气升式一体化A/O生物膜反应器脱氮研究

构建了新型气升式一体化A/O生物膜反应器用于生活污水的脱氮处理,考察了进水碳氮比和曝气速率对反应器硝化和反硝化的影响.试验结果表明,一定曝气速率条件下,反应器硝化效果随着进水碳氮比的提高而下降;提高曝气速率可以增加反应器好氧区和缓冲区的DO浓度,降低有机物氧化对硝化作用的影响;低进水碳氮比条件下,进水中的有机碳源能在缺氧区作为反硝化反应的电子供体被有效利用;在进水TN负荷为0.01 kg/(m3.d)、有机物负荷为0.26~0.76 kg/(m3.d)、进水碳氮比为2.7~5.3条件下,反应器COD和TN去除率分别达到96.0%和80.0%.     

改性水处理用生物填料性能的研究

通过添加亲水、生物亲和性及磁性粒子等物质对普通聚乙烯填料进行改性,研究了改性填料的表面结构、物理机械性能,以及填料亲水性、生物亲和性等综合性能。实验结果证实：改性填料的物理性能变化不大,SEM图显示其表面结构发生了变化,表面粗糙度加大,表面积增高;改性填料的表面润湿角降低23％,含水率提高60％;挂膜试验中,改性填料的挂膜时间缩短了2d,生物膜的形成速率加快,膜厚度增加和膜稳定性增强,生物相丰富。研究表明改性填料符合水处理用填料物理性能要求,其亲水性、生物亲和性能有较大程度的改善。     

炼油废水处理中生物膜活性的研究

以新型高效填料固定微生物 ,用生物接触氧化法处理难降解的炼油废水。通过观察废水中NH 4- N的去除情况 ,发现废水中存在一些物质抑制硝化细菌的活性。实验还发现在 COD≥ 50 0mg/ L的废水中 ,生物膜内异养细菌并不影响硝化细菌的代谢。最后用生物接触氧化工艺高效且稳定地同时把废水中 COD和 NH 4- N去除了 ,负荷较现场分别提高 2倍和 15倍以上     

醋酸废水的压力生物膜法处理

将物理中总压与分压的概念应用于醋酸废水的生物膜法处理中.实验结果表明,适当增加空气的压力,不会伤害微生物,并且由于氧分压的增加更提高了氧的传递推动力,有利于生物氧化处理对比在0.2MPa、0.3MPa较常压下COD去除率增加30%-40%.     

PVF悬浮填料的制备及其污水处理效果的研究

制备了一种新型的高分子多孔载体——活性泡沫填料，它是聚乙烯醇和甲醛的缩聚物(PVF)。其比表面积大、密度接近于水，具有良好的亲生物特性，可作为悬浮填料在移动床工艺中为微生物提供附着生长的载体。研究表明，在复合式生物反应器中加入不同活性炭质量分数的两种活性PVF泡沫填料处理模拟生活污水，其COD的去除率在95%以上，氨氮的去除率为80%左右。在相同的工艺条件下活性炭质量分数为8％的PVF填料COD的去除效果和反硝化效果更为理想。当两填料体系中COD与NH_4⁺-N的质量浓度比为20时，两系统的同时硝化反硝化（SND）效果均为最理想。     

二株细菌处理石油废水的比较研究

从成都市郊区加油站附近分离到二株以石油烃类为碳源与能源的优势菌C-1与C-2,初步鉴定为假单胞菌(Pseudomonassp.)与芽孢杆菌(Bacillussp.),采用生物膜法对二株菌降解石油废水能力进行了比较.30℃,1.25L/min通气挂膜2星期后,处理南充炼油厂石油废水,处理效果C-1好于C-2,不同营养盐NH4NO3、K2HPO4·2H2O、NaH2PO4、NH4Cl对菌株C-1处理石油废水的作用不同,浓度为1000mg/LNH4NO3对菌株C-1处理石油废水效果最佳.     

