Strategy and mechanisms of sulfamethoxazole removal from aqueous systems by single and combined Shewanella oneidensis MR-1 and nanoscale zero-valent iron-enriched biochar

Enhanced tetracycline degradation through electron transfer activated by Bacillus cereus synthesized bio-FeS nanoparticles

The synthesis of bio-FeS nanoparticles (NPs) was generally using Gram-negative bacteria and mostly in anaerobic systems, thus limiting their application in the degradation of toxic wastewater. In this study, we successfully synthesized bio-FeS NPs for the first time using the resilient Gram-positive bacterium Bacillus cereus, with the objective of investigating the mechanism of promoting electron transfer in the aerobic/anaerobic degradation of tetracycline (TC). The degradation efficiency of TC was increased by 2.84 and 4.74 times, respectively, under aerobic and anaerobic conditions. Furthermore, the bio-FeS NPs were observed to significantly reduce the activation energy and Gibbs free energy, especially under aerobic conditions. It was found that bio-FeS NPs promoted intracellular electron transfer mainly through activating or replacing the Fe-S centers. The bio-FeS NPs significantly increased ETS activity and NADH levels, indicating that the dehydrogenase activity and intracellular electron transfer efficiency were increased. The bio-FeS NPs formed electron transfer channels inside and outside the cell, provided an effective way for the transfer of electron shuttles from intracellular to extracellular, and improved the extracellular redox activity. This study offered new insights and theories into the role of Gram-positive bacteria in the synthesis of bio-FeS NPs for the remediation of toxic wastewater.

The key role of magnetic iron-to-biochar mass ratios in the dissipation of oxytetracycline and its resistance genes in soils with and without biodegradable microplastics

There are challenges involved in the synergistic dissipation of antibiotics and antibiotic resistance genes (ARGs) in soil because ARGs are affected by not only the selective pressure of antibiotics but also microbial community succession and co-existing pollutants. Here, magnetic biochars (MBCs) at various magnetic iron-to-biochar mass ratios (3:1, 2:1, 1:1, 1:2, 1:3, 1:5, and 1:7) were synthesized to develop a strategy for the synergistic dissipation of oxytetracycline (OTC) and its resistance gene (tet) in soils with and without polybutylene adipate terephthalate (PBAT) microplastics (MPs). The results showed that MBC12 (1:2) achieved the greatest dissipation efficiencies of OTC in soils without and with PBAT MPs (95.27% and 94.50%, respectively). The reductive degradation of OTC via promoting the electron transfer during conversion between Fe(III) and Fe(II) overwhelmed biodegradation of OTC. MBCs effectively hindered the spread of tet in soil without PBAT MPs, with the efficiencies more than 60%; but they had little influence on its spread in soil with PBAT MPs, excluding MBC15 (1:5). The absolute abundance of tet, regardless of PBAT MPs, just significantly positively correlated with Serratia (the added exogenous tet-host bacterium), indicating that MBCs inhibited the horizontal transfer of tet at the inter-genus level. Down-regulating the degradation/utilization/assimilation metabolic function by MBCs (excluding MBC31, 3:1) contributed to the hindering class 1 integron gene (intI1)-driven tet propagation. After considering efficiency, cost and toxic effects, MBC12 (1:2) was recommended to use for synergistic dissipation of OTC and tet in soils without and with PBAT MPs.

Nano-micro materials regulated biocatalytic metabolism for efficient environmental remediation: Fine engineering the mass and electron transfer in multicellular environments

The escalating energy and environmental crises have spurred significant research interest into developing efficient biological remediation technologies for sustainable contaminant and resource conversion. Integrating engineered nano-micro materials (NMMs) with these biocatalytic processes offers a promising approach to improve the microbial performance for environmental remediation. Core to such material-enhanced hybrid biocatalysis systems (MHBSs) is the rational regulation of metabolic processes with the assistance of NMMs, where a fine engineered mass and electron transfer is beneficial for the improved biocatalytic activity. However, the specific mechanisms of those NMMs-enhanced microbial metabolisms are normally overlooked. Here, we review the recent progress in MHBSs, focusing primarily on the mass/electron transfer regulation strategies for an enhanced microbial behavior. Specifically, the NMMs-regulated mass and electron transfer in extracellular, interfacial, and intracellular environment are summarized, where the patterns of diverse microbiological response are discussed thoroughly. Notably, fine modifications of cell interfaces and intracellular compartments by NMMs could even endow the biohybrids with new metabolic functions beyond their natural capabilities. Further, we also emphasize the importance of matching the various metabolic demands of biosystems with the diverse properties of NMMs to achieve efficient environmental remediation through a coordinated regulation strategy. Finally, major challenges and opportunities for the future development and practical implementation of MHBSs for environment remediation practices are given, aiming to provide future system design guidelines for attaining desirable biological behaviors.

