Surfactant Activity Research Articles

Synthesis, physicochemical property, and antibacterial activity of novel nonionic 1-alkylaminoglycerol Gemini surfactants

Four novel nonionic 1-alkylaminoglycerol Gemini surfactants, represented by m-s-m (m = C8 and C12, s = 3 and 4), were synthesized through a two-step reaction in high yields, and confirmed by 1H NMR, 13C NMR, and HRMS. The synthesized Gemini surfactants exhibited low CMC (1.41–5.25 mmol/L), excellent surface-tension-reducing ability (25.45–26.83 mN/m), and wetting ability on hydrophobic interface. Gemini surfactants in aqueous solutions were in stable nanoscale dispersion, and exhibited strong and long-lasting foaming ability and emulsifying abilities for benzene/water and triacylglyceride/water systems. Especially, 12–4-12 solution displayed excellent tolerance to wide pH range and high salinity. Biological evaluation demonstrated that these Gemini surfactants, except for 8–4-8, showed significant antibacterial activities against Staphylococcus aureus and Escherichia coli at 25 and 50 µg/mL. Hence, these Gemini surfactants have the potential to be used in a varieties of fields as highly efficient agents.

Use of marine microorganisms in designing anti-infective strategies for sustainable aquaculture production.

Aquaculture, a noteworthy food production sector, is confronted with disease occurrences. Treatment of aquaculture pathogens with antibiotics is often rendered ineffective due to biofilm formation and the development of resistant strains. Marine ecosystems encompass unusual microorganisms that produce novel bioactive compounds, including agents that could be used as alternatives to antibiotics. Moreover, biomass and/or biomolecules associated with these microorganisms could act as feed supplements to enhance overall health of aquaculture species' and improve water quality parameters. The present review summarizes contents of studies on such marine microorganisms with the potential to be developed as agents for tackling bacterial diseases in the aquaculture segment. Bioactive compounds produced by marine bacteria are known to inhibit biofilm associated infections mediated by their bactericidal properties (produced by Bacillus, Vibrio, Photobacterium and Pseudoalteromonas species), surfactant activity (obtained from different species of Bacillus and Staphylococcus lentus), anti-adhesive activity (derived from Bacillus sp. and Brevibacterium sp.) and quorum sensing inhibition. Several marine fungal isolates capable of producing antibacterial agents have also been effective in inhibiting aquaculture associated pathogens. Another strategy followed by investigators to reduce severity of infections is the use of bacterial, yeast and microalgae biomass as feed supplements, probiotics and immunostimulants. In some cases, marine microalgae have been employed as sustainable alternatives to fish oil and fish meal without compromising on nutritional quality. Their inclusion in aquaculture feed have enhanced growth, favoured better survival of cultured species and improved water quality parameters. Marine microorganisms (by providing effective bioactive compounds and being used as feed supplements) could enable aquaculture practices to be more sustainable in the future.

Role of PPARγ in dyslipidemia and altered pulmonary functioning in mice following ozone exposure.

Exposure to ozone causes decrements in pulmonary function, a response associated with alterations in lung lipids. Pulmonary lipid homeostasis is dependent on the activity of peroxisome proliferator activated receptor gamma (PPARγ), a nuclear receptor that regulates lipid uptake and catabolism by alveolar macrophages (AMs). Herein, we assessed the role of PPARγ in ozone-induced dyslipidemia and aberrant lung function in mice. Exposure of mice to ozone (0.8 ppm, 3 h) resulted in a significant reduction in lung hysteresivity at 72 h post exposure; this correlated with increases in levels of total phospholipids, specifically cholesteryl esters, ceramides, phosphatidylcholines, phosphorylethanolamines, sphingomyelins, and di- and triacylglycerols in lung lining fluid. This was accompanied by a reduction in relative surfactant protein-B (SP-B) content, consistent with surfactant dysfunction. Administration of the PPARγ agonist, rosiglitazone (5 mg/kg/day, i.p.) reduced total lung lipids, increased relative amounts of SP-B, and normalized pulmonary function in ozone-exposed mice. This was associated with increases in lung macrophage expression of CD36, a scavenger receptor important in lipid uptake and a transcriptional target of PPARγ. These findings highlight the role of alveolar lipids as regulators of surfactant activity and pulmonary function following ozone exposure and suggest that targeting lipid uptake by lung macrophages may be an efficacious approach for treating altered respiratory mechanics.

