor consuming to evaluate the practical performance of UV-AOPs. This study developed a novel method, through combination of model simulation with portable measurement (MS-PM), to facilitate prediction of the photon fluence-based rate constant of micropollutant degradation (k'_p,MP) by UV/H₂O₂, a commercially available UV-AOP. Model simulation was performed with photochemical, hydroxyl radical (HO^•) concentration steady-state approximation, and quantitative structure-activity relationship models; and portable measurement was conducted on a mini-fluidic photoreaction system to quantify the HO^• scavenging capacity (HRSC) of a water matrix. The method was established and further verified experimentally in seven test waters by taking sulfamethazine (SMN) as a model micropollutant. A lower k'_p,SMN was predicted in a water matrix with a higher HRSC, for example, 57.5 and 347.8 m² einstein^-1 in the raw water (HRSC = 5.91 × 10⁵ s^-1) and sand-filtered effluent (HRSC = 5.25 × 10⁴ s^-1) of a drinking water treatment plant at an H₂O₂ dose of 25 mg L^-1, respectively. The predicted values agreed generally well with the experimental ones. The MS-PM method has advantages of high efficiency and convenience, low cost, and acceptable accuracy, which will significantly facilitate the design and field assessment of UV-AOPs for micropollutant removal from drinking water.

Degradation of sulfamethazine in water by sulfite activated with zero-valent Fe-Cu bimetallic nanoparticles

In this work, zero-valent Fe-Cu bimetallic nanoparticles were synthesized using a facile method, and applied to activate sulfite for the degradation of sulfamethazine (SMT) from the aqueous solution. The key factors influencing SMT degradation were investigated, namely the theoretical loading of Cu, Fe-Cu catalyst dosage, sulfite concentration and initial solution pH. The experimental results showed that the Fe-Cu/sulfite system exhibited a much better performance in SMT degradation than the bare Fe⁰/sulfite system. The mechanism and possible degradation pathway of SMT in Fe-Cu/sulfite system were revealed. The reactive radicals that played a dominant role in the SMT degradation process were •OH and SO₄^•-, while the loading of Cu induced the synergistic effect between Fe and Cu. The redox cycle between Cu(I)/Cu(II) remarkably contributed to the conversion of Fe(III) to Fe(II), greatly enhancing the catalytic performance of Fe-Cu bimetal. In real groundwater applications, the Fe-Cu/sulfite system also exhibited satisfactory SMT degradation. The 30-day aging tests of Fe-Cu particles demonstrated that the aging of catalyst was not obviously affecting the removal of SMT. Furthermore, the reusability of catalyst was evidenced by the recycling experiments. This study provides a promising application of bimetal activated sulfite for enhanced contaminant degradation in groundwater.

Exploring kinetics, removal mechanism and possible transformation products of tigecycline by Chlorella pyrenoidosa

The accumulation of antibiotics in wastewater leads to broad antibiotic resistance, threating human health. Microalgae have been receiving attention due to their ability to remove antibiotics from wastewater. Tigecycline (TGC) is a broad-spectrum glycylcycline antibiotic. It has not been investigated for removal by microalgae. The removal kinetics of TGC by Chlorella pyrenoidosa were evaluated under different initial dry cell densities, TGC concentrations, temperatures and light intensity conditions. Approximately 90% of TGC could be removed when the TGC concentration was 10 mg∙L^-1 and the initial dry cell density was more than 0.2 g∙L^-1. A low value of TGC per g dry cell weight ratio led to a high removal efficiency of TGC. The initial dry cell density of microalgae was also critical for the removal of TGC. A high initial dry cell density is better than a low initial dry cell density to remove TGC when the ratio of the TGC concentration to dry cell weight are the same at the beginning of the cultivation. The removal mechanisms were investigated. Photolysis was a slow process that did not lead to removal at the beginning. Adsorption, hydrolysis, photolysis and biodegradation by microalgae were the main contributors to the removal of TGC. TGC was easily hydrolyzed under high -temperature conditions. Three transformation products of TGC by microalgae were identified. The stability of TGC was evaluated in water and salt solutions of citric acid, K₂HPO₄·3H₂O and ferric ammonium citrate. TGC was stable in ultrapure water and citric acid solution. TGC was hydrolyzed in K₂HPO₄·3H₂O and ferric ammonium citrate solutions.

