Chemical Surfactants Research Articles

Biosurfactants: An Alternative Approach to Synthetic Surfactants

Biosurfactants are surface-active secondary metabolites, produced by microorganisms, such as bacteria, fungi, and yeasts. Biosurfactants have been identified as an alternative approach to chemical surfactants due to its remarkable characteristics such as eco-friendliness, biological protection, biodegradability, and lower toxicity. Initially, it was suggested that biosurfactants could serve as emulsifiers of biodegradable hydrocarbons. However, later on, many studies have explained clearly their multi properties, such as antimicrobial, anti-adhesive, and antioxidant. This has widened the applications of biosurfactants in many fields including; petroleum, agriculture, food production, chemistry, cosmetics and pharmaceutics etc. This review outlined the structural characterization, classification, properties, biosynthesis, and mechanism of action. As well, considerable space is given to emphasise their potential applications along with recent developments. Since, commercial productions of biosurfactants are expensive, future research should be targeted to find alternative and cost-effective raw materials (carbon sources) to cut down the production cost. Sources of most biosurfactants are restricted into several groups of terrestrial microorganisms, more research works need to be focused on targeting different other microbial populations, including, marine dwellings to find novel biosurfactants.

Utilisation of oil-based waste for biosurfactant production

Chemical surfactants produced in large amounts globally have severe adverse effects on environment and human health due to their non-degradable and toxic nature. Eco-friendly biosurfactants with high stability, biodegradability, and low toxicity are the need of the hour. However, biosurfactants are less preferred due to high substrate cost and cumbersome extraction process. This study focused on repurposing of lipid-rich waste like coconut oil cake, rice husk and used cooking oil as a substrate for bacterial biosurfactant production. P. aeruginosa and B. subtilis were evaluated for production and P. aeruginosa was found to be an efficient biosurfactant producer. Among the substrates, coconut oil cake gave maximum yield of 19 mg/ml. The study also focussed on optimisation of biosurfactant extraction using organic solvents and precipitation methods. The yield obtained was maximum using chloroform and methanol (2:1) extraction method. The product obtained was characterised using standard methods and confirmed for its properties. It also exhibited promising antimicrobial activity against gram-positive species.

Sophorolipids: A review on production and perspectives of application in agriculture

Sophorolipids are bioactive molecules that have gained a lot of attention in the recent decades due to their unique functional properties of reducing surface and interfacial tension, emulsification and solubilization. They are mainly produced by the yeast Candida bombicola and are composed of a sugar moiety linked to a fatty acid chain. Sophorolipids are non-toxic, highly efficient and stable at extreme conditions and possess environmentally friendly characteristics over the chemical surfactants. This review is focused on the main characteristics of sophorolipids, fermentation processes, and their utilization in the agricultural field. In this context, sophorolipids are very suitable for use in agriculture, as enhancers of solubility and mobility of plant nutrients, which could result in increased plant biomass, root size and fruit yield. In addition, they could be used for biodegradation of oils, bioremediation of heavy metals in contaminated soils, and as potential biopesticides, to control phytopathogenic microorganisms in agriculture. The extensive use of chemical pesticides has led to widespread insecticide resistance and to hazards to human health and the environment due to their high toxicity. Thus, the introduction of a new biomolecule to control plant diseases and increase crop yield has become an interesting alternative. As a result of the demonstrated antimicrobial activity towards phytopathogenic bacteria and fungi, sophorolipids could be extensively explored in the agriculture field, as a sustainable and natural multifunctional agent for plant crops and soils.

Sustainable strategy for the enhancement of hazardous aromatic amine degradation using lipopeptide biosurfactant isolated from Brevibacterium casei

The application of biosurfactants for the degradation of various toxic compounds has received much attention among researchers worldwide. A stimulated degrading method was carried out in this research to determine the efficiency of surfactant on the biodegradation of aromatic amine 4-Aminobiphenyl (4-ABP). The biosurfactant mediated process is an alternative strategy for chemical surfactants because chemical surfactants are toxic and nonbiodegradable. The bacterium was isolated through the enrichment process and identified using 16S rRNA sequencing method. The molecular characterization showed that the isolate belongs to Brevibacterium casei-4AB. Biosurfactant produced in this study was examined through screening activities like oil spreading, emulsification activity and surface tension measurement. Instrumental characterization like Fourier Transform Infrared Spectrophotometer (FT-IR) results suggested that there is a presence of NH group, aliphatic hydrocarbons, ester groups, amide and alkenes and further Gas chromatography- Mass Spectrometry (GC-MS) results confirmed the presence of fatty acids such as Hexadecanoic and Octadecadienoic acid which showed that the produced surfactant is lipopeptide. Protein content and lipid content in the biosurfactant was found to be 18 ± 0.8% and 30 ± 0.1%. The degraded metabolites of 4-ABP were analyzed through the GC-MS process which revealed the presence of metabolites such as 5-Amino-2-methoxy phenol.