Synthesis, surface activity and performance in “green” shampoo formulations of new carboxybetaine‐type surfactants

AbstractNovel zwitterionic surfactants—(N‐methylalkylamide‐derived) [3‐(alkylmethylamino)‐3‐oxopropyl] dimethylammonium acetates (abbr. CnDMPAB, n = 10, 12, 14, and 16) have been rationally designed as multifunctional surface active compounds with the intended characteristics toward their application in natural shampoo formulations. The synthetic routes included the alkylation of N‐methyl‐N‐alkylamines with methyl 3‐(dimethylamino)propionate, followed by betainization, while the purification steps enabled the isolation of high‐purity products for physicochemical analyses. Surface activity and micellization properties of novel CnDMPAB surfactants were studied by surface tension isotherms, and their wettability by advancing and receding contact angle measurements utilizing the Wilhelmy method. The aim of these studies was to exhibit the full potential of CnDMPAB series compounds as the multifunctional components of modern, salt‐free shampoo formulations with confirmed natural origin. The performance activity studies of shampoos, containing CnDMPAB surfactants, as well as model formulation (with commercial cocoamidopropyl betaine), included organoleptic and foaming characteristics, viscosity measurements, dispersibility in distilled and tap water as well as microbiological characteristics. Our studies showed great potential of novel CnDMPAB surfactants in replacing commercial cocoamidopropyl betaine, especially considering their increased viscosity, faster dispersibility as well as enhanced natural origin content.

Interaction of crude oil with halogen-free ionic liquid-based catanionic surfactants

Chemical injection has proved to have superior performance in improving oil recovery. The injected chemicals are typically designed to participate in interfacial interactions at liquid–liquid and rock-liquid interfaces while having minimum adsorption onto the rock surface. This study endeavors to investigate the interfacial activity of several environmentally-friendly halogen-free ionic liquid-based catanionic surfactants synthesized via an ion exchange reaction between cationic imidazolium-based ionic liquids, [Cnmim][Cl] (n = 4,8,12), and anionic surfactants, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and dioctyl sodium sulfosuccinate. Results revealed that the catanionic surfactant synthesized with medium-chain ionic liquid (n = 8) and sodium dodecyl sulfate exhibited higher interfacial activity, demonstrating a minimum crude oil-brine interfacial tension of 0.17 mN/m and wettability alteration index of 0.79. The results of the adsorption study also revealed the adsorption density of 2.19 mg/g onto the dolomite surface for 2000 mg/L of catanionic surfactant in seawater, which was considerably lower than cetyltrimethylammonium bromide adsorption (11.55 mg/g) in the control experiment. Finally, the surface energy analysis of liquid-rock interactions was conducted using the concept of work of adhesion to scrutinize the wettability alteration and adsorption processes, where a direct relationship between work of adhesion and adsorption density was proposed. According to the results of this study, medium chain ionic liquid-based catanionic surfactant containing dodecyl sulfate anion, exhibiting excellent interfacial activity and low adsorption tendency onto the dolomite surface, could be considered in future chemical enhanced oil recovery applications.

