Efficient phosphorus removal by a novel halotolerant fungus Aureobasidium sp. MSP8 and the application potential in saline industrial wastewater treatment

Montmorillonite‑sodium alginate/chitosan beads: A green potential solution for phosphorus removal from wastewater and slow-release phosphorus fertilizer application

Effective recovery of phosphorus from wastewater and its subsequent reutilization are crucial for controlling water eutrophication and promoting resourceful utilization of pollutants. In this study, an eco-friendly and highly efficient montmorillonite‑sodium alginate/chitosan beads (CS/SA-FeMT) was synthesized via the semi-interpenetrating network method for phosphorus adsorption, and its potential application as a fertilizer after phosphorus adsorption was also preliminarily investigated. The results revealed that the surface of CS/SA-FeMT was coated with granular montmorillonite, exhibiting a rougher layered stacking structure. Consequently, the phosphorus adsorption capacity of CS/SA-FeMT was significantly enhanced compared to montmorillonite or sodium alginate/chitosan beads alone, reaching a maximum adsorption capacity of 88.3 mg P/g. Furthermore, the adsorption interference experiment indicated that the CS/SA-FeMT composite demonstrated exceptional resistance to interference from common ions (Cl-, SO42- and NO3-) and organic acids (humic acid and fulvic acid) typically found in wastewater. Additionally, the CS/SA-FeMT exhibited low leaching of Fe and Ca, and maintained 81.65 % phosphorus adsorption efficiency after five adsorption/desorption cycles. The adsorption mechanism of CS/SA-FeMT was primarily attributed to electrostatic attraction, surface precipitation, ligand exchange, and ion exchange. In addition, the phosphorus release characteristics showcased the CS/SA-FeMT hydrogel beads' exceptional slow-release capabilities, with complete phosphorus release (>99 %) achieved within 19, 19, and 20 days in deionized water at pH levels of 5, 7, and 9, respectively. Overall, CS/SA-FeMT demonstrated excellent potential for removal phosphorus from water and further use as a phosphorus fertilizer.

Boosting the phosphate adsorption of calcite by low Mg2+-Doping

Calcite is a promising material choice for adsorbing phosphates because of its abundance and environmentally benign nature. However, the slow adsorption kinetics and hence low adsorption capacity within a short time frame hinders its practical application. In this work, we solve these problems by presenting a low Mg2+-doped calcite adsorbent, Mg-10. With a 3.75 wt% of Mg2+ doping, Mg-10 exhibits a remarkable adsorption capacity of 157.7 mg P/g. It also demonstrates a substantial boost in the adsorption kinetics, achieving a sixfold increase in adsorption capacity within 24 h compared to the undoped calcite. Meanwhile, Mg-10 not only offers improved adsorption selectivity but also maintains a stable effluent pH, underscoring its environmental compatibility. By conducting soil column experiments, we find that Mg-10 quickly captures the excess phosphates during the mimicking fertilization process, and slowly releases the nutrient afterwards, which can increase the feralization efficiency. These results provide alternative strategies for managing phosphate pollution originated from fertilization, and underscores the potential of Mg-10 in sustainable agriculture and environmental remediation.

Simultaneous aerobic nitrogen and phosphorus removal by novel halotolerant fungus Mucor circinelloides SNDM1: Function and metabolism pathway

Fungi capable of simultaneous nitrogen and phosphorus removal from wastewater is rarely found. Here, a novel fungal strain (SNDM1) performing heterotrophic nitrification, aerobic denitrification, and phosphate removal was isolated and identified as Mucor circinelloides. The favorable nutrient removal conditions by the strain using glucose were C/N ratios of 25-30, salinities of 0 %-3 %, and pH of 7.5. Strain SNDM1 achieved ammonium, nitrite, nitrate, and phosphate removal rates of 5.23, 10.08, 4.88, and 0.97 mg/L/h. Nitrogen balance indicated that gaseous (18.60 %-24.55 %) and intracellular nitrogen (43.76 %-70.63 %) were primary fate of initial nitrogen. Enzyme activity revealed that ammonium removal occurred through heterotrophic nitrification and aerobic denitrification. Removed phosphorus was mainly transformed into cell membranes (56 %-64 %) and extracellular polymeric substances (20 %-26 %). Orthophosphate was the major intracellular phosphorus species, while polyphosphate and pyrophosphate existed extracellularly. These findings highlight the potential of this fungal strain for bioremediating polluted wastewater.