A review on new aspects of lipopeptide biosurfactant: Types, production, properties and its application in the bioremediation process

Nowadays, the worldwide search regarding renewable products from natural resources is increasing due to the toxicity of chemical counterparts. Biosurfactants are surface-active compounds that contain several physiological functions that are used in industries like food, pharmaceutical, petroleum and agriculture. Microbial lipopeptides have gained more attention among the researchers for their low toxicity, efficient action and good biodegradability when compared with other surfactants. Because of their versatile properties, lipopeptide compounds are utilized in the remediation of organic and inorganic pollutants. This review presented a depth evaluation of lipopeptide surfactants in the bioremediation process and their properties to maintain a sustainable environment. Lipopeptide can acts as a replacement to chemical surfactants only if they meet industrial-scale production and low-cost substrates. This review also demonstrated the production of a lipopeptide biosurfactant from a low-cost substrate and depicted plausible techniques to manage the substrate residues to determine its ability in the different applications particularly in the bioremediation process.

Crude oil/water nanoemulsions stabilized by biosurfactant: Stability and pH-Switchability

Emulsification is one of the proposed mechanisms for enhancing crude oil recovery in chemical flooding. The replacement of chemical surfactants in enhanced oil recovery (EOR) applications with biosurfactants is an attractive alternative; yet, there is a lack of studies on the crude oil emulsification using biosurfactants. Particularly, the formulation of crude oil/water (crude O/W) nanoemulsions with an extreme stability and a pH-responsiveness behavior is still not documented in the literature, to the best of our knowledge. Accordingly, we report in this study the preparation of both light and heavy crude oil/water emulsions using different concentrations of the rhamnolipid biosurfactant. The emulsions were prepared in a two-step process: stirring overnight to create coarse emulsions followed by sonication. All the prepared emulsions have a nanoscale size (e.g., about 50% of the formed droplets at 0.1 wt% rhamnolipid are < 200 nm in size), which decreases with increasing the biosurfactant concentration. The zeta potential values of the formed crude O/W nanoemulsions were highly negative (≤−39.3). Increasing the biosurfactant concentration resulted in a more negative zeta potential. The formulated crude O/W nanoemulsions were extremely stable with 0% oil or water separation even after a month of storage. Despite the extreme stability of these crude O/W nanoemulsions, they could be easily switched off (i.e., demulsified) within 1 h by pH-swing via the addition of 50 mM sulfuric acid (H2SO4) regardless of the bioemulsifier (i.e., rhamnolipid) concentration. It was also possible to switch on/off the crude O/W nanoemulsions a number of times (at least five times) through this pH-swing mechanism. We also demonstrated that the crude O/W nanoemulsions can be completely switched off through the addition of NaOH, particularly, when these crude O/W nanoemulsions are stabilized by low rhamnolipid dosages (≤0.5 wt%); such an observation is very unusual. The findings reported in this study clearly demonstrate the ability of creating extremely stable crude O/W nanoemulsions, which is desirable in EOR; however, the emulsified crude oil can be easily and economically recovered via a simple and an economic process (i.e., pH-switch) with the ability to switch off/on the emulsion several times.