Synthesis of PEG-PPG-PEG templated polydopamine nanoparticles under intensified conditions: Kinetics investigation, continuous process design and demonstration for photothermal application

Polydopamine is a nature inspired functional material with promising applications in a plethora of fields due to its structural, chemical, and optical properties. While there is significant interest in the preparation of polydopamine based nanomaterials that take advantage of its properties, less attention has been given to the optimisation of the synthetic process, which typically involves the oxidative self-polymerisation of dopamine under basic pH and requires 24–72 h for reaction completion. The present work investigated the kinetics of polydopamine formation in the presence of Pluronic P-123 (PEG-PPG-PEG) micelles acting as a soft template, in low monomer concentrations (that promote particle growth instead of nucleation) as a function of temperature and pressure. Simultaneous increase of pressure and temperature (up to 50 °C and 5 bar O2) was found to significantly reduce the reaction time to 20–40 min without compromising the particle quality. Based on the results of the kinetic investigation, the polydopamine synthesis was translated into a continuous process utilising a millifluidic co-axial membrane reactor with a focus on ease of use, process conditions’ reproducibility and safety of operation. The reactor produced nanoparticles similar to the batch synthesis and resisted fouling (which is generally expected in a compact flow reactor) due to the action of the P-123 surfactant. Due to the nontoxic process that utilises only biocompatible materials and oxygen as the oxidising agent, and the melanin-like structure of polydopamine, photothermal heating of the synthesised nanoparticles under concentrated IR irradiation at 808 nm light was studied, as this can potentially be used for photo-induced hyperthermia. The hyperthermia threshold of 10 °C temperature increase at relatively low laser power settings (fluence 1.77 W/cm2) was achieved, making it a promising candidate for this application.

Mass transfer during surfactant-enhanced DNAPL remediation: Pore-scale experiments and new correlation

Surfactant-enhanced solubilization has been proven successful to remediate aquifers contaminated with non-aqueous phase liquids (DNAPLs). Understanding mass transfer from DNAPLs to the surfactant solution is highly important for improving remediation efficiency. However, the pore-scale mechanisms underlying the effect of surfactants on mass transfer behaviors have not been fully understood. Here we use microfluidic experiments to investigate the fundamental physical processes and quantify the impacts of surfactants on mass transfer rate at the pore scale. We find that surfactants can induce droplet breakup behaviors due to the interfacial disparity of mass transfer strength, resulting in the subsequent micro-movement of daughter blobs due to capillary force. Through image-based measurements, we find a significant inhibition of the mass transfer rates by surfactants at concentrations above the critical micelle concentration, and the inhibition becomes more pronounced as the concentration increases, which can be explained by an increase in stagnant film thickness. But the total mass transfer flux is improved because of the enhanced driving force caused by the surfactant-enhanced concentration gradient. In light of the observed physical processes and the behavior of mass transfer inhibition, we finally develop a new empirical model that explicitly considers the effects of surfactant concentration, DNAPL distribution, effective interface area, and flow rate to predict the mass transfer rate. This work provides pore-scale underpinnings of the mass transfer behaviors and a new mass transfer model considering the effect of surfactants, which improves the understanding of interphase mass transfer processes under the action of surfactants in subsurface hydrological and engineering systems.

Tracking the Spatio-Temporal Distribution of Organic Particles to Predict Macroaggregation in the Northern Adriatic Sea

In the last two decades, the phenomenon of macroaggregation has become more frequent in the Mediterranean Sea and beyond, but it has disappeared in the northern Adriatic. The aim of this study was to present, for the first time, the concentration of surface-active particles (SAP) at selected sampling stations in the northern Adriatic Sea, as well as phytoplankton and chlorophyll data and physical properties of seawater, in order to investigate the role of SAP in macroaggregation. We used an electrochemical method (polarography and amperometry) to directly and throughput characterize fragile organic material in terms of its dissolved and particulate state in seawater samples. The results show that the concentration of SAP is subject to seasonal variations and was generally higher in the western region. In addition, an increase in surfactant activity and concentration of SAP was detected in the subsurface layer and in the stratified column prior to the mucilage event, which may be related to the very high abundance of Skeletonema marinoi, a diatom characteristic of the winter bloom in the region. We noted an order of magnitude higher concentration of SAP than typically observed in late winter/early spring, which serves as a precursor to the macroaggregation that occurs under certain environmental and oceanographic conditions in marine systems.

