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

Bioinspired Carbon-Silver Sulfide Scaffold with Synergistic Enhanced Light Capture and Anti-Biofouling Property for Stable Solar Steam Generation

Carbon material is a hot topic in solar evaporation. Due to the widely distributed microorganisms in natural water, biofouling has limited the actual application of solar evaporation material. Although carbon material lacks of nutrition for microbe, it is still vulnerable to biofouling because of the efficient pollutant adsorption property. However, current anti-biofouling design focuses on microbial control, neglects its influence on evaporators light absorption, that is usually a trade-off with evaporation efficiency. Herein, a bioinspired aligned carbon-Ag2S scaffold is introduced with synergistical enhanced light absorption (increased to 98.0% from 97.4%) and anti-biofouling property. The bioinspired aligned carbon-Ag2S scaffold exhibits a 1.87 kg m-2 h-1 evaporation rate under one sun, superior to pure carbon scaffold (1.78 kg m-2 h-1). It also maintains efficient light capture (-97.2%) and evaporation rate (1.73 kg m-2 h-1) after bacterial interference, avoiding sharp decline in light absorption (reduced to 83.3-87.6%) and evaporation performance (reduced to 1.24-1.28 kg m-2 h-1) which occurs in carbon scaffold due to biofouling. The carbon-Ag2S scaffold shows solid advantage in balancing light captures and biofouling control, compared to carbon-ZnO scaffold with conventional anti-biofouling design, which inhibits biofouling sacrificing light absorption (reduced to 89.8%) and evaporation performance (reduced to 1.41 kg m-2 h-1).

Intensified microalgae production and development of microbial communities on suspended carriers and municipal wastewater

Wastewater represents an alternative source of nutrients in which to grow microalgae, whilst improving the quality of the wastewater, and reducing the downstream treatment required. However, commercialisation of microalgal cultures for such duties faces a number of challenges, predominantly high cost and low productivity. Suspended-solid reactors (ssPBR) can reduce the operational costs, while promoting attached and suspended microalgae growth. In the present study, a novel approach was developed by integrating microalgal wastewater treatment with carrier systems to favour the growth of both attached and suspended cells of T. obliquus. This study found that T. obliquus was able to uptake nutrients from municipal wastewater, achieving removals of 99.3-99.9 % NH3-N, 54.5-88.5 % PO43- and 92.8-94.5 % DTC. The addition of a 12.5 % volumetric fill ratio of carriers in ssPBRs produced higher microalgal cell productivity (1.2·106 ± 2.5·105 cell ml-1 d-1) than the control (4.3·105 ± 2.8·105 cell ml-1 d-1). MinION nanopore sequencing was conducted to assess the impact of microalgal and carrier treatment on wastewater bacterial communities. It was found not only that bacterial communities had changed after the treatment but also the ones attached differed from the ones suspended. Untreated wastewater was characterised by the abundance of sewer bacteria genera such as Aliarcobacter and Arcobacter, whilst, after treatment, microbial communities were characterised by the presence of photosynthetic freshwater (Limnococcus, Stanieria) and bioremediation-like bacteria genera (Pseudomonas, Rheinheimera). In conclusion, the addition of 12.5 % fill carrier ratio increased microalgal productivity, while stimulating changes in the algal microbiome, and creating distinctly different populations in the free and attached environments.

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.