Effect of chlortetracycline on the growth and intracellular components of Spirulina platensis and its biodegradation pathway

Optimizing Chlorella vulgaris Cultivation to Enhance Biomass and Lutein Production

Lutein is widely used in medicine, health care, and food processing due to its antioxidant effects; however, it is difficult for the traditional extraction of lutein using marigolds to meet the increasing market demand for lutein. To achieve high-efficiency lutein production, we investigated the effects of different conditions on the biomass accumulation and lutein yield of Chlorella vulgaris. The optimized cultivation conditions include mixotrophic cultivation using sodium nitrate as a nitrogen source, maintaining a total-organic-carbon-to-total-nitrogen ratio of 12:1, a total-nitrogen-to-total-phosphorus ratio of 10:1, and lighting duration of 24 h. The results of the study indicated that under these specific conditions, Chlorella vulgaris attained a final biomass concentration, biomass productivity, and growth yield of 6.08 g·L-1, 1.00 g·L-1·d-1, and 1.67 g biomass/g TOC, respectively. Additionally, the concentrations of total chlorophyll, carotenoid, lutein, and protein reached 139.20 mg·L-1, 31.87 mg·L-1, 15.02 mg·L-1, and 2.17 g·L-1, respectively, and the content of lutein reached 2.47 mg·g-1. This study supplies a theoretical basis for the industrial application of lutein production using Chlorella vulgaris.

Mechanism of self-supporting montmorillonite composite material for bio-enhanced degradation of chlorotetracycline: Electron transfer and microbial response

The efficient degradation of antibiotics holds significant implications for mitigating environmental pollution. This study synthesized a montmorillonite chitosan composite material (MMT-CS) using the gel template method. Subsequently, a bio-enhanced reactor was constructed to facilitate the degradation of chlorotetracycline (CTC). The addition of MMT-CS composite material enables the degradation of different concentrations of CTC. MMT-CS, a conductive carrier, effectively promotes microbial adhesion and boosts the metabolic activity of functional microorganisms. Additionally, it facilitates the maintenance of microbial activity under CTC pressure by promoting the secretion of extracellular polymeric substances, increasing critical enzyme activity, and enhancing the electron transfer capacity within the system. In this MMT-CS bio-enhanced process, Paracoccus (11.4%) and Bacillus (3.9%) are utilized as essential bacteria genes. The results of metabolic pathways prediction indicated significant enhancements in membrane-transport, nucleotide-metabolism, replication-repair, and lipid-metabolism. Thus, the developed self-supporting MMT-CS bio-enhanced process ensured the stability of the system during the removal of antibiotics.

The extracellular polymeric substances (EPS) accumulation of Spirulina platensis responding to Cadmium (Cd2+) exposure

Spirulina platensis can secrete extracellular polymeric substances (EPS) helping to protect damage from stress environment, such as cadmium (Cd2+) exposure. However, the responding mechanism of S. platensis and the secreted EPS to exposure of Cd2+ is still unclear. This research focuses on the effects of Cd2+ on the composition and structure of the EPS and the response mechanism of EPS secretion from S. platensis for Cd2+ exposure. S. platensis can produce 261.37 mg·g-1 EPS when exposing to 20 mg·L-1 CdCl2, which was 2.5 times higher than the control group. The S. platensis EPS with and without Cd2+ treatment presented similar and stable irregularly fibrous structure. The monosaccharides composition of EPS in Cd2+ treated group are similar with control group but with different monosaccharides molar ratios, especially for Rha, Gal, Glc and Glc-UA. And the Cd2+ treatment resulted in a remarkable decline of humic acid and fulvic acid content. The antioxidant ability of S. platensis EPS increased significantly when exposed to 20 mg·L-1 CdCl2, which could be helpful for S. platensis protecting damage from high concentration of Cd2+. The transcriptome analysis showed that sulfur related metabolic pathways were up-regulated significantly, which promoted the synthesis of sulfur-containing amino acids and the secretion of large amounts of EPS.

Bioadsorption, bioaccumulation and biodegradation of antibiotics by algae and their association with algal physiological state and antibiotic physicochemical properties

Bioadsorption, bioaccumulation and biodegradation processes in algae, play an important role in the biomagnification of antibiotics, or other organic pollutants, in aquatic food chains. In this study, the bioadsorption, bioaccumulation and biodegradation of norfloxacin [NFX], sulfamethazine [SMZ] and roxithromycin [RTM]) is investigated using a series of culture experiments. Chlorella vulgaris was exposed to these antibiotics with incubation periods of 24, 72, 120 and 168 h. Results show the bioadsorption concentration of antibiotics in extracellular matter increases with increasing alkaline phosphatase activity (AKP/ALP). The bioaccumulation concentrations of NFX, SMZ and RTM within cells significantly increase after early exposure, and subsequently decrease. There is a significant positive antibiotics correlation to superoxide dismutase (SOD), the photosynthetic electron transport rate (ETR) and maximum fluorescence after dark adaptation (Fv/Fm), while showing a negative correlation to malondialdehyde (MDA). The biodegradation percentages (Pb) of NFX, SMZ and RTM range from 39.3 - 97.2, 41.3 - 90.5, and 9.3 - 99.9, respectively, and significantly increase with increasing Fv/Fm, density and chlorophyll-a. The accumulation of antibiotics in extracellular and intracellular substances of C. vulgaris is affected by antibiotic biodegradation processes associated with cell physiological state. The results succinctly explain relationships between algal growth during antibiotics exposure and the bioadsorption and bioaccumulation of these antibiotics in cell walls and cell matter. The findings draw an insightful understanding of the accumulation of antibiotics in algae and provide a scientific basis for the better utilization of algae treatment technology in antibiotic contaminated wastewaters. Under low dose exposures, the biomagnification of antibiotics in algae is affected by bioadsorption, bioaccumulation and biodegradation.

Concurrent enhancement of biomass production and phycocyanin content in salt-stressed Arthrospira platensis: A glycine betaine- supplementation approach

In industrial-scale cultivation of microalgae, salinity stress often stimulates high-value metabolites production but decreases biomass yield. In this research, we present an extraordinary response of Arthrospira platensis to salinity stress. Specifically, we observed a significant increase in both biomass production (2.58 g L-1) and phycocyanin (PC) content (22.31%), which were enhanced by 1.26-fold and 2.62-fold, respectively, compared to the control, upon exposure to exogenous glycine betaine (GB). The biochemical analysis reveals a significant enhancement in carbonic anhydrase activity and chlorophyll a level, concurrent with reductions in carbohydrate content and reactive oxygen species (ROS) levels. Further, transcriptomic profiling indicates a downregulation of genes associated with the tricarboxylic acid (TCA) cycle and an upregulation of genes linked to nitrogen assimilation, hinting at a rebalanced carbon/nitrogen metabolism favoring PC accumulation. This work thus presents a promising strategy for simultaneous enhancement of biomass production and PC content in A. platensis and expands our understanding of PC biosynthesis and salinity stress responses in A. platensis.