γ-Cyclodextrin-based metal-organic frameworks for lactonic sophorolipid application in enhanced oil recovery

Lactonic sophorolipid (LSL) exhibits numerous surfactant activities, such as emulsification, wetting action, dispersion effect, and oil-washing activities. Nevertheless, LSLs have poor water solubility, which restrains their application in the petroleum industry. In this research, a new compound, lactonic sophorolipid cyclodextrin metal-organic framework (LSL-CD-MOFs), was obtained by loading LSL into γ-cyclodextrin metal-organic frameworks (γ-CD-MOFs). The LSL-CD-MOFs were characterized by N2 adsorption analysis, X-ray powder diffraction analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Loading LSL into γ-CD-MOFs significantly increased the apparent water solubility of LSL. However, the critical micelle concentration of LSL-CD-MOFs was similar to that of LSL. Furthermore, LSL-CD-MOFs effectively reduced the viscosities and improved the emulsification indices of oil–water mixtures. Oil-washing tests, which were conducted using oil sands, revealed that the LSL-CD-MOFs yielded an oil-washing efficiency of 85.82 % ± 2.04 %. Overall, γ-CD-MOFs are promising carriers for LSL, and LSL-CD-MOFs are a potential, low-cost, new, green surfactant for enhanced oil recovery.

Synthesis, Surface and Antimicrobial activity of Piperazine-Based Cationic Oligomeric Surfactants

Synthesis, Surface and Antimicrobial activity of Piperazine-Based Cationic Oligomeric Surfactants

Physicochemical investigations on the interaction of an anionic surfactant with cellulose based polymer microgel

Abstract This work focuses on the interaction of cellulose-based colloidal microgel dispersions with the anionic surfactant sodium dodecyl sulfate (SDS) at different concentrations. First, a Cellulose-P(NIPAAm-MAA)-based responsive microgel sample was prepared by a radical polymerization method using a one-pot process. The samples thus obtained were purified, characterized and used to study microgel-surfactant interactions. To this end, SDS solutions with different concentrations were prepared and the interactions of SDS in the premicellar and micelle regions with polymer microgel were investigated using different physicochemical techniques. Experiments were also performed at different temperatures to obtain the degree of binding of SDS to microgel in gel surfactant mixtures. Due to the temperature-sensitive properties of microgel, we observed significant changes in various properties of microgel-surfactant mixtures when the solution temperature changed. The overall results showed that various experimental variables, such as the polymer gel/surfactant ratio and temperature, affect the gel–surfactant interaction quantitatively and qualitatively. With increasing surfactant concentration, conductance, viscosity and absorbance values ​​increased, but a decrease in surface tension was observed. This is due to the adsorption of SDS at the air-water interface. The micellar activity of surfactants is enhanced by the addition of microgels. It was found that the strength and nature of the interaction depended not only on the gel/surfactant ratio, solvent type and test temperature, but also on the chemical structure of the surfactant used. Furthermore, the visual stability of the colloidal particles in the mixture of microgel and SDS was also noticeable over time.

Role of Microbial Interactions across Food-Related Bacteria on Biofilm Population and Biofilm Decontamination by a TiO2-Nanoparticle-Based Surfactant.

