Polysaccharide Substances Research Articles

Adsorption of Bacteria Extracellular Polysaccharide Substances on the Graphite (002) Surface: A DFT and MD Study.

Understanding the principle of the bacteria-anode surface interaction can enhance electron transfer in microbial fuel cells and aid in antibiofouling. In this article, we investigate the adsorption propensity of common adhesins [N-acetylglucosamine (NAG), d-glucose, and alginate] found in microbial biofilms on the surface of unmodified and modified graphite through density functional theory and molecular dynamics simulations. DFT results showed that all the molecules could interact with the graphite surface, with NAG (ΔE gap = 3.677 eV) being the most reactive molecule. The Fukui function results show that the most active sites were located at O, C13, and N on the adsorbates. The optimum conditions were basic medium at 303 K across all systems. All adsorbates show energetically favorable adsorption, with NAG showing the maximum adsorption energy irrespective of the modification. The modified graphite system showed increased adsorption compared to the unmodified graphite system. Electrostatic interactions, H-bonding, and π-π stacking or interactions are the driving forces responsible for the chemical bond formation in the adsorbates-adsorbent complexes. Altogether, this research provides theoretical support for bacterial adhesin adsorption onto graphite anodes and new ideas for studying bacteria-anode interactions in fuel cells, biofouling and antifouling, dental science, clean energy production, and wastewater treatment.

Ionic microsphere therapy for skin trauma

The skin is an important barrier for the body. Normal wound healing can be severely impeded by inadequate angiogenesis, excessive inflammation, and increased susceptibility to infection. Therefore, effective wound therapy should focus on accelerating the healing process and providing antimicrobial properties that are essential for wound recovery. Alginate (ALG) is a biocompatible polysaccharide substance capable of forming hydrogel dressings by cross-linking with metal ions, especially with Zn2+, Fe3+, Cu2+, and Ca2+ metal ions. The hydrogel formed by them can gradually release Zn2+, Fe3+, Cu2+, and Ca2+ during the process of wound repair, which has an important role in promoting angiogenesis and collagen deposition. Here, we prepared hydrogel microspheres (MS) based on cross-linking of different ions such as Zn-MS, Fe-MS, Cu-MS, and Ca-MS and investigated the effect of these ions on wound healing. In vitro and in vivo experiments showed that MS formed by Zn2+ enhanced antimicrobial activity, MS formed by Fe3+ and Cu2+ increased the formation of collagen fibers, and MS formed by Zn2+ and Ca2+ promoted the development of capillaries. So, the hydrogel MS formed by cross-linking ALG with these four ions are of great significance and research value in the field of skin wound application.

Polysaccharide-Based Edible Biopolymer-Based Coatings for Fruit Preservation: A Review

Over the last decades, a significant rise in fruit consumption has been noticed as they contain numerous nutritional components, which has led to the rise in fruit production globally. However, fruits are highly liable to spoilage in nature and remain vulnerable to losses during the storage and preservation stages. Therefore, it is crucial to enhance the storage life and safeness of fruits for the consumers. To keep up the grade and prolong storage duration, various techniques are employed in the food sector. Among these, biopolymer coatings have gained widespread acceptance due to their improved characteristics and ideal substitution for synthetic polymer coatings. As there is concern regarding the safety of the consumers and sustainability, edible coatings have become a selective substitution for nurturing fruit quality and preventing decay. The application of polysaccharide-based edible coatings offers a versatile solution to prevent the passage of moisture, gases, and pathogens, which are considered major threats to fruit deterioration. Different polysaccharide substances such as chitin, pectin, carrageenan, cellulose, starch, etc., are extensively used for preparing edible coatings for a wide array of fruits. The implementation of coatings provides better preservation of the fruits such as mango, strawberry, pineapple, apple, etc. Furthermore, the inclusion of functional ingredients, including polyphenols, natural antioxidants, antimicrobials, and bio-nanomaterials, into the edible coating solution matrix adds to the nutritional, functional, and sensory attributes of the fruits. The blending of essential oil and active agents in polysaccharide-based coatings prevents the growth of food-borne pathogens and enhances the storage life of the pineapple, also improving the preservation of strawberries and mangoes. This paper aims to provide collective data regarding the utilization of polysaccharide-based edible coatings concerning their characteristics and advancements for fruit preservation.

