Interactions between tannins allelochemicals and extracellular polymeric substance (EPS) of Microcystis aeruginosa

Use of Plant Extracts in Polymeric Scaffolds in the Regeneration of Mandibular Injuries

Severe loss of bone mass may require grafting, and, among the alternatives available, there are natural biomaterials that can act as scaffolds for the cell growth necessary for tissue regeneration. Collagen and elastin polymers are a good alternative due to their biomimetic properties of bone tissue, and their characteristics can be improved with the addition of polysaccharides such as chitosan and bioactive compounds such as jatoba resin and pomegranate extract due to their antigenic actions. The aim of this experimental protocol was to evaluate bone neoformation in experimentally made defects in the mandible of rats using polymeric scaffolds with plant extracts added. Thirty rats were divided into group 1, with a mandibular defect filled with a clot from the lesion and no graft implant (G1-C, n = 10); group 2, filled with collagen/chitosan/jatoba resin scaffolds (G2-CCJ, n = 10); and group 3, with collagen/nanohydroxyapatite/elastin/pomegranate extract scaffolds (G3-CHER, n = 10). Six weeks after surgery, the animals were euthanized and samples from the surgical areas were submitted to macroscopic, radiological, histological, and morphometric analysis of the mandibular lesion repair process. The results showed no inflammatory infiltrates in the surgical area, indicating good acceptance of the scaffolds in the microenvironment of the host area. In the control group (G1), there was a predominance of reactive connective tissue, while in the grafted groups (G2 and G3), there was bone formation from the margins of the lesion, but it was still insufficient for total bone repair of the defect within the experimental period standardized in this study. The histomorphometric analysis showed that the mean percentage of bone volume formed in the surgical area of groups G1, G2, and G3 was 17.17 ± 2.68, 27.45 ± 1.65, and 34.07 ± 0.64 (mean ± standard deviation), respectively. It can be concluded that these scaffolds with plant extracts added can be a viable alternative for bone repair, as they are easily manipulated, have a low production cost, and stimulate the formation of new bone by osteoconduction.

Egeria densa organic extracts: an eco-friendly approach to suppress Microcystis aeruginosa growth through allelopathy

Macrophytes play a significant role in shaping plankton communities by shading, controlling water turbulence, and nutrient availability, while also producing allelochemicals causing varying effects on different organisms. Many researchers have shown that when live macrophytes are present, they inhibit cyanobacteria. However, their widespread use is often limited due to numerous concerns, including invasive characteristics. This study focused on the applicability of Egeria densa extracts to suppress Microcystis aeruginosa. We employed pure water and dimethyl sulfoxide, to obtain compounds from E. densa. The results revealed that E. densa aqueous extracts stimulated M. aeruginosa growth, whereas organic extracts exhibited suppression. Specifically, at low concentrations of organics extracts (0.5 and 1 g/L), after day 4, the growth inhibition was confirmed by significantly higher (p < 0.05) stress levels shown in cells treated with low concentrations. The highest inhibition rate of 32% was observed at 0.5 g/L. However, high concentrations of organic extracts (3 and 6 g/L), showed increased growth compared with control. These results suggest that high concentrations of organic extracts from E. densa potentially suppress allelochemical-induced M. aeruginosa inhibition due to high nutrient availability. In comparison with an aqueous solvent, the use of organic solvent seems to be more effective in efficiently extracting allelochemicals from E. densa.

Positive responses and mechanisms of nitrifying sludge to carbon quantum dots: reactor performance, microbial behavior, and antioxidant defense

Extensive application of carbon quantum dots (CQDs) enlarges its concentration in sewage treatment system. The response of nitrifying sludge to CQDs after long-term exposure was investigated. Results showed that CQD concentrations of 0-100 mg/L presented positive effect to enzymes involved in nitrification, accelerating NH4+-N degradation and NO2--N transformation. The oxidation rate of NO2--N was significantly improved from 3.14 to 7.91 mg/(L h) under the stress of 100 mg/L CQDs. Besides, CQDs stimulated the production of sludge biomass and kept the stability of sludge settleability. Additionally, CQDs were mainly captured by loosely bound extracellular polymeric substances, reducing aromatic-like protein. Microbes alleviated CQD stress by secreting tryptophan-like protein and polysaccharides. After few CQDs entered cells, intracellular antioxidant defense was activated. Total antioxidant capacity level was heightened at least 31%. The activities of superoxide dismutase and catalase were enhanced at relatively low and high CQD concentration levels. Hence, microbial metabolic pathways, microbial community, and nitrifying bacteria were not significantly affected by CQDs. The findings of this work provide new insight for understanding the environmental implication of CQDs in the biological treatment system.