Simultaneous removal of ammonia nitrogen, phosphate, zinc, and phenol by degradation of cellulose in composite mycelial pellet bioreactor: Enhanced performance and community co-assembly mechanism.

In this experiment, the prepared tea biochar-cellulose@LDH material (TB-CL@LDH) was combined with mycelium pellets to form the composite mycelial pellets (CMP), then assembled and immobilized with strains Pseudomonas sp. Y1 and Cupriavidus sp. ZY7 to construct a bioreactor. At the best operating parameters, the initial concentrations of phosphate (PO43--P), ammonia nitrogen (NH4+-N), chemical oxygen demand (COD), zinc (Zn2+), and phenol were 22.3, 25.0, 763.8, 1.0, and 1.0 mg L-1, the corresponding removal efficiencies were 80.4, 87.0, 83.4, 91.8, and 96.6%, respectively. Various characterization analyses demonstrated that the strain Y1 used the additional carbon source produced by the strain ZY7 degradation of cellulose to enhance the removal of composite pollutants and clarified the principle of Zn2+ and PO43--P removal by adsorption, co-precipitation and biomineralization. Pseudomonas and Cupriavidus were the dominant genera according to the high-throughput sequencing. As shown by KEGG results, nitrification and denitrification genes were affected by phenol. The study offers prospects for the simultaneous removal of complex pollutants consisting of NH4+-N, PO43--P, Zn2+, and phenol.

Immobilized bioreactor for enhanced ammonia, phosphorus, and phenol removal and effects of phenol on microbial communities, potential functions, and nitrogen metabolism.

In the present study, an immobilized bioreactor was established to remove ammonia (NH4+-N), phosphate (PO43--P), and phenol using composite mycelium spheres (CMP) as the immobilization material in combination with Pseudomonas sp. Y1. Under optimal operating conditions, the bioreactor achieved 98.07, 91.71, and 92.57 % removal of NH4+-N, PO43--P, and phenol, respectively. The results showed that the bioreactor removed PO43--P by biomineralization and co-precipitation. Phenol removal relied on a Fenton-like reaction achieved by CMP-induced quinone redox cycling. High-throughput sequencing analysis and functional gene prediction indicated that Pseudomonas was the dominant genus and that the bioreactor had much potential for nitrogen removal, respectively. In addition, phenol affected the performance of functional genes and the associated enzymes, which influenced the nitrogen metabolism process in the bioreactor. This work serves as a guideline for the development of more stable and sustainable composite pollution removal technologies and fungal-bacterial symbiotic systems.

Enhanced ammonia nitrogen and phenol removal by immobilized bacteria through composite mycelium pellet-driven quinone redox cycle.

The composite mycelium pellet (CMP) was coupled with Pseudomonas sp. Y1 (CMP-Y1) to remove phenol and ammonia nitrogen (NH4+-N). The CMP was formed by the self-assembly of fungal mycelium with sponge iron (SIO), gallic acid (GA), and oxalic acid. The results showed that CMP with abundant pore size and successful internal loading of sponge iron containing iron nanoparticles. CMP could induce GA redox cycle to form Fenton-like reaction and thus achieve efficient phenol removal (93.32%, 24 h). Meanwhile, the removal efficiencies of phenol, NH4+-N, and chemical oxygen demand (COD) using CMP-Y1 at 12 h were 93.71, 92.40, and 89.00%, respectively. The increase in the electron transfer activity of strain Y1 by the addition of CMP could facilitate the nitrogen removal processes. In addition, high-throughput sequencing results indicated the abundance of antioxidant and repair genes was increased, which might be a strategy of strain Y1 to cope with oxidative stress. This strategy provided the possibility for the practical application of the combination of advanced oxidation and biological treatment, and offered new insights into the symbiotic system of fungi and bacteria.

Simultaneous removal of ammonia nitrogen, recovery of phosphate, and immobilization of nickel in a polyester fiber with shell powder and iron carbon spheres bioreactor: Optimization and pathways mechanism.

Composite pollutants are prevalent in wastewater, whereas, the simultaneous accomplishment of efficient nitrogen removal and resources recovery remains a challenge. In this study, a bioreactor was constructed to contain Pseudomonas sp. Y1 using polyester fiber wrapped with shell powder and iron carbon spheres, achieving ammonia nitrogen (NH4+-N) removal, phosphate (PO43--P) recovery, and nickel (Ni2+) immobilization. The optimal performance of bioreactor was average removal efficiencies of NH4+-N, PO43--P, calcium (Ca2+), and Ni2+ as 82.42, 96.67, 76.13, and 98.29% at a hydraulic retention time (HRT) of 6 h, pH of 7.0, and influent Ca2+ and Ni2+ concentrations of 100.0 and 3.0 mg L-1, respectively. The bioreactor could remove PO43--P, Ca2+, and Ni2+ by biomineralization, co-precipitation, adsorption, and lattice substitution. Moreover, microbial community analysis suggested that Pseudomonas was the predominant genus and had possessed tolerance to Ni2+ toxicity in wastewater. This study presented an effective method to synchronously remove NH4+-N, recover PO43--P, and fix heavy metals through microbially induced carbonate precipitation (MICP) and heterotrophic nitrification and aerobic denitrification (HNAD) technology.