Molecular insights into flavone-mediated quorum sensing interference: A novel strategy against Serratiamarcescens biofilm-induced antibiotic resistance"

Antibiotic resistance poses a significant challenge in modern medicine, urging the exploration of innovative approaches to combat bacterial infections. Biofilms, complex bacterial communities encased in a protective matrix, contribute to resistance by impeding antibiotic efficacy and promoting genetic exchange. Understanding biofilm dynamics is crucial for developing effective antimicrobial therapies against antibiotic resistance. This study explores the potential of flavone to combat biofilm-induced antibiotic resistance by employing in-vitro biochemical, cell biology, and Insilico (MD simulation), approaches. Flavone exhibited potent antibacterial effects with a low minimum inhibitory concentration by inducing intracellular reactive oxygen species. Flavones further inhibited the formation of biofilms by 50–60 % and disrupted the pre-formed biofilms by reducing the extracellular polysaccharide substance protective layer formed on the biofilm by 80 %. Quorum sensing (QS) plays a crucial role in bacterial pathogenicity and flavone significantly attenuated the production of QS-induced virulence factors like urease, protease, lipase, hemolysin and prodigiosin pigment in a dose-dependent manner. Further Insilico molecular docking studies along with molecular dynamic simulations run for 100 ns proved the stable binding affinity of flavone with QS-specific proteins which are crucial for biofilm formation. This study demonstrates the therapeutic potential of flavone to target QS-signaling pathway to combat S.marcescens biofilms.

L-lysine as a Potential Agent for Controlling Biofilm Formation Using Fusobacterium nucleatum and Porphyromonas gingivalis

Background Periodontitis, a globally-pervasive chronic inflammatory condition, is precipitated by forming microbial biofilms. A key player in this process is Fusobacterium nucleatum (F. nucleatum), an anaerobic bacterium exhibiting invasive and pro-inflammatory characteristics primarily associated with the onset of periodontitis. Consequently, developing novel biofilm control strategies specifically targeting F. nucleatum is essential. The objective of this research is to examine the suppressive impact of L-lysine on biofilm formation using F. nucleatum. Methods Fusobacterium nucleatum(F. nucleatum) and Porphyromonas gingivalis (P. gingivalis) were cultured in a liquid medium containing L-lysine of different concentrations. The antimicrobial activity of L-lysine was evaluated using the broth microdilution method. The effect of L-lysine on the mono-species and dual-species F. nucleatum biofilms was assessed using techniques such as crystal violet staining. The synthesis of extracellular polysaccharide substances (EPSs) from biofilms was measured using phenol-sulfuric acid. The expression level of virulence factors (FN1420, FN0669, FN0634, FN1162) and the biofilm-formation-related gene radD were quantified using real-time PCR. Results L-lysine exhibited the antibacterial and antibiofilm activity of F. nucleatum and F. nucleatum/ P. gingivalis double strains, which was concentration-dependent. The MIC and MBC values were 10 mg/ml and 20 mg/ml in F. nucleatum single strains, while those in F. nucleatum/ P. gingivalis double strains were 20 mg/ml and 40 mg/ml. L-lysine with a concentration ≥20 mg/ml could reduce the EPS production in F. nucleatum and F. nucleatum/ P. gingivalis dual-species biofilms. L-lysine also inhibited the expression of genes encoding the F. nucleatum virulence factor (FN1420, FN0669, FN0634, FN1162) and the adhesive factor radD. Conclusion These findings corroborate the potential of L-lysine as an agent impeding the development of both mono-species biofilms of F. nucleatum and dual-species biofilms of F. nucleatum and P. gingivalis.