Using Amaranthus green proteins as universal biosurfactant and biosorbent for effective enzymatic degradation of diverse lignocellulose residues and efficient multiple trace metals remediation of farming lands

Improving biomass enzymatic saccharification is effective for crop straw utilization, whereas phytoremediation is efficient for trace metal elimination from polluted agricultural soil. Here, we found that the green proteins extracted from Amaranthus leaf tissue could act as active biosurfactant to remarkably enhance lignocellulose enzymatic saccharification for high bioethanol production examined in eight grassy and woody plants after mild chemical and green-like pretreatments were performed. Notably, this study estimated that total green proteins supply collected from one-hectare-land Amaranth plants could even lead to additional 6400–12,400 tons of bioethanol, being over 10-fold bioethanol yield higher than those of soybean seed proteins and chemical surfactant. Meanwhile, the Amaranth green proteins were characterized as a dominated biosorbent for multiple trace metals (Cd, Pb, As) adsorption, being 2.9–6 folds higher than those of its lignocellulose. The Amaranth plants were also assessed to accumulate much more trace metals than all other plants as previously examined from large-scale contaminated soils. Furthermore, the Amaranth green proteins not only effectively block lignin to release active cellulases for the mostly enhanced biomass hydrolyzes, but also efficiently involve in multiple chemical bindings with Cd, which should thus address critical issues of high-costly biomass waste utilization and low-efficient trace metal remediation.

Investigation on Heavy Metal Removal from a Crude Oil Contaminated Soil using Rhamnolipid Biosurfactant as a New Eco-Friendly Method

Abstract Many studies have been conducted on the removal of heavy metals from industrial wastewater using biosurfactants, but few papers have been published on the removal of heavy metals from soil contaminated with crude oil using this method. The aim of this study is to evaluate the performance of rhamnolipid biosurfactants in removing nickel, chromium, and cadmium from soil contaminated with crude oil. In this study, first rhamnolipid was produced from Pseudomonas aeruginosa PTCC1340 and then confirmed by Thin-Layer-Chromatography (TLC) and Fourier-Transformation-Infrared-Spectroscopy (FTIR). In the next step, a sandy soil (2 mm diameter) was mixed with the crude oil (API = 32.83, viscosity = 6.21cp) at 258C for 2 weeks. The washing parameters included temperature, pH and rhamnolipid dosage. Based on our results, the heavy metal removal of nickel, chromium and cadmium from soil contaminated with crude oil at the optimum condition (258C, 0.8 g/L and pH 11) was 43.05%, 34.73% and 52.81%, respectively. Based on the results, rhamnolipids are found to have considerable potential for removing heavy metals especially cadmium, and the soil washing by the produced biosurfactant leads to the removal of heavy metals without the destructive effects of chemical surfactants and subsequently reduces environmental pollution. Therefore, this biosurfactant rhamnolipid may have a good potential for application in bioremediation of crude oil contamination.

Biodegradation of hydrocarbons and biosurfactants production by a newly halotolerant Pseudomonas sp. strain isolated from contaminated seawater

Abstract A strain NAPH6 of Pseudomonas aeruginosa, isolated from contaminated seawater taken from the fishing harbor of Sfax, Tunisia, was able to degrade almost completly the naphthalene (200 mg/l) and the aliphatic hydrocarbons of crude oil (1%, v/v), after 7 and 20 days of culture, respectively, at 30 g/l NaCl. Moreover, the isolated NAPH6 exhibited a notable potentiality to synthesize biological surfactants (BS-NAPH6) on inexpensive carbon sources. The Fourier Transform Infrared (FTIR) analysis suggested that BS-NAPH6 belonged to the glycolipid family. Besides, BS-NAPH6 displayed a high steadiness against a wide spectrum of pHs, temperatures and salinities. The treatment of human HEK293 cells by different concentrations of BS-NAPH6 displayed that this latter exhibited no cytotoxic effect at concentrations below 200 μg/mL. Furthermore, the application of BS-NAPH6 in hydrocarbons removal from polluted soil, demonstrated that it was more efficient than tested chemical surfactants. Interestingly, BS-NAPH6 highlighted a significant healing activity on the wound site in a rat model compared to a commercial cream. Due to their attractive biological properties, strain NAPH6 as well as its biosurfactant BS-NAPH6 are considered as promising candidates for various applications including environmental and biomedical ones.