Occurrence and fate of pharmaceutical pollutants in wastewater: Insights on ecotoxicity, health risk, and state-of-the-art removal

Pharmaceutical active compound (PhAC) residues are considered an emerging micropollutant that enters the aquatic environment and causes harmful ecotoxicity. The significant sources of PhACs in the environment include the pharmaceutical industry, hospital streams, and agricultural wastes (animal husbandry). Recent investigations demonstrated that wastewater treatment plants (WWTPs) are an important source of PhACs discharging ecosystems. Several commonly reported that PhACs are detected in a range level from ng L-1 to μg L-1 concentration in WWTP effluents. These compounds can have acute and chronic adverse impacts on natural wildlife, including flora and fauna. The approaches for PhAC removals in WWTPs include bioremediation, adsorption (e.g., biochar, chitosan, and graphene), and advanced oxidation processes (AOPs). Overall, adsorption and AOPs can effectively remove PhACs from wastewater aided by oxidizing radicals. Heterogeneous photocatalysis has also proved to be a sustainable solution. Bioremediation approaches such as membrane bioreactors (MBRs), constructed wetlands (CWs), and microalgal-based systems were applied to minimize pharmaceutical pollution. Noteworthy, applying MBRs has illustrated high removal efficiencies of up to 99%, promising prospective future. However, WWTPs should be combined with advanced solutions, e.g., AOPs/photodegradation, microalgae-bacteria consortia, etc., to treat and minimize their accumulation. More effective and novel technologies (e.g., new generation bioremediation) for PhAC degradation must be investigated and specially designed for a low-cost and full-scale. Investigating green and eco-friendly PhACs with advantages, e.g., low persistence, no bioaccumulation, less or non-toxicity, and environmentally friendly, is also necessary.

Occurrence, fate, and remediation for per-and polyfluoroalkyl substances (PFAS) in sewage sludge: A comprehensive review

Addressing per-and polyfluoroalkyl substances (PFAS) contamination is an urgent environmental concern. While most research has focused on PFAS contamination in water matrices, comparatively little attention has been given to sludge, a significant by-product of wastewater treatment. This critical review presents the latest information on emission sources, global distribution, international regulations, analytical methods, and remediation technologies for PFAS in sludge and biosolids from wastewater treatment plants. PFAS concentrations in sludge matrices are typically in hundreds of ng/g dry weight (dw) in developed countries but are rarely reported in developing and least-developed countries due to the limited analytical capability. In comparison to water samples, efficient extraction and cleaning procedures are crucial for PFAS detection in sludge samples. While regulations on PFAS have mainly focused on soil due to biosolids reuse, only two countries have set limits on PFAS in sludge or biosolids with a maximum of 100 ng/g dw for major PFAS. Biological technologies using microbes and enzymes present in sludge are considered as having high potential for PFAS remediation, as they are eco-friendly, low-cost, and promising. By contrast, physical/chemical methods are either energy-intensive or linked to further challenges with PFAS contamination and disposal. The findings of this review deepen our comprehension of PFAS in sludge and have guided future research recommendations.

Understanding microplastic pollution: Tracing the footprints and eco-friendly solutions

Microplastics (MPs) pollution has emerged as a critical environmental issue with far-reaching consequences for ecosystems and human health. These are plastic particles measuring <5 mm and are categorized as primary and secondary based on their origin. Primary MPs are used in various products like cosmetics, scrubs, body wash, and toothpaste, while secondary MPs are generated through the degradation of plastic products. These have been detected in seas, rivers, snow, indoor air, and seafood, posing potential risks to human health through the food chain. Detecting and quantifying MPs are essential to understand their distribution and abundance in the environment. Various microscopic (fluorescence microscopy, scanning electron microscopy) and spectroscopy techniques (FTIR, Raman spectroscopy, X-ray photoelectron spectroscopy) have been reported to analyse MPs. Despite the challenges in scalable removal methods, biological systems have emerged as promising options for eco-friendly MPs remediation. Algae, bacteria, and fungi have shown the potential to adsorb and degrade MPs in wastewater treatment plants (WWTPs) offering hope for mitigating this global crisis. This review examines the sources, impacts, detection, and biological removal of MPs, highlighting future directions in this crucial field of environmental conservation. By fostering global collaboration and innovative research a path towards a cleaner and healthier planet for future generations can be promised.

Biodegradation mechanism of chlortetracycline by a novel fungal Aspergillus sp. LS-1

Chlortetracycline (CTC), a widely used typical tetracycline antibiotic, has raised increasing concerns due to its potential health and environmental risks. Biodegradation is considered an effective method to reduce CTC in environment. In this study, a strain Aspergillus sp. LS-1, which can efficiently degrade CTC, was isolated from CTC-rich activated sludge. Under optimal conditions, the maximum removal efficiency of CTC could reach 95.41%. Temperature was the most significant factor affecting the degradation efficiency of LS-1. The 19 products were identified in the CTC degradation by strain LS-1, and three degradation pathways were proposed. All the degradation pathways for CTC exhibited ring-cleaving, which may accelerate the mineralization of CTC. To gain more comprehensive insights into this strain, we obtained the genome of LS-1, which had high GC content (50.1%) and completeness (99.3%). The gene annotation revealed that LS-1 contains some vital enzymes and resistance genes that may carry functional genes involved in the CTC degradation. In addition, other antibiotic resistance genes were found in the genome of LS-1, indicating that LS-1 has the potential to degrade other antibiotics. This study provides a more theoretical basis for the investigation of CTC degradation by fungi and new insights into the biodegradation of CTC.