Understanding Protein and Polysaccharide Fouling with Silicon Dioxide and Aluminum Oxide in Low-Pressure Membranes.

Humic, protein, and polysaccharide substances have been recognized as significant types of foulants in membrane systems. Despite the remarkable amount of research that has been performed on the interaction of these foulants, particularly humic and polysaccharide substances, with inorganic colloids in RO systems, little attention has been paid to the fouling and cleaning behavior of proteins with inorganic colloids in UF membranes. This research examined the fouling and cleaning behavior of bovine serum albumin (BSA) and sodium alginate (SA) with silicon dioxide (SiO2) and α-aluminum oxide (Al2O3) in individual and combined solutions during dead-end UF filtration. The results showed that the presence of SiO2 or Al2O3 in water alone did not cause significant fouling or a flux decline in the UF system. However, the combination of BSA and SA with inorganics was observed to have a synergistic effect on membrane fouling, in which the combined foulants caused higher irreversibility than individual foulants. Analysis of blocking laws demonstrated that the fouling mechanism shifted from cake filtration to complete pore blocking when the combined organics and inorganics were present in water, which resulted in higher BSA and SA fouling irreversibility. The results suggest that membrane backwash needs to be carefully designed and adjusted for better control of BSA and SA fouling with SiO2 and Al2O3.

Anti-Bacterial and Anti-Biofilm Activities of Anandamide against the Cariogenic Streptococcus mutans

Streptococcus mutans is a cariogenic bacterium in the oral cavity involved in plaque formation and dental caries. The endocannabinoid anandamide (AEA), a naturally occurring bioactive lipid, has been shown to have anti-bacterial and anti-biofilm activities against Staphylococcus aureus. We aimed here to study its effects on S. mutans viability, biofilm formation and extracellular polysaccharide substance (EPS) production. S. mutans were cultivated in the absence or presence of various concentrations of AEA, and the planktonic growth was followed by changes in optical density (OD) and colony-forming units (CFU). The resulting biofilms were examined by MTT metabolic assay, Crystal Violet (CV) staining, spinning disk confocal microscopy (SDCM) and high-resolution scanning electron microscopy (HR-SEM). The EPS production was determined by Congo Red and fluorescent dextran staining. Membrane potential and membrane permeability were determined by diethyloxacarbocyanine iodide (DiOC2(3)) and SYTO 9/propidium iodide (PI) staining, respectively, using flow cytometry. We observed that AEA was bactericidal to S. mutans at 12.5 µg/mL and prevented biofilm formation at the same concentration. AEA reduced the biofilm thickness and biomass with concomitant reduction in total EPS production, although there was a net increase in EPS per bacterium. Preformed biofilms were significantly affected at 50 µg/mL AEA. We further show that AEA increased the membrane permeability and induced membrane hyperpolarization of these bacteria. AEA caused S. mutans to become elongated at the minimum inhibitory concentration (MIC). Gene expression studies showed a significant increase in the cell division gene ftsZ. The concentrations of AEA needed for the anti-bacterial effects were below the cytotoxic concentration for normal Vero epithelial cells. Altogether, our data show that AEA has anti-bacterial and anti-biofilm activities against S. mutans and may have a potential role in preventing biofilms as a therapeutic measure.