Occurrence of antibiotics in waters, removal by microalgae-based systems, and their toxicological effects: A review

Global antibiotics consumption has been on the rise, leading to increased antibiotics release into the environment, which threatens public health by selecting for antibiotic resistant bacteria and resistance genes, and may endanger the entire ecosystem by impairing primary production. Conventional bacteria-based treatment methods are only moderately effective in antibiotics removal, while abiotic approaches such as advanced oxidation and adsorption are costly and energy/chemical intensive, and may cause secondary pollution. Considered as a promising alternative, microalgae-based technology requires no extra chemical addition, and can realize tremendous CO₂ mitigation accompanying growth related pollutants removal. Previous studies on microalgae-based antibiotics removal, however, focused more on the removal performances than on the removal mechanisms, and few studies have concerned the toxicity of antibiotics to microalgae during the treatment process. Yet understanding the removal mechanisms can be of great help for targeted microalgae-based antibiotics removal performances improvement. Moreover, most of the removal and toxicity studies were carried out using environment-irrelevant high concentrations of antibiotics, leading to reduced guidance for real-world situations. Integrating the two research fields can be helpful for both improving antibiotics removal and avoiding toxicological effects to primary producers by the residual pollutants. This study, therefore, aims to build a link connecting the occurrence of antibiotics in the aquatic environment, the removal of antibiotics by microalgae-based processes, and the toxicity of antibiotics to microalgae. Distribution of various categories of antibiotics in different water environments were summarized, together with the antibiotics removal mechanisms and performances in microalgae-based systems, and the toxicological mechanisms and toxicity of antibiotics to microalgae after either short-term or long-term exposure. Current research gaps and future prospects were also analyzed. The review could provide much valuable information to the related fields, and provoke interesting thoughts on integrating microalgae-based antibiotics removal research and toxicity research on the basis of environmentally relevant concentrations.

Application of BiVO4–Microalgae Combined Treatment to Remove High Concentration Mixture of Sulfamethazine and Sulfadiazine

Sulfonamides (SAs) are the most common and bio-refractory antibiotics detected in surface water systems, which cause long-term toxic effects on aquatic organisms. This study used the combination of a BiVO4 photocatalyst and freshwater micro-green alga (Dictyosphaerium sp.) to remove sulfadiazine (SD) and sulfamethazine (SM2) at an initial concentration of 5 mg/L (1:1 v/v) for 7 days. We set up three gradient concentrations of BiVO4 (0.5, 1 and 2 g/L) combined with the same concentration (80 mg/L) of Dictyosphaerium sp. and then prepared corresponding concentrations of pure BiVO4 and pure microalgae as controls. We evaluated the ability of BiVO4 and Dictyosphaerium sp. combined technology to remove SAs by observing the removal efficiency of antibiotics and explained the degradation mechanism of antibiotics and the key role of microalgae by studying the changes of reactive oxygen species (ROS) and inorganic ions (nitrogen, sulfur). The results showed that the degradation rate of these two SAs in the 0.5 g/L BiVO4–algae group could reach >96% within 7 d, which was higher than that in the 2 g/L BiVO4 group (93%) and the algae group (28%). The increased degradation efficiency of SAs in BiVO4 and microalgae systems was mainly due to the increased amount of ROS. Meanwhile, more SAs were degraded to inorganic compounds such as NH4+-N, NO3−-N and SO42−-S under ROS stress. It was found that microalgae can absorb the degradation products of antibiotics such as NH4+-N for their own growth, thereby reducing the toxicity of antibiotic by-products. In addition, BiVO4 had no damaging effect on the autofluorescence intensity of the microalgae. Our study provides an efficient and eco-economic approach to remove antibiotics using visible-light irradiation in aquatic environments and provides new insights into the biological removal of other antibiotic contaminants in aquatic environments.

