The synergistic effect of oxidant-peroxide coupling systems for water and wastewater treatments

With the growing complexity and severity of water pollution, it has become increasingly challenging to effectively remove contaminants or inactivate microorganisms just by traditional chemical oxidants such as O3, chlorine, Fe(VI) and Mn(VII). Up till now, numerous studies have indicated that these oxidants in combination with peroxides (i.e., hydrogen peroxide (H2O2), peroxymonosulfate (PMS), peracetic acid (PAA) and periodate (PI)) exhibited excellent synergistic oxidation. This paper provided a comprehensive review on the combination of aforementioned oxidant-peroxide applied in water and wastewater treatments. From one aspect, the paper thoroughly elucidated the synergy mechanism of each oxidant-peroxide combination in turn. Among these combinations, H2O2 or PMS generally performed as the activator of four traditional oxidants above to accelerate reactive species generation and therein various reaction mechanisms, including electron transfer, O atom abstraction and oxo ligand substitution, were involved. In addition, although neither PAA nor PI was able to directly activate Fe(VI) and Mn(VII), they could act as the stabilizer of intermediate reactive iron/manganese species to improve the latter utilization efficiency. From another aspect, this paper summarized the influence of water quality parameters, such as pH, inorganic ions and natural organic matter (NOM), on the oxidation performance of most combined systems. Finally, this paper highlighted knowledge gaps and identified areas that require further research.

Antimicrobial peptides in combination with citronellal efficiently kills multidrug resistance bacteria

BACKGROUND

Antimicrobial peptides (AMPs) are considered as the most potential alternatives to antibiotics, but they have several drawbacks, including high cost, medium antimicrobial efficacy, poor cell selectivity, which limit clinical application. To overcome the above problems, combination therapy of AMPs with adjuvants might maximize the effectiveness of AMPs. We found that citronellal can substantially potentiate the ZY4R peptide efficacy against Escherichia coli ATCC25922. However, it is unclear whether ZY4R/citronellal combination poses synergistic antimicrobial effects against most bacteria, and their synergy mechanism has not been elucidated.

PURPOSE

To investigate synergistic antimicrobial efficacies, biosafety, and synergy mechanism of ZY4R/citronellal combination.

METHOD

Checkerboard, time-kill curves, cytotoxicity assays, and in vivo animal models were conducted to assess synergistic antimicrobial effects and biosafety of the ZY4R/citronellal combination. To evaluate their synergy mechanism, a series of cell-based assays and transcriptome analysis were performed.

RESULTS

ZY4R/citronellal combination exhibited synergistic antimicrobial effects against 20 clinically significant pathogens, with the fractional inhibitory concentration index (FICI) ranging from 0.313 to 0.047. Meanwhile, ZY4R/citronellal combination enhanced antimicrobial efficacies without compromising cell selectivity, contributing to decreasing drug dosage and improving biosafety. Compared with ZY4R (4 mg/kg) and citronellal (25 mg/kg) alone, ZY4R (4 mg/kg)/citronellal (25 mg/kg) combination significantly decreased the bacterial load in peritoneal fluid, liver, and kidney (P < 0.05) and alleviated pathological damage of the organs of mice. Mechanistic studies showed that ZY4R allowed citronellal to pass through the outer membrane rapidly and acted on the inner membrane together with citronellal, causing more potent membrane damage. The membrane damage prompted the continuous accumulation of citronellal in cells, and citronellal further induced energy breakdown and inhibited exopolysaccharide (EPS) production, which aggravated ZY4R-induced outer membrane damage, thereby resulting in bacterial death.

CONCLUSIONS

ZY4R/citronellal combination exhibited broad-spectrum synergy with a low resistance development and high biosafety. Their synergy mechanism acted on two important cellular targets (energy metabolism and membrane integrity). Combination therapy of ZY4R with citronellal may be a promising mixture to combat bacterial infections facing an antibiotic-resistance crisis.

Synergy with farnesol rejuvenates colistin activity against Colistin-resistant Gram-negative bacteria in vitro and in vivo

Colistin (COL) is considered the last line of treatment against infections due to multidrug-resistant (MDR) Gram-negative bacteria (GNB). However, the increasing number of colistin-resistant (COL-R) bacteria is a great threat to public health. In this study, a strategy of combining farnesol (FAR), which has anti-inflammatory and antitumor properties, with COL to restart COL activity was proposed. The synergistic effect of FAR combined with COL against COL-R GNB in vivo and in vitro were investigated. The excellent synergistic antibacterial activity of the COL-FAR combination was confirmed by performing the checkerboard assay, time-killing assay, and LIVE/DEAD bacterial cell viability assay. Crystal violet staining and scanning electron microscopy results showed that COL-FAR prevented biofilm formation and eradicated pre-existing mature biofilm. Cytotoxicity assay showed that FAR at 64 µg/mL was not cytotoxic to RAW264.7 cells. In vivo infection experiments showed that COL-FAR increased the survival rate of infected Galleria mellonella and decreased the bacterial load in a mouse thigh infection model. These results indicate that COL-FAR is a potentially effective therapeutic option for combating COL-R GNB infections.

