Insights into the Viscoelastic Peculiarities of Cyanobacterial Extracellular Polymeric Substance (EPS)

Extracellular polymeric substances (EPSs) can be defined as renewable, high molecular weight polymeric materials produced by bacteria and microorganisms. EPSs are composed of primarily polysaccharides and proteins, with minor amounts of nucleic acids, lipids, and humic substances. Cyanobacterial extracellular polymeric subtances have a significant physiological effect on bloom formation and stress tolerance in adverse conditions. Therefore, cyanobacterial EPS has an important factor for aquatic life, environment and human life. For these reasons, determining the structure and structure-property relationships of cyanobacterial EPS is important for understanding its behavior and performance. In this study, the identification of the structure-property relationships, thermal and viscoelastic properties of cyanobacterial extracellular polymeric substance, X-ray diffraction (XRD) analysis, differential thermal analysis (DTA) and dynamic mechanical analysis (DMA) have been performed. Viscoelastic properties of the polymeric materias have been interpreted by certain DMA parameters at a fixed frequency depending on the temperature to understand the performance of cyanobacterial EPS.

Impact of light on anoxic/oxic reactors: performance, quorum sensing, and metagenomic characteristics

The effect of light has raised attention on wastewater treatment. However, little research has concentrated on the influences of light on activated sludge. In this study, the influences of light on the performance, quorum sensing (QS) and metagenomic characteristics of anoxic/oxic reactors were investigated. The reactor without light (AO1) showed higher total nitrogen (TN) removal (79.15 ± 1.69%) than the reactor with light (AO2) (74.54 ± 1.30%), and significant differences were observed. It was observed that light facilitated the production of protein-like and tryptophan-like substances by employing parallel factor analysis for extracellular polymeric substance (EPS), resulting in more EPS production in AO2, indicating light was beneficial to EPS production. The concentrations of N-acyl-homoserine lactones (AHLs) were various in the two reactors, so the AHLs-mediated QS behaviors in both reactors were also different. These results revealed that light significantly influenced nitrogen removal, EPS, and QS. Metagenomic analysis based on Tax4Fun demonstrated that light reduced the denitrification, stimulated the polysaccharide and protein biosynthesis pathways and down-regulated the AHLs synthesis pathway, resulting in lower TN removal, more EPS production, and lower AHLs concentrations. Based on the above, the likely mechanism was proposed for the influences of light on the reactor.

Extracellular Polymeric Substance (EPS) Degradation of Enterococcus Faecalis biofilm after irradiation with 405nm diode laser

This research aimed to determine whether irradiation of 405 nm diode laser with chlorophyll as photosensitizer could degrade the extracellular polymeric substance (EPS) of Enterococcus faecalis (E. faecalis) biofilm. The material for this study needs 25 biofilm formed by E. faecalis was divided equally into five groups. The control negative group (C-) consisted of E. faecalis biofilm, the control positive group (C+) consisted of E. faecalis biofilm and chlorophyll photosensitizers, and the other three treatment group (T1, T2, T3) consisted of E. faecalis biofilm and chlorophyll photosensitizers. Each treatment groups were irradiated for 90 second (s) for T1 group, 105 s for T2 group, and 120 s for T3 group with 405nm diode laser. The degradation EPS of E. faecalis’ biofilm was determined using Confocal Laser Scanning Microscope (CLSM). Irradiation duration affected the degradation EPS of E. faecalis’ biofilm. Chlorophyll with 120 s laser irradiation showed significant degradation EPS of E. faecalis’ biofilm compared to other groups (p < 0.05). Irradiation of diode laser 405nm with chlorophyll photosensitizer 120 s could degrade EPS of E. faecalis biofilm up to 97.51%.