Chemical and Resistive Switching Properties of Elaeodendron buchananii Extract-Carboxymethyl Cellulose Composite: A Potential Active Layer for Biodegradable Memory Devices.

Biodegradable electronic devices play a crucial role in addressing the escalating issue of electronic waste accumulation, which poses significant environmental threats. In this study, we explore the utilization of a methanol-based extract of the Elaeodendron buchananii plant blended with a carboxymethyl cellulose biopolymer to produce a biodegradable and environmentally friendly functional material for a resistive switching memory system using silver and tungsten electrodes. Our analyses revealed that these two materials chemically interact to generate a perfect composite with near semiconducting optical bandgap (4.01 eV). The resultant device exhibits O-type memory behavior, with a low ON/OFF ratio, strong endurance (≥103 write/erase cycles), and satisfactory (≥103) data retention. Furthermore, through a comprehensive transport mechanism analysis, we observed the formation of traps in the composite that significantly improved conduction in the device. In addition, we established that altering the voltage amplitude modifies the concentration of traps, leading to voltage amplitude-driven multiple resistance states. Overall, our findings underscore the potential of functionalizing polymers that can be functionalized by incorporating plant extracts, resulting in biodegradable and nonvolatile memory devices with promising performance metrics.

Complete photodynamic inactivation of Pseudomonas aeruginosa biofilm with use of potassium iodide and its comparison with enzymatic pretreatment.

Pseudomonas aeruginosa, a gram-negative bacterium, accounts for 7% of all hospital-acquired infections. Despite advances in medicine and antibiotic therapy, P. aeruginosa infection still results in high mortality rates of up to 62% in certain patient groups. This bacteria is also known to form biofilms, that are 10 to 1000 times more resistant to antibiotics compared to their free-floating counterparts. Photodynamic Inactivation (PDI) has been proved to be an effective antimicrobial technique for microbial control. This method involves the incubation of the pathogen with a photosensitizer (PS), then, a light at appropriated wavelength is applied, leading to the production of reactive oxygen species that are toxic to the microbial cells. Studies have focused on strategies to enhance the PDI efficacy, such as a pre-treatment with enzymes to degrade the biofilm matrix and/or an addition of inorganic salts to the PS. The aim of the present study is to evaluate the effectiveness of PDI against P. aeruginosa biofilm in association with the application of the enzymes prior to PDI (enzymatic pre-treatment) or the addition of potassium iodide (KI) to the photosensitizer solution, to increase the inactivation effectiveness of the treatment. First, a range of enzymes and PSs were tested, and the best protocols for combined treatments were selected. The results showed that the use of enzymes as a pre-treatment was effective to reduce the total biomass, however, when associated with PDI, mild bacterial reductions were obtained. Then, the use of KI in association with the PS was evaluated and the results showed that, PDI mediated by methylene blue (MB) in the presence of KI was able to completely eradicate the biofilm. However, when the PDI was performed with curcumin and KI, no additive reduction was observed. In conclusion, out of all strategies evaluated in the present study, the most promising strategy to improve PDI against P. aeruginosa biofilm was the use of KI in association with MB, resulting in eradication with 108 log bacterial inactivation.

Sugarcane bagasse derived xylooligosaccharides produced by an arabinofuranosidase/xylobiohydrolase from Bifidobacterium longum in synergism with xylanases.

Arabinoxylan is a major hemicellulose in the sugarcane plant cell wall with arabinose decorations that impose steric restrictions on the activity of xylanases against this substrate. Enzymatic removal of the decorations by arabinofuranosidases can allow a more efficient arabinoxylan degradation by xylanases. Here we produced and characterized a recombinant Bifidobacterium longum arabinofuranosidase from glycoside hydrolase family 43 (BlAbf43) and applied it, together with GH10 and GH11 xylanases, to produce xylooligosaccharides (XOS) from wheat arabinoxylan and alkali pretreated sugarcane bagasse. The enzyme synergistically enhanced XOS production by GH10 and GH11 xylanases, being particularly efficient in combination with the latter family of enzymes, with a degree of synergism of 1.7. We also demonstrated that the enzyme is capable of not only removing arabinose decorations from the arabinoxylan and from the non-reducing end of the oligomeric substrates, but also hydrolyzing the xylan backbone yielding mostly xylobiose and xylose in particular cases. Structural studies of BlAbf43 shed light on the molecular basis of the substrate recognition and allowed hypothesizing on the structural reasons of its multifunctionality.