Influence of cold atmospheric pressure plasma treatment of Spirulina platensis slurry over biomass characteristics

Cold atmospheric pressure plasma (CAPP) technique is an innovative non-thermal approach for food preservation and decontamination. This study aimed to evaluate the effect of CAPP power density on microorganism inactivation and quality of Spirulina platensis (S. platensis) slurry. 91.31 ± 1.61% of microorganism were inactivated within 2.02 ± 0.11 min by 26.67 W/g CAPP treatment under 50 ℃. Total phenolic, Chlorophyll-a (Chl-a), and carotenoids contents were increased by 20.51%, 63.55%, and 70.04% after 20.00 W/g CAPP treatment. Phycobiliproteins (PBPs), protein, intracellular polysaccharide, and moisture content of S. platensis was decreased, while vividness, lightness, color of yellow and green, antioxidant activity, Essential Amino Acid Index were enhanced after CAPP treatment. The nutrient release and filaments breakage of CAPP-treated S. platensis improved its bio-accessibility. The findings provided a deep understanding and insight into the influence of CAPP treatment on S. platensis, which were meaningful for optimizing its sterilization and drying processing condition.

Higher toxicity induced by co-exposure of polystyrene microplastics and chloramphenicol to Microcystis aeruginosa: Experimental study and molecular dynamics simulation

Antibiotics and microplastics (MPs) inevitably coexist in natural waters, but their combined effect on aquatic organisms is still ambiguous. This study investigated the individual and combined toxicity of chloramphenicol (CAP) and micro-polystyrene (mPS) particles to Microcystis aeruginosa by physiological biomarkers, related gene expression, and molecular dynamics simulation. The results indicated that both individual and joint treatments threatened algal growth, while combined toxicity was higher than the former. Photosynthetic pigments and gene expression were inhibited by single CAP and mPS exposure, but CAP dominated and aggravated photosynthetic toxicity in combined exposure. Additionally, mPS damaged cell membranes and induced oxidative stress, which might further facilitate the entry of CAP into cells during co-exposure. The synergistic effect of CAP and mPS might be explained by the common photosynthetic toxicity target of CAP and mPS as well as oxidative stress. Furthermore, the molecular dynamics simulation revealed that CAP altered conformations of photosynthetic assembly protein YCF48 and SOD enzyme, and competed for functional sites of SOD, thus disturbing photosynthesis and antioxidant systems. These findings provide useful insights into the combined toxicity mechanism of antibiotics and MPs as well as highlight the importance of co-pollutant toxicity in the aquatic environment.

Preparation and Characterization of Intracellular and Exopolysaccharides during Cycle Cultivation of Spirulina platensis

The dried cell weight (DCW) of Spirulina platensis gradually decreased from 1.52 g/L to 1.18 g/L after five cultivation cycles. Intracellular polysaccharide (IPS) and exopolysaccharide (EPS) content both increased with increased cycle number and duration. IPS content was higher than EPS content. Maximum IPS yield (60.61 mg/g) using thermal high-pressure homogenization was achieved after three homogenization cycles at 60 MPa and an S/I ratio of 1:30. IPS showed a more fibrous, porous, and looser structure, and had a higher glucose content and Mw (272.85 kDa) compared with EPS, which may be indicative of IPS's higher viscosity and water holding capacity. Although both carbohydrates were acidic, EPS had stronger acidity and thermal stability than IPS; this was accompanied by differences in monosaccharide. IPS exhibited the highest DPPH (EC₅₀ = 1.77 mg/mL) and ABTS (EC₅₀ = 0.12 mg/mL) radical scavenging capacity, in line with IPS's higher total phenol content, while simultaneously showing the lowest HO^• scavenging and ferrous ion chelating capacities; thus characterizing IPS as a superior antioxidant and EPS as a stronger metal ion chelator.

How do freshwater microalgae and cyanobacteria respond to antibiotics?

Antibiotic pollution is an emerging environmental challenge. Residual antibiotics from various sources, including municipal and industrial wastewater, sewage discharges, and agricultural runoff, are continuously released into freshwater environments, turning them into reservoirs that contribute to the development and spread of antibiotic resistance. Thus, it is essential to understand the impacts of antibiotic residues on aquatic organisms, especially microalgae and cyanobacteria, due to their crucial roles as primary producers in the ecosystem. This review summarizes the effects of antibiotics on major biological processes in freshwater microalgae and cyanobacteria, including photosynthesis, oxidative stress, and the metabolism of macromolecules. Their adaptive mechanisms to antibiotics exposure, such as biodegradation, bioadsorption, and bioaccumulation, are also discussed. Moreover, this review highlights the important factors affecting the antibiotic removal pathways by these organisms, which will promote the use of microalgae-based technology for the removal of antibiotics. Finally, we offer some perspectives on the opportunities for further studies and applications.

A review on microalgae-mediated biotechnology for removing pharmaceutical contaminants in aqueous environments: Occurrence, fate, and removal mechanism

Pharmaceutical compounds in aquatic environments have been considered as emerging contaminants due to their potential risks to living organisms. Microalgae-based technology showed the feasibility of removing pharmaceutical contaminants. This review summarizes the occurrence, classification, possible emission sources, and environmental risk of frequently detected pharmaceutical compounds in aqueous environments. The efficiency, mechanisms, and influencing factors for the removal of pharmaceutical compounds through microalgae-based technology are further discussed. Pharmaceutical compounds frequently detected in aqueous environments include antibiotics, hormones, analgesic and non-steroidal anti-inflammatory drugs (NSAIDs), cardiovascular agents, central nervous system drugs (CNS), antipsychotics, and antidepressants, with a concentration ranging from ng/L to μg/L. Microalgae-based technology majorly remove the pharmaceutical compounds through bioadsorption, bioaccumulation, biodegradation, photodegradation, and co-metabolism. This review identifies the opportunities and challenges for microalgae-based technology and proposed suggestions for future studies to tackle challenges. The findings of this review advance our understanding of the occurrence and fate of pharmaceutical contaminants in aqueous environments, highlighting the potential of microalgae-based technology for pharmaceutical contaminants removal.

Interaction of Scenedesmus quadricauda and native bacteria in marine biopharmaceutical wastewater for desirable lipid production and wastewater treatment

Improving knowledge of the alga-bacterium interaction can promote the wastewater treatment. The untreated marine biopharmaceutical wastewater (containing native bacteria) was used directly for culturing microalgae. Unlike previous studies on specific bacteria in algal-bacterial co-culture systems, the effect of native bacteria in wastewater on microalgae growth was investigated in this study. The results showed that the coexistence of native bacteria greatly promoted the microalgae growth, ultimately producing biomass of 0.64 g/L and biomass productivity of 56.18 mg/L·d. Moreover, the lipid accumulation in the algae + bacteria group was 1.31 and 1.13 times higher than those of BG11 and pure algae, respectively, mainly attributed to the fact that bacteria provided a good environment for microalgae growth by using extracellular substances released from microalgae for their own growth, and providing micromolecules of organic matter and other required elements to microalgae. This study would lay the theoretical foundation for improving biopharmaceutical wastewater treatment.

