Domain III ß4-ß5 Loop and ß14-ß15 Loop of Bacillus thuringiensis Vip3Aa Are Involved in Receptor Binding and Toxicity.

Vip3Aa, secreted by Bacillus thuringiensis, is effective at controlling major agricultural pests such as Spodoptera frugiperda. However, to control Vip3Aa resistance evolved in the field by different lepidoptera species, an in-depth study of sequence--structure--activity relationships is necessary to design new Vip3Aa variants. In this study, the four specific loops (ß4-ß5 loop, ß9-ß10 loop, ß12-ß13 loop, and ß14-ß15 loop) in domain III were selected and four loop mutants were constructed by replacing all residues in each specific loop with alanine. We obtained soluble proteins for three of the loop mutants, excluding the ß9-ß10 loop. These loop mutants have been characterized by toxicity bioassays against S. frugiperda, proteolytic processing, and receptor binding. These results indicate that the ß4-ß5 loop and ß14-ß15 loop are involved in receptor binding and Vip3Aa toxicity. Based on this, we constructed numerous mutants and obtained three single mutants (Vip3Aa-S366T, Vip3Aa-S366L, and Vip3Aa-R501A) that exhibited significantly increased toxicity of 2.61-fold, 3.39-fold, and 2.51-fold, respectively. Compared to Vip3Aa, the receptor affinity of Vip3Aa-S366T and Vip3Aa-S366L was significantly enhanced. Furthermore, we also analyzed and aligned the three-dimensional structures of the mutants and Vip3Aa. In summary, these results indicate that the loops in domain III have the potential to be targeted to enhance the insecticidal toxicity of the Vip3Aa protein.

Enhanced activation of peroxymonosulfate for advanced oxidation processes using solid waste: A novel and easy implement high-value utilization process of slag.

A simple, efficient and low energy-consuming process available to generate resultful radicals from PMS for organic pollutants removal had been employed in this study. Slag had been used as the activator for organic pollutants degradation under slag/PMS advanced oxidation process. In this work, effects of slag with or without pretreatment on pollutant removal were studied and radical species generated by slag were measured. Calcination pretreatment is one efficient method to enhance the degradation efficiency significantly. Due to Fe3O4 and Fe2O3 became the dominant phases after calcination, it was about 8.6-flods increasing after comparing the pollutant removal efficiency for different slag/PMS system with calcination pretreatment or not. Organic pollutant neither degraded in PMS system at 25 °C nor being absorbed by slag system for 60 min. On the contrary, up to 90% pollutant concentration reduction achieved in the slag/PMS process. During this process, both •OH and SO4•- had been detected once slag and PMS interaction in wastewater. Through the free radicals quenching tests,•OH should be the key free radical in this advanced oxidation process for the organic pollutant removal under this alkaline condition. In general, organic degradation rate was determined by the slag dosage, and the maximum degradation efficiency was mainly controlled by the PMS usage. This work is expected to broaden the high-value reutilization way for industrial solid waste.

Waste plastic resource recovery from landfilled refuse: A novel waterless cleaning method and its cost-benefit analysis.

The efficient classification and resource conversion of landfilled refuse can simultaneously realize the secondary pollution prevention and land replacement. This work aimed to investigate the waste plastic resource recovery from landfilled refuse via a novel waterless cleaning method. Composition analysis showed that the content of waste plastic from landfilled refuse had differences between different regions, and the specific weight content range was between 15-40%. Moreover, when the landfill time was less than 7 years, the high calorific value (>35 MJ/kg) and mechanical property (declining range <3%) of waste plastic were basically the same as those of the original waste plastic, indicating a high resource attribute. However, due to the high degree of pollution, it was difficult to directly make high-value utilization. Furthermore, a waterless device was designed for waste plastic cleaning, and 94% cleaning rate was obtained with the optimal conditions of the sand medium particle size of 4-14 mesh, stirring speed of 50 r/min, and the operation time of 45 min. The actual on-site pilot test was carried out under the best conditions, and the results showed that the cleaning rate of waste plastic could reach 90%. On the basis, cost-benefit analysis of different waste plastic recycling methods was carried out. Compared with the other four methods, direct extrusion molding after multi-effect cleaning had lower resource consumption (cost of 88.64 RMB), higher economic benefit (net income of 311.36 RMB), and was more in line with the characteristics of raw materials. This research can provide scientific basis and technical support for the cleaning and upgrading and resource utilization of plastic in refuse.