Browsing by Author "Yu, Cong"
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Item Effect of D-Tyrosine on Bacterial Biofilms: Mechanisms and Potential Applications in Membrane Biofouling Control(2016-04-22) Yu, Cong; Li, QilinBiofouling leads to diverse detrimental effects in water treatment and distribution systems. D-Tyrosine can be produced by a variety of bacteria and inhibits formation as well as triggers disassembly of biofilms thus has been proposed for biofouling control applications. The impact of D-tyrosine in different biofilm formation stages in G+ and G- bacteria was studied, and a non-monotonic correlation between D-tyrosine concentration and biofilm inhibition effect was revealed. D-Tyrosine inhibited attachment and biofilm formation in Pseudomonas aeruginosa and Bacillus subtilis with an effective concentration of 5 nM. Extracellular protein was decreased in P. aeruginosa biofilms, but increased in those of B. subtilis. Exopolysaccharides production by P. aeruginosa was increased at low concentrations and reduced at high concentrations while no impact was found in B. subtilis. These results suggest that distinct mechanisms are involved at different D-tyrosine concentrations and they may be species specific. Further investigation of the biofilm related gene expression in P. aeruginosa indicated repression of quorum sensing genes at high (200 µM) and low (5nM) effective concentrations but not at non-inhibitive concentrations (1 µM). Lipopolysaccharides production was reduced and the genes were down regulated by D-tyrosine at 5 nM but not at 200 µM. The efflux pump, flagella and racemase genes were also repressed by 5 nM D-tyrosine. Efflux pump is closely related to quorum sensing while how flagella and racemase are affected is unclear. At low concentration, D-tyrosine may serve as a signal molecule to regulate LPS production and quorum sensing, biofilm formation is inhibited through which. At micromolar level, the biofilm inhibition effect decreased with D-tyrosine concentration and could possibly be attributed to the repression of quorum sensing. D-Tyrosine was incorporated onto a nanofiltration membrane using FAU type zeolite nanoparticles covalently bound to the membrane surface as carriers to develop a long-lasting environmentally friendly anti-biofouling membrane. The initial P. aeruginosa cell attachment and subsequent biofilm formation were inhibited. D-tyrosine was gradually released from the membrane in ultrapure water for 5 days and the membrane retained its anti-biofouling capability for 6 days. The membrane alleviated flux decline and irreversible cell adhesion on membrane surface in dead-end filtration.Item Potential Application of D-Amino Acids in Biofouling Control of Nanofiltration (NF) Membranes(2012) Yu, Cong; Li, QilinBiofouling is a major impediment for the application of reverse osmosis filtration and nanofiltration in water and wastewater treatment as well as seawater desalination. In this study, a novel biofouling control strategy of using D-amino acids to interfere with biofilm formation was evaluated. Impact of D-amino acids on the surface attachment and biofilm formation of Pseudomonas aeruginosa was investigated in batch and continuous flow filtration systems. All 19 D-amino acids demonstrated inhibitive effects on P. aeruginosa biofilm formation. In particular, D-tyrosine was found to strongly inhibit P. aeruginosa attachment and biofilm formation on an NF membrane. When continuously supplemented to the membrane feed water in a bench scale nanofiltration system, it prohibited irreversible biofouling of the NF membrane at concentrations as low as 3 μM. The effectiveness of biofilm control by these D-amino acids seems to strongly depend on the ratio of D-amino acid concentration to bacterial cell number.Item Use of surface modified porous membranes for fluid distillation(2022-05-17) Li, Qilin; Wu, Jinjian; Halas, Nancy C.; Zodrow, Katherine R.; Guo, Haoli; Xu, Jiarui; Yu, Cong; Rice University; William Marsh Rice University; United States Patent and Trademark OfficeIn some embodiments, the present disclosure pertains to systems and methods for distilling a fluid by exposing the fluid to a porous membrane that includes a surface capable of generating heat. In some embodiments, the heat generated at the surface propagates the distilling of the fluid by converting the fluid to a vapor that flows through the porous membrane and condenses to a distillate. In some embodiments, the surface capable of generating heat is associated with a photo-thermal composition that generates the heat at the surface by converting light energy from a light source to thermal energy. In some embodiments, the photo-thermal composition includes, without limitation, noble metals, semiconducting materials, dielectric materials, carbon-based materials, composite materials, nanocomposite materials, nanoparticles, hydrophilic materials, polymers, fibers, meshes, fiber meshes, hydrogels, hydrogel meshes, nanomaterials, and combinations thereof. Further embodiments pertain to methods of making the porous membranes of the present disclosure.Item Use of surface modified porous membranes for fluid distillation(2020-11-24) Li, Qilin; Wu, Jinjian; Halas, Nancy J.; Zodrow, Katherine R.; Guo, Haoli; Xu, Jiarui; Yu, Cong; Rice University; United States Patent and Trademark OfficeIn some embodiments, the present disclosure pertains to systems and methods for distilling a fluid by exposing the fluid to a porous membrane that includes a surface capable of generating heat. In some embodiments, the heat generated at the surface propagates the distilling of the fluid by converting the fluid to a vapor that flows through the porous membrane and condenses to a distillate. In some embodiments, the surface capable of generating heat is associated with a photo-thermal composition that generates the heat at the surface by converting light energy from a light source to thermal energy. In some embodiments, the photo-thermal composition includes, without limitation, noble metals, semiconducting materials, dielectric materials, carbon-based materials, composite materials, nanocomposite materials, nanoparticles, hydrophilic materials, polymers, fibers, meshes, fiber meshes, hydrogels, hydrogel meshes, nanomaterials, and combinations thereof. Further embodiments pertain to methods of making the porous membranes of the present disclosure.