Evolutionary game study of crowdsourcing open innovation synergy mechanism

Open innovation crowdsourcing can help enterprises meet the challenges of a rapidly changing environment and improve their innovation performance. This study introduces network externalities as influencing factors of the crowdsourcing open innovation synergy mechanism. This study constructed the game payment matrix of the crowdsourcing open innovation synergy mechanism, and the evolutionary game method obtained the equilibrium solution of the crowdsourcing open innovation synergy mechanism. The impact of changes in the main influencing factors on the issuers' and receivers' willingness to collaborate and innovate was explored through numerical and case studies. The study shows that the higher the synergy benefit and its allocation coefficient need to be within a reasonable range for the willingness to collaborate and innovate to increase; the lower the original cost of both parties, and the higher the cost reduction coefficient under the policy support of the crowdsourcing platform, the higher the willingness to collaborate and innovate; the higher the network externality and the lower the penalty for breach of contract, the higher the desire to collaborate and innovate. The study recommends strengthening non-school education to guide innovation for all, and refining relevant policies to tailor innovation to local conditions. This study provides a new perspective and theoretical guidance for enterprises to build a crowdsourcing open innovation synergy mechanism and is a valuable reference for open innovation management.

Polyethylenimine-grafted nitrogen-doping magnetic biochar for efficient Cr(VI) decontamination: Insights into synthesis and adsorption mechanisms

Herein, polyethylenimine (PEI)-grafted nitrogen (N)-doping magnetic biochar (PEI_MW@MNBC_BM) was synthesized, and characterization results showed that the microwave-assisted PEI grafting and ball milling-assisted N doping introduced abundant amino, pyridine N and pyrrole N structures onto biochar, which possessed high affinity to Cr(VI) in the anion form. The as-prepared PEI_MW@MNBC_BM displayed pH-dependence adsorption performance and high tolerance to co-existing ions with maximum uptake capacity of Cr(VI) identified as 183.02 mg/g. Furthermore, PEI_MW@MNBC_BM could bind Cr(VI) through electrostatic attraction, complexion, precipitation, reduction and pore filling. Especially, effective reduction of Cr(VI) was ascribed to cooperative electron transfer of partial oxygen-containing functional groups, intramolecular pyridine/pyrrole N, protonated amino and Fe²⁺ on the adsorbent, while oxygen-containing and amino functional groups from N-doping biochar and PEI synergistically complexed Cr(III) via providing lone pair electrons to form coordinate bonds. Furthermore, the stable precipitation was formed between Fe³⁺ and Cr(III). Additionally, the Cr(VI) elimination efficiency could maintain 95.83% even after four adsorption-desorption cycles, suggesting PEI_MW@MNBC_BM as a high-performance adsorbent for Cr(VI) contaminated water remediation.

Redesign of urban biowaste sustainable management system based on industrial ecology concept: A case study in China

Urban biowaste, which refers to the organic fraction of municipal solid waste (MSW), is a predominant type of waste in low- and middle-income countries. Therefore, the sustainable management of urban biowaste is a key problem in solid waste management (SWM). However, treatment technologies usually come with secondary pollution and by-products that need further treatment, which would limit the economic and environmental benefits of the waste management system. The concept of industrial ecology has the potential to be introduced into the waste management field to solve this problem. Based on a practical case study of a city in eastern China, this paper conducted a complete urban biowaste treatment system planning exercise using concepts in industrial ecology. The establishment of the new system has significant economic, environmental and social benefits. The total output value of the project would reach 342 million yuan in 2025, corresponding to 945,000 tons of solid wastes consumed every year, which would significantly reduce the environmental pollution caused by solid waste. More than 700 jobs could also be created. In addition, the establishment of an urban biowaste sustainable management system requires the joint effort of enterprise, government and the public, which in turn requires innovation in business models and management policies. Therefore, a special management committee should be established to promote collaboration among stakeholders, and an online platform that enables end-to-end process supervision covering the entire system, including emergency management mechanisms, needs to be established to ensure the long-term stable operation of various treatment facilities. The results of this paper show that synergies among technologies should be promoted to provide systemic benefit, and that the infrastructure for pollution control should be shared to ensure high utilization.