Oil Spreading Method Research Articles

Isolation and Identification of Bacterial Biosurfactant Activity from Mangrove Sediments

Background: Ujung Pangkah mangroves are reported to have been contaminated with heavy metals. Such heavy metals can induce microorganisms to produce biosurfactants. Biosurfactants with amphiphilic characteristics can lower surface tension. Biosurfactants can be used as antibacterial, antifungal, and antiviral for biomedical purposes. Purpose: This study aimed to identify and test the activity of biosurfactant isolates of bacteria from Ujung Pangkah Mangrove sediments, Gresik Regency. Methods: Biosurfactant activity test methods include emulsification index, oil spreading, drop collapse, and parafilm test. Results: The results of the identification of bacterial isolates in this study obtained the genus Bacillus sp. because bacterial isolates show rod shape, Gram-positive, aerobic, and have ellipse-shaped endospores on the subterminal. The results of the biosurfactant activity test with the Emulsification index method showed an average result of 54.39% and the results of the biosurfactant activity test with the oil spreading method showed that there was a clear zone. The average result of the clear zone obtained is 54.83 mm. The average result in the parafilm test was 8.02 mm and the drop collapse test showed positive results characterized by falling and spreading of bacterial isolate fermentation broth supernatants.

Exploration and characterization of a newly isolated bacterium, Enterobacter quasihormaechei strain BDIFST24001, capable of producing rhamnolipid biosurfactant for oil remediation.

Biosurfactants are naturally occurring compounds synthesized by micro-organisms that increasingly attract attention due to both their living area and application in various industries. In this study, we explore and characterize a novel bacterium, Enterobacter quasihormaechei strain BDIFST24001, isolated for its ability to produce rhamnolipid biosurfactants, with the aim of facilitating oil remediation processes. The isolation of this bacterium was carried out using Luria-Bertani (LB) broth media from environmental samples collected from oil-contaminated sites in Dhaka City. Screening tests, including the oil spreading method and drop collapse assay, were conducted to identify potential biosurfactant-producing strains, leading to the selection of E. quasihormaechei strain BDIFST24001 based on its favourable performance. Subsequent molecular identification revealed a high similarity of the strain's 16S rRNA gene to E. quasihormaechei, which was corroborated through phylogenetic analysis. Further analysis of the biosurfactant produced by this strain indicated its rhamnolipid nature, as confirmed by FT-IR spectroscopy. The rhamnolipids exhibited promising surface-active properties, including a significant reduction in surface tension and emulsification activity, as evidenced by surface tension measurements and emulsification index assays. Optimization studies revealed that the optimal conditions for rhamnolipid production by E. quasihormaechei strain BDIFST24001 were a temperature of 37 °C, pH 10.0 and salinity of 4 %. The rhamnolipids produced by this strain demonstrated effective oil remediation capabilities, as observed through controlled experiments using petrol oil. The rhamnolipids effectively reduced the surface tension of the oil-water interface, facilitating the dispersion and emulsification of the oil phase in water. Overall, our findings highlight the potential of E. quasihormaechei strain BDIFST24001 as a promising candidate for biosurfactant-mediated oil spill cleanup and environmental remediation efforts.

Enhancing the ability of two kinds of oil-degrading bacteria to treat oily sludge by optimising the growth conditions using a response surface methodology.