Unraveling the effects and mechanisms of antibiotics on aerobic simultaneous nitrogen and phosphorus removal by Acinetobacter indicus CZH-5

The effects of antibiotics, such as tetracycline, sulfamethoxazole, and ciprofloxacin, on functional microorganisms are of significant concern in wastewater treatment. This study observed that Acinetobacter indicus CZH-5 has a limited capacity to remove nitrogen and phosphorus using antibiotics (5 mg/L) as the sole carbon source. When sodium acetate was supplied (carbon/nitrogen ratio = 7), the average removal efficiencies of ammonia-N, total nitrogen, and orthophosphate-P increased to 52.46 %, 51.95 %, and 92.43 %, respectively. The average removal efficiencies of antibiotics were 84.85 % for tetracycline, 39.32 % for sulfamethoxazole, 18.85 % for ciprofloxacin, and 23.24 % for their mixtures. Increasing the carbon/nitrogen ratio to 20 further improved the average removal efficiencies to 72.61 % for total nitrogen and 97.62 % for orthophosphate-P (5 mg/L antibiotics). Additionally, the growth rate and pollutant removal by CZH-5 were unaffected by the presence of 0.1-1 mg/L antibiotics. Transcriptomic analysis revealed that the promoted translation of aceE, aarA, and gltA genes provided ATP and proton -motive forces. The nitrogen metabolism and polyphosphate genes were also affected. The expression of acetate kinase, dehydrogenase, flavin mononucleotide enzymes, and cytochrome P450 contributed to antibiotic degradation. Intermediate metabolites were investigated to determine the reaction pathways.

Advances in Aureobasidium research: Paving the path to industrial utilization

We here explore the potential of the fungal genus Aureobasidium as a prototype for a microbial chassis for industrial biotechnology in the context of a developing circular bioeconomy. The study emphasizes the physiological advantages of Aureobasidium, including its polyextremotolerance, broad substrate spectrum, and diverse product range, making it a promising candidate for cost-effective and sustainable industrial processes. In the second part, recent advances in genetic tool development, as well as approaches for up-scaled fermentation, are described. This review adds to the growing body of scientific literature on this remarkable fungus and reveals its potential for future use in the biotechnological industry.

Black yeasts in hypersaline conditions

Extremotolerant and extremophilic fungi are an important part of microbial communities that thrive in extreme environments. Among them, the black yeasts are particularly adaptable. They use their melanized cell walls and versatile morphology, as well as a complex set of molecular adaptations, to survive in conditions that are lethal to most other species. In contrast to extremophilic bacteria and archaea, these fungi are typically extremotolerant rather than extremophilic and exhibit an unusually wide ecological amplitude. Some extremely halotolerant black yeasts can grow in near-saturated NaCl solutions, but can also grow on normal mycological media. They adapt to the low water activity caused by high salt concentrations by sensing their environment, balancing osmotic pressure by accumulating compatible solutes, removing toxic salt ions from the cell using membrane transporters, altering membrane composition and remodelling the highly melanized cell wall. As protection against extreme conditions, halotolerant black yeasts also develop different morphologies, from yeast-like to meristematic. Genomic studies of black yeasts have revealed a variety of reproductive strategies, from clonality to intense recombination and the formation of stable hybrids. Although a comprehensive understanding of the ecological role and molecular adaptations of halotolerant black yeasts remains elusive and the application of many experimental methods is challenging due to their slow growth and recalcitrant cell walls, much progress has been made in deciphering their halotolerance. Advances in molecular tools and genomics are once again accelerating the research of black yeasts, promising further insights into their survival strategies and the molecular basis of their adaptations. KEY POINTS: • Black yeasts show remarkable adaptability to environmental stress • Black yeasts are part of microbial communities in hypersaline environments • Halotolerant black yeasts utilise various molecular and morphological adaptations.

Municipal sludge biochar skeletal sodium alginate beads for phosphate removal

A novel Fe/La decorative biochar filled in sodium alginate beads (SA-KBC-Fe/La) was prepared by a simple sol-gel method and applied to adsorb phosphate (P) efficiently from water in this study. The morphology, structure and chemical component of the hydrogel beads were characterized in detail. And the synthesized bead exhibited easy separation and high P uptake of 46.65 mg/g when the Fe: La was of 1: 2 at 298 K with initial P of 100 mg/L, which was much higher than SA gel bead. The adsorption showed that the optimal pH was 6, and the adsorption was met with pseudo-second-order kinetics and Langmuir isothermal models, indicating a chemical adsorption process. The adsorption capacity remained 82 % after 5 cycles of adsorption. The adsorption mechanism of P was mainly of ligand exchange and electrostatic attraction. Compared with other reported adsorbents, the modification of Fe/La could enhance the mechanical property of SA-KBC-Fe/La beads with increasing active sites. Additionally, the involved biochar could lead to excellent thermal stability and hierarchical porous structure of beads with larger specific surface area (54.22 m2/g). The study could provide new ideas for P removal and strategy for the final disposal of municipal sludge.

