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MgO nanoparticles (NPs) are widely used in bactericides, fuel cells and electronic materials and are frequently detected in aquatic environments. Anaerobic ammonium oxidation (anammox) is a highly efficient and economical autotrophic nitrogen removal process. To date, the effects of MgO NPs on anammox granular sludge have remained unknown. This work systematically evaluated the short- and long-term effects of MgO NPs on anammox process performance and explored an effective strategy to relieve stress. The half maximal inhibitory concentration (IC50) of MgO NPs to anammox granular sludge was 69.5 mg L−1. During the long-term experiment, the anammox process experienced a reduction in nitrogen removal ability under the stress of 50.0 mg L−1MgO NPs. Moreover, the enzymatic activity and synthesis of heme c significantly decreased. Adding 40.0 mg L−1bull serum albumin (BSA) effectively relieved the stress caused by 50.0 mg L−1MgO NPs, and the anammox activity recovered to 97.0% of the original level. Multiple spectral analyses verified the adsorption of MgO NPs by BSA. Furthermore, the formation of an eco-corona was observed by transmission electron microscopy, which also contributed to decreasing the biotoxicity of the MgO NPs. The results of this study provide guidance for treating NP-containing wastewater during the anammox process.

The implementation of mainstream anammox has gained increasing attention. In this study, the feasibility of using sidestream anammox granules to start up mainstream reactors was investigated by comparing two switching strategies. A maximum nitrogen removal potential of 3.6 ± 0.2 kg N m–3d–1was obtained for the reactor after direct switching to mainstream conditions (70 mg TN L–1, 15 °C). Nevertheless, the reactor preacclimatized to 25 °C (Ma) exhibited a higher nitrogen removal potential of 7.0 ± 0.3 kg N m–3d–1at 15 °C, which is the highest volumetric nitrogen removal rate of mainstream anammox reactors to date. Candidatus Kuenenia stuttgartiensiswas identified as the dominant anammox bacterium, and its relative abundance in two reactors remained stable throughout the whole operation (200 days). Moreover, with the aid of acclimatization, the activation energy was reduced and the specific growth rate became higher. These results indicated that the physiological evolution of the dominant anammox bacterium instead of interspecies selection was the main reason for the high potential during the switch to mainstream conditions. Therefore, using sidestream anammox granules as seed sludge to start up mainstream reactors was demonstrated to be feasible, and a switching strategy of acclimatization at 25 °C was recommended.

The development and application of anammox-based nitrogen removal technology is thought to have the potential to boost the evolution of wastewater treatment to a more sustainable model. However, due to the long doubling time and vulnerability to the varying operating conditions of anammox bacteria, the actual application of this technology remains restrained. Nanomaterials have been proposed as external suppliers to stimulate the activity of anammox bacteria. To date, although there are lots of experimental results, the actual effects relating to different types of nanomaterials still remain unclear. Moreover, besides artificially added nanoparticles, anammox may be inhibited by nanomaterials released during the use of nanotechnology products. Addressing the above challenges requires a better understanding of the performance, fate, and mechanism of interaction between various nanomaterials and anammox bacteria. Herein, this review describes the effects of various engineered nanomaterials on the nitrogen removal performance and metabolic properties of anammox bacteria. Also, the intoxication routes of nanomaterials and the detoxification mechanisms of anammox are analyzed and discussed. Finally, future development trends and research directions in this field are proposed.

Nonphotosynthetic microorganisms are typically unable to directly utilize light energy, but light might change the metabolic pathway of these bacteria indirectly by forming intermediates such as reactive oxygen species (ROS). This work investigated the role of light on nitrogen conversion by anaerobic ammonium oxidation (anammox) consortia. The results showed that high intensity light (>20000 lx) caused ca. 50% inhibition of anammox activity, and total ROS reached 167% at 60,000 lx. Surprisingly, 200 lx light was found to induce unexpected promotion of the nitrogen conversion rate, and ultraviolet light (<420 nm) was identified as the main contributor. Metagenomic and metatranscriptomic analyses revealed that the gene encoding cytochrome cperoxidase was highly expressed only under 200 lx light. 15N isotope tracing, gene abundance quantification, and external H2O2addition experiments showed that photoinduced trace H2O2triggered cytochrome cperoxidase expression to take up electrons from extracellular nonfermentative organics to synthesize NADH and ATP, thereby expediting nitrogen dissimulation of anammox consortia. External supplying reduced humic acid into a low-intensity light exposure system would result in a maximal 1.7-fold increase in the nitrogen conversion rate. These interesting findings may provide insight into the niche differentiation and widespread nature of anammox bacteria in natural ecotopes.