The different toxicological effects and removal efficiencies of norfloxacin and sulfadiazine in culturing Arthrospira (Spirulina) platensis

Norfloxacin (NFX) and sulfadiazine (SDZ) are two widely used antibiotics belonging to fluoroquinolone and sulfonamide groups, respectively, and have become the commonly detected micropollutants in aquatic environments. However, only few works have been conducted to investigate the highly probable inhibition of these antibiotic pollutants to Arthrospira platensis, which is an important species of cyanobacteria that is one of primary producers in aquatic ecosystems and should be remarkably sensitive to environmental pollutants due to its prokaryotic characteristics. Hence, the toxicological effects and removal efficiencies of NFX and SDZ in culturing A. platensis were studied by analyzing the biomass growth, photosynthetic pigments, primary biocomponents, and antibiotics concentration. The corresponding variations of these characteristics showed the higher sensitivity of A. platensis to NFX than to SDZ, indicating the specifically targeted effect of NFX on A. platensis, which could be confirmed in silico by the higher binding affinity of NFX with the critical enzyme. The obtained results illustrated the roles of NFX and SDZ on the growth of A. platensis, thus providing the great support in employing A. platensis to reduce hazards from contaminated water and recover biomass resources.

Assessing the potential for nevirapine removal and its ecotoxicological effects on Coelastrella tenuitheca and Tetradesmus obliquus in aqueous environment

Remediation of the antiretroviral (ARV) drug, nevirapine (NVP) has attracted considerable scientific attention in recent years due to its frequent detection and persistence in aquatic environments and potential hazards to living organisms. Algae-based technologies have been emerging as an environmentally friendly option for the removal of pharmaceutical compounds, but their ARV drug removal potential has not been fully explored yet. This study aimed to explore the ecotoxicity and removal potential of NVP by two microalgal species, Coelastrella tenuitheca and Tetradesmus obliquus. Lower environmental concentrations (up to 200 ng L^-1) of NVP enhanced the microalgal growth, and the highest dry cell weight of 941.27 mg L^-1 was obtained in T. obliquus at 50 ng L^-1 NVP concentration. Both microalgae showed varying removal efficiencies (19.53-74.56%) when exposed to NVP concentration levels of up to 4000 ng L^-1. At the late log phase (day 8), T. obliquus removed the highest percentage of NVP (74.56%), while C. tenuitheca removed 48% at an initial NVP concentration of 50 ng L^-1. Photosynthetic efficiency (Fv/Fm and rETR) of the two microalgal species, however, was not affected by environmental concentrations of NVP (up to 4000 ng L^-1) at the mid log phase of growth. SEM analysis demonstrated that both algal species produced distinct ridges on their cell surfaces after NVP uptake. In the ecotoxicity study, the calculated IC₅₀ values of NVP (0-100 mg L^-1) after 96 h of exposure were 23.45 mg L^-1 (C. tenuitheca) and 18.20 mg L^-1 (T. obliquus). The findings of the present study may contribute to a better understanding of the environmental hazards associated with NVP and the efficacy of microalgae in removing this pharmaceutical from aquatic environments.

An efficient removal approach for degradation of metformin from aqueous solutions with sulfate radicals

Metformin consumption for diabetes treatment is increasing, leading to its presence in wastewater treatment plants where conventional methods cannot remove it. Therefore, this work aims to analyze the performance of advanced oxidation processes using sulfate radicals in the degradation of metformin from water. Experiments were performed in a photoreactor provided with a low-pressure Hg lamp, using K₂S₂O₈ as oxidant and varying the initial metformin concentration (C_A0), oxidant concentration (C_ox), temperature (T), and pH in a response surface experimental design. The degradation percentages ranged from 26.1 to 87.3%, while the mineralization percentages varied between 15.1 and 64%. Analysis of variance (ANOVA) showed that the output variables were more significantly affected by C_A0, C_ox, and T. Besides, a reduction of C_A0 and an increase of C_ox up to 5000 μM maximizes the metformin degradation since the generation of radicals and their interaction with metformin molecules are favored. For the greatest degradation percentage, the first order apparent rate constant achieved was 0.084 min^-1. Furthermore, while in acidic pH, temperature benefits metformin degradation, an opposite behavior is obtained in a basic medium because of recombination and inhibition reactions. Moreover, three degradation pathways were suggested based on the six products detected by HPLC-MS: N-cyanoguanidine m/z = 85; N,N-dimethylurea m/z = 89; N,N-dimethyl-cyanamide m/z = 71 N,N-dimethyl-formamide m/z = 74; glicolonitrilo m/z = 58; and guanidine m/z = 60. Finally, it was shown that in general the toxicity of the degradation byproducts was lower than the toxicity of metformin toward Chlamydomonas reinhardtii.

Effect of time and temperature of pretreatment and anaerobic co-digestion of rice straw and swine wastewater by domesticated paddy soil microbes

Rice straw and swine wastewater are abundant, easy to obtain, and inexpensive biomass materials. Anaerobic digestion of rice straw and swine wastewater effectively regulates the carbon-to-nitrogen ratio and also improves methane production efficiency. The dense lignocellulosic structure, unsuitable carbon-to-nitrogen ratio, and light texture of rice straw hinder its application in anaerobic digestion. Effective pretreatment technologies can improve degradation efficiency and methane production. Our study is the first to apply domesticated paddy soil microbes to enhance the efficiency of hydrolytic acidification of rice straw and swine wastewater at varying temperatures and times. The results show that the highest total organic carbon (1757.2 mg/L), soluble chemical oxygen demand (5341.7 mg/L), and organic acid concentration (4134.6 mg/L) appeared in the hydrolysate after five days of hydrolytic acidification at 37 °C. Moreover, the use of hydrolysate produced 13% more gas and reduced the anaerobic digestion period by ten days compared to the untreated control. This suggests that using domesticated paddy soil microbes as a pretreatment might be a sustainable and cost-effective strategy for improving the degradation efficacy and methane production from lignocellulosic materials.