Biosurfactant are Surfactants produced by certain microorganisms. These biosurfactants increase the biodegradability of insoluble pollutants. In this study, the fermentation products of Pseudomonas stutzeri Lh-42 (PS) and Rhodococcus sp. PR-1 (RD) were studied by Oil spreading method, emulsifying activity and infrared spectrum analysis. It was proved that these fermentation products were biosurfactant. And then the fermentation conditions of PS, RD were optimised by Placket-Burman (PB) design, hill-climbing experiment and response surface methodology (RSM). N source and liquid loading were significant factors in the fermentation of PS, while C source and speed were significant factors in the fermentation of RD. The surface tension was found to be as low as 39.53 ± 0.25 mN/m for the fermentation conditions of PS with an N source of 4.62 ± 0.41 g and a liquid loading of 28.4 ± 0.3%. The surface tension was 40.70 ± 0.47 mN/m for the incubation conditions of RD with a C source of 26.94 ± 0.62 g and a rotational speed of 210 r/min. Finally, the experimental results for the degradation of oily sludge showed that the degradation rate of oily sludge was improved when the fermentation conditions were optimised. The results of the infrared spectroscopy analysis showed that the organic matter content of the oily sludge treated with PS bacteria was significantly reduced after the optimised fermentation. This study provides a theoretical reference for further use of these bacteria to produce biosurfactants to treat organic matter.

Detection of Atypical Motile Staphylococcus aureus from Rain Floods

Abstract:
 Heavy rain floods is one of the primary risk factors for human health, and it can significantly
 regulate microbial communities and enhance the transfer of infections within the affected areas. Recently, the flood crisis is becoming one of the severe natural events in Mosul / Iraq. It may continue for months during which samples of accumulated rainwater were collected.
 Twelve Staphylococcus aureus were isolated by using two selective media: Mannitol Salt agar and Vogel-Johnson media in addition to Blood agar. An unusual colony spreading which resembles. "Bacillus colonies in twelve Staphylococcus aureus isolates was observed on Mannitol Salt agar and semisolid nutrient agar. Actively motile cocci in single and cluster arrangements that is not characteristic of brownian movement was shown in wet mount microscopic observation Furthermore, biosurfactant detection by oil spreading method ( oil displacement activity) showed that all isolates demonstrated various degrees of surfactant production which has beeen reported. to be responsible for stimulating "colony spreading" phenomenon in S. aureux. Motility can play a crucial role for survival bacterial species by which they get nutrients, avoid toxins and predators, and genetic information exchange by mating.
 The present study highlights for the first time. Mosul city a motile opportunistic aureus obtained from harvested rainwater samples during high-rainfall periods. Utilization of untreated harvested rainwater could thus offer a significant health threat to consumers, especially children.
 and immunocompromised individuals.

Isolation And Characterization Of Biosurfactant Producing Bacteria From Different Environmental Soil Samples

Isolation And Characterization Of Biosurfactant Producing Bacteria From Different Environmental Soil Samples

The biosurfactants iturin, lichenysin and surfactin, from vaginally isolated lactobacilli, prevent biofilm formation by pathogenic Candida.

Lactic acid bacteria (LAB), particularly lactobacilli, are major components of the vaginal microbiota. Lactobacilli are facultative anaerobes forming a critical line of defense against pathogenic microorganisms, including those forming biofilms, such as Candida spp. This study aimed to investigate the anti-adhesion capabilities of vaginal Lactobacillus isolates against biofilms formed by pathogenic Candida species. When the extracellular biosurfactant activities of culture supernatants from 120 Lactobacillus isolates were evaluated by the oil-spreading method, clear spreading zones were recognized. Biofilm formation was quantified by the crystal violet plate assay, and different isolates exhibited anti-adhesion activity that ranged from 65.6to 74.4% inhibition against Candida spp. biofilms. Liquid chromatography high-resolution electrospray ionization mass spectrometry (LC-HRESIMS) identified biosurfactants, extracted from three representative Lactobacillus isolates, as surfactin, iturin and lichenysin. Finally, the distribution of representative genes from six different biosynthetic clusters, related to the production of different biosurfactants, was investigated by the polymerase chain reaction. In conclusion, surfactin, iturin and lichenysin were identified for the first time in vaginal Lactobacillus spp. These biosurfactants, which showed strong anti-adherence activity may be used as promising antibiofilm agents in equipment care to prevent vaginal infections by pathogenic Candida spp. with the prospect of reducing nosocomial infections.