Sequential combination of photocatalysis and microalgae technology for promoting the degradation and detoxification of typical antibiotics

Antibiotic contamination has become the primary environmental concern due to its potential to induce the emergence and spread of antibiotic resistance genes (ARGs). To obtain the efficient antibiotic removal approach, the combination of photocatalysis and microalgae technology for the efficient removal and reducing environmental risk of three typical antibiotics (norfloxacin, oxytetracycline and sulfamethoxazole) was demonstrated in this study. The g-C₃N₄ material, with advantages of low cost, simple synthesizing, nontoxic, and wider spectral absorption, was selected and synthesized by an easy thermal polymerization process of urea. Characterization results showed that the prepared material exhibited a typical structure of g-C₃N₄ and irregular nanosheet structure with the large BET surface area and mesoporous structure. The irradiation wavelength and solution pH showed great influences on the photocatalytic degradation of norfloxacin over g-C₃N₄ nanosheets. ^•O₂^-, h⁺, and ^•OH generated by the photocatalysis of g-C₃N₄ nanosheets were confirmed based on energy band results and electron spin resonance detection, while ^•O₂^- was the main contributor to the antibiotics degradation in accordance with scavenging experiments. Many NOR photocatalytic products were identified and degradation pathway was proposed. Due to the formation of many unmineralized products, the acute toxicity of NOR photocatalytic reaction solution was increased. And then, the introduction of microalgae promoted the degradation of some photocatalytic degradation products of NOR, but only Chlorella pyrenoidosa treatment resulted in the decrease of toxicity of NOR reaction solution. This study provides useful information on the application of the combination of photocatalysis and microalgae technology for removal of antibiotics.

Algae-mediated antibiotic wastewater treatment: A critical review

The existence of continually increasing concentrations of antibiotics in the environment is a serious potential hazard due to their toxicity and persistence. Unfortunately, conventional treatment techniques, such as those utilized in wastewater treatment plants, are not efficient for the treatment of wastewater containing antibiotic. Recently, algae-based technologies have been found to be a sustainable and promising technique for antibiotic removal. Therefore, this review aims to provide a critical summary of algae-based technologies and their important role in antibiotic wastewater treatment. Algal removal mechanisms including bioadsorption, bioaccumulation, and biodegradation are discussed in detail, with using algae-bacteria consortia for antibiotic treatment, integration of algae with other microorganisms (fungi and multiple algal species), hybrid algae-based treatment and constructed wetlands, and the factors affecting algal antibiotic degradation comprehensively described and assessed. In addition, the use of algae as a precursor for the production of biochar is highlighted, along with the modification of biochar with other materials to improve its antibiotic removal capacity and hybrid algae-based treatment with advanced oxidation processes. Furthermore, recent novel approaches for enhancing antibiotic removal, such as the use of genetic engineering to enhance the antibiotic degradation capacity of algae and the integration of algal antibiotic removal with bioelectrochemical systems are discussed. Finally, some based on the critical review, key future research perspectives are proposed. Overall, this review systematically presents the current progress in algae-mediated antibiotic removal technologies, providing some novel insights for improved alleviation of antibiotic pollution in aquatic environments.