Optimization of biosurfactant production from Pseudomonas sp. CQ2 and its application for remediation of heavy metal contaminated soil

The present study was conducted to enhance the biosurfactant production yield of Pseudomonas sp. CQ2 isolated from the Chongqing oilfield (China). Besides, the capability of biosurfactant and underlying mechanism for remediation of heavy metal contaminated soil was also investigated. Our results suggested that maximum biosurfactant production (40.7 g/L) was attained at 35 °C by using soybean oil and ammonium nitrate as carbon and nitrogen sources with pH 7, rotational speed of 175 rpm and inoculation ratio of 3%). The removal efficiencies of 78.7, 65.7 and 56.9% for Cd, Cu and Pb respectively were achieved at optimized bioleaching conditions (pH: 11, soil/solution ratio: 30:1 and non-sterilized soil), comparative tests between common chemical surfactants (SDS, Tween-80) and biosurfactants demonstrated the larger removal capacity of biosurfactants. Through SEM-EDX, it was found that the granular material disappeared, the content of Cd, Cu and Pb decreased significantly, and the soil surface became smooth with hole formation after soil washing following bioleaching. ATR-FTIR results showed that the carboxyl functional groups in biosurfactants could chelate heavy metals. These results indicated that biosurfactants from Pseudomonas sp. CQ2 could effectively eliminate Cd, Cu, and Pb from soil.

Guiding environmental sustainability of emerging bioconversion technology for waste-derived sophorolipid production by adopting a dynamic life cycle assessment (dLCA) approach.

Microbial biosurfactants are surface-active molecules that are naturally produced by a range of microorganisms. They have certain advantages over chemical surfactants, such as lower toxicity, higher biodegradability, anti-tumor, and anti-microbial properties. Sophorolipids (SLs) in particular are one of the most promising biosurfactants, as they hold the largest share of the biosurfactant market. Currently, researchers are developing novel approaches for SL production that utilize renewable feedstocks and advanced separation technologies. However, challenges still exist regarding consumption of materials, enzymes, and electricity, that are primarily fossil based. Researchers lack a clear understanding of the associated environmental impacts. It is imperative to quantify and optimize the environmental impacts associated with this emerging technology very early in its design phase to guide a sustainable scale-up. It is necessary to take a collaborative perspective, wherein life cycle assessment (LCA) experts work with experimentalists, to quantify environmental impacts and provide recommendations for improvements in the novel waste-derived SL production pathways. Studies that have analyzed the environmental sustainability of microbial biosurfactant production are very scarce in literature. Hence, in this work, we explore the possibility of applying LCA to evaluate the environmental sustainability of SL production. A dynamic LCA (dLCA) framework that quantifies the environmental impacts of a process in an iterative manner, is proposed and applied to evaluate SL production. The first traversal of the dLCA was associated with the selection of an optimal feedstock, and results identified food waste as a promising feedstock. The second traversal compared fermentation coupled with alternative separation techniques, and highlighted that the fed-batch fermentation of food waste integrated with the in-situ separation technique resulted in less environmental impacts. These results will guide experimentalists to further optimize those processes, and improve the environmental sustainability of SL production. Resultant datasets can be iteratively used in subsequent traversals to account for technological changes and mitigate the corresponding impacts before scaling up.

Oil washing proficiency of biosurfactant produced by a novel Bacillus tequilensis MK 729017 isolated from Assam reservoir soil

The present study describes elaborately the isolation of a potential biosurfactant producing and crude oil degrading (1-5%) strains isolated from the Assam oil reservoir field. The produced biosurfactant was chemically characterized for its applicability for the enhanced oil recovery applications in terms of wetting, interfacial tension (IFT) and oil washing. From the seven isolated strains, Bacillus tequilensis MK 729017 was chosen based on the better surface active properties as it reduced the surface tension to 30 ± 2 mN/m along with a moderate emulsification index of 66 ± 2 %. The produced biosurfactant was chemically identified to be lipopeptide, surfactin with a lower critical micelle concentration value of 90 mg/L. The carbon source and environmental parameters were optimized for the maximum concentration of the biosurfactant using RSM-CCD. The maximum biosurfactant concentration was measured to be 7.46 ± 0.39 g/L and Y_PS was determined as 0.45. The specific growth rate of the isolate was 0.15 ± 0.01 h-1 and Y_XS was estimated as 0.1. The produced biosurfactant was also found to be thermal and colloidal stable. The biosurfactant solutions altered wettability of hydrophobic rock surface from 90 ± 1o to 26 ± 1o indicating a better interfacial interaction. The IFT of the produced biosurfactant was found to be 0.32 ± 0.02 mN/m. The oil washing efficiency (80 ± 2 %) of the produced surfactin was comparable with chemical surfactants and the process involved two-steps: initial a faster (surface) washing followed by a slower (internal) washing. The first process was dependent on micelle sizes, while the later was dependent on water-oil emulsion size. The lower emulsion size of surfactin contributed to a greater internal washing as compared to chemical surfactants. These observations endorse the potential of the isolated strain towards biosurfactant production and its application in microbial enhanced oil recovery process.