Two-domain GH30 xylanase from human gut microbiota as a tool for enzymatic production of xylooligosaccharides: Crystallographic structure and a synergy with GH11 xylosidase.

Production of value-added compounds and sustainable materials from agro-industrial residues is essential for better waste management and building of circular economy. This includes valorization of hemicellulosic fraction of plant biomass, the second most abundant biopolymer from plant cell walls, aiming to produce prebiotic oligosaccharides, widely explored in food and feed industries. In this work, we conducted biochemical and biophysical characterization of a prokaryotic two-domain R. champanellensis xylanase from glycoside hydrolase (GH) family 30 (RcXyn30A), and evaluated its applicability for XOS production from glucuronoxylan in combination with two endo-xylanases from GH10 and GH11 families and a GH11 xylobiohydrolase. RcXyn30A liberates mainly long monoglucuronylated xylooligosaccharides and is inefficient in cleaving unbranched oligosaccharides. Crystallographic structure of RcXyn30A catalytic domain was solved and refined to 1.37 Å resolution. Structural analysis of the catalytic domain releveled that its high affinity for glucuronic acid substituted xylan is due to the coordination of the substrate decoration by several hydrogen bonds and ionic interactions in the subsite -2. Furthermore, the protein has a larger ß5-α5 loop as compared to other GH30 xylanases, which might be crucial for creating an additional aglycone subsite (+3) of the catalytic site. Finally, RcXyn30A activity is synergic to that of GH11 xylobiohydrolase.

Molecular mechanism of cellulose depolymerization by the two-domain BlCel9A enzyme from the glycoside hydrolase family 9.

Carbohydrate-active enzymes from the glycoside hydrolase family 9 (GH9) play a key role in processing lignocellulosic biomass. Although the structural features of some GH9 enzymes are known, the molecular mechanisms that drive their interactions with cellulosic substrates remain unclear. To investigate the molecular mechanisms that the two-domain Bacillus licheniformis BlCel9A enzyme utilizes to depolymerize cellulosic substrates, we used a combination of biochemical assays, X-ray crystallography, small-angle X-ray scattering, and molecular dynamics simulations. The results reveal that BlCel9A breaks down cellulosic substrates, releasing cellobiose and glucose as the major products, but is highly inefficient in cleaving oligosaccharides shorter than cellotetraose. In addition, fungal lytic polysaccharide oxygenase (LPMO) TtLPMO9H enhances depolymerization of crystalline cellulose by BlCel9A, while exhibiting minimal impact on amorphous cellulose. The crystal structures of BlCel9A in both apo form and bound to cellotriose and cellohexaose were elucidated, unveiling the interactions of BlCel9A with the ligands and their contribution to substrate binding and products release. MD simulation analysis reveals that BlCel9A exhibits higher interdomain flexibility under acidic conditions, and SAXS experiments indicate that the enzyme flexibility is induced by pH and/or temperature. Our findings provide new insights into BlCel9A substrate specificity and binding, and synergy with the LPMOs.

Low-resolution molecular shape, biochemical characterization and emulsification properties of a halotolerant esterase from Bacillus licheniformis.

Bacterial esterases are highly versatile enzymes, currently widely used in detergents, biosurfactants, bioemulsifiers and as biocatalysts in paper and food industries. Present work describes heterologous expression, purification, and biophysical and biochemical characterization of a halotolerant esterase from Bacillus licheniformis (BlEstA). BlEstA preferentially cleaves pNP-octanoate and both activity and stability of the enzyme increased in the presence of 2 M NaCl, and also with several organic solvents (ethanol, methanol and DMSO). Furthermore, BlEstA has considerable emulsifying properties, particularly with olive oil as substrate. Our studies also show that the enzyme is monomeric in solution and its small-angle X-ray scattering low-resolution molecular envelope fits well its high-resolution homology model.