Surface Tension Reduction Research Articles

Biosurfactant from Pseudomonas fragi enhances the competitive advantage of Pseudomonas but reduces the overall spoilage ability of the microbial community in chilled meat

Biosurfactants from Pseudomonas spp. have been reported to exhibit antibacterial and anti-adhesive properties, but their role during meat spoilage remains unclear. In this study, the biosurfactant was isolated from an isolate of Pseudomonas fragi with strong spoilage potential, and its surface tension and emulsification ability were determined. The chemical and microbial characteristics of the biosurfactant-treated meat samples were periodically analyzed. The results demonstrated that the biosurfactant produced by P. fragi could reduce surface tension and showed good emulsification properties. For the in situ spoilage trials, biosurfactant from P. fragi changed the microbial diversity on meat, helping Pseudomonas establish a dominant position in the population. However, biosurfactant treatment caused chicken meat to exhibit a weaker spoilage state, as indicated by the growth of psychrophilic microorganisms, total volatile basic nitrogen (TVBN) and meat color. These results provide practical information for understanding the role of P. fragi biosurfactant during chilled meat storage.

Effect of atmospheric pin-to-plate cold plasma on oat protein: Structural, chemical, and foaming characteristics

The impact of novel pin-to-plate atmospheric cold plasma was investigated with input voltage (170 V, 230 V) and exposure time (15 & 30 min) on oat protein by studying structural (FTIR, circular dichroism (CD), UV–vis, Fluorescence), morphological (particle size analysis, SEM, turbidity), chemical (pH, redox potential (ORP), ζ potential, carbonyl, sulfhydryl, surface hydrophobicity), and foaming characteristics. The plasma treatment reduced the pH while increasing the ORP of the dispersions. These ionic environment changes affected the ζ potential and particle size leading to the formation of larger aggregates (170–15; 230–15) and distorted smaller ones (170–30; 230–30) as confirmed by SEM. The FTIR spectra showed reduced intensity at specific amide bands (1600–1700 cm−1) and also an increase in carbonyl stretching (1743 cm−1) representing oxidative carbonylation (increase in carbonyl content). Thus, the partial exposure of hydrophobic amino acids increases surface hydrophobicity. The altered secondary structure (rise in α-helix, decrement in β-sheets and turns), and tertiary structures were observed in circular dichroism (CD) and UV absorbance and fluorescence characteristics of proteins respectively. Furthermore, the increase in free sulfhydryl content and disulfide content was highly affected by the plasma treatments due to observed protein unfolding and aggregations. Besides, the increased solubility and reduced surface tension contributed to the improved foaming characteristics. Thus, plasma processing influences protein structure affecting their characteristics and other functionalities.

Optimization of Calcium Alginate Hydrogel Bioencapsulation of Acinetobacter junii B6, a Lipopeptide Biosurfactant Producer

Background: Biosurfactants are derived from microbes, plants, and animals. Acinetobacter junii B6 is a lipopeptide biosurfactant producer previously investigated for its structure, physicochemical, and product aggregation properties. Objectives: In this study, we investigated and optimized the bioencapsulation of A. junii B6 in calcium alginate hydrogel. Methods: Acinetobacter junii B6 was encapsulated using calcium alginate hydrogel. The formulation of the hydrogel was optimized using a full factorial approach. Sodium alginate concentration, calcium chloride concentration, and hardening time were selected as the main factors, and surface tension was the response measure. A scanning electron microscope (SEM) was used to study the bead's morphology. Results: Scanning electron microscope image showed rounded and smooth beads. The most biosurfactant production and reduced surface tension (35.98 mN/m) were observed at concentrations of 1% calcium chloride, (1%) sodium alginate, and 15 minutes of hardening time. Acinetobacter junii B6 can be encapsulated in alginate hydrogels producing biosurfactant at optimum experimental design. Conclusions: This represents a practical method for optimizing the bioencapsulation of A. junii B6 to produce biosurfactants.

