Film mulching reduces antibiotic resistance genes in the phyllosphere of lettuce.

Phyllosphere is an important reservoir of antibiotic resistance genes (ARGs), but the transfer mechanism of ARGs from soil and air to phyllosphere remains unclear. This study demonstrated that soil-air-phyllosphere was the dominant ARG transfer pathway, and blocking it by film mulching can reduce typical phyllosphere ARGs in lettuce by 80.7% - 98.7% (89.5% on average). To further eliminate phyllosphere ARGs in lettuce grown with film mulching, the internal soil-endosphere-phyllosphere transfer pathway deserves more attention. We analyzed the ARG hosts and the resistome in lettuce rhizosphere and phyllosphere with film mulching via hybrid Illumina-Nanopore sequencing. Pseudomonas sp. 7SR1 was more abundant than other ARG hosts, accounting for 1.0% and 47.1% of the total bacteria in rhizosphere and phyllosphere, respectively. The species has flagella that can promote mobility and can excrete extracellular polymeric substances and/or surfactant-like microbial products, which benefits its colonization in the phyllosphere. Impeding the migration of Pseudomonas sp. 7SR1 via the soil-endosphere-phyllosphere pathway would be effective to further reduce ARGs in phyllosphere. Multidrug resistant genes were predominant in phyllosphere (40.3% of the total), and 87.6% of the phyllosphere ARGs were located on chromosomes, indicating relatively low horizontal gene transfer (HGT) potentials. This study provides insights into the transfer mechanism, hosts, and control strategies of phyllosphere ARGs in typical plants.

A stacked transmembrane electro-chemisorption system connected by hydrophobic gas permeable membranes for on-site utilization of authigenic acid and base to enhance ammonia recovery from wastewater.

The ammonia recovery from wastewater via electrochemical technologies represents a promising way for wastewater treatment, resource recovery, and carbon emissions reduction. However, chemicals consumption and reactors scalability of the existing electrochemical systems have become the key challenges for their development and application. In this study, a stacked transmembrane electro-chemisorption (sTMECS) system was developed to utilize authigenic acid and base on site for enhancing ammonia recovery from wastewater. The easily scaled up system was achieved via innovatively connecting the cathode chamber in a unit with the anode chamber in the adjacent unit by a hydrophobic gas permeable membrane (GPM). Thus, authigenic base at cathodes and authigenic acid at anodes could be utilized as stripper and absorbent on site to enhance the transmembrane chemisorption of ammonia. Continuous power supply, reducing the distances of electrodes to GPM and moderate aeration of the catholyte could promote ammonia recovery. Applied to the ammonia recovery from the simulated urine, the sTMECS under the current density 62.5 A/cm2 with a catholyte aeration rate of 3.2 L/(L⋅min) for operation time 4 h showed the transmembrane ammonia flux of 26.00 g N/(m2·h) and the system energy consumption of 10.5 kWh/kg N. Accordingly, the developed sTMECS system with chemicals saving, easy scale-up and excellent performance shows good prospects in recovering ammonia from wastewater.

Gas permeable membrane electrode assembly with in situ utilization of authigenic acid and base for transmembrane electro-chemisorption to enhance ammonia recovery from wastewater.

Ammonia recovery from wastewater is of great significance for aquatic ecology safety, human health and carbon emissions reduction. Electrochemical methods have gained increasing attention since the authigenic base and acid of electrochemical systems can be used as stripper and absorbent for transmembrane chemisorption of ammonia, respectively. However, the separation of electrodes and gas permeable membrane (GPM) significantly restricts the ammonia transfer-transformation process and the authigenic acid-base utilization. To break the restrictions, this study developed a gas permeable membrane electrode assembly (GPMEA), which innovatively integrated anode and cathode on each side of GPM through easy phase inversion of polyvinylidene fluoride binder, respectively. With the GPMEA assembled in a stacked transmembrane electro-chemisorption (sTMECS) system, in situ utilization of authigenic acid and base for transmembrane electro-chemisorption of ammonia was achieved to enhance the ammonia recovery from wastewater. At current density of 60 A/m2, the transmembrane ammonia flux of the GPMEA was 693.0 ± 15.0 g N/(m2·d), which was 86 % and 28 % higher than those of separate GPM and membrane cathode, respectively. The specific energy consumption of the GPMEA was 9.7∼16.1 kWh/kg N, which were about 50 % and 25 % lower than that of separate GPM and membrane cathode, respectively. Moreover, the application of GPMEA in the ammonia recovery from wastewater is easy to scale up in the sTMECS system. Accordingly, with the features of excellent performance, energy saving and easy scale-up, the GPMEA showed good prospects in electrochemical ammonia recovery from wastewater.