Enhanced nitrate and cadmium removal performance at low carbon to nitrogen ratio through immobilized redox mediator granules and functional strains in a bioreactor.

The coexistence of multiple pollutants and lack of carbon sources are challenges for the biological treatment of wastewater. To achieve simultaneous removal of nitrate (NO3--N) and cadmium (Cd2+) at low carbon to nitrogen (C/N) ratios, 2-hydroxy-1,4-naphthoquinone (HNQ) was selected from three redox mediators as an accelerator for denitrification of heterotrophic strain Pseudomonas stutzeri sp. GF2 and autotrophic strain Zoogloea sp. FY6. Then, halloysite nanotubes immobilized with 2-hydroxy-1,4-naphthoquinone (HNTs-HNQ) were prepared and a bioreactor was constructed with immobilized redox mediator granules (IRMG) as the carrier, which was immobilized with HNTs-HNQ and inoculated with the two strains. The immobilized HNQ and the inoculated strains jointly improved the removal ability of NO3--N and Cd2+ and the removal efficiency of NO3--N (25.0 mg L-1) and Cd2+ (5.0 mg L-1) were 92.81% and 93.94% at C/N = 1.5 and hydraulic retention time (HRT) = 4 h. The Cd2+ was removed by adsorption of iron oxides (FeO(OH) and Fe3O4) and IRMG. The electron transport system activity (ETSA) of bacteria was improved and the composition of dissolved organic matter in the effluent was not affected by HNQ. The HNQ promoted the production of FeO(OH) and up-regulated the proportion of Zoogloea (54.75% in the microbial community), indicating that Zoogloea sp. FY6 was dominant in the microbial community. In addition, HNQ influenced the metabolic pathways and improved the relative abundance of some genes involved in nitrogen metabolism and the iron redox cycle.

Effect of fungal pellets on denitrifying bacteria at low carbon to nitrogen ratio: Nitrate removal, extracellular polymeric substances, and potential functions.

This research aims to elucidate the effect of fungal pellets (FP) on denitrifying bacteria regarding nitrate (NO3--N) removal, extracellular polymeric substances (EPS), and potential functions at a low carbon to nitrogen (C/N) ratio. A symbiotic system of FP and denitrifying bacteria GF2 was established. The symbiotic system showed 100% NO3--N removal efficiency (4.07 mg L-1 h-1) at 6 h and enhanced electron transfer capability at C/N = 1.5. The interactions between FP and denitrifying bacteria promoted the production of polysaccharides (PS) in EPS. Both the increased PS and the PS provided by FP as well as protein and humic acid-like substances in EPS could be consumed by denitrifying bacteria. FP acted as a protector and provided habitat and nutrients for denitrifying bacteria as well as improved the ability of carbohydrate metabolism, amino metabolism, and nitrogen metabolism of denitrifying bacteria. This study provides a new perspective on the relationship between FP and denitrifying bacteria.

Fungal-sponge composite carriers coupled with denitrification and biomineralization bacteria to remove nitrate, calcium, and cadmium in a bioreactor.

The coexistence of nitrate (NO3--N) and heavy metals in the aquatic environment causes harm to both the aquatic ecosystem and human health. Here, fungal-sponge composite carriers (FSC) were assembled and immobilized with strain WZ39 in a bioreactor to remove NO3--N, Ca2+, and Cd2+. Stable bioreactor performance under heavy metal pressure was achieved. The highest removal efficiencies of NO3--N, Ca2+, and Cd2+ reached 100, 71.81, and 92.50%, respectively. Bacteria and precipitates were found in fungal mycelium and sponge. The precipitates composed of Ca3.9(Ca4.7Cd0.7)(PO4)6(OH)1.8, CaCO3, and CdCO3. Fluorescence excitation-emission matrix (EEM) and flow cytometric (FCM) analysis indicated bacteria in FSC exhibited a strong metabolic activity and high percentage of intact cells under heavy metal stress. High-throughput sequencing results showed Pseudomonas sp. WZ39 played a major role in the bioreactor. The potential functions associated with metabolism, heavy metal transfer, and biofilm formation had high relative abundance in the bioreactor.

Denitrifying bacteria immobilized magnetic mycelium pellets bioreactor: A new technology for efficient removal of nitrate at a low carbon-to-nitrogen ratio.

This study integrated spores and magnetite (Fe3O4) to form magnetic mycelium pellets (MMP) as bio-carriers immobilized with denitrifying bacteria in a bioreactor. Different carbon-to-nitrogen (C/N) ratios and hydraulic retention time (HRT) were established for investigating the performance of the bioreactor. The nitrate removal efficiency was 98.14% at C/N = 2.0 and HRT = 6 h. Gas chromatography (GC) results indicated that the main component of the produced gas was N2. Fe3O4 was well-integrated into MMP according to X-ray diffraction (XRD) results and infrared spectrometer (FTIR) analysis. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that bacteria were successfully immobilized on MMP. Fluorescence excitation-emission matrix (EEM) indicated that functional bacteria GF2 might enhance the metabolic activity of the microbial community in the bioreactor and microbial activity was highest at C/N = 2.0. Pseudomonas stutzeri sp. GF2 might be immobilized and had a major role in the bioreactor according to high throughput sequencing results.