Substrate Optimization for Bioemulsification Using Saccharomyces cerevisiae 2031 by Response Surface Methodology

Biosurfactants are microbially derived amphiphilic molecules that can be used as biodegradable emulsifiers in various applications. For biosurfactant production to be economically viable, inexpensive raw materials should be used. In this study, substrate optimization of biosurfactant production from Saccharomyces cerevisiae 2031 was done using molasses as an additional carbon source to glucose, and coco paring meal extract as a nitrogen source. Optimum conditions were determined as pH 5.69, 10.60% (w.v-1) molasses and 7.27% (v.v-1) coco paring meal extract using Box-Behnken design. At these conditions, the obtained responses: namely biomass concentration and % emulsification index determined with kerosene, were 6.43 g.L-1 and 82.81%, respectively. The highest emulsification activity (84.60%) was attained after 4 days of shake-flask fermentation. On the other hand, a bioreactor system observed the maximum yield for emulsification activity (93.33) after 4 days. The biosurfactant extracted was characterized by its total sugar, protein content and surface tension reduction.

Sustainable production of bioemulsifiers, a critical overview from microorganisms to promising applications

Microbial bioemulsifiers are molecules of amphiphilic nature and high molecular weight that are efficient in emulsifying two immiscible phases such as water and oil. These molecules are less effective in reducing surface tension and are synthesized by bacteria, yeast and filamentous fungi. Unlike synthetic emulsifiers, microbial bioemulsifiers have unique advantages such as biocompatibility, non-toxicity, biodegradability, efficiency at low concentrations and high selectivity under different conditions of pH, temperature and salinity. The adoption of microbial bioemulsifiers as alternatives to their synthetic counterparts has been growing in ongoing research. This article analyzes the production of microbial-based emulsifiers, the raw materials and fermentation processes used, as well as the scale-up and commercial applications of some of these biomolecules. The current trend of incorporating natural compounds into industrial formulations indicates that the search for new bioemulsifiers will continue to increase, with emphasis on performance improvement and economically viable processes.

Potential application of polysaccharide mucilages as a substitute for emulsifiers: A review

Mucilages are natural compounds consisting mainly of polysaccharides with complex chemical structures. Mucilages also contain uronic acids, proteins, lipids, and bioactive compounds. Because of their unique properties, mucilages are used in various industries, including food, cosmetics, and pharmaceuticals. Typically, commercial gums are composed only of polysaccharides, which increase their hydrophilicity and surface tension, reducing their emulsifying ability. As a result of the presence of proteins in combination with polysaccharides, mucilages possess unique emulsifying properties due to their ability to reduce surface tension. In recent years, various studies have been conducted on using mucilages as emulsifiers in classical and Pickering emulsions because of their unique emulsifying feature. Studies have shown that some mucilages, such as yellow mustard, mutamba, and flaxseed mucilages, have a higher emulsifying capacity than commercial gums. A synergistic effect has also been shown in some mucilages, such as Dioscorea opposita mucilage when combined with commercial gums. This review article investigates whether mucilages can be used as emulsifiers and what factors affect their emulsifying properties. A discussion of the challenges and prospects of using mucilages as emulsifiers is also presented in this review.

Improvements in the surface tension measurement using the capillary rise method and its application to water under external magnetic fields

Using a micro ruler and charge-coupled device image acquisition system, we have improved the capillary rise method for an easy, quick and accurate measurement of liquid surface tension. We have determined and assessed the surface tension coefficients and temperature characteristics of purified water, ethylene glycol and anhydrous ethanol. Our results demonstrate low uncertainties for stable liquids and good linearity with temperature, with a measuring percentage deviation of less than 0.1% at 20 °C for purified water. Furthermore, we exposed purified water to a series of external magnetic fields ranging from 0 to 5 T for 40 min, followed by a withdrawal of fields for 5 min and observed a drop peak of surface tension at 1.0 T and a saturating transition at approximately 1.2 T. Furthermore, we found that the surface tension coefficients rapidly decrease with increasing magnetic fields from 0 to 1.0 T, increase rapidly from 1.0 to 1.2 T and then increase slowly at fields higher than 1.2 T. The maximum reduction of surface tension affected by external fields is approximately 11%. These magnetic behaviours of water surface tension have scientific significance in the study of water molecular liquids and their potential applications in water treatments.