Significant removal of bacterial biofilm induced by multiple-Short ranges of electric interventions

BackgroundBiofilm-related infections are serious problems in the Orthopedics field, and Staphylococcus aureus are the most popular causative agents of bacterial infections associated with arthroplasty. Several studies demonstrated a synergistic effect of the electric intervention (EI) and the antibiotic administration in killing bacteria in biofilm; however, a constant, long-time EI was needed. In the present study, the effective removal of biofilm formed with S. aureus on a titanium ring by multiple times of one minute-EI was observed and described. MethodsA methicillin-sensitive S. aureus clinical isolate was used to form biofilm on a titanium ring. After applying a series of EI with various combinations of the frequencies and timings, the amount and principal components of biofilms were assessed with crystal violet staining, live bacterial cell count, and fluorescence staining with confocal laser scanning microscopy. ResultsMore than 60% biofilm removal was observed in the 2-time EI applied at 24 (1) and 72 (3) h (days) post bacterial exposure (PBE) and in the 3-time EI at 0 (0), 24 (1), and 72 (3) h (days) PBE, or at 24 (1), 48 (2), and 72 (3) h (days) PBE. The live bacterial cell numbers, the proportion of live and dead cells, and the amount of extracellular polysaccharide substances (EPS) of biofilm were similar with or without EI. It was assumed that an excess amount of the biofilm removal shown in the several EI was not attributed to the effect of the electrolysis. ConclusionsThe effective removal of biofilm was observed when multiple times 1 min EI was applied without any changes in the proportion of live and dead bacteria or the amount of EPS. The mechanisms to explain extra biofilm removal remain to be elucidated.

Synthesis of heteropolyacid (HPA) functionalized graphitic carbon nitride as effective catalysts for converting polysaccharides into high-value chemicals

Using renewable biomass resources to replace fossil resources has been regarded as an effective way to restore and protect the natural environment. Cellulose as a polysaccharide exists in nature or environmental pollution control facilities in the production process. To recover and effectively transform cellulose or other polysaccharide substances into more valuable products, a series of heteropolyacid (HPA) functionalized graphitic carbon nitride (g-C3N4) HPA/g-C3N4 (n wt%) was synthesized, which was evaluated their catalytic performance in the conversion of polysaccharides as cellobiose, sucrose, starch, and cellulose. The high yield (58.6%) of 5-hydroxymethylfurfural (5-HMF) was obtained in one-pot upon H3PW12O40(HPW)/g-C3N4(30) at 100% cellulose conversion, which was contributed to the nature of HPW/g-C3N4(30). HPW/g-C3N4 was determined as an efficient, recyclable solid catalyst with high stability and long duration for high selectivity to 5-HMF in one-pot. The design of novel HPA with the functionalized candidate will be necessary for polysaccharides hydrolysis to selectively obtain high-value products.

A comparative analysis of perforation and blister features on internally corroded aged water pipeline wall

AbstractDespite well‐controlled chlorination, no known operational outages and physicochemical parameters of the water indicating a slight tendency to form carbonate deposits, aged and internally uncoated pipelines may experience unexpected internal corrosion events that raise integrity concerns. A typical corrosion damage was investigated consisting of a single perforation covered by a corrosion product cap (CPC) approximately 5 cm in diameter and surrounded by a relatively dense population of blisters of approx. 1 cm in diameter covering shallow corrosion pits. It was observed on the inner wall of an aged on‐land water distribution pipeline after decades of corrosion‐free operation. A dense population of bacteria, sulphides and extracellular polysaccharide substances were detected in the CPC, but none at the pit bottom surrounding the perforation and within the blisters, but abundant fungi were observed on scanning electron microscopy images of the blister bottom. The morphology of the blisters suggests that the blister formation is due to the loss of adhesion of the corrosion product layer, which is influenced by the formation of spherulitic crystals. The Fourier transform infra‐red spectroscopy results suggest that the growth of these carbonate crystals is related to the adsorption of microbially generated carbonyl groups. The results support a likely scenario of the effect of biomineralization on the appearance of corrosion through the formation of blisters, which may provide a niche for microbes that eventually cause corrosion damage.

Identification, Structure and Characterization of Bacillus tequilensis Biofilm with the Use of Electrophoresis and Complementary Approaches.

