Search Results (238)

To enhance quantitativeness and interpretability in identifying the mechanisms of complex oil–mineral–surfactant systems, this paper introduces an algorithmic molecular simulation analysis approach, transforming molecular dynamics trajectory data into comparable multidimensional molecular descriptors. Specifically, based on parameters such as radial distribution functions, mean square displacement, interface concentration distribution, adsorption energy attenuation, hydrogen bond statistics, and electrostatic interactions, an algorithm analysis framework was constructed covering “trajectory data acquisition—feature descriptor extraction—interface behavior recognition—separation mechanism classification.” This framework can identify differentiated regulatory patterns of different surfactants on SARA (saturates, aromatics, resins, asphaltenes) component migration, adsorption, and desorption behavior from a large amount of dynamic simulation data, thereby improving the structural expression and mechanism discrimination capabilities of molecular simulation results. In order to clarify the component-selective microscopic mechanisms of surfactants in the separation of heavy oil from oil sands, this work employs molecular dynamics simulations to study the interactions of the non-ionic surfactant TX-100 and the biosurfactants sophorolipid and rhamnolipid with the SARA fractions of heavy oil, both in the absence and presence of calcite mineral surfaces. The results show that all three surfactants act mainly through weak long-range interactions, but with distinct mechanisms: TX-100 preferentially screens small-molecule saturates through long-chain steric hindrance and hinders the diffusion of asphaltenes; sophorolipid promotes the preferential desorption of resins via hydrogen bonding; and rhamnolipid drives the desorption of aromatics at later stages through hydrophobic–electrostatic synergy. The C001 crystal surface exhibits the strongest adsorption affinity across all systems; the mineral surface overall prolongs the diffusion equilibrium time and amplifies the above kinetic differences. This study establishes three molecular-scale mechanisms—steric hindrance sieving, hydrogen-bond-promoted desorption, and electrostatically driven desorption—and reveals the universal adsorption platform effect of the C001 crystal surface, providing a theoretical basis for the molecular design of surfactants aimed at the selective separation of heavy oil components. Full article

The prevalence of diabetes has increased considerably in recent decades, representing a global health problem. Although several pharmacological approaches for the treatment of diabetes are available, it is pertinent to explore more effective alternatives with reduced adverse effects. In this work, the hypoglycemic activity of rhamnolipids was studied using the chicken embryo (in ovo) model. The results obtained demonstrated that rhamnolipids produced by Pseudomonas aeruginosa #112 and commercial rhamnolipids (RL-90) significantly reduced blood glucose levels of chicken embryos on embryonic day 11 (from 135 ± 11 mg/dL to 94–107 mg/dL). These values were similar to those achieved with human insulin (104 ± 20 mg/dL) and the rapid-acting human insulin analog FIASP^® (95 ± 18 mg/dL). It was also verified that rhamnolipids did not have a negative effect on chicken embryo development at the concentrations tested. Regarding the molecular mechanisms involved in the decrease in blood glucose levels, for both insulins, a reduction in the expression of genes encoding the glucose transporter 2 (glut2) and the gluconeogenic enzymes phosphoenolpyruvate carboxykinase 2 and fructose-1,6-biphosphatase 1 was observed. However, in the case of rhamnolipids, only a reduction in the expression of glut2 was observed. According to the results obtained, rhamnolipids are potential candidates for further studies on the development of new alternative treatments for diabetes symptoms. Full article

This study investigated rhamnolipid synthesis in Pseudomonas aeruginosa ATCC 27853. Two constitutive promoters, P_rpsJ and P_oprL, were isolated and cloned upstream of the rhlABRI and rmlBDAC gene clusters to evaluate their impact on rhamnolipid titers. The overexpression of rhlB, driven by the P_rpsJ promoter, significantly enhanced rhamnolipid production. Subsequent glycine-scanning mutagenesis of RhlB identified an optimal variant (RhlBM328G), which increased the titer 1.82-fold (to 24.6 g·L⁻¹) compared to the wild type, achieving a product yield of 0.39 g·g⁻¹. Characterization of the extracted rhamnolipids revealed a critical micelle concentration of 1 mg/L, a corresponding surface tension of 53.9 mN/m, and a hydrophilic–lipophilic balance (HLB) value of 14. This HLB value indicated that the synthesized rhamnolipids possess superior hydrophilicity, robust oil-in-water emulsifying capabilities, and excellent solubilization and dispersion properties. Furthermore, molecular docking and molecular dynamics simulations demonstrated that in the RhlBM328G mutant, the nucleophilic attack distances between the substrates and the catalytic moiety are optimized for catalysis, thereby boosting rhamnolipid production. Full article