Effect of extracellular proteins on Cd(II) adsorption in fungus and algae symbiotic system

Fungus-algae symbiotic systems (FASS) are typically used to assist in the immobilization of algae and strengthen the adsorption of heavy metals. However, the adsorption behavior of the symbiotic system and the molecular regulation mechanism of extracellular proteins in the adsorption of heavy metals have not been reported in detail. In this study, a stable FCSS (fungus-cyanobacterium symbiotic system) was used to study Cd(II) adsorption behavior. The fixation efficiency of fungus to cyanobacterium reached more than 95% at pH7.0, 30 °C, 150 rpm, and a medium ratio of 100%. The biomass, chlorophyll content, and total fatty acid content of the symbiotic system were much higher than those of cyanobacterium and fungus alone. The photosynthetic fluorescence parameters showed that the presence of fungus enhanced the light tolerance of cyanobacterium. The original light energy conversion efficiency and potential activity of PSII were enhanced, indicating that symbiosis could promote the photosynthetic process of cyanobacterium. The Cd(II) adsorption efficiency can achieve 90%. The system maintained excellent adsorption after six adsorption cycles. Differential proteins were mainly enriched in areas such as metabolism, ABC transport system, and pressure response. Cd(II) stress promotes an increase in efflux proteins. Moreover, cadmium can be fixed as much as possible by secreting extracellular proteins, and the toxicity of cadmium to cells can be alleviated by regulating the metabolism of glutathione, reducing oxidative phosphorylation level, and reducing oxidative stress, thus improving the resistance to Cd(II). Meanwhile, the expression of enzymes involved in glycolysis and the pentose phosphate pathway was upregulated, while the expression of those in the TCA cycle was downregulated. The expression of substances related to PSI and PSII in the photosynthetic system and rubisco, a key enzyme in the Calvin cycle, was significantly upregulated, indicating that the glucose metabolism and photosynthetic pathways of the symbiotic system were involved in resistance to Cd toxicity. This revealed the response mechanism of the fungus-algal symbiotic system in the process of Cd adsorption, and also provided reference value for industrial application in water treatment.

Removal mechanisms of erythromycin by microalgae Chlorella pyrenoidosa and toxicity assessment during the treatment process

Microalgae-based biotechnology for antibiotic removal has received increasing attention as an economical and green method. This study investigated the removal mechanism of erythromycin by Chlorella pyrenoidosa and its correlation with the ecotoxic responses of microalgae. The degradation products (DPs) were identified, and their toxicity was predicted. The results indicated that only 4.04 %, 6.28 % and 23.53 % of erythromycin were left after 21-day microalgae treatment in 0.1, 1.0 and 10 mg/L treatments, respectively. Biodegradation contributed 48.62-67.01 %, 16.67-52.32 % and 6.42-24.82 %, while abiotic degradation contributed 8.76-29.61 %, 5.19-41.39 %, and 16.55-51.22 % to erythromycin attenuation in 0.1, 1.0, and 10 mg/L treatments, respectively. The growth and physiological-biochemical parameters of microalgae were slightly affected in low concentration treatment, which may be the main reason that biodegradation was the prominent removal mechanism. By contrast, oxidative damage in high concentration treatment inhibited the cell growth and chlorophyll content of microalgae, which hindered erythromycin biodegradation. In addition, eleven erythromycin degradation products (DPs) were identified during microalgae treatment of 21 days. Seven DPs including DP717, DP715, DP701A, DP701B, DP657, DP643, and DP557, represented higher toxicity to aquatic organisms than erythromycin.

Mechanisms and application of microalgae on removing emerging contaminants from wastewater: A review

This study reviews the development of the ability of microalgae to remove emerging contaminants (ECs) from wastewater. Contaminant removal by microalgae-based systems (MBSs) includes biosorption, bioaccumulation, biodegradation, photolysis, hydrolysis, and volatilization. Usually, the existence of ECs can inhibit microalgae growth and reduce their removal ability. Therefore, three methods (acclimation, co-metabolism, and algal-bacterial consortia) are proposed in this paper to improve the removal performance of ECs by microalgae. Finally, due to the high removal performance of contaminants from wastewater by algal-bacterial consortia systems, three kinds of algal-bacterial consortia applications (algal-bacterial activatedsludge, algal-bacterial biofilm reactor, and algal-bacterial constructed wetland system) are recommended in this paper. These applications are promising for ECs removal. But most of them are still in their infancy, and limited research has been conducted on operational mechanisms and removal processes. Extra research is needed to clarify the applicability and cost-effectiveness of hybrid processes.

Removal of oxytetracycline and ofloxacin in wastewater by microalgae-bacteria symbiosis for bioenergy production

The development of microalgae-bacteria symbiosis for treating wastewater is flourishing owing to its high biomass productivity and exceptional ability to purify contaminants. A nature-selected microalgae-bacteria symbiosis, mainly consisting of Dictyosphaerium and Pseudomonas, was used to treat oxytetracycline (OTC), ofloxacin (OFLX), and antibiotic-containing swine wastewater. Increased antibiotic concentration gradually reduced biomass productivity and intricately changed symbiosis composition, while 1 mg/L OTC accelerated the growth of symbiosis. The symbiosis biomass productivity reached 3.4-3.5 g/L (5.7-15.3 % protein, 18.4-39.3 % carbohydrate, and 2.1-3.9 % chlorophyll) when cultured in antibiotic-containing swine wastewater. The symbiosis displayed an excellent capacity to remove 76.3-83.4 % chemical oxygen demand, 53.5-62.4 % total ammonia nitrogen, 97.5-100.0 % total phosphorus, 96.3-100.0 % OTC, and 32.8-60.1 % OFLX in swine wastewater. The microbial community analysis revealed that the existence of OTC/OFLX increased the richness and evenness of microalgae but reduced bacteria species in microalgae-bacteria, and the toxicity of OFLX to bacteria was stronger than that of OTC.

Mechanisms of promotion in the heterotrophic growth of Chlorella vulgaris by the combination of sodium acetate and hydrolysate of broken rice

In order to reduce the culture cost and increase the growth rate of heterotrophic Chlorella vulgaris, the effects of hydrolysate of broken rice (HBR) combined with sodium acetate on its growth were evaluated. Results showed that the addition of 0.4 g/L of sodium acetate could stabilize the pH of the medium via the co-metabolism of acetate, ammonia and nitrate by Chlorella vulgaris. Meanwhile, isocitrate lyase activity increased threefold, which further promoted the glyoxylate cycle and the citric acid cycle, which finally provided more energy and metabolic precursors for cell growth. The biomass production (5.04 g/L), biomass productivity (1.65 g/L/day) and protein content (64.14 %) were 1.56, 1.81 and 1.77 times higher than the glucose group. This study demonstrated that HBR combined with sodium acetate could effectively promote the heterotrophic metabolism of microalgae, which provided scientific basis and guidance for industrial production of high-value products using Chlorella vulgaris as a fermentation platform.