Screening and functional identification of antioxidant microRNA-size sRNAs from Spirulina platensis using high-throughput sequencing

MiRNA-size small RNAs, abbreviated as sRNAs, are increasingly being discovered as research progresses and omics technologies development in prokaryotes. However, there is a paucity of data concerning whether or not sRNAs exist in cyanobacteria and regulate the resistance to oxidative stress. In this investigation, small RNA libraries were constructed from the control, 50-nM and 100-nM H2O2 treatments of Spirulina platensis. By high-throughput sequencing, 23 candidate sRNAs showed significantly differential expression under oxidative stress, among which eight sRNAs were identified with the similar expression patterns as the sequencing results by real-time qPCR. By nucleic acid hybridisation, the corresponding expression changes also demonstrated that sequencing results of sRNAs were feasible and credible. By bioinformatics prediction and structure identification, 43 target genes were predicted for 8 sRNAs in plant miRNA database, among which 29 were annotated into the genome and related metabolic pathways of S. platensis. By COG functional classification and KEGG pathway analysis, 31 target genes were predicted to be directly or indirectly involved in the defence mechanism of H2O2 stress. Thirteen target genes displayed reversely changing patterns compared with those of their sRNAs under H2O2 treatment. These findings provide compelling evidence that these sRNAs in S. platensis play a crucial role in oxidative stress responses, and thus provide a theoretical reference for improving the stress-triggering physiological regulation.

Enhanced degradation of tetracycline in water over Cu-doped hematite nanoplates by peroxymonosulfate activation under visible light irradiation

Herein, Cu-doped hematite nanoplates (named as CuHNPs) with abundant oxygen-vacancies were prepared through a facile one-pot solvothermal method and used for efficient peroxymonosulfate (PMS) activation to degrade tetracycline (TC) in water. The catalytic activity of optimal CuHNPs-7.5 catalyst to activate PMS for the degradation of TC in water under visible light irradiation is 7.74 and 2.93 times higher than that of pure one without and with visible light irradiation. CuHNPs-7.5 exhibited excellent degradation for TC in the broad pH range from 2.14 to 10.75, and the removal of TC was barely inhibited by co-anions. The combination of free radicals and non-radical pathway, including sulfate radicals (SO₄^·-), hydroxide radicals (·OH), superoxide radical (·O₂^-) and single oxygen (¹O₂), contributed to TC oxidation. The introduction of Cu²⁺ not only accelerated the transformation of Fe(III)/Fe(II) redox cycle but also induced rich oxygen defects in the structure of hematite, boosting more generation of reactive oxygen species (ROSs) for TC degradation. Density functional theory (DFT) calculation and electrochemical impedance spectroscopy (EIS) tests confirmed the accelerated electrons transfer of CuHNPs-7.5 in PMS activation. This study provides a strategy to construct effective catalysts of PMS activation combining radicals and non-radical pathways for environmental remediation.

F- regulate the preparation of polyhedral BiVO4 enclosed by High-Index facet and enhance its photocatalytic activity

The selective exposure of high-index facets at the surface of nanocrystals is an important and challenging research topic. Herein, polyhedral bismuth vanadate (BiVO₄) crystals predominantly surrounded by {2 1 3} and {1 2 1} high-index facets were fabricated through the engineering of high-index surfaces by fluorinion (F^-) mediated hydrothermal process. The as-prepared BiVO₄-0.2F (the feeding amount of NaF was 0.2 g) catalyst exhibited high apparent quantum efficiency of 17.7% under 420 nm light irradiation and 9.3 fold enhancement of O₂ evolution relative to its low-index counterparts. Moreover, the growth of high-index facets results in significant enhancement of hydroxyl radical (•OH) production, photocatalytic degradation of Rhodamine B (RhB) and photoelectrochemical (PEC) properties by the BiVO₄ polyhedron, relative to its low-index counterparts. The enhanced photoreactivity is the result of the synergistic effect of F^- on the surface of the BiVO₄ crystals and exposed high-index facets. For one thing, F^- on the surface of the BiVO₄ facilitate the separation and transport of photo-induced charge carriers. For another, the exposed high-index facets on polyhedral BiVO₄ provided much more reactive sites for photocatalytic reactions. Hopefully, this F^- mediated method will be a useful guideline for designing and synthesizing novel high-index faceted micro-/nanostructures for overcoming the practical energy and environment problems.