Microbial interactions play an important role in initial cell adhesion and the endurance of biofilm toward disinfectant stresses. The present study aimed to evaluate the effect of microbial interactions on biofilm formation and the disinfecting activity of an innovative photocatalytic surfactant based on TiO2 nanoparticles. Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli, Leuconostoc spp., Latilactobacillus sakei, Serratia liquefaciens, Serratia proteomaculans, Citrobacter freundii, Hafnia alvei, Proteus vulgaris, Pseudomonas fragi, and Brochothrix thermosphacta left to form mono- or dual-species biofilms on stainless steel (SS) coupons. The effectiveness of the photocatalytic disinfectant after 2 h of exposure under UV light on biofilm decontamination was evaluated. The effect of one parameter i.e., exposure to UV or disinfectant, was also determined. According to the obtained results, the microbial load of a mature biofilm depended on the different species or dual species that had adhered to the surface, while the presence of other species could affect the biofilm population of a specific microbe (p < 0.05). The disinfectant strengthened the antimicrobial activity of UV, as, in most cases, the remaining biofilm population was below the detection limit of the method. Moreover, the presence of more than one species affected the resistance of the biofilm cells to UV and the disinfectant (p < 0.05). In conclusion, this study confirms that microbial interactions affected biofilm formation and decontamination, and it demonstrates the effectiveness of the surfactant with the photocatalytic TiO2 agent, suggesting that it could be an alternative agent with which to disinfect contaminated surfaces.

REMODELING OF THE AERO-HEMATIC LUNG BARRIER COMPONENTS UNDER HIGH ALTITUDES

The aim of the study is to examine structural and ultrastructural aero-hematic barrier (AHB) changes in rats during adaptation to high-altitude hypoxia.&#x0D; Materials and Methods. The experiments were carried out on 60 sexually mature outbred laboratory male rats weighing 140–160 g at high altitude (3200 m above sea level). The authors followed Mayer's hematoxylin and eosin staining protocol, and used transmission and scanning electron microscopy on the 7th, 15th and 30th days of the animals' life in the mountains. Statistical data processing was carried out using Statistica 6.0 (USA) and StatTech v. 2.8.4 (Russia) and Student's t-test. Differences were considered statistically significant at p&lt;0.05.&#x0D; Results. At early stages of high-altitude adaptation, dystrophic changes in the epithelial layer of lung capillaries, hypertrophy and hyperplasia of histiocytes, fibroblasts and lipofibroblasts were noted. The authors also revealed proliferation of type II alveolocytes, thickening of the interalveolar septa (IAS) and cytoplasmic processes of endotheliocytes, destruction of type II alveolocytes (apocrine method, with the release of surfactant into the alveoli lumen), multivesicular lamellar bodies in the cytoplasm of type II alveolocytes; interstitial edema with transudate in the alveoli lumen. In later periods, surfactant system activity decreases due to a reduced release of osmiophilic lamellated corpuscles (OLC) into the alveoli lumen. The main AHB components are next to control data, while the IAS thickness exceeds the norm. In the alveoli wall, the number of fibroblasts increases, causing an increase in the number of Kohn's pores and providing collateral breathing.&#x0D; Conclusion. The study of AHD components in experimental animals at different periods of high-altitude adaptation revealed dystrophic processes of AHD in IAS, compensated by type I alveolocytes and proliferation of type II alveolocytes, confirming the adaptive mechanisms of ultrastructural alteration of all epithelial and endothelial components of the pulmonary alveoli.

Molecular insight into the effect of the number of introduced ethoxy groups on the calcium resistance of anionic-nonionic surfactants at the oil/water interface

The salinity seriously affects the recovery efficiency of surfactant flooding, and it is demonstrated the introduced ethoxy (EO) groups can enhance the interfacial activity of surfactants at harsh salinity via various experimental methods. In this study, sodium dodecyl sulfate (SDS) and sodium dodecyl ether sulfate (AES) are selected to investigate the effects of EO group number on the salt resistance of surfactants at the air/water interface by experiments and molecular dynamics (MD) simulation method. Optical microscopy and static multiple light scattering results show that the AES stabilized emulsions with Ca2+ ions have better stability than those of SDS, which is further explored by molecular MD simulation method. The interface formation energy (IFE) and self-diffusion coefficients (Dα) are calculated to systematically study the effects of introduced EO group number on calcium resistance of surfactants. The interaction between surfactants and Ca2+ ions at the oil/water interface is evaluated by the potential of mean of force (PMF) and the radial direction functions (RDF), which is confirmed by the calculation of molecular electrostatic potential (MEP) and coordination number. The simulation results indicate that the introduced EO groups can combine Ca2+ ions to fabricate salt bridge via intermolecular or intramolecular interactions to highly improve the calcium resistance of surfactants. The present work proposes a microcosmic perspective of the roles of EO group number on the calcium resistance of AES at the oil/water interface.