Effects of C/N ratio on the growth and protein accumulation of heterotrophic Chlorella in broken rice hydrolysate

BACKGROUND

Microalgae protein is considered as a sustainable alternative to animal protein in the future. Using waste for microalgal culture can upgrade low-value raw materials into high-value products, helping to offset the cost of microalgal protein production. In this study we explored the feasibility of using microalgae heterotrophic fermentation to convert broken rice hydrolysate (BRH) into protein.

RESULTS

The results showed that the increase of BRH supplemental ratio was beneficial to the increase of biomass production but not beneficial to the increase of intracellular protein content. To further improve protein production, the effect of C/N ratio on intracellular protein accumulation was studied. It was found that low C/N ratio was beneficial to the synthesis of glutamate in microalgae cells, which in turn promoted the anabolism of other amino acids and further the protein. When the C/N ratio was 12:1, the biomass productivity and protein content could reach a higher level, which were 0.90 g/L/day and 61.56%, respectively. The obtained Chlorella vulgaris biomass was rich in essential amino acids (41.80%), the essential amino acid index was as high as 89.07, and the lysine content could reach up to 4.05 g/100 g.

CONCLUSIONS

This study provides a theoretical basis and guidance for using Chlorella vulgaris as an industrial fermentation platform to convert broken rice into products with high nutritional value.

Ecotoxicological response of Spirulina platensis to coexisted copper and zinc in anaerobic digestion effluent

Copper ion (Cu²⁺) and zinc ion (Zn²⁺) are widely co-existent in anaerobic digestion effluent as typical contaminants. This work aims to explore how Cu²⁺-Zn²⁺ association affects physiological properties of S. platensis using Schlösser medium (SM) and sterilized anaerobic digestion effluent (SADE). Microalgae cells viability, biochemical properties, uptake of Cu²⁺ and Zn²⁺, and risk assessment associated with the biomass reuse as additives to pigs were comprehensively assessed. Biomass production ranged from 0.03 to 0.28 g/L in SM and 0.63 to 0.79 g/L in SADE due to the presence of Cu²⁺ and Zn²⁺. Peak value of chlorophyll-a and carotenoid content during the experiment decreased by 70-100% and 40-100% in SM, and by 70-77% and 30-55% in SADE. Crude protein level reduced by 4-41% in SM and by 65-75% in SADE. The reduction ratio of these compounds was positively related to the Cu²⁺ and Zn²⁺ concentrations. Maximum value of saturated and unsaturated fatty acids was both obtained at 0.3 Cu + 2.0 Zn (50.8% and 22.8%, respectively) and 25% SADE reactors (33.8% and 27.7%, respectively). Uptake of Cu in biomass was facilitated by Zn²⁺ concentration (> 4.0 mg/L). Risk of S. platensis biomass associated with Cu²⁺ was higher than Zn²⁺. S. platensis from SM (Cu²⁺ ≤ 0.3 mg/L and Zn²⁺ ≤ 4.0 mg/L) and diluted SADE (25% and 50% SADE) reactors could be used as feed additives without any risk (hazard index <1), which provides sufficient protein and fatty acids for pig consumption. These results revealed the promising application of using S. platensis for bioremediation of Cu²⁺ and Zn²⁺ in anaerobic digestion effluent and harvesting biomass for animal feed additives.

Response of fungi-microalgae pellets to copper regulation in the removal of sulfonamides and release of dissolved organic matters

Both sulfonamides (SAs) and copper (Cu(II)) were frequently detected together in swine wastewater. In this study, the regulation of Cu(II) on SAs adsorption and release of dissolved organic matters (DOMs) by fungi-microalgae pellets (FM-pellets) were investigated. Aspergillus oryzae pellets were prepared for combination with Chlorella vulgaris and the optimal conditions were at agitation speed of 130 rpm, fungi to microalgae ratio of 10:1 and the combined time of 3 h with the highest combination efficiency of 98.65%. The results showed that adsorption was the main mechanism for SAs removal. FM-pellets exhibited a high SAs adsorption potential within 6 h, and the adsorption capacity of sulfamethazine (SMZ), sulfamonomethoxine (SMM) and sulfamethoxazole (SMX) was 1.07, 0.94 and 1.67 mg/g, respectively. Furthermore, the removal of SMX, SMZ and SMM was greatly promoted from 62.31% to 85.21%, 58.71-67.91% and 64.17-80.31%, respectively, under the presence of 2 mg/L Cu(II) through ion exchange and adsorption bridging. DOMs were analyzed by the parallel factor (PARAFAC) to demonstrate the response mechanism of FM-pellets to Cu(II). Protein-like substances and NADH in DOMs released by FM-pellets formed complexes with Cu(II) to alleviate the damage on the organism. These findings provide new insights into the mechanism and response of Cu(II) in the removal of SAs by FM-pellets.

Effects of Culture Conditions on the Performance of Arthrospira platensis and Its Production of Exopolysaccharides

Exopolysaccharides (EPS) produced by Arthrospira platensis (A. platensis) has been widely applied in industry and commerce for its various activities but the accumulation of EPS in culture medium may influence the growth of A. platensis reversely. This work aims to explore the impacts of initial pH, nitrogen source and concentration, phosphate concentration and recycle times of the culture medium on the growth of A. platensis and the secretion of its EPS. The results showed that EPS accumulated with the increase in recycle times of culture medium. The optimal initial pH for the growth of A. platensis was 8.50, and high pH of 11.5 inhibited the growth of biomass while resulting in highest EPS content of 92.87 mg/g DW. Excessive and limited nitrogen (NaNO3 of 25.00 g/L and NaNO3 < 2.50 g/L) and phosphate (K2HPO4 of 5.00 g/L and K2HPO4 < 0.50 g/L) inhibited the biomass production of A. platensis by 1.28−30.77% and 14.29−45.05%, respectively. EPS yield of 97.57 mg/g DW and 40.90 mg/g DW were obtained under NaNO3 of 25.00 g/L and K2HPO4 of 5.00 g/L due to salt stress. These findings are beneficial in providing a theoretical basis for high yield EPS from A. platensis without affecting biomass yield.