Microbial Biosurfactants in Cosmetic and Personal Skincare Pharmaceutical Formulations.

Cosmetic and personal care products are globally used and often applied directly on the human skin. According to a recent survey in Europe, the market value of cosmetic and personal care products in Western Europe reached about 84 billion euros in 2018 and are predicted to increase by approximately 6% by the end of 2020. With these significant sums of money spent annually on cosmetic and personal care products, along with chemical surfactants being the main ingredient in a number of their formulations, of which many have been reported to have the potential to cause detrimental effects such as allergic reactions and skin irritations to the human skin; hence, the need for the replacement of chemical surfactants with other compounds that would have less or no negative effects on skin health. Biosurfactants (surfactants of biological origin) have exhibited great potential such as lower toxicity, skin compatibility, protection and surface moisturizing effects which are key components for an effective skincare routine. This review discusses the antimicrobial, skin surface moisturizing and low toxicity properties of glycolipid and lipopeptide biosurfactants which could make them suitable substitutes for chemical surfactants in current cosmetic and personal skincare pharmaceutical formulations. Finally, we discuss some challenges and possible solutions for biosurfactant applications.

Utilisation of oil-based waste for biosurfactant production

Chemical surfactants produced in large amounts globally have severe adverse effects on environment and human health due to their non-degradable and toxic nature. Eco-friendly biosurfactants with high stability, biodegradability, and low toxicity are the need of the hour. However, biosurfactants are less preferred due to high substrate cost and cumbersome extraction process. This study focused on repurposing of lipid-rich waste like coconut oil cake, rice husk and used cooking oil as a substrate for bacterial biosurfactant production. P. aeruginosa and B. subtilis were evaluated for production and P. aeruginosa was found to be an efficient biosurfactant producer. Among the substrates, coconut oil cake gave maximum yield of 19 mg/ml. The study also focussed on optimisation of biosurfactant extraction using organic solvents and precipitation methods. The yield obtained was maximum using chloroform and methanol (2:1) extraction method. The product obtained was characterised using standard methods and confirmed for its properties. It also exhibited promising antimicrobial activity against gram-positive species.

Amphoteric and cationic surfactants for enhancing oil recovery from carbonate oil reservoirs

In recent decades, chemical surfactants have significantly been utilized in enhanced oil recovery (EOR) process and researchers still have a distinctive look to applications of these chemicals. In this study, Hexadecyl-tetra Methyl Ammonium Bromide (henceforth; HTMAB) and Hexadecyl-Amino-Benzene Sulfonic Acid (henceforth; HABSA) were used as surfactants to derive relative permeability curves for carbonate rocks. To this end, the contact angles for different concentrations of the two surfactants in solutions were measured in the bulk volume of kerosene using a VIT-6000 apparatus. Additionally, the unsteady state core flooding process (JBN method) in three steps (water injection, surfactant HTMAB injection and surfactant HABSA injection) was performed to analyze the relative permeability measurements and finally oil recovery was evaluated at different conditions. According to the results of this study, HTMAB has the maximum oil recovery factor of 63.50% in comparison with the other scenarios assessed in this work. Hence, it is concluded that in carbonate rocks, HTMAB is more effective than HABSA as it has better efficiency to modify the wettability toward water-wet. Furthermore, for HTMAB flooding, it is indicated that relative permeability curves intersection depicts the water saturation of 0.67 and according to the outcomes; the end-point of water is less than oil in relative permeability curve. Therefore, it can be concluded that HTMAB is more impressive than HABSA in wettability variation of these sorts of rocks.