Andrographolide Inhibits Biofilm and Virulence in Listeria monocytogenes as a Quorum-Sensing Inhibitor

Listeria monocytogenes is a major foodborne pathogen that can cause listeriosis in humans and animals. Andrographolide is known as a natural antibiotic and exhibits good antibacterial activity. We aimed to investigate the effect of andrographolide on two quorum-sensing (QS) systems, LuxS/AI-2 and Agr/AIP of L. monocytogenes, as well as QS-controlled phenotypes in this study. Our results showed that neither luxS expression nor AI-2 production was affected by andrographolide. Nevertheless, andrographolide significantly reduced the expression levels of the agr genes and the activity of the agr promoter P₂. Results from the crystal violet staining method, confocal laser scanning microscopy (CLSM), and field emission scanning electron microscopy (FE-SEM) demonstrated that andrographolide remarkably inhibited the biofilm-forming ability of L. monocytogenes 10403S. The preformed biofilms were eradicated when exposed to andrographolide, and reduced surviving cells were also observed in treated biofilms. L. monocytogenes treated with andrographolide exhibited decreased ability to secrete LLO and adhere to and invade Caco-2 cells. Therefore, andrographolide is a potential QS inhibitor by targeting the Agr QS system to reduce biofilm formation and virulence of L. monocytogenes.     

Molecular Modeling Approaches Can Reveal the Molecular Interactions Established between a Biofilm and the Bioactive Compounds of the Essential Oil of Piper divaricatum

Molecular modeling approaches are used in a versatile way to investigate the properties of diverse organic and inorganic structures such as proteins, biomolecules, nanomaterials, functionalized nanoparticles, and membranes. However, more detailed studies are needed to understand the molecular nature of interactions established in gelatin biofilms impregnated with bioactive compounds. Because of this, we used computational methods to evaluate how the major compounds of Piper divaricatum essential oil can interact with the gelatin biofilm structure. For this, we used as inspiration the paper published, where various properties of the essential oil impregnated gelatin biofilm P. divaricatum are reported. After our computer simulations, we related our molecular observations to biofilm’s structural and mechanical properties. Our results suggest that the major compounds of the essential oil were able to interrupt intermolecular interactions between the chains of the biofilm matrix. However, the compounds also established interactions with the amino acid residues of these chains. Our molecular analyses also explain changes in the structural and mechanical properties of the essential oil-impregnated biofilm. These results can support the planning of functional packaging impregnated with bioactive compounds that can protect food against microorganisms harmful to human health.     

The Antibacterial Activity Mode of Action of Plantaricin YKX against Staphylococcus aureus

We aimed to evaluate the inhibitory effect and mechanism of plantaricin YKX on S. aureus. The mode of action of plantaricin YKX against the cells of S. aureus indicated that plantaricin YKX was able to cause the leakage of cellular content and damage the structure of the cell membranes. Additionally, plantaricin YKX was also able to inhibit the formation of S. aureus biofilms. As the concentration of plantaricin YKX reached 3/4 MIC, the percentage of biofilm formation inhibition was over 50%. Fluorescent dye labeling combined with fluorescence microscopy confirmed the results. Finally, the effect of plantaricin YKX on the AI-2/LuxS QS system was investigated. Molecular docking predicted that the binding energy of AI-2 and plantaricin YKX was −4.7 kcal/mol and the binding energy of bacteriocin and luxS protein was −183.701 kcal/mol. The expression of the luxS gene increased significantly after being cocultured with plantaricin YKX, suggesting that plantaricin YKX can affect the QS system of S. aureus.     

Functional Bacterial Amyloids: Understanding Fibrillation,Regulating Biofilm Fibril Formation and Organizing Surface Assemblies

Functional amyloid is produced by many organisms but is particularly well understood in bacteria, where proteins such as CsgA (E. coli) and FapC (Pseudomonas) are assembled as functional bacterial amyloid (FuBA) on the cell surface in a carefully optimized process. Besides a host of helper proteins, FuBA formation is aided by multiple imperfect repeats which stabilize amyloid and streamline the aggregation mechanism to a fast-track assembly dominated by primary nucleation. These repeats, which are found in variable numbers in Pseudomonas, are most likely the structural core of the fibrils, though we still lack experimental data to determine whether the repeats give rise to β-helix structures via stacked β-hairpins (highly likely for CsgA) or more complicated arrangements (possibly the case for FapC). The response of FuBA fibrillation to denaturants suggests that nucleation and elongation involve equal amounts of folding, but protein chaperones preferentially target nucleation for effective inhibition. Smart peptides can be designed based on these imperfect repeats and modified with various flanking sequences to divert aggregation to less stable structures, leading to a reduction in biofilm formation. Small molecules such as EGCG can also divert FuBA to less organized structures, such as partially-folded oligomeric species, with the same detrimental effect on biofilm. Finally, the strong tendency of FuBA to self-assemble can lead to the formation of very regular two-dimensional amyloid films on structured surfaces such as graphite, which strongly implies future use in biosensors or other nanobiomaterials. In summary, the properties of functional amyloid are a much-needed corrective to the unfortunate association of amyloid with neurodegenerative disease and a testimony to nature’s ability to get the best out of a protein fold.