Progress in microalgal mediated bioremediation systems for the removal of antibiotics and pharmaceuticals from wastewater

Worldwide demand for antibiotics and pharmaceutical products is continuously increasing for the control of disease and improvement of human health. Poor management and partial metabolism of these compounds result in the pollution of aquatic systems, leading to hazardous effects on flora, fauna, and ecosystems. In the past decade, the importance of microalgae in micropollutant removal has been widely reported. Microalgal systems are advantageous as their cultivation does not require additional nutrients: they can recover resources from wastewater and degrade antibiotics and pharmaceutical pollutants simultaneously. Bioadsorption, degradation, and accumulation are the main mechanisms involved in pollutant removal by microalgae. Integration of microalgae-mediated pollutant removal with other technologies, such as biodiesel, biochemical, and bioelectricity production, can make this technology more economical and efficient. This article summarizes the current scenario of antibiotic and pharmaceutical removal from wastewater using microalgae-mediated technologies.

Development of microalgae-bacteria symbiosis system for enhanced treatment of biogas slurry

In this study, microalgae-bacteria consortia were developed using bacteria and microalgae isolated from biogas slurry for enhanced nutrients recovery and promoted microalgae growth in wastewater. The enhancement rate was introduced to quantify the interaction between bacteria and microalgae. Co-culture of the indigenous microalgae and bacteria could significantly improve the tolerance of microorganisms to pollutants, increase value-added products' production, promote nutrients removal, and reduce carbon emissions compared to mono-culture. The co-culture of Chlorella sp. GZQ001 and Lysinibacillus sp. SJX05 performed best, with its biomass, lipid, protein and fatty acid methyl ester productivities achieved 113.3, 19.2, 40.9 and 3.7 mg·L^-1·d^-1, respectively. The corresponding nutrients removal efficiencies for ammonia nitrogen, total nitrogen, total organic carbon, and total phosphorus were 83.2%, 82.1%, 34.0% and 76.6%, respectively. These results indicated that co-culture of certain indigenous bacteria and microalgae is beneficial to biogas slurry treatment and microalgae growth.

Removal of veterinary antibiotics in swine wastewater using microalgae-based process

Phycoremediation of swine wastewater is an attractive treatment to remove contaminants and simultaneously produce valuable feedstock biomass. However, there is a lack of information about the application of phycoremediation on veterinary antibiotic removal. Thus, this research investigated the degradation of tetracycline, oxytetracycline, chlortetracycline and doxycycline in swine wastewater treated with phycoremediation. The tetracyclines degradation kinetics was adjusted to the pseudo-first-order kinetics model, with kinetic constant k₁ in the following: 0.36 > 0.27>0.19 > 0.18 (d^-1) for tetracycline, doxycycline, oxytetracycline and chlortetracycline, respectively. The maximum concentration of microalgae biomass (342.4 ± 20.3 mg L^-1) was obtained after 11 days of cultivation, when tetracycline was completely removed. Chlortetracycline concentration decreased, generating iso-chlortetracycline and 4-epi-iso-chlortetracycline. Microalgae biomass harvested after antibiotics removal presented a carbohydrate-rich content of 52.7 ± 8.1, 50.1 ± 3.3, 51.4 ± 5.4 and 57.4 ± 10.4 (%) when cultured with tetracycline, oxytetracycline, chlortetracycline and doxycycline, respectively, while the control culture without antibiotics presented a carbohydrate content of 40 ± 6.5%. These results indicate that could be a valuable source for bioenergy conversion.

Quorum sensing signals improve the power performance and chlortetracycline degradation efficiency of mixed-culture electroactive biofilms

Electroactive biofilms (EABs) play an important role in bioelectrochemical systems due to their abilities to generate electrons and perform extracellular electron transfer (EET). Here, we investigated the effects of quorum sensing (QS) signals on power output, chlortetracycline degradation, and structure of EABs in MFCs treating antibiotic wastewater. The voltage output of MFCs with C4-HSL and PQS increased by 21.57% and 13.73%, respectively, compared with that without QS signals. The chlortetracycline degradation efficiency in closed-circuit MFCs with C4-HSL and PQS increased by 56.53% and 50.04%, respectively, which resulted from the thicker biofilms, higher biomass, and stronger activities. Additionally, QS signals induced the heterogeneous distribution of EPS for a balance between self-protection and EET under environmental pressure. Geobacter prevailed by the addition of QS signals to resist high chlortetracycline concentration. Our results provided a broader understanding on regulating EABs within electrode interface to improve their performance for environmental remediation and clean energy development.

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The voltage output of MFCs was enhanced with the addition of QS signals

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QS signals increased the bioelectrochemical degradation efficiency of CTC

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EABs exhibited heterogeneity in composition and interaction by the QS signals

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QS signals induced a balance between self-protection and EET of EABs

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.

Efficient biodegradation of chlortetracycline in high concentration from strong-acidity pharmaceutical residue with degrading fungi

Chlortetracycline (CTC) pharmaceutical residue with strong acidity and in high CTC concentration is a hazardous solid waste. There is a huge attention but few studies on whether and how the CTC raw residue (CRR) can be degraded in microbiological way. In this study, three self-screened fungi, LJ245, LJ302 and LJ318, were used and thoroughly investigated to remove CTC, strong acidity and biotoxicity in CRR. The result disclosed that the concentration of CTC decreased rapidly in the first seven days and declined slowly subsequently, and the decreasing curve was similar to "L" shape. the corresponding degradation ratios of three strains were 95.73%, 98.53% and 98.07%, respectively. Meanwhile, numerous intermediates in degradation appeared in early days and gradually reduced, and eventually disappeared once the degradation time was long enough, among which eleven intermediates from CTC were identified. Moreover, the strong acidity of CRR declined dramatically using this biological method along with the CTC being metabolized, the pH value increased from 2.30 to 8.32 in the first 7 days. The toxicity of CRR was significantly reduced by LJ302 with inhibition rate from 96.02% to no inhibition effect to Micrococcus luteus. Therefore, CTC, strong acidity and biotoxicity of CRR could be effectively removed simultaneously through a biodegradation process driven with proposed strains.

Improving the efficiency of anaerobic digestion: Domesticated paddy soil microbes enhance the hydrolytic acidification of rice straw and pig manure

Improving the efficiency of hydrolytic acidification is critical for methane production from agricultural waste. This study is the first to apply domesticated paddy soil microbes to (DPSM) enhance the hydrolytic acidification of rice straw (RS) and pig manure (PM) to obtain acidizing fluid for anaerobic digestion (AD). At a substrate concentration of 20%, the inoculation of an RS-PM mixture (1:3) with 35% DPSM degraded the volatile solids by 48.1% and yielded 6.8 g/L of volatile fatty acids and 4.7 g/L of acetic acid after seven days of hydrolytic acidification. After 10 days of subsequent AD, the cumulative methane production of the acidizing fluid was 304.96 mL/g COD, similar (P ＞ 0.05) to the control (318.27 mL/g COD). However, the methane production time decreased by 43.4% (from 30 to 17 days), thereby improving the AD efficiency. Inoculation with DPSM is therefore an effective pre-treatment for agricultural waste for methane production.

