Biofouling and Biofilm Fomation in Engineered Surfaces

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología. Fecha de lectura: 22-09-2017Esta tesis tiene embargado el acceso al texto completo hasta el 22-03-201

Charged ultrafiltration membranes based on TEMPO-oxidized cellulose nanofibrils/poly(vinyl alcohol) antifouling coating

This study reports the potential of TEMPO-oxidized cellulose nanofibrils (T-CNF)/poly(vinyl alcohol) (PVA) coatings to develop functionalized membranes in the ultrafiltration regime with outstanding antifouling performance and dimensional/pH stability. PVA acts as an anchoring phase interacting with the polyethersulfone (PES) substrate and stabilizing for the hygroscopic T-CNF via crosslinking. The T-CNF/PVA coated PES membranes showed a nano-textured surface, a change in the surface charge, and improved mechanical properties compared to the original PES substrate. A low reduction (4%) in permeance was observed for the coated membranes, attributable to the nanometric coating thickness, surface charge, and hydrophilic nature of the coated layer. The coated membranes exhibited charge specific adsorption driven by electrostatic interaction combined with rejection due to size exclusion (MWCO 530 kDa that correspond to a size of ∼35–40 nm). Furthermore, a significant reduction in organic fouling and biofouling was found for T-CNF/PVA coated membranes when exposed to BSA and E. coli. The results demonstrate the potential of simple modifications using nanocellulose to manipulate the pore structure and surface chemistry of commercially available membranes without compromising on permeability and mechanical stability

Chemotactic Motility of Pseudomonas fluorescens F113 under Aerobic and Denitrification Conditions.

The sequence of the genome of Pseudomonas fluorescens F113 has shown the presence of multiple traits relevant for rhizosphere colonization and plant growth promotion. Among these traits are denitrification and chemotactic motility. Besides aerobic growth, F113 is able to grow anaerobically using nitrate and nitrite as final electron acceptors. F113 is able to perform swimming motility under aerobic conditions and under anaerobic conditions when nitrate is used as the electron acceptor. However, nitrite can not support swimming motility. Regulation of swimming motility is similar under aerobic and anaerobic conditions, since mutants that are hypermotile under aerobic conditions, such as gacS, sadB, kinB, algU and wspR, are also hypermotile under anaerobic conditions. However, chemotactic behavior is different under aerobic and denitrification conditions. Unlike most pseudomonads, the F113 genome encode three complete chemotaxis systems, Che1, Che2 and Che3. Mutations in each of the cheA genes of the three Che systems has shown that the three systems are functional and independent. Mutation of the cheA1 gene completely abolished swimming motility both under aerobic and denitrification conditions. Mutation of the cheA2 gene, showed only a decrease in swimming motility under both conditions, indicating that this system is not essential for chemotactic motility but is necessary for optimal motility. Mutation of the cheA3 gene abolished motility under denitrification conditions but only produced a decrease in motility under aerobic conditions. The three Che systems proved to be implicated in competitive rhizosphere colonization, being the cheA1 mutant the most affected

Water filtration membranes based on non-woven cellulose fabrics:Effect of nanopolysaccharide coatings on selective particle rejection, antifouling, and antibacterial properties

This article presents a comparative study of the surface characteristics and water purification performance of commercially available cellulose nonwoven fabrics modified, via cast coating, with different nano-dimensioned bio-based carbohydrate polymers, viz. cellulose nanocrystals (CNC), TEMPO-oxidized cellulose nanofibers (T-CNF), and chitin nanocrystals (ChNC). The surface-modified nonwoven fabrics showed an improvement in wettability, surface charge modification, and a slight decrease of maximum pore size. The modification improved the water permeance in most of the cases, enhanced the particle separation performance in a wide range of sizes, upgraded the mechanical properties in dry conditions, and showed abiotic antifouling capability against proteins. In addition, T-CNF and ChNC coatings proved to be harmful to the bacteria colonizing on the membranes. This simple surface impregnation approach based on green nanotechnology resulted in highly efficient and fully bio-based high-flux water filtration membranes based on commercially available nonwoven fabrics, with distinct performance for particle rejection, antifouling and antibacterial properties

Fully bio-based zwitterionic membranes with superior antifouling and antibacterial properties prepared via surface-initiated free-radical polymerization of poly(cysteine methacrylate)

This article proposes a strategy to prepare membranes that combine the network characteristics of micro/nanocellulose with grafted zwitterionic poly(cysteine methacrylate) (PCysMA) to develop fully bio-based membranes with antifouling properties. The surface characteristics of the membranes were studied, together with static adsorption of bovine serum albumin (BSA) and S. aureus for evaluating the antifouling properties of the membranes. Experimental data revealed a homogeneous modification that resulted in excellent antifouling properties with a reduction of 85% in biofilm formation and enhanced antimicrobial activity. Moreover, we introduced a novel method to determine the pore size of membranes in the wet-state and assess the antifouling performance in situ by synchrotron-based SAXS. This allowed us to observe in real-time the decrease in pore size upon adsorption of BSA during filtration, and how this phenomenon is strongly suppressed by grafting of PCysMA. The importance of this work lies in introducing a simple method to yield cellulosic membranes with superior antifouling properties, which could significantly increase their potential for water treatment applications

Nanolignocellulose Extracted from Environmentally Undesired Prosopis juliflora

Rising sustainability demands the search of new low-market-value sources of lignocellulosic biomass as raw material for nanocellulose processing. In this paper, we accordingly propose the isolation of nanocellulose from Prosopis juliflora, an abundant but environmentally undesired tree. P. juliflora wood was powered, refined by steam explosion and bleaching, and subsequently used to isolate cellulose nanocrystals and nanofibers by means of acid hydrolysis and mechanical fibrillation. The derived nanocrystals had a rod-shaped structure with an average diameter of 20 nm and length of 150 nm, whereas the nanofibers had a diameter of 10 nm and length in micron size. Moreover, we report a simple method to isolate nanolignocellulose by using partially bleached P. juliflora as feedstock. The presence of lignin provided antioxidant and antimicrobial activity to nanocellulose, as well as hydrophobicity and increased thermal stability. The study demonstrates the successful use of P. juliflora to extract functional nanomaterials, which compensate for its environmental concern and declining market interest

The three chemotaxis systems are important for rhizosphere colonization.

<p>Competitive colonization root-tip assay of <i>P</i>. <i>fluorescens</i> F113 and isogenic mutants affected in either of the <i>cheA</i> genes. Equal amounts (10⁸ cells) of F113 and its competitors were inoculated per plant. F113 was also compared with an isogenic strain tagged with a kanamycin resistance gene as a control. Experiments were done in triplicate with 20 plants in each experiment. Different letters indicate statistically significant differences (p<0.05).</p

Growth of <i>P</i>. <i>fluorescens</i> F113 under denitrification conditions.

<p>Growth curves of F113 with different final electron acceptors. Nitrate concentration was 40mM, nitrite concentration was 10mM. Anaerobic conditions were obtained by flushing inoculated medium with argon. For anaerobic conditions, air-tight tubes were used. F113 was unable to grow anaerobically in LB or SA media without nitrate or nitrite. Experiments were done in triplicate (A) Growth curves of F113 in LB and SA media supplemented with nitrate (B) Growth curves of F113 in LB medium (aerobic), LB supplemented with nitrate and LB supplemented with nitrite.</p