Biofilms rapidly form on medical devices such as urinary catheters and surgical materials. These biofilms compromise patient safety and undermine infection prevention and control (IPC). Biofilms also reduce the effectiveness of antibiotics and disinfectants. As a result, they increase healthcare-associated infections and increase costs through device failure and the need for maintenance or replacement. Researchers are increasingly exploring biosurfactants (BSs) as surface coatings and cleaning additives to prevent microbial attachment and disrupt early biofilm formation on medical devices and healthcare-related surfaces. This review examines the translational potential of biosurfactants as preventive, disruptive, and adjunctive antibiofilm agents for medical devices and healthcare-related surfaces. Literature evidence on glycolipids (rhamnolipids, sophorolipids) and lipopeptides (surfactin) from static, flow-based, and microfluidic in vitro models that used clinically relevant materials, such as silicone and polydimethylsiloxane (PDMS), were examined. In our literature search, we focused on pathogens central to IPC, such as Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus spp., and Candida spp., and it was generally noted that BSs reduced microbial adhesion and delayed early biofilm formation on medical devices and healthcare-related surfaces. Significant evidence also suggests that they partially disrupt biofilms and improve antimicrobial penetration when co-applied, mainly through membrane disruption, destabilization of extracellular substances, interfering with quorum sensing, and synergistic and/or antagonistic interactions with other molecules. Their performance varied with class, formulation, hydrodynamic conditions, and microbial composition. BSs function better as preventive and adjunctive IPC tools than stand-alone antimicrobial agents and can help to reduce biofilm formation on devices and improve surface disinfection. However, translating this promise into practice demands more robust data on long-term safety, stability, and product quality. Full article

Although teixobactin, a promising cyclic undecadepsipeptide, exhibits efficacy against Gram-positive bacteria due to its novel mode of action and low potential for resistance, its clinical application is limited by two key shortcomings: ineffectiveness against Gram-negative bacteria and poor penetration of the protective extracellular polymeric substance (EPS) in biofilms. This renders it unsuitable for targeting the polymicrobial biofilms, which are the cause of periodontitis and peri-implantitis. We designed a modified teixobactin analog by integrating rhamnolipid, Ag@Fe₃O₄ nanoparticles, and _L-Chg₁₀-teixobactin to obtain a novel magnetic nanoparticle (MNP). The MNP demonstrates the ability to simultaneously degrade EPS, penetrate biofilm structures, and eliminate both G⁺ and G⁻ pathogens under a rotating magnetic field (RMF). Rhamnolipid grafting degraded 52.5% of biofilm EPS. MNPs showed broad-spectrum antimicrobial activity, with minimal inhibitory concentrations from 100 to 200 µg/mL. Combined with RMF, biofilm eradication rates reached 97.0% (E. faecalis), 97.7% (S. gordonii), 88.4% (P. gingivalis), and 74.2% (F. nucleatum). The biofilm thickness was reduced from 19.4 ± 2.9 µm to 7.4 ± 1.0 µm, and the biofilm biomass was reduced by 68.5%. This combined strategy integrates enzymatic EPS degradation, magneto-mechanical disruption, and dual antimicrobial action, offering a promising topical therapy for periodontitis and peri-implantitis. Full article

Biosurfactants offer a green, sustainable approach to many environmental bioremediations, especially for oil contamination. In this study, the aim is to evaluate the effectiveness of biosurfactants in accelerating hydrocarbon removal from mature fine tailings under anaerobic conditions. The bacteria were isolated from mature fine tailings and tested for biosurfactant production using different biosurfactant screening methods (i.e., blood agar, cetyltrimethylammonium bromide (CTAB) blue agar, oil displacement, and drop collapse). The most efficient strain showed high similarity to Stutzerimonas stutzeri by 16S rRNA gene sequencing. Results showed that this strain produces rhamnolipids with a critical micelle concentration (CMC) of 600 mg/L and a minimum surface tension of 38.70 ± 0.08 mN/m. Moreover, when supplemented with whey, the strain showed a high emulsification index of 24 toward toluene (66%) and hexane (60%). The bioremediation of mature fine tailings (MFTs) was conducted under anaerobic conditions by adding a consortium of the four strains that were positive in biosurfactant screening tests. The results showed 53% removal of n-alkane C9-C30 and a reduction in surface tension from 69 ± 0.5 mN/m to a minimum of 54.33 ± 0.5 mN/m. The results suggest the potential successful application of bioaugmentation for in situ biological treatment in the oil sands industry. Full article