Investigation of halotolerant marine Staphylococcus sp. CO100, as a promising hydrocarbon-degrading and biosurfactant-producing bacterium, under saline conditions

A halotolerant strain CO100 of Staphylococcus sp. was isolated from contaminated sediments taken from the fishing harbour of Sfax, Tunisia, as an efficient hydrocarbonoclastic candidate. Strain CO100 exhibited a high capacity to break down almost 72% of the aliphatic hydrocarbons contained in crude oil (1%, v/v), used as the sole carbon and energy source, after 20 days of culture, at 100 g/l NaCl, 37 °C and 180 rpm. The isolate CO100 displayed also its ability to grow on phenanthrene, fluoranthene and pyrene (100 mg/l), at 100 g/l NaCl. Moreover, the isolate CO100 showed a notable aptitude to synthesize an efficient tensioactive agent namely BS-CO100, on low-value substrates including residual frying oil and expired milk powder, thus reducing the high cost of biosurfactant production. The ESI/MS analysis designated that BS-CO100 belonged to lipopeptide class, in particular lichenysin and iturine members. Critical micelle concentrations of BS-CO100 were varying between 65 and 750 mg/l, depending on of the purity of the biosurfactant and the used carbon sources. BS-CO100 showed a high steadiness against a wide spectrum of pH (4.3–12), temperature (4–121 °C) and salinity (0–300 g/l NaCl), supporting its powerful tensioactive properties under various environmental conditions. Likewise, BS-CO100 exhibited no cytotoxic effect toward human HEK293 cells, at concentrations within 125 and 1000 μg/ml. Furthermore, the biosurfactant BS-CO100 exhibited remarkable anti-adhesive and anti-biofilm activities, being able to avoid and disrupt the biofilm formation by certain pathogenic microorganisms. In addition, BS-CO100 was found to have more potential to remove hydrocarbons from contaminated soils, compared to some chemical surfactants. In light of these promising findings, strain CO100, as well as its biosurfactant, could be successfully used in different biotechnological applications including the bioremediation of oil-polluted areas, even under saline conditions.

Automotive Wash Effluent Treatment Using Combined Process of Coagulation/Flocculation/Sedimentation–Adsorption

In the treatment of wastewater from vehicle washing, the coagulation/flocculation process using inorganic coagulant is mostly applied; it may or may not be combined with other processes. In literature, few studies use natural coagulants and assess the surfactants’ removal among the physical-chemical parameters, particularly using the adsorption process. In order to fill this knowledge gap, this work aimed to treat the car wash wastewater, applying a combined process of coagulation/flocculation/sedimentation (C/F/S) and adsorption. Process efficiency was evaluated according to the removal of color, turbidity, total solids, volatile solids, total dissolved solids, chemical oxygen demand and surfactants. For primary effluent treatment, C/F/S experiments were performed with Tanfloc SG to investigate the influence of the natural coagulant concentration in color and turbidity removal efficiency. The results showed that 220 mg L−1 was the best coagulant concentration (turbidity = 97.5%; color = 92.5%) (p < 0.05). The supernatant of the C/F/S process was applied to the sequential adsorption process (kinetics and isotherm) with mineral activated carbon. The equilibrium time of the kinetic experiment was established after 2 h of contact, and the Langmuir isotherm model best described the surfactant adsorption behavior (R2 = 0.93; qmax = 5.65 mg g−1). The combined process enhanced the treatment efficiency achieving an overall removal efficiency of 97.3% for color, 98.8% for turbidity, 92.6% for chemical oxygen demand, and 97.2% for surfactants. The combined process proved to be promising for the treatment of car wash wastewater, presenting a reduction surfactant concentration and on the other parameters evaluated, contributing to environmental sustainability.

Investigation of factors affecting phytoremediation of multi-elements polluted calcareous soil using Taguchi optimization