A characteristic wavelength for measuring flesh browning of apple was put forward based on FT-NIR spectroscopy. Cluster analysis algorithm based on Euclidean distance was applied to selection of representative samples. The multivariable analysis concluding PLS and MLR were applied to build the regression models and seek the characteristic wavelengths of apple flesh browning. The loading weights from PLS model found the sensitive flesh browning wavelengths. The significance of these wavelengths was by ANOVA, and seven wavelengths (1132, 1411, 1429, 1494, 1580, 1879, and 2151nm) were selected with statistical significance at 95% confidence level. These wavelengths were strongly related with apple flesh browning by MLR models evaluated with high prediction correlation (r=0.937). These suggest the model of apple flesh browning was reliable with good predict ability and can meet the requirement to quick determination of flesh browning of apples.

A rapid and nondestructive method for measuring internal browning of apple was put forward based on FT-NIR spectroscopy and the relationship between NIR spectroscopy nondestructive measurement and internal browning was developed. The NIR spectroscopies were acquired from 512 apples. Cluster analysis algorithm based on Euclidean distance was applied to selection of representative samples. The multivariable analysis concluding partial least squares (PLS) and multiple linear regression (MLR) were applied to build the regression models. The excellent model with high R2 (0.871) was obtained by PLS based on 3 wavelength ranges (950–1440 nm, 1480–1890 nm, 1960–2300 nm) and with multiplicative scatter correction (MSC) pretreatment. These suggest the model of apple internal browning was reliable with good predict ability and can meet the requirement to quick determination of internal browning of apples.

Ganglioside is a kind of acidic glycosphingolipid containing sialic acid. It is the major component of nerve cells and has a very important biological activity. This study is based on the molecular structure of ganglioside and the absorption of stovall stone to various ions. The chromatography media made by stovall stone loading chitosan has a better adsorption to gangliosides. The experiment showed that the best adsorption parameters are 8BV, chloroform: methanol (1:4), PH = 5.5, temperature is 2.0˚C; Resolution: the mixture of chloroform, methanol and 0.9 mol/L NaAC (30:58:12 v/v/v) which is 10 times the volume of the filtrate, 8BV, PH = 5.5, temperature is 1.5˚C and 22BV, 0.3mol/L methanol solution of potassium acetate; 180mg gangliosides with 75% purity were obtained from 300g fresh porcine brain. The recovery rate reached 95%. The target compound was confirmed by IR, UV and HPLC. Compared with the current method, this method is more suitable for industrial production.

Antibiotics are widely found in nitrogen-containing wastewater, which may affect the operation stability of anaerobic ammonium oxidation (anammox)-based biological treatment systems. Extracellular polymeric substances (EPSs) of anammox sludge play a pivotal role in combining with antibiotics; however, the exact role and how the structure of the leading component of EPSs (i.e., extracellular proteins) changes under antibiotic stress remain to be elucidated. Here, the interaction between sulfamethoxazole and the extracellular proteins of anammox sludge was investigated via multiple spectra and molecular simulation. Results showed that sulfamethoxazole statically quenched the fluorescent components of EPSs, and the quenching constant of the aromatic proteins was the largest, with a value of 1.73 × 104M–1. The overall binding was an enthalpy-driven process, with ΔH= −75.15 kJ mol–1, ΔS= −0.175 kJ mol–1K–1, and ΔG= −21.10 kJ mol–1at 35 °C. The O-P-O and C═O groups responded first under the disturbance of sulfamethoxazole. Excessive sulfamethoxazole (20 mg L–1) would decrease the ratio of α-helix/(β-sheet + random coil) of extracellular proteins, resulting in a loose structure. Molecular docking and dynamic simulation revealed that extracellular proteins would provide abundant sites to bind with sulfamethoxazole, through hydrogen bond and Pi-Akyl hydrophobic interaction forces. Once sulfamethoxazole penetrates into the cell surface and combines with the transmembrane ammonium transport domain, it may inhibit the NH4+transport. Our findings enhance the understanding on the interaction of extracellular proteins and sulfamethoxazole, which may be valuable for deciphering the response property of anammox sludge under the antibiotic stress.