Synergism for lowering interfacial tensions between betaines and extended surfactants: The role of self-regulating molecular size

The synergism for reducing interfacial tensions (IFTs) between betaines and anionic extended surfactants with self-regulating ability was validated by experiments and molecular dynamics simulation. The IFTs of different betaines and different alkyl polypropylene ether sulfonates (APS) mixed solutions against decane and crude oil were investigated via the spinning drop method. The results demonstrate that the IFTs order of the three betaines is EDAS > ASB > XSB, which is consistent with their interfacial vacancies. Moreover, the interfacial activity of APS surfactants increases significantly and the IFTs decrease notably with the increase of propylene oxide (PO) numbers. For the betaines and APS surfactants mixed systems, the determining factor to reduce IFTs is not hydrophilic-lipophilic balance (HLB) but “size compatibility”. APS molecules can achieve a superior synergistic effect with different betaines by electrostatic attraction and size compatibility. The self-regulating characteristic of the flexible PO group enables the extended surfactants to exhibit certain synergistic effects with different betaines. What’s more, betaines and APS surfactants have a certain synergistic effect to reduce IFT values during a wide concentration ratio against crude oil. The findings of this study can help for better understanding of mixed surfactant solutions in enhanced oil recovery.

The saponin bomb: a nucleolar-localized β-glucosidase hydrolyzes triterpene saponins in Medicago truncatula.

Plants often protect themselves from their own bioactive defense metabolites by storing them in less active forms. Consequently, plants also need systems allowing correct spatiotemporal reactivation of such metabolites, for instance under pathogen or herbivore attack. Via co-expression analysis with public transcriptomes, we determined that the model legume Medicago truncatula has evolved a two-component system composed of a β-glucosidase, denominated G1, and triterpene saponins, which are physically separated from each other in intact cells. G1 expression is root-specific, stress-inducible, and coregulated with that of the genes encoding the triterpene saponin biosynthetic enzymes. However, the G1 protein is stored in the nucleolus and is released and united with its typically vacuolar-stored substrates only upon tissue damage, partly mediated by the surfactant action of the saponins themselves. Subsequently, enzymatic removal of carbohydrate groups from the saponins creates a pool of metabolites with an increased broad-spectrum antimicrobial activity. The evolution of this defense system benefited from both the intrinsic condensation abilities of the enzyme and the bioactivity properties of its substrates. We dub this two-component system the saponin bomb, in analogy with the mustard oil and cyanide bombs, commonly used to describe the renowned β-glucosidase-dependent defense systems for glucosinolates and cyanogenic glucosides.

Surfactant Improved Interface Morphology and Mass Transfer for Electrochemical Oxygen-Evolving Reaction

The surface microstructure of a catalyst coating layer directly affects the active area, hydrophilicity and hydrophobicity, and the high porosity is desirable especially for solid–liquid–gas three-phase catalytic reactions. However, it remains challenging to customize catalyst distribution during the coating process. Here, we report a simple strategy for achieving ultrafine nanocatalyst deposition in a porous structure via introducing the surfactant into coating inks. For a proof-of-concept demonstration, we spin-coated the nanoscale IrO2 sol with a surfactant of sodium dodecyl sulfate (SDS) onto the glassy carbon (GC) electrode for oxygen evolution reaction (OER). Due to the surfactant action, the deposited IrO2 nanocatalyst is evenly distributed and interconnected into a highly porous overlayer, which facilitates electrolyte permeation, gas bubble elimination and active-site accessibility, thus affording high-performance OER in alkaline media. Particularly, the SDS-modified electrodes enable the industrial-level high-current-density performance via enhanced mass transfer kinetics. Such manipulation is effective to improve the coating electrodes’ catalytic activity and stability, and scalable for practical applications and suggestive for other gas-evolving electrodes.