The role of tricalcium aluminate and gypsum dehydration level in cement for effective air entrainment of concrete

In this paper, the role of tricalcium aluminate (C3A) and gypsum dehydration level in the air-entraining mechanism in concrete was studied. A higher-performance air system was achieved when anionic surfactant was used, C3A content was higher and gypsum dehydration didn’t occur. Adsorption on cement particles dominates the air-entraining mechanism when anionic admixture is used. Anionic surfactant performs higher quality air microstructure than cationic, despite much lower surface tension reduction. Thus, the adsorption of admixture had a major role in the effective air-entraining mechanism process. This effect has significant implications on the selection of the best-suited surfactants, cement optimum composition and the cement production procedure for the highest frost resistance concretes used for roads and bridges.

Cooling enhancement for light-emitting diode using plasma-activated water

We exploit the two-phase heat transfer enhancement using plasma-activated water for application in LED cooling. Within the steady-state LED temperature 80 °C ≤TLED≤ 110 °C, up to 73% increase in heat transfer coefficient can be achieved by replacing deionized water with plasma-activated water; concomitantly, we observe up to 14% increase in illuminance. This enhancement can be attributed to the presence of reactive oxygen and nitrogen species in the plasma-activated water that reduces surface tension, and, quite unexpectedly, minimizes the oxidation of the copper (heat source) surface. Specifically, the lower surface tension of plasma-activated water can lead to smaller vapor bubbles as well as reduction in their residence times on the heated surface. On the other hand, by increasing the electrical conductivity of plasma-activated water, i.e., higher concentrations of reactive oxygen and nitrogen species, we observe significant reductions in surface oxidation on the copper (heat source) surface. Peculiarly, unlike the copper surface oxidized by deionized water, for the plasma-activated water, we observe isolated oxidized islands that consist of nanosphere structures; these islands are hydrophobic and can lead to significantly shorter residence times of vapor bubbles. Since plasma-activated water can be produced easily via the corona discharge plasma, these promising results highlight its potential to be used in two-phase cooling systems.

Production, characterization, and kinetic modeling of biosurfactant synthesis by Pseudomonas aeruginosa gi |KP 163922|: a mechanism perspective.

Kinetic studies and modeling of production parameters are essential for developing economical biosurfactant production processes. This study will provide a perspective on mechanistic reaction pathways to metabolize Waste Engine Oil (WEO). The results will provide relevant information on (i) WEO concentration above which growth inhibition occurs, (ii) chemical changes in WEO during biodegradation, and (iii) understanding of growth kinetics for the strain utilizing complex substrates. Laboratory scale experiments were conducted to study the kinetics and biodegradation potential of the strain Pseudomonas aeruginosa gi |KP 163922| over a range (0.5-8% (v/v)) of initial WEO concentration for 168h. The kinetic models, such as Monod, Powell, Edward, Luong, and Haldane, were evaluated by fitting the experimental results in respective model equations. An unprecedented characterization of the substrate before and after degradation is presented, along with biosurfactant characterization. The secretion of biosurfactant during the growth, validated by surface tension reduction (72.07 ± 1.14 to 29.32 ± 1.08 mN/m), facilitated the biodegradation of WEO to less harmful components. The strain showed an increase in maximum specific growth rate (µmax) from 0.0185 to 0.1415h-1 upto 49.92mg/L WEO concentration. Maximum WEO degradation was found to be ~ 94% gravimetrically. The Luong model (adj. R2 = 0.97) adapted the experimental data using a non-linear regression method. Biochemical, 1H NMR, and FTIR analysis of the produced biosurfactant revealed a mixture of mono- and di- rhamnolipid. The degradation compounds in WEO were identified using FTIR, 1H NMR, and GC-MS analysis to deduce the mechanism.

Abstract 678: Use Of Extracellular Substrates By Alveolar Type 2 Pneumocytes For Surfactant Lipid Synthesis.