Luminescent porous metal–organic gels for efficient adsorption and sensitive detection of chlortetracycline hydrochloride assisted by smartphones and test paper-based analytical device

Developing dual functional materials for chlortetracycline hydrochloride (CTC) adsorption and detection is of great importance for wastewater treatment and pollution monitoring. Herein, three novel (Fe-Tb) JLUE-MOGs are synthesized through the...

Enhanced biodegradation of chlortetracycline via a microalgae-bacteria consortium

Microbial removal of Chlortetracycline (CTC) at low CTC concentrations (in the order of 10-20 mg/L) has been reported. In this study, a novel microalgae-bacteria consortium was developed for effective CTC biodegradation at higher concentrations (up to 80 mg/L). The microalgae-bacteria consortium is resistant to up to 80 mg/L CTC, while the pure microalgal culture could only tolerate 60 mg/L CTC. CTC removal in the initial 12 h was primarily via biosorption by the microalgae-bacteria consortium and the adsorption capacity increased from 61.71 to 102.53 mg/g biomass in 12 h. Further, CTC biodegradation by the microalgae-bacteria consortium was catalyzed by extracellular enzymes secreted under antibiotic stress. The symbiotic bacterial diversity was analyzed by high throughput sequencing. The aerobic bacteria Porphyrobacter and Devosia were the dominant genera in the consortium. In the presence of CTC, a microbial community shift occurred with Chloroptast, Spingopyxis, and Brevundimonas being the dominant genera.

Evaluation of growth and biochemical responses of freshwater microalgae Chlorella vulgaris due to exposure and uptake of sulfonamides and copper

Sulfonamides (SAs) and heavy metals are frequently detected together in livestock wastewater. In this study, evaluations regarding their potentially adverse effects on microalgae and according removals were investigated. Results showed that the growth of C. vulgaris was inhibited by SAs and Cu. There was an obvious recovery period in photosynthetic activity (Fv/Fm), indicating that the damage to the photosystem of microalgae was reversible. The co-existence of SAs and Cu significantly affected the biochemical characteristics, including the activities of antioxidant enzyme and the contents of photosynthetic pigments, proteins and polysaccharides. The addition of Cu obviously promoted the removal efficiencies of SMZ, SMX and SMM, which might be ascribed to the bridging effect of Cu in the bioadsorption of SAs. This study is conducive to understand the changes in the biochemical responses of microalgae under the combined impacts of SAs and Cu, and provides a new insight for the simultaneous removals.

Biochemical wastewater from landfill leachate pretreated by microalgae achieving algae's self-reliant cultivation in full wastewater-recycling chain with desirable lipid productivity

Heightened awareness of additional pretreatment for wastewater, has driven studies towards building a full wastewater-recycling chain wherein the wastewater pretreatment is performed by microalgae themselves. We applied biochemical wastewater from landfill leachate with added K₂HPO₄ (BWLL + P) directly to microalgal cultivation. The results showed that the pretreatment provided by the 1st cultivation reduced suspended solids by nearly half, greatly boosting microalgal growth, which thus yielded 1.06 g/L of dry mass and 87.06 mg/L·d of biomass productivity. From the 2nd to the 4th cultivation, lipid accumulation in BWLL + P was 1.12-1.27 times and 1.95-2.36 times higher than in BG11 and BWLL, respectively, mainly attributed to the comfortable environment engendered by the microalgal pretreatment and the organic carbon in the wastewater. Strikingly, the biodiesel production fed with BWLL + P could save 99% of the cost compared with in BG11. In combination, our pioneering full wastewater-recycling chain achieved microalgae's self-reliant cultivation, with wastewater nourishment.

New concept in swine wastewater treatment: development of a self-sustaining synergetic microalgae-bacteria symbiosis (ABS) system to achieve environmental sustainability

Much attention has been paid to developing methods capable of synchronous removal of pollutants from swine wastewater. Due to the natural symbiotic interactions between microalgae and bacteria, the microalgae-bacteria symbiosis (ABS) system has been found to have potential for treating wastewater. However, the corresponding biological mechanisms in the ABS system and the role of dynamic microbial community evolution in pollutant removal systems remain poorly understood. Therefore, we investigate the potential of an ABS system for pollutant removal applications and analyze the bacterial consortium symbiotically combined with Chlorella sp. MA1 and Coelastrella sp. KE4. The NH₄⁺-N and PO₄^3--P removal efficiencies were significantly increased from 12.79% to 99.52% and 35.66% to 96.06% due to biotic interactions between the microalgae and bacteria. The abundance of bacterial taxa and genes related to oxidative stress, cell growth and nitrogen transfer were found to increase in response to photosynthesis, respiration and NH₄⁺-N uptake. Furthermore, pathogen inactivation was induced via microalgae, co-driven by microbial succession under high dissolved oxygen conditions. In this microalgae-enhanced ABS system, the interactions between microalgae and bacteria are established for pathogens elimination and nitrogen cycling, verifying that the ABS system is an effective and environmentally sustainable swine wastewater treatment method.

Effect of acclimatized paddy soil microorganisms using swine wastewater on degradation of rice straw

Rice straw (RS) is one of abundant agricultural waste for biogas production in China. However, the low carbon-methane conversion rate limits its wide application due to the low degradation rate of RS during fermentation. This study investigated the effect of acclimatized paddy soil microorganisms using swine wastewater on degradation of RS before anaerobic digestion. The total organic carbon, reducing sugar and NH₄⁺-N content of paddy soil + RS + swine wastewater (PRS) (653.50 mg/L) was higher than that of other groups after 19 days. The carboxymethyl cellulose activity (4.01 IU), cellulose/lignin ratio (5.25) and the degradation rate of lignin (51.96%) in PRS were higher than those of other groups. The Firmicutes (21.02%), Chloroflexi (12.48%), Proteobacteria (20.92%), and Bacteroidetes (25.78%) were the main fermentation phyla in PRS during acclimatization. These results indicated that the acclimatized paddy soil microorganisms using swine wastewater (SW) could degrade RS more efficiently.