SYNTHESIS AND PROPERTIES OF POLYMER SUSPENSIONS OBTAINED BY HETEROPHASE POLYMERIZATION IN THE PRESENCE OF α,ω BIS[3 GLYCIDOXYPROPYL]POLYDIMETHYLSILOXANE

Polymeric microspheres with glycidoxy groups on the surface can be used as bioligand carriers in diagnostic test systems. However, the possibility of synthesizing aggregatively stable functional polymeric microspheres in a wide range of diameters is an urgent problem of modern polymer chemistry. This article is devoted to a systematic study of the kinetics of styrene and methyl methacrylate polymerization in the presence of an organosiloxane surfactant with terminal glycidoxy groups – α,ω-bis[3-glycidoxyproopyl]-polydimethylsiloxane, PDMS(CHOCH2). The article shows the influence of phases volume ratio, initiator and surfactant concentration, synthesis temperature and pH of initial medium on the properties of polymer suspensions (their aggregative stability, monodispersity, particle diameter). The formation of polymer-monomer particles during polymerization has been studied and it has been shown that polymer suspensions retain high aggregation stability from early period of monomer conversion, and the particle diameter changes untill 30% of the monomer conversion. Due to the high surface activity of the organosiloxane surfactant used and its incompatibility with the resulting polymer, aggregatively stable functional polymer suspensions with diameters from 0.09 to 1.1 μm were obtained by a single-stage synthesis. Studies of the hydration degree of polymer microspheres have shown that the presence of functional glycidoxy groups on their surface ensures the formation of a hydration shell, which increases the stability of polymer particles, and also makes it possible to use the resulting microspheres as carriers of bioligands. Thus, the use of water-insoluble organosiloxane surfactants as stabilizers for the heterophase polymerization of vinyl monomers makes it possible to synthesize aggregatively stable functional polymer suspensions in a wide range of diameters. The use of organosiloxane surfactants with various functional groups expands the range of functional polymer microspheres used in various fields of application.

Effect of Tryptophane on Synthesis of Certain Exometabolites by Bacteria of Genus Acinetobacter, Nocardia, and Rhodococcus and Their Properties