Biofilm is a complex structure formed as a result of the accumulation of bacterial cell clusters on a surface, surrounded by extracellular polysaccharide substances (EPSs). Biofilm-related bacterial infections are a significant challenge for clinical treatment. Therefore, the main goal of our study was to design a complementary approach in biofilm characterization before and after the antibiotic treatment. The 16S rRNA gene sequencing allowed for the identification of Bacillus tequilensis, as a microbial model of the biofilm formation. Capillary electrophoresis demonstrates the capability to characterize and show the differences of the electrophoretic mobility between biofilms untreated and treated with antibiotics: amoxicillin, gentamicin and metronidazole. Electrophoretic results show the clumping phenomenon (amoxicillin and gentamicin) as a result of a significant change on the surface electric charge of the cells. The stability of the dispersion study, the molecular profile analysis, the viability of bacterial cells and the scanning morphology imaging were also investigated. The microscopic and spectrometry study pointed out the degradation/remodeling of the EPSs matrix, the inhibition of the cell wall synthesis and blocking the ribosomal protein synthesis by amoxicillin and gentamicin. However, untreated and treated bacterial cells show a high stability for the biofilm formation system. Moreover, on the basis of the type of the antibiotic treatment, the mechanism of used antibiotics in cell clumping and degradation were proposed.

Hydrogen peroxide potentiates antimicrobial photodynamic therapy in eliminating Candida albicans and Streptococcus mutans dual-species biofilm from denture base

BackgroundCandida albicans (C.albicans) is the primary pathogen of denture biofilm. Moreover, it could establish a cross-kingdom relationship with bacteria to enhance its virulence and resistance to antifungal drugs. This study aimed to investigate the efficacy of antimicrobial photodynamic therapy (aPDT) in combination with hydrogen peroxide (H2O2) against C.albicans and Streptococcus mutans (S.mutans) dual-species biofilm formed on polymethyl methacrylate (PMMA) disk, and explore its involved mechanisms. MethodsC.albicans and S.mutans were grown on PMMA disk for 48 h to form biofilm and received different treatments. The treatments included:1) phosphate-buffered saline (PBS) group,2) 100 mM H2O2 group,3) aPDT group,4) aPDT+ H2O2 and 5) H2O2+aPDT group. Colony forming units (CFU), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and scanning electron microscope (SEM) were used to evaluate the antimicrobial effects. Extracellular polysaccharide substance (EPS) production and observation, cell permeability of biofilm, and uptake of toluidine blue O (TBO) by biofilm were assessed to investigate the involved mechanism. ResultsThere was no significant difference between PBS group and H2O2 group in viable microorganisms and metabolic activity of biofilm. The treatment protocols containing aPDT group reduced microorganism numbers and metabolic activity when compared to PBS group or H2O2 group (P<0.05). H2O2+aPDT treatment showed the highest antimicrobial efficacy in comparison with other treatments (P<0.05). Pretreatment with H2O2 could decrease EPS production and enhance cell permeability, leading to increased TBO uptake in biofilm. ConclusionPretreatment with H2O2 improved aPDT efficiency in eliminating dual-species biofilm from PMMA disk by reducing EPS amount, enhancing cell permeability, and increasing TBO uptake.

Antifouling with Chloride Ion Electrolytic Recycling through a Momentum Boundary Layer

AbstractSeaLite Engineering, after a 10-yr research and development program, has produced an operational antifouling system for ocean sensors and instruments designed for low power consumption and long (&gt;1 yr) deployments. The important innovation is the replacement of pumps by gravity and external motion to significantly reduce energy consumption. Also, a prototype system for autonomous underwater vehicle control surfaces is now undergoing laboratory testing. The effectiveness of SeaLite’s technology has been demonstrated year-round in northern estuaries and in the Gulf of Mexico, the latter by an independent agency. The process leading to this result was, first starting in 2010, an extensive laboratory evaluation of electrode alloys, calibration of chlorine production versus electric power input, and the location for attaching electrodes to various objects requiring protection from fouling. After 2015 the experimentation moved to the ocean, first in a Cape Cod estuary and then to the Gulf of Mexico. Comparisons with a mechanical antifouling system were done in situ, and with a UV antifouling system from AML Oceanographic, Ltd., by comparing the data. Starting in 2019, the development of biofilms, from their initial deposition through the extra polysaccharide substance stage, were experimentally investigated by taking samples from an estuary near SeaLite’s laboratory. Biofilms on microscope slides and water column samples were collected. This was done in different seasons, from spring bloom, summer doldrums, autumn temperature decline, and the winter freeze. The objective was to determine the level of biofilm growth that would require antifouling, and its’ seasonal, temperature, and solar radiation dependence, and thus to conserve power.