Rhamnolipids (RLs) are natural biosurfactants produced by microbial fermentation. They exhibit excellent surface activity, environmental compatibility, and versatile biological activities, with broad application potential in energy development, environmental remediation, personal care, and biomedicine. In recent years, RLs have garnered significant attention due to the structural divergence between mono-rhamnolipids (mono-RLs) and di-rhamnolipids (di-RLs). Their distinct physicochemical and biological properties necessitate structure-function-guided “tailor-made” synthesis. Notably, the compositional fluctuation of naturally occurring RL mixtures constrains their high-value utilization. This review systematically summarizes the structure–function relationships, microbial biosynthetic pathways, and regulatory approaches of mono-RLs and di-RLs, with a core focus on the targeted production of RLs with specific mono-/di-RL ratios. The review also highlights the application-specific suitability of the two RL congeners. It aims to provide a theoretical foundation and technical reference for the precision manufacturing and commercialization of RLs in energy, environment, health, and other related fields. Full article

Background and Objectives: Pseudomonas aeruginosa is a versatile, opportunistic pathogen responsible for a wide spectrum of infections, particularly in immunocompromised patients and those with disrupted epithelial barriers and chronic respiratory conditions. Its clinical significance is amplified by intrinsic and acquired antibiotic resistance, contributing to high mortality rates and treatment challenges. The bacterium’s pathogenic success stems from a multifaceted repertoire of virulence factors, including adhesins, pili, fimbriae, flagella, exopolysaccharides, biofilm-associated proteins, secreted toxins, proteases, lipases, phospholipases, rhamnolipids and redox-active metabolites. These factors are tightly regulated through complex networks, such as quorum sensing and c-di-GMP signaling, enabling dynamic adaptation to host environments and modulation of acute and chronic infection phenotypes. Biofilm formation and nutrient acquisition strategies further support survival in resource-limited conditions and protect against immune clearance and antibiotic pressure. Antibiotic resistance in P. aeruginosa limits therapeutic options. In addition, it may indirectly enhance virulence through modulation of stress responses and quorum sensing. P. aeruginosa’s pathogenicity emerges from the synergy between traditional virulence determinants and adaptive survival strategies, supporting long-term persistence, chronic infection, and resistance to host immunity and therapy. Materials and Methods: This narrative review is based on a comprehensive analysis of recent peer-reviewed literature focusing on virulence regulation, biofilm formation, nutrient acquisition strategies, and the interplay between antibiotic resistance and pathogenicity. Results: The reviewed evidence indicates that virulence expression in P. aeruginosa is highly dynamic and context-dependent, with regulatory networks integrating environmental signals to fine-tune pathogenic responses. A consistent finding across studies is the central role of biofilm-associated adaption in promoting persistence and antimicrobial tolerance. Moreover, the interaction between resistance mechanisms and global regulatory pathways appears to enhance bacterial fitness and long-term survival within the host. Conclusions: A deeper understanding of these interconnected mechanisms may facilitate the development of more effective anti-virulence and therapeutic strategies. Full article

The spoilage phenotype of microorganisms is a key mechanism leading to food spoilage, but how their metabolic environment affects the spoilage phenotype remains unclear. This study utilized metabolomics and spoilage phenotype analysis to reveal metabolic differences between different quorum sensing (QS) genotypes of Hafnia. alvei H4 and their impact on spoilage phenotypes. Ultra-high performance liquid chromatography–fluorescence detection revealed that the QS system participated in the differential metabolic regulation of eight amino acids, with serine exerting the most significant influence on the spoilage phenotype. Subsequent studies demonstrated that QS-promoted serine inhibited bacterial motility by affecting the biosynthesis of rhamnolipid (rather than c-di-GMP) and inhibiting flagellar/chemotactic genes expression. Moreover, QS-promoted serine induced the difference of bacterial inner membrane, further inhibiting bacterial motility. These findings provided fundamental information for the control of biofilms conformation within complex food nutritional background. Full article