Introduction: Pulmonary surfactant is a lipoprotein complex essential for lung function. It reduces surface tension during inspiration and avoids alveolar collapse during expiration. It is synthetized by alveolar type 2 pneumocytes (T2C) and it is composed of phospholipids (~90%), mainly phosphatidylcholine (PC), and specific proteins. Decreased surfactant and altered composition are associated with multiple adult lung diseases. However, T2C lipid metabolism and their use of extracellular glucose and lipid for surfactant synthesis has not been studied. Our prior results showed that the low density lipoprotein receptor-related 1 (LRP1) is needed for surfactant synthesis. We hypothesized that nutritional conditions and LRP1 function impact the pathways used by T2C to synthetize surfactant. Methods: Control and LRP1 knockdown T2C-derived A549 cells were cultured in DMEM (4.5 g/L glucose) with 10% FBS and maintained at the air-liquid interface for 24 hours to promote their differentiation and polarization. Then, cells were cultured in DMEM with delipidated FBS and BSA-complexed palmitic acid (PA) at different concentrations (0-0.25 mM) for 2 hours and mRNA of surfactant synthetic enzymes was analyzed. Results: mRNA expression of Fatty acid synthase (FASN) and Choline kinase (CK) decreased 80% and 93% (p<0.001) respectively when at least 0.05 mM PA was present. Phospholipase A2 ( PLA2) followed the opposite pattern, with 21.5-fold increase (p<0.001) when PA was present. FASN and CK expression was downregulated in the absence of LRP1. mRNA expression of genes involved in cholesterol metabolism was assessed too. HMG-CoA reductase decreased only at the highest concentration of PA (41% decrease, p<0.01), while expression of HMG-CoA synthase and lipid exporters ABCA1 and ABCG1 was not affected. ABCG1 expression was compromised in LRP1 knockdown cells. Conclusions: Extracellular availability of glucose and fatty acids affects mRNA expression of genes involved in surfactant lipid synthesis in T2C, suggesting metabolic pathway flexibility during different nutritional conditions. In the absence of extracellular lipid sources, glucose can be used by T2C for fatty acid synthesis. Furthermore, LRP1 expression affects the metabolic pathways used by T2C.

Evaluation of interfacial, micellar, and foaming properties of the solutions comprising fluorocarbon surfactant, cocamidopropyl betaine, and Gleditsia saponin as fire-extinguishing agents

The interfacial, micellar, and foam properties of unitary, binary, and ternary aqueous solutions containing a non-ionic fluorocarbon surfactant (FC-170C), an ionic hydrocarbon surfactant (CAB), and Gleditsia saponin (GS) were comprehensively investigated. FC-170C showed the highest surface activity and micellization ability, CAB and GS showed the strongest foaming ability and foam stability, respectively. For binary mixtures, the interaction in each pair of mixtures synergistically enhanced the ability of surface tension reduction, but had little synergistic effect on the efficiency of surface tension reduction. For the ternary mixtures, at an optimal formulation of 7.43 × 10-6 mol/L FC-170C, 5.26 × 10-3 mol/L CAB, and 1.60 × 10-4 mol/L GS, the values of γ, h0, R5min, and bubble size were 17.3 mN/m, 117 mm, 98%, and 115–116 μm, respectively. In particular, the required amount of fluorocarbon was reduced to 6.78 mg/kg, which is significantly<50 mg/kg limit set by international conventions for fire extinguishing agents.

Surfactant dysfunction due to e-cigarette aerosol exposure with and without additional insults