The efficiency of integrated microbial biotechnologies for obtaining several practically valuable metabolites in one technological process is determined both by the maximum concentration of these substances and their properties. This is especially true for secondary metabolites, the composition and properties of which vary depending on the cultivation conditions of the producer. Aim. To research the effect of tryptophan (a precursor of auxin biosynthesis) in the culture media on the synthesis of certain exometabolites by Rhodococcus erythropolis IMV Ac-5017, Acinetobacter calcoaceticus IMV B-7241, and Nocardia vaccinii IMV B-7405 as well as their properties. Methods. R. erythropolis IMV Ac-5017, A. calcoaceticus IMV B-724, and N. vaccinii IMV B-7405 were cultivated in a medium containing refined and waste sunflower oil, biodiesel waste, or ethanol as a carbon source. The concentration of tryptophan in the medium was 300 mg/L. Surfactants were extracted from the supernatant of the cultural liquid with a modified Folch mixture. Phytohormones were isolated from the supernatant by sequential extraction with organic solvents after surfactant extraction. Thin-layer chromatography was used for preliminary purification and concentration of phytohormones. Qualitative and quantitative determination of auxins was performed using high-performance liquid chromatography. The antimicrobial activity of surfactants was analysed by the minimum inhibitory concentration. The activity of enzymes of surface-active glycoand aminolipids biosynthesis (phosphoenolpyruvate synthetase, phosphoenolcarboxykinase, and NADP+-dependent glutamate dehydrogenase) was determined spectrophotometrically during the oxidation of NADH or NADP. Results. It was found that the presence of tryptophan in the culture medium of the strains under study did not affect the number of synthesized surfactants, which was 1.80−1.90, 1.55−1.75, and 1.50−1.65 g/L, respectively. At the same time, cultivation of R. erythropolis IMV Ac-5017, A. calcoaceticus IMV B-724, and N. vaccinii IMV B-7405 in the media with tryptophan increased the number of phytohormones: it was higher than the amount of phytohormones synthesized during cultivation without a precursor. The introduction of tryptophan into the culture medium of the strains was accompanied by the formation of surfactants. These compounds showed 2−4 times higher antimicrobial activity against the phytopathogenic bacteria (Agrobacterium tumefaciens UCM B-1000, Pseudomonas syringae UCM B-1027T, Xanthomonas vesicatoria UCM B-1106, Pectobacterium carotovorum UCM B-1075T, Clavibacter michiganensis IMV B-102 and Pseudomonas syringae pv. tomato IMV B-9167) than compounds synthesized on a medium without a precursor. The antimicrobial activity of surfactants synthesized by A. calcoaceticus IMV B-7241 in the presence of tryptophan either did not change compared to that for surfactants obtained without tryptophan, or increased slightly. Data on the activity of surfactant biosynthesis enzymes correlated with the indicators of their antimicrobial activity. In the presence of tryptophan in the culture medium of N. vaccinii IMV B-7405 and R. erythropolis IMV Ac-5017, NADP+-dependent glutamate dehydrogenase activity in the cells of these strains (a key enzyme for biosynthesis of aminolipids responsible for antimicrobial activity) increased almost by 1.4 times compared to that on a tryptophan-free medium. Conclusions. As a result of this work, it was found that the presence of tryptophan in the culture medium of researched strains did not affect the number of surfactants. The antimicrobial activity of surfactants against phytopathogenic bacteria either increased or remained unchanged compared to that established for surfactants synthesized without a precursor of auxin biosynthesis. The obtained data testify to the high efficiency of the potential use of surfactants complex preparations and phytohormones in crop production to stimulate the growth of plants and biocontrol of phytopathogenic bacteria.

Impact of Natural-Based Viscosity Modifiers of Inhalation Drugs on the Dynamic Surface Properties of the Pulmonary Surfactant

The effectiveness of inhalation therapy depends on aerosol size distribution, which determines the penetration and regional deposition of drug in the lungs. As the size of droplets inhaled from medical nebulizers varies depending on the physicochemical properties of the nebulized liquid, it can be adjusted by adding some compounds as viscosity modifiers (VMs) of a liquid drug. Natural polysaccharides have been recently proposed for this purpose and while they are biocompatible and generally recognized as safe (GRAS), their direct influence of the pulmonary structures is unknown. This work studied the direct influence of three natural VMs (sodium hyaluronate, xanthan gum, and agar) on the surface activity of the pulmonary surfactant (PS) measured in vitro using the oscillating drop method. The results allowed for comparing the variations of the dynamic surface tension during breathing-like oscillations of the gas/liquid interface with the PS, and the viscoelastic response of this system, as reflected by the hysteresis of the surface tension. The analysis was done using quantitative parameters, i.e., stability index (SI), normalized hysteresis area (HAn), and loss angle (φ), depending on the oscillation frequency (f). It was also found that, typically, SI is in the range of 0.15-0.3 and increases nonlinearly with f, while φ slightly decreases. The effect of NaCl ions on the interfacial properties of PS was noted, which was usually positive for the size of hysteresis with an HAn value up to 2.5 mN/m. All VMs in general were shown to have only a minor effect on the dynamic interfacial properties of PS, suggesting the potential safety of the tested compounds as functional additives in medical nebulization. The results also demonstrated relationships between the parameters typically used in the analysis of PS dynamics (i.e., HAn and SI) and dilatational rheological properties of the interface, allowing for easier interpretation of such data.