Surfactants are harmful, persistent pollutants that are often found in contaminated soils, wastewater, and industrial effluents in complex mixes. Due to their chemical diversity and persistence, they present a bioremediation challenge. Using long-read shotgun metagenomics, 16S rRNA amplicon sequencing, PICRUSt2 functional prediction, and physicochemical proxies (total organic carbon, dissolved oxygen, chemical oxygen demand, foaming activity, etc.), this study investigated the aerobic biodegradation of SDS, SLS, rhamnolipids, Triton X-100, and CTAB (individually/mixed, 4% w/v) by microbial consortia enriched from oil-contaminated soil for 14 days. Pseudomonadota was dominant (85–90%), with Pseudomonas (60%) driving SLS and SDS degradation, while Paraburkholderia and Bordetella were dominant in recalcitrant surfactant degradation. Among the surfactants, SLS, rhamnolipids, and the combination of all surfactants demonstrated higher degradation by virtue of total organic carbon reductions of 50%, 56%, and 50%, respectively, and a foaming activity decline of 45–64%. The combination of surfactants with CTAB showed a 21% reduction in TOC, most likely due to CTAB’s known bactericidal effects. PICRUSt2 showed differential enrichment in alkyl oxidation, sulfate ester hydrolysis, aromatic ring cleavage, and fatty acid/sulfur genes and pathways. This study establishes inexpensive, scalable proxy indicators for monitoring surfactant bioremediation when direct metabolite analysis is impractical. Full article

Background/Objectives: The emergence of hypervirulent Pseudomonas aeruginosa strains resistant to β-lactamase inhibitor antibiotics is a critical health problem as they impede the treatment of infections. The objective of this study was to determine the different molecular arrangements of the virulence genotype related to β-lactamase genotype and the resistance phenotype to a combination of β-lactam antibiotics and β-lactamase inhibitors, and the phylogroups in P. aeruginosa strains isolated from patients with healthcare-associated infections and community-acquired infections. Methods: P. aeruginosa, virulence genes, β-lactamase genes and phylogroups were identified using polymerase chain reaction. Resistance to β-lactam antibiotics and β-lactamase inhibitors was determined using the disk diffusion method. The MIC determination of ticarcillin/clavulanic acid and piperacillin/tazobactam was performed using the MIC test strip for antimicrobial susceptibility testing. Results: In total, 124 P. aeruginosa strains from patients with healthcare-associated (67/124) and community-acquired infections (57/124) were analyzed. Most strains from patients with healthcare-associated infections and community-acquired infections harbored genes for proteases (aprA), phospholipases (pIcH and pIcN), elastases (lasA and lasB), rhamnolipids (rhLA), quorum-sensing system (lasI and rhII), and β-lactamase (bla_oxa-4, bla_oxa-1, and bla_GES). In total, 100% (124/124) and 99.1% (123/124) of the strains isolated from patients with healthcare-associated and community-acquired infections were resistant to the β-lactamase inhibitor antibiotics, amoxicillin/clavulanic acid and ampicillin/sulbactam, respectively, while 54% (67/124) of the strains were resistant to piperacillin/tazobactam. Phylogroup 1 (22/124) was detected more frequently among the strains in relation to phylogroup 2 (8/12). Conclusions: We demonstrated different association profiles of virulence genotype related to the β-lactamase genotype, the β-lactamase inhibitor resistome, phylogroups, and clinical origin of the strains. Therefore, medical treatment regimens against infections caused by P. aeruginosa should be improved. Full article

Rhamnolipids (RL) are biosurfactants produced mainly by Pseudomonas aeruginosa strains that have environmental and industrial applications. However, their industrial-scale production still faces the challenge of improving the efficiency and cost-effectiveness of the process. The aim of this work was to optimize the cultivation conditions to increase the RL production by using Response Surface Methodology with key parameters of the process, such as oxygen level, agitation, temperature, nutrients, and residual frying oil as a low-cost carbon source. The optimized parameters were 3.04 g/L of nitrogen, 0.5 vvm of aeration and 180 rpm of agitation, with which 52.2 g/L was obtained in 168 h. The critical micellar concentration (CMC) of this RL was 3.14 g/L, and the Oil Spreading assay confirmed the presence of surface-active compounds in the purified RL that generated an average halo area of 2746.7 ± 72.0 mm², which represents an increase of 2063.41% ± 28.36% compared to the negative control. These advances could contribute to more sustainable, cost-effective RL production, promoting its application in bioremediation processes and other industries. Full article