Introduction: The use of e-cigarettes (ECs) remains a popular habit for young populations, in part due to the variety of appealing flavours available. However, EC use has been associated with acute lung injury via unknown mechanisms. During a deep inhalation, one of the first compounds the EC aerosol comes into contact within the lungs is pulmonary surfactant. This complex mixture of lipids and surfactant associated proteins lines the alveolar surface and reduces surface tension to near zero values upon exhalation. Surfactant dysfunction, associated with serum protein leak and oxidative stress, contributes to lung injury. We hypothesized that exposure to EC aerosol impairs pulmonary surfactant function, and thereby increases its susceptibility to protein inhibition or oxidative stress. Methods: Bovine lipid extract surfactant (BLES) was used as a model exogenous surfactant. 2ml of BLES (2mg/ml) was placed in a syringe (30ml) attached to an EC, drawing in and expelling the aerosol 30 times. Vehicle e-liquid (VG:PG 50:50) as well as e-liquid containing flavouring additives and nicotine were utilized. Two models of injury were used, the first being addition of serum containing plasma proteins and the second oxidization by hypochlorous acid following aerosol exposure. Surface tension reduction of all samples after exposure was performed using a constrained drop surfactometer (CDS), where samples underwent 20 dynamic compression and expansion cycles. Results: Minimum surfaces tensions were significantly higher after exposure to EC aerosol across 20 compression/expansion cycles. Menthol and red wedding flavoured aerosol exposure resulted in significantly increased minimum surface tensions compared to unflavoured vehicle e-liquid, although nicotine had no additional effects beyond that of the vehicle e-liquid. The addition of plasma containing serum proteins significantly increased minimum surface tensions in aerosol exposed samples compared to those unexposed to serum and air controls. Oxidized surfactant had higher minimum surface tensions compared to control, however EC aerosol exposure had no additional effect on the inhibition of the surfactant’s function. Conclusion: EC aerosols alter surfactant function through increases in minimum surface tension. Variability in the severity of inhibition exists between flavouring additives, however the base common across all e-liquids is able to effectively inhibit surfactant. This inhibition is amplified in the presence of serum proteins. From these results we conclude that vaping impairs the pulmonary surfactant system and increases susceptibility to damage by secondary insults. Lawson Health Research Institute, NSERC This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Synthesis and characterization of silica-based nanofluids for enhanced oil recovery

The use of nanofluids in enhanced oil recovery processes has gained attention due to the possibility to intensify oil recovery from mature oil fields. When nanofluids are injected into oil wells, different mechanisms are involved such as wettability alteration, reduction of interfacial surface tension, increase in the viscosity of the aqueous solution, and decrease in oil viscosity. Silica nanoparticles are extensively used for nanofluid formulations but there are important obstacles to the use of nanofluids in enhanced oil recovery. Stability is the most evident, in addition to environmental and economic aspects, and the need to design suitable large-scale production processes for nanoparticle synthesis with the required characteristics. Thus, the present study aims to evaluate oil recovery using silica-based nanofluids from various sources (natural rice husk ash, sol-gel synthesis, and commercial nanosilica) under different operational conditions. Silica nanoparticles were characterized by XRF, XRD, TEM, FTIR, specific surface area, and XPS. Nanofluids with different nanoparticles concentration were characterized by their viscosity, surface tension, zeta potential, and stability. Oil recovery from an oil-saturated sand-packed bed increased due to the nanofluid injection after secondary recovery. An additional 5–10% oil recovery is achieved after flooding due to the injection of nanofluids, proving that silica from rice husk ash has comparable efficiency to other synthetic silica nanoparticles that are used in enhanced oil recovery.

Mixed micellization analysis of tri-substituted SAIL and amphiphilic drug mixture in aqueous/salt media at diverse temperatures

Abstract The present work aimed to study the mixed micellar behaviour of a tri-substituted imidazolium based surface-active ionic liquid (SAIL), 1-tetradecyl-2,3-dimethylimidazolium bromide [C14bmim][Br], with a drug Nortriptyline hydrochloride (NOT) in the water/salt (Na2SO4) medium using surface tension measurements (298.15 K) alongwith conductivity measurements (298.15K–313.15K). Lower experimentally obtained cmc values compared to their ideal values suggest that the investigated amphiphiles interact strongly. The values of micellar mole fraction (X 1) based on the several proposed models (Rubingh, Motomura, and Rodenas) and the ideal micellar mole fraction (X id ) were assessed, and the predicted outcomes indicate that NOT has a significant contribution to the formation of mixed micelles, which increases as the [C14bmim][Br] mole fraction is increased. The negative values of micellization’s Gibbs free energy (ΔGm 0) between the examined amphiphiles were an indication of spontaneous mixed micelle formation. Micellar changes in entropy (ΔSm 0) and enthalpy (ΔHm 0) were also computed and discussed. Using surface tension measurements, surface-active parameters like surface tension at cmc (γ cmc ), minimum surface area per IL molecule (A min), maximum surface excess concentration (τ max), effectiveness of surface tension reduction (π cmc ), and cmc of mixed system have been estimated. The results showed an improved adsorption and micellization properties of these mixtures which will surely contribute to the tremendous rise of these mixed systems in drug delivery applications.