Simultaneous inorganic nitrogen and phosphate removal by aerobic-heterotrophic fungus Fusarium keratoplasticum FSP1: Performance, pathway and application

Fungi with multiple contaminant removal function have rarely been studied. Here, a novel fungal strain Fusarium keratoplasticum FSP1, which was isolated from halophilic granular sludge, is reported for first time to perform simultaneous nitrogen and phosphate removal. The strain showed wide adaptability under C/N ratios of 30-35, salinities of 0 %-3 % (m/v), and pH of 7.5-9.5. The maximum removal rates of ammonium, nitrate and nitrite were 4.43, 4.01 and 2.97 mg N/L/h. The nitrogen balance, enzyme activity and substrate conversion experiments demonstrated a single strain FSP1 can assimilate inorganic nitrogen and convert inorganic nitrogen to gaseous nitrogen through heterotrophic nitrification or aerobic denitrification. About 39 %-42 % of the degraded phosphorus was in the extracellular polymeric substances (EPS). Orthophosphate was the main phosphorus species in the cell, whereas phosphate monoester and diester were in the EPS. The novel strain FSP1 is a potential candidate for wastewater treatment.

A novel hypothermic strain, Pseudomonas reactans WL20-3 with high nitrate removal from actual sewage, and its synergistic resistance mechanism for efficient nitrate removal at 4 °C

Nitrate can be well removed by bacteria at 25-30 °C. However, nitrate removal almost ceases at temperatures lower than 5 °C. In this study, a novel hypothermic strain, Pseudomonas reactans WL20-3 exhibited an excellent aerobic nitrate removal ability at 4 °C. It had high capability for the removal of nitrate, total dissolved nitrogen (TDN), and dissolved organic carbon (DOC) at 4 °C, achieving removal efficiencies of 100%, 87.91%, and 97.48%, respectively. The transcriptome analysis revealed all genes involved in the nitrate removal pathway were significantly up-regulated. Additionally, the up-regulation of ABC transporter genes and down-regulation of respiratory chain genes cooperated with the nitrate metabolism pathway to resist low-temperature stress. In actual sewage, inoculated with WL20-3, the nitrate removal efficiency was found to be 70.70%. Overall, these findings demonstrated the impressive capacity of the novel strain WL20-3 to remove nitrate and provided novel insights into the synergistic resistance mechanism of WL20-3 at low temperature.

An overview of deploying membrane bioreactors in saline wastewater treatment from perspectives of microbial and treatment performance

The discharged saline wastewater has severely influenced the aquatic environment as the treatment performance of many wastewater treatment techniques is limited. In addition, the sources of saline wastewater are also plentiful from agricultural and various industrial fields such as food processing, tannery, pharmaceutical, etc. Although high salinity levels negatively impact the performance of both physicochemical and biological processes, membrane bioreactor (MBR) processes are considered as a potential technology to treat saline wastewater under different salinity levels depending on the adaption of the microbial community. Therefore, this study aims to systematically review the application of MBR widely used in the saline wastewater treatment from the perspectives of microbial structure and treatment efficiencies. At last, the concept of carbon dioxide capture and storage will be proposed for the MBR-treating saline wastewater technologies and considered toward the circular economy with the target of zero emission.

Eggshell based biochar for highly efficient adsorption and recovery of phosphorus from aqueous solution: Kinetics, mechanism and potential as phosphorus fertilizer

Development of an efficient and green adsorbent is of great significance for phosphorus removal and recovery from eutrophic water. This work prepared an eggshell modified biochar (ESBC) by co-pyrolysis of eggshells and corn stalk. ESBC exhibited an excellent performance for phosphorus adsorption over a wide pH range (5-13), and achieved a maximum adsorption of 557.0 mg P/g. The adsorption process was well fitted by pseudo-second-order model (R² > 0.962) and Sips model (R² > 0.965), and it was endothermic (ΔH⁰ > 0) and spontaneous (ΔG⁰ < 0) according to thermodynamic analysis. The column experiment confirmed the feasibility of ESBC as a filter media for phosphorus removal in flow condition, and obtained a P removal of 460.0 mg/g. Soil burial tests indicated P-laden ESBC has a good P slow-release performance (maintained for up to 25 days). Overall, ESBC has a promising application potential as an efficient adsorbent for phosphorus recovery and subsequently as a slow-release fertilizer.

A novel biotechnology based on periphytic biofilms with N-acyl-homoserine-lactones stimulation and lanthanum loading for phosphorus recovery

This study presents an approach for developing periphytic biofilm with N-acyl-homoserine-lactones (AHLs) stimulation and lanthanum (La, a rare earth element) loading, to achieve highly efficient and stable phosphorus (P) recovery from wastewater. AHLs stimulated biofilm growth and formation, also improved stable P entrapment by enhancing extracellular polymeric substance (EPS) production and optimizing P-entrapment bacterial communities. Periphytic biofilms loading La is based on ligand exchanges, and La loading achieved initial rapid P entrapment by surface adsorption. The combination of AHLs stimulation and La loading achieved 99.0% P entrapment. Interestingly, the enhanced EPS production stimulated by AHLs protected biofilms against La. Moreover, a method for P and La separately recovery from biofilms was developed, achieving 89-96% of P and 88-93% of La recovery. This study offers a promising biotechnology to reuse La from La-rich wastewater and recover P by biofilm doped with La, which results in a win-win situation for resource sustainability.