Antimicrobial resistance (AMR) poses a global health threat, which is becoming more challenging due to the involvement of bacterial virulence mechanisms such as quorum sensing (QS) and biofilm formation. These systems regulate pathogenic traits and shield bacteria from conventional therapies. Phytocompounds offer promising antivirulence strategies by disrupting QS and biofilms without exerting selective pressure. In this study, emodin, a natural anthraquinone, was evaluated for its anti-QS and antibiofilm efficacy. Emodin inhibited violacein production by 63.86% in C. violaceum 12472. In P. aeruginosa PAO1, it suppressed pyocyanin (68.04%), pyoverdin (48.79%), exoprotease (58.55%), elastase (43.13%), alginate (74.12%), and rhamnolipids (56.37%). In S. marcescens MTCC 97, emodin reduced prodigiosin (55.94%), exoprotease (48.80%), motility (83.27%), and cell surface hydrophilicity (41.20%). Biofilm formation was inhibited by over 50% in all three bacteria, highlighting emodin’s potential as a broad-spectrum antibiofilm agent. Molecular docking analyses indicated that emodin exhibited affinity towards QS regulatory proteins CviR, LasR, and SmaR, implying a possible competitive interaction at their ligand-binding sites. Subsequent molecular dynamics simulations confirmed these observations by demonstrating structural stability in emodin-bound proteins. The collective insights from in vitro assays and computational studies underscore the potential of emodin in interfering with QS-mediated virulence expression and biofilm development. Such findings support the exploration of non-antibiotic QS inhibitors as therapeutic alternatives for managing bacterial infections and reducing dependence on traditional antimicrobial agents. Full article

As an important economic forest tree species on the Qinghai Plateau, the outbreak of gummosis in Zanthoxylum bungeanum seriously threatens the sustainable development of the regional industry. This study is the first to clearly identify Fusarium equiseti as the pathogen responsible for the gummosis disease of Z. bungeanum on the Qinghai Plateau. To identify effective control agents, based on the indoor virulence screening of 13 fungicides, it was found that 80% ethylicin exhibited the strongest inhibitory activity against the pathogen (EC₅₀ = 0.396 μg/mL). Transmission electron microscopy revealed that ethylicin acts through multi-target effects, including disruption of cell membrane integrity and induction of mitochondrial cristae disintegration. Field trials have shown that the control efficacy of 80% ethylicin alone reaches 93.10%, and when combined with rhamnolipid in a 1:1 ratio, the control efficacy remains at 85.77% even when its dosage is reduced by 50%. Additionally, a novel Xuan paper imprint method was developed for precise quantification of lesion areas in the field. This study demonstrates the potential of ethylicin as a core fungicide for controlling Z. bungeanum gummosis, offering a scientific basis for integrated disease management in plateau ecosystems. Full article

Cadmium (Cd) accumulation in rice poses a serious threat to global food safety and human health. Foliar application of nano-silica (Si) offers a promising remediation strategy, but its efficacy is often limited by poor droplet retention on hydrophobic leaf surfaces. This study hypothesized that surfactants could overcome this barrier by enhancing the foliar performance of nano-Si. Through field experiments, we evaluated the synergistic effects of five surfactants (Polyvinylpyrrolidone (PVP) powder, Aerosol OT (AOT), Rhamnolipid (RH), Didecyldimethylammonium bromide (DDAB), and Alkyl Polyglycoside (APG)) when combined with nano-silica. The results demonstrated that all surfactants significantly improved wetting and retention, with alkyl polyglycoside (APG) and polyvinylpyrrolidone (PVP) being the most effective. These improvements translated into a remarkable suppression of Cd translocation within rice plants. The PVP–nano-Si combination emerged as the most potent treatment, reducing grain Cd content by 50% and achieving the lowest levels of As and Cr among all treatments. Furthermore, this synergistic effect was linked to a significant increase in grain concentrations of manganese (Mn) and zinc (Zn), which exhibit a competitive relationship with Cd. The findings reveal that surfactant co-application not only optimizes the physical application of nano-Si but also triggers beneficial nutrient–Cd interactions, providing a novel and efficient strategy for mitigating Cd contamination in rice. This study provides critical theoretical support for developing efficient and environmentally friendly foliar barrier technologies and supports safe production of rice in lightly to moderately contaminated paddy fields. Full article