Growing environmental concern regarding multi elements-contaminated soils reveals the necessity of paying more attention to environmentally friendly remediation techniques such as phytoremediation. A large number of factors influences phytoremediation of potentially toxic elements (PTEs) and investigation on a variety of these factors need appropriate statistical approaches such as “Taguchi optimization” which effectively decreases time and cost of experiments. In the present study, based on the Taguchi optimization method, the effects of several biological (plant type and mycorrhizal fungi (AMF)) and chemical (chelating agents, surfactants and organic acids) factors, on the phytoremediation of soils contaminated with zinc (Zn), lead (Pb), cadmium (Cd) and nickel (Ni) were investigated. The goal was to find out the most effective factors as well as the best level for each factor. The values of dry weights in roots and aerial parts of the studied plants were in orders of maize > sorghum > sunflower and sorghum > maize > sunflower, respectively. AMF was the main factor in increasing dry weight of shoots. Inoculation of AMF caused increases in root and shoot uptake of some PTEs. Resultsshowed that phytoremediation of PTEs is element-dependent; as Zn showed the highest translocation factor (TF) and bioconcentration factor (BCF) values, while Ni showed the lowest ones and the intermediate values belonged to Pb and Cd. These results show the diverse distribution of elements in plant parts, as Zn and Ni were mostly accumulated in shoot and root, respectively. Although different factors caused impacts on phytoremediation criteria, the role of plant type in the phytoremediation of PTEs was at the first rank. Mean TF of PTEs in sunflower was 6.3 times that of maize. Sunflower showed high TF value for the four elements and translocated most of the PTEs from root to the aerial parts demonstrating phytoextraction as the main mechanism in this plant. Maize and sorghum, however, showed low TF and accumulated most of PTEs in their roots revealing phytostabilization as the main mechanism. In general, it can be concluded that plant type was the most influential factor in the phytoremediation of PTEs followed by EDTA and AMF. Taguchi optimization revealed the appropriateness and significance of different chemical and biological treatments on phytoremediation criteria of different elements.

Enhanced Oil Recovery by Potential Biosurfactant-Producing Halo-thermotolerant Bacteria Using Soil Washing and Sand-Packed Glass Column Techniques.

Biosurfactants offer numerous advantages over the chemical surfactants, especially in energy and environment-related applications. Microbial enhanced oil recovery (MEOR) is a technique to recover oil from reservoirs by using microbes and their metabolites. In present study, total sixteen morphologically distinct bacterial strains isolated from different salty areas of the district Khairpur Mir's, Pakistan, were investigated for their MEOR potential. Screening assays for thermotolerance and halotolerance declared 7 out of 16 (43.75%) bacterial isolates as thermotolerant (capable of growing in the temperature range 60-70°C) and halotolerant (tolerating NaCl concentrations up to 17%, w/v). Moreover, five of them were screened as biosurfactant producers. Among, the lowest surface tension reduction was achieved with biosurfactants produced by the strains KJ2MO (27.8mN/m) and KJ2SK (29.3mN/m). The biosurfactant activity was found stable at temperature (100-121°C, 1h) and pH (4-10). Moreover, maximum oil recovery was obtained with biosurfactant of bacterial strain KJ2MO (54.7%, 51.25%) followed by KJ2SK (44.7%, 40.5%), KJ1WB (37%, 35.5%) and KJ2MD (37.8%, 31.9%) by using either techniques, i.e., soil washing and sand-packed column, respectively. Moreover, the potent species were identified as Pseudomonas pseudoalcaligenes KJ1WB, Bacillus aerius KJ2MD, Bacillus licheniformis KJ2SK, and Bacillus subtilis KJ2MO using 16S rRNA ribo-typing. The investigated species were found to be promising biosurfactants producers having potential for enhanced oil recovery and could be used in other environmental applications like bioremediation.

Comparative study of antimicrobial efficiency of biosurfactant producing Pseudomonas spp. from different soil samples

Amphiphilic biosurfactants are surface-active biological molecules secreted by hydrocarbanoclastic microorganisms. Biosurfactants are eco-friendly, less toxic, biodegradable, and low-cost material, so it has more advantages over chemical surfactants. In this research, Pseudomonas spp., biosurfactant producing microorganisms isolated from different sources of soil samples. IS1, IS2, IS3, IS4 isolates obtained from Garden soil sample; Metal contaminated soil sample; Petroleum contaminated soil sample; Oil contaminated soil sample; respectively. Each isolates identified as Pseudomonas spp. Furthermore, screened for biosurfactant producers. Each isolate showed positive results for the hemolysis test, drop collapse test, oil displacement test, and emulsification test. All isolate incubated in mineral salt medium for biosurfactant production. Biosurfactant extracted from IS1, IS2, IS3, IS4 showed 35%, 65%, 20%, 52% emulsification index respectively. Antimicrobial activity of extracted biosurfactants against pathogenic microorganisms checked by agar cup method. IS2 isolate shows the highest antimicrobial activity among all. All isolate showed a higher zone of inhibition against gram-positive microorganisms than gram-negative microbes. The purpose of this study involves the assessment of the antimicrobial activity of biosurfactant producers from the soil environment.