Effect of the liquid-to-powder ratio on physicochemical properties of calcium phosphate cements and of these properties over Biofilm thickness of adhered Staphylococcus Aureus

Tricalcium phosphate (TCP) synthetized by high temperature solid state reaction at 1400°C and three derived calcium phosphate cements (CPCs) prepared at liquid to powder (L/P) ratios of 0.33, 0.44 and 0.55 ml/g, respectively, were physicochemically characterized. Calcium deficient hydroxyapatite crystals were identified by scanning electron microscopy on CPC, and differences in crystal sizes were observed at different L/P ratios. Also, the biofilm thickness of two Staphylococcus Aureus (S.aureus) strains grown for 24 hours on the three CPC are reported. A dependence of the biofilm thickness with the specific surface area (SSA) of CPC was identified. They are directly proportional for non-extracellular polysaccharide substances (EPS) producing S.aureus and inversely proportional for EPS producing S.aureus. Non-proportional behavior between the SSA and mechanical strength of the CPC was observed as L/P ratio increases.

Антибиопленочная активность антиматриксных молекул

Внеклеточный матрикс биопленок обеспечивает фиксацию биопленки на биологической поверхности и защиту ее бактерий от внешних неблагоприятных факторов. Основным структурным компонентом био­пленок является внеклеточное полисахаридное вещество. Ключевыми молекулярными структурами, поддерживающими трехмерную структуру биопленки, считают экзополисахариды и амилоидоподобные волокна. До недавнего времени предполагалось, что большинство механизмов диспергирования биопленок ассоциировано с функционированием матриксных деградирующих ферментов, таких как гликозидгидролазы, полисахаридные лиазы и протеазы. Однако продемонстрировано, что в процессе разрушения матриксных экзополисахаридов и амилоидоподобных волокон играют самостоятельную роль малые молекулы. Среди соединений, нарушающих матрикс биопленки, различают антиматриксные молекулы, соединения, взаимодействующие с микродоменами бактериальной мембраны, и бактериальные поверхностно-активные вещества (биосурфагенты). Продемонстрировано, что соединения данных групп могут ингибировать образование биопленок и способствовать их диспергированию. Из группы антиматриксных молекул полиаминное соединение норспермидин взаимодействует с экзополисахаридами, а производные бензохинона AA-861 и сесквитерпеновый лактон партенолид — с TasA-амилоидоподобными волокнами. Норспермидин предотвращает образование и диспергирует биопленки различных бактерий, включая Acinetobacter baumannii, Bacillus subtili, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis. Соединение AA-861 проявляет активность против биопленок, которые образованы бактериями Streptococcus mutans, Bacillus cereus, Escherichia coli, а партенолид диспергирует биопленки, сформированные Escherichia coli и Bacillus cereus. Сарагосовые кислоты, взаимодействуя с микродоменами бактериальной мембраны, нарушают функционирование рафт-ассоциированных протеинов бактерий. Малые антиматриксные молекулы и нацеленные на микродомены мембраны бактерий, инициирующие диспергирование биопленки, безусловно, станут основанием для разработки эффективных антибиопленочных терапевтических лекарственных средств.