Performances of a novel BAF with ferromanganese oxide modified biochar (FMBC) as the carriers for treating antibiotics, nitrogen and phosphorus in aquaculture wastewater

In this paper, a biological aerated filter (BAF) based on ferromanganese oxide-biochar (FMBC) was constructed to investigated the removal performance and mechanism for conventional pollutants and four kinds of antibiotic, in contrast of conventional zeolite loaded BAF (BAF-A) and bamboo biochar filled BAF (BAF-B). Results showed that the average removal efficiency of total nitrogen (TN), total phosphorus (TP) and antibiotics in a FMBC-BAF (named by BAF-C) were 52.97 ± 2.27%, 51.58 ± 1.92% and 70.36 ± 1.00% ~ 81.65 ± 0.99% respectively in running period (39-100 d), which were significantly higher than those of BAF-A and BAF-B. In the BAF-C, the expression of denitrification enzyme activities and the secretion of extracellular polymeric substance (EPS) especially polyprotein (PN) were effectively stimulated, as well as accelerated electron transfer activity (ETSA) and lower electrochemical impedance spectroscopy (EIS) were acquired. After 100 days of operation, the abundance of nitrogen, phosphorus and antibiotic removal functional bacteria like Sphingorhabdus (4.52%), Bradyrhizobium (1.98%), Hyphomicrobium (2.49%), Ferruginibacter (7.80%), unclassified_f_Blastoca tellaceae (1.84%), norank_f_JG30-KF-CM45 (6.82%), norank_f_norank_o_SBR1031 (2.43%), Nitrospira (2.58%) norank_f_Caldilineaceae (1.53%) and Micropruina (1.11%) were enriched. Mechanism hypothesis of enhanced performances of nutrients and antibiotics removal pointed that: The phosphorus was removed by adsorption and precipitation, antibiotics removal was mainly achieved through the combined action of adsorption and biodegradation, while nitrogen removal was realized by biologic nitrification and denitrification in a FMBC-BAF for aquaculture wastewater treatment.

Sonophotocatalytic degradation of sulfamethoxazole using lanthanum ferrite perovskite oxide anchored on an ultrasonically exfoliated porous graphitic carbon nitride nanosheet

The lanthanum ferrite perovskite (La0.8FO) was synthesized using a citric combustion route and then modified with a porous graphitic nitride nanosheet via the wet impregnation-assisted ultrasonic method to produce La0.8FO@PgNS. Various techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet diffuse reflectance spectroscopy (UV-DRS), and Tauc plot analysis were employed to confirm the functional moieties, crystallinity, phase change, morphology, composition, and bandgap of La.0.8FO and La0.8FO@PgNS. La0.8FO and La0.8FO@PgNS were used for the sonophotocatalytic oxidative degradation of sulfamethoxazole (SMX) under low energy and ultrasound wave frequency in the presence of visible light. La0.8FO and La0.8FO@PgNS exhibited a sonophotocatalytic degradation capacity of 52.06 and 99.60%, respectively. Furthermore, the rate constant at the optimum condition of pH 7 and 5 mg L-1 concentration was 0.01343 and 0.01494 min-1 for La0.8FO and La0.8FO@PgNS, respectively. The integration of sonolysis and photocatalysis in the remediation process of SMX resulted in a synergy of 2.5-fold. Ultrasonic waves and hydroxyl and superoxide radicals are the main species governing the degradation process while La0.8FO@PgNS was stable over 8 cycles, proving to be a sustainable material for environmental remediation.

Affecting factors and mechanism of removing antibiotics and antibiotic resistance genes by nano zero-valent iron (nZVI) and modified nZVI: A critical review

Antibiotics and antibiotic resistance genetic pollution have become a global environmental and health concern recently, with frequent detection in various environmental media. Therefore, finding ways to control antibiotics and antibiotic resistance genes (ARGs) is urgently needed. Nano zero-valent iron (nZVI) has shown a positive effect on antibiotics degradation and restraining ARGs, making it a promising solution for controlling antibiotics and ARGs. However, given the current increasingly fragmented research focus and results, a comprehensive review is still lacking. In this work, we first introduce the origin and transmission of antibiotics and ARGs in various environmental media, and then discuss the affecting factors during the degradation of antibiotics and the control of ARGs by nZVI and modified nZVI, including pH, nZVI dose, and oxidant concentration, etc. Then, the mechanisms of antibiotic and ARGs removal promoted by nZVI are also summarized. In general, the mechanism of antibiotic degradation by nZVI mainly includes adsorption and reduction, while promoting the biodegradation of antibiotics by affecting the microbial community. nZVI can also be combined with persulfates to degrade antibiotics through advanced oxidation processes. For the control of ARGs, nZVI not only changes the microbial community structure, but also affects the proliferation of ARGs through affecting the fate of mobile genetic elements (MGEs). Finally, some new ideas on the application of nZVI in the treatment of antibiotic resistance are proposed. This paper provides a reference for research and application in this field.