Correlation between the Protein Pharmaceutical Surface Activity and Interfacial Stability.

The interaction of protein drugs with the air-liquid interface plays a crucial role in the overall stability in aqueous formulations, particularly when the adsorbed proteins are subjected to the surface flow. Nonionic surfactants are usually added into the formulation solutions to address this issue. A diversity of studies have been focused on the usage of surfactants, the stability mechanism of surfactants, or seeking new pharmaceutical surfactants. However, the real protagonist, the basic properties of protein drugs, was neglected, which may play a vital role in the stability of protein drugs. Herein, we aim to clarify the correlation between the surface behavior of proteins and the interfacial stability. A force tensiometer is used to track the surface tension reduction and the competition between surfactants and proteins at the surface. We find that the surface behaviors of proteins vary with storage temperature and protein types including monoclonal antibodies (mAb), bispecific monoclonal antibodies (BsAb), and antibody-drug conjugates (ADCs). Especially for the protein stored at 5 °C, the surface activity of proteins is better than that of surfactants. It indicates that the ability of proteins to adsorb at the interface should not be ignored compared to surfactants. The significant difference in the interfacial stability of protein pharmaceuticals formulated in the same buffer and excipients as well as the surfactants with the same concentration further confirms the interfacial adsorption capacity of proteins that should not be ignored. These findings provide a new angle and valuable insights into the correlation between the surface activity of the proteins and interfacial stability, which may pave the way for future preformulation studies on therapeutic proteins and broaden the thoughts of formulation development.

Composite lithium with high ionic conducting Li3Bi alloy enabled high-performance garnet-type solid-state lithium batteries

Solid-state lithium metal batteries (SSLMBs) are regarded as an important development direction due to their high energy density and safety. Nevertheless, the application of SSLMBs is hampered by the poor interfacial contact with large resistance and dendrite issue, as well as volume variation of metallic lithium anode. Here, a high-performance Li-BiF3 composite lithium having successive ion-conducting phase was constructed via the conversion reaction between commercial BiF3 powders and molten lithium, which shows reduced surface tension of lithium and improved wettability toward Li6.4La3Zr1.4Ta0.6O12 electrolytes. The as-formed Li3Bi in the anode with high ionic diffusion coefficient can quickly transport lithium from the bulk to the solid-state interface to compensate for the lithium depletion during stripping, thus ensuring tight interface contact, inhibiting the generation of gaps, and homogenizing current and Li+ flux. The Li-BiF3/LLZTO/Li-BiF3 symmetric cells present small interfacial resistance (7.4 Ω cm2), large critical current density (1.1 mA cm−2) and superior cyclic stability of 850 h under 0.3 mA cm−2 at 25 °C. In addition, full cells assembled together with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 cathodes demonstrate exceptional cyclic performance with 92.9% and 86.5% capacity maintenance upon 100 cycles under 0.5 C.

Inclusion complexation of surfactant with β-cyclodextrin and its effect on the mixed micellization of cationic/anionic surfactants