CsrA Enhances Cyclic-di-GMP Biosynthesis and Yersinia pestis Biofilm Blockage of the Flea Foregut by Alleviating Hfq-Dependent Repression of the hmsT mRNA.

ABSTRACTPlague-causing Yersinia pestis is transmitted through regurgitation when it forms a biofilm-mediated blockage in the foregut of its flea vector. This biofilm is composed of an extracellular polysaccharide substance (EPS) produced when cyclic-di-GMP (c-di-GMP) levels are elevated. The Y. pestis diguanylate cyclase enzymes HmsD and HmsT synthesize c-di-GMP. HmsD is required for biofilm blockage formation but contributes minimally to in vitro biofilms. HmsT, however, is necessary for in vitro biofilms and contributes to intermediate rates of biofilm blockage. C-di-GMP synthesis is regulated at the transcriptional and posttranscriptional levels. In this, the global RNA chaperone, Hfq, posttranscriptionally represses hmsT mRNA translation. How c-di-GMP levels and biofilm blockage formation is modulated by nutritional stimuli encountered in the flea gut is unknown. Here, the RNA-binding regulator protein CsrA, which controls c-di-GMP-mediated biofilm formation and central carbon metabolism responses in many Gammaproteobacteria, was assessed for its role in Y. pestis biofilm formation. We determined that CsrA was required for markedly greater c-di-GMP and EPS levels when Y. pestis was cultivated on alternative sugars implicated in flea biofilm blockage metabolism. Our assays, composed of mobility shifts, quantification of mRNA translation, stability, and abundance, and epistasis analyses of a csrA hfq double mutant strain substantiated that CsrA represses hfq mRNA translation, thereby alleviating Hfq-dependent repression of hmsT mRNA translation. Additionally, a csrA mutant exhibited intermediately reduced biofilm blockage rates, resembling an hmsT mutant. Hence, we reveal CsrA-mediated control of c-di-GMP synthesis in Y. pestis as a tiered, posttranscriptional regulatory process that enhances biofilm blockage-mediated transmission from fleas.

Optimization of Extracellular Polysaccharide Substances from Lactic Acid Bacteria Isolated from Fermented Dairy Products

Optimization of Extracellular Polysaccharide Substances from Lactic Acid Bacteria Isolated from Fermented Dairy Products

Interplay of water temperature and fouling during ceramic ultrafiltration for drinking water production

Ceramic ultrafiltration (UF) is an emerging technology for drinking water production, but the interplay and influence of water temperature on fouling is lacking. This research investigates temperatures from 5 to 35 °C and explored the fouling impacts of humic, protein, and polysaccharide substances on a ceramic UF membrane. Water temperature not only affected water viscosity but also altered the fouling behavior of organics. At 5 °C, while approximately 50 % of the change in the unified membrane fouling index (UMFI) was attributed to the change in water viscosity the remaining 50 % was due to change in organic fouling behavior. Conversely, at 35 °C, the overall UMFI decreased relative to the 20 °C standard, of which 36–53 % of the decrease was associated with changes in fouling behavior. Constant flux blocking models determined that standard pore blocking dominated the first filtration cycle for all temperature cases, suggesting that material accumulation inside the pores was responsible for fouling during the initial stages of filtration. The standard blocking continued throughout filtration for 20 and 35 °C suggesting that fouling was mostly reversible. In contrast, at 5 °C condition, fouling transitioned to intermediate blocking, suggesting deposition inside the pores causing irreversible fouling. UMFI and carbon analysis showed lower backwash and chemical cleaning efficiencies at the 5 °C condition indicating higher irreversible fouling mass, while better cleaning was observed at the warmer water temperatures. The exacerbated fouling at low temperatures demonstrates that changes in membrane backwash and chemical cleaning should be implemented under fluctuating water temperature conditions.

