A peptide of PilZ domain-containing protein controls wastewater-treatment-membrane biofouling by inducing bacterial attachment

Visible-light-driven water-soluble zinc oxide quantum dots for efficient control of citrus canker

BACKGROUND

Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is a devastating bacterial disease that reduces citrus yield and quality, posing a serious threat to the citrus industry. Several conventional chemicals have been used to control citrus canker. However, this approach often leads to the excessive use of chemical agents, can exacerbate environmental pollution and promotes the development of resistant Xcc. Therefore, there is significant interest in the development of efficient and environmentally friendly technologies to control citrus canker.

RESULTS

In this study, water-soluble ZnO quantum dots (ZnO QDs) were synthesised as an efficient nanopesticide against Xcc. The results showed that the antibacterial activity of ZnO QDs irradiated with visible light [half-maximal effective concentration (EC50) = 33.18 μg mL-1] was ~3.5 times higher than that of the dark-treated group (EC50 = 114.80 μg mL-1). ZnO QDs induced the generation of reactive oxygen species (•OH, •O- 2 and 1O2) under light irradiation, resulting in DNA damage, cytoplasmic destruction, and decreased catalase and superoxide dismutase activities. Transcription analysis showed downregulation of Xcc genes related to 'biofilms, virulence, adhesion' and 'DNA transfer' exposure to ZnO QDs. More importantly, ZnO QDs also promoted the growth of citrus.

CONCLUSION

This research provides new insights into the photocatalytic antibacterial mechanisms of ZnO QDs and supports the development of more efficient and safer ZnO QDs-based nanopesticides to control citrus canker. © 2024 Society of Chemical Industry.

Adsorptive chito-beads for control of membrane fouling

Chitosan has excellent antimicrobial, adsorption, heavy metal removal, and adhesion properties, making it a good substitute for microplastic-based cleaners. Here, chitosan microbeads (chito-beads) of various sizes ranging from 32 μm to 283 μm were prepared via emulsion using a liquid on oil method and the feasibility of using them as an essential constituent in a chemical cleaning solution for a reverse-osmosis (RO) membrane-fouling-control process was assessed. Prior to the assessment the cleaning efficiency of a solution containing chito-beads, the interaction energy between chitosan and a representative organic foulant (humic acid (HA)) in a RO membrane fouling was analyzed using colloidal atomic force microscopy, and the strongest attraction between chitosan and HA was observed in an aqueous solution. When comparing the membrane cleaning efficiency of cleaning solutions with and without chito-beads, smaller chito-beads (32 μm and 70 μm) were found to have higher cleaning efficiency. Applications of chito-beads to the membrane cleaning process can enhance the cleaning efficiency through the physicochemical interaction with organic foulants. This study can widen the use of chito-beads as an additive to membrane chemical cleaning solutions to control membrane fouling in other membrane processes as well.