Inclusion complexation of surfactant with β-cyclodextrin (β-CD) is an active research topic in supramolecular chemistry. For the mixed system of β-CD and cationic/anionic surfactants, the thermodynamic and molecular dynamics (MD) simulation studies can provide valuable information about synergism between cationic and anionic surfactants and competition between inclusion complexation and mixed micellization. Experimental results indicated a synergistic effect between CTAB and SL in surface tension reduction efficiency and effectiveness, and in mixed micelle formation. The surface tension experiments indicated that for single surfactant CTAB or SL, the binding stoichiometry was β-CD:surfactant = 1:1. For the 1:1 β-CD/surfactant inclusion complexes, umbrella sampling simulation results indicated that SL bound preferentially to the wide rim of β-CD, while, CTAB had a similar probability of binding to either rim of β-CD. Both experimental and simulation results indicated that the inclusion affinity of β-CD with CTAB was significantly stronger than that of β-CD with SL. Due to the electrostatic attraction between the oppositely charged headgroups, the distance between adjacent CTA+ and L− ions was significantly shorter than that between two adjacent CTA+ (or L−) ions. It encouraged us to explore whether the 1:1:1 β-CD/CTAB/SL inclusion complex could form. The MD simulation results indicated that all four possible initial 1:1:1 conformations were unstable. The final stable inclusion complexes were in 1:1 β-CD/CTAB and 1:1 β-CD/SL forms consistent with the umbrella sampling simulation results of the single surfactant. The results suggested that the inclusion interaction becomes less competitive with mixed micellization as the composition approaches the equimolar ratio of CTAB and SL.

Use of Agro-Industrial Waste for Biosurfactant Production: A Comparative Study of Hemicellulosic Liquors from Corncobs and Sunflower Stalks

Biosurfactants have attracted considerable attention because of their lower toxicity, biocompatibility, and effectiveness over chemical surfactants. The use of renewable sources and the concept of sustainable production for such biomolecules supports the increased demand for eco-friendly products. Herein, the present study investigated corncobs (CC) and sunflower stalks (SS) as substitutes for conventional substrates in submerged fermentation with B. subtilis. The agro-industrial residues were submitted to an alkaline pretreatment to obtain hydrolysates rich in hemicelluloses, whose concentrations were determined at 48.8% and 65.7% for corncob and sunflower stalk liquors, respectively. The influence of different concentrations of glucose (0, 2.5, and 5%) and liquor (0, 20%, and 40%) were evaluated according to cell concentration, surface tension reduction rate (STRR), and emulsification index (EI24). Biosurfactants obtained with the hemicellulose liquor of sunflower stalk showed the highest cell concentration (4.57 g/L) and STRR (58.07%), whereas the maximum values of EI24 (56.90% in hexane, 65.63% in toluene, and 64.86% in kerosene) were achieved by using corncob liquor. All top results were observed at 2.5% glucose, 20% liquor (CC or SS), and 1% mineral salts. Notably, excess glucose or liquor (CC or SS) negatively affected cell growth and biosurfactant performance. The results indicated the potential of corncobs and sunflower stalks as low-cost substrates to produce a high added-value biosurfactant with promising tensoative and emulsifying properties.

Antagonistic Toxic Effects of Surfactants Mixtures to Bacteria Pseudomonas putida and Marine Microalgae Phaeodactylum tricornutum.

Surfactants can be found in an ever-widening variety of products and applications, in which the combination of several types of surfactants is used to reinforce their properties, looking for synergistic effects between them. After use, they tend to be discarded into wastewater, ending up in aquatic bodies with concerning harmful and toxic effects. The aim of this study is the toxicological assessment of three anionic surfactants (ether carboxylic derivative, EC) and three amphoteric surfactants (amine-oxide-based, AO), individually and in binary mixtures of them (1:1 w/w), to bacteria Pseudomonas putida and marine microalgae Phaeodactylum tricornutum. Critical Micelle Concentration (CMC) was determined to demonstrate the capacity to reduce surface tension and the toxicity of the surfactants and mixtures. Zeta potential (ζ-potential) and micelle diameter (MD) were also determined to confirm the formation of mixed surfactant micelles. The Model of Toxic Units (MTUs) was used to quantify the interactions of surfactants in binary mixtures and to predict if the concentration addition or response addition principle can be assumed for each mixture. The results showed a higher sensitivity of microalgae P. tricornutum to the surfactants tested and their mixtures than bacteria P. putida. Antagonism toxic effects have been detected in the mixture of EC + AO and in one binary mixture of different AOs; this is to say, the mixtures showed lower toxicity than expected.