Aktivitas Antiinflamasi Crude Extract Fukoidan dari Sargassum crassifolium pada Sel RAW 264.7 yang Diinduksi LPS

Inflammation is known as the basic mechanism underlying various chronic diseases. Macrophage activation by inflammatory stimulus induces the release of inflammatory mediators, thus the mediators becoming a promising target of anti-inflammatory drug development. Previous studies indicated that fucoidan has anti-inflammatory activity by inhibiting the release of proinflammatory mediators. The aim of this study is determining anti-inflammatory activity of fucoidan crude extract form Sargassum crassifolium Garut waters by observing its effect on proinflammatory cytokines TNF-α, IL-1β, dan IL-6. Fucoidan is a polysaccharide substance which has various characteristics, depending on the source and the extraction method which is influencing its bioactivity. Sargassum crassifolium collected from Garut-West Java is extracted using diluted HCl 0,1 M and precipitated with ethanol to obtain fucoidan crude extract. The crude extract is tested on LPS-induced RAW 264.7 cells to evaluate its effect on TNF-α, IL-1β, and IL-6 level using ELISA method. The result showed that fucoidan crude extract decreased the level of TNF-α by the dose of 25 and 50 μg/ml, and decreased the level of IL-1β and IL-6 by the dose of 25 μg/ml. The dose of 50 μg/ml failed to inhibit IL-1β and IL-6 production. This study showed that fucoidan crude extract derived from S. crassifolium has anti-inflammatory activity to RAW 264.7 cells by the dose of 25 μg/ml.

Mechanistic Model for the Coexistence of Nitrogen Fixation and Photosynthesis in Marine Trichodesmium.

The cyanobacterium Trichodesmium is an important contributor of new nitrogen (N) to the surface ocean, but its strategies for protecting the nitrogenase enzyme from inhibition by oxygen (O2) remain poorly understood. We present a dynamic physiological model to evaluate hypothesized conditions that would allow Trichodesmium to carry out its two conflicting metabolic processes of N2 fixation and photosynthesis. First, the model indicates that managing cellular O2 to permit N2 fixation requires high rates of respiratory O2 consumption. The energetic cost amounts to ∼80% of daily C fixation, comparable to the observed diminution of the growth rate of Trichodesmium relative to other phytoplankton. Second, by forming a trichome of connected cells, Trichodesmium can segregate N2 fixation from photosynthesis. The transfer of stored C to N-fixing cells fuels the respiratory O2 consumption that protects nitrogenase, while the reciprocal transfer of newly fixed N to C-fixing cells supports cellular growth. Third, despite Trichodesmium lacking the structural barrier found in heterocystous species, the model predicts low diffusivity of cell membranes, a function that may be explained by the presence of Gram-negative membrane, production of extracellular polysaccharide substances (EPS), and "buffer cells" that intervene between N2-fixing and photosynthetic cells. Our results suggest that all three factors-respiratory protection, trichome formation, and diffusion barriers-represent essential strategies that, despite their energetic costs, facilitate the growth of Trichodesmium in the oligotrophic aerobic ocean and permit it to be a major source of new reactive nitrogen.IMPORTANCE Trichodesmium is a major nitrogen-fixing cyanobacterium and exerts a significant influence on the oceanic nitrogen cycle. It is also a widely used model organism in laboratory studies. Since the nitrogen-fixing enzyme nitrogenase is extremely sensitive to oxygen, how these surface-dwelling plankton manage the two conflicting processes of nitrogen fixation and photosynthesis has been a long-standing question. In this study, we developed a simple model of metabolic fluxes of Trichodesmium capturing observed daily cycles of photosynthesis, nitrogen fixation, and boundary layer oxygen concentrations. The model suggests that forming a chain of cells for spatially segregating nitrogen fixation and photosynthesis is essential but not sufficient. It also requires a barrier against oxygen diffusion and high rates of oxygen scavenging by respiration. Finally, the model indicates an extremely short life span of oxygen-enabling cells to instantly create a low-oxygen environment upon deactivation of photosynthesis.