Assessment of biosurfactant-producing bacteria from oil contaminated soils and their hydrocarbon degradation potential

Biosurfactants (BSs) are amphiphilic compounds produced by microorganisms and have diverse applications in various industries. This study was aimed to identify and characterize BS producing bacteria from three oil-polluted sites from Pune, Maharashtra, India. Out of the total 48 bacterial isolates, 14 BS producing isolates were detected through drop collapse method (DCM) and oil spreading method (OSM), hemolytic activity, cetyl trimethyl ammonium bromide (CTAB) test, emulsification index (E24), and surface tension (SFT) measurement. The BS producing isolates were identified by matrix-assisted laser desorption/ionization time of flight mass spectrophotometry (MALDI-TOF MS) and 16S rRNA gene sequencing. Results indicated that the isolates belonged to six genera, including Bacillus, Agrococcus, Arthrobacter, Kocuria, Dietzia, and Lysinibacillus. We are reporting BS producing Agrococcus terreus for the first time. Out of 14 BS producing bacteria, four isolates showed β hemolysis in blood agar plates, while all isolates showed negative results on CTAB agar plate. A positive correlation was observed between DCM, OSM, and SFT measurements. Bacillus sp. (isolate PR170) presented the maximum diameter of the clear zone (32 mm) in OSM. The E24 was found to be in the range of 15–57%. Four isolates including PR170, PP151, PP168, and PG138 significantly reduced the SFT of the medium by up to 26.79, 27.81, 28.83, and 30.99 mN/m, respectively. Nine isolates were able to grow in media containing various polyaromatic hydrocarbons. Results gathered in this study demonstrated that isolates belonging to four genera from the contaminated sites had an outstanding potential for further application in biotechnological processes such as large-scale BS production or bioremediation of hydrocarbon polluted sites, and will contribute towards environmental sustainability.

Application of biosurfactant produced by an adaptive strain of C.tropicalis MTCC230 in microbial enhanced oil recovery (MEOR) and removal of motor oil from contaminated sand and water

Microbial enhanced oil recovery (MEOR) represents the use of microorganisms or their products to recover remaining oil trapped up in oil reservoirs. In this study adaptive strain C. tropicalis MTCC230 was used to determine its suitability in MEOR. Biosurfactant produced from an adaptive strain C. tropicalis MTCC230 was characterized as lipopeptide surfactin by Near IR, FTIR spectrum and HPLC and mass spectroscopy analysis. It can significantly reduce the surface tension 72 mN/m to 32 mN/m, with the critical micelle concentration (CMC) of 32.5 mg/l and B. subtilis MTCC2423 used as a standard surfactin (Biosurfactant) producing strain for comparative study. It shows stable Physiochemical properties under the extreme pH(2–12), temperature(30°C-90 °C) and salinity(2%–10%) that promote its potential use in enhanced oil recovery. Oil spreading method and soil washing analysis confirmed it suitability to remove the hydrocarbon contaminants from water and soil. Laboratory scale sand pack column saturated with four stroke engine oil resulted ∼39.80% additional oil recovery (AOR), suggesting its suitability for commercial use in microbial enhanced oil recovery (MEOR) in oil reservoirs.

Screening and identification of biosurfactant producing marine bacteria from the Caspian Sea

Marine microorganisms have unique physiological properties and novel metabolites such as biosurfactant to live in extreme habitats (e.g. oil polluted environment). The aim of this study was to characterize some biosurfactant-producing bacteria collected from sediment and seawater samples from the Caspian Sea. These bacteria were isolated using enrichment method in ONR7a medium with crude oil as sole carbon source. Five screening tests were used for selection of the bacteria including hemolysis in blood agar, oil spreading, drop collapse, emulsification activity and bacterial adhesion to hydrocarbon test (BATH). The bacteria isolated were identified using molecular methods. Eighteen biosurfactant-producing bacteria (from 44 different colonies isolated) were selected and 9 isolates were screened as predominant biosurfactant producer belonging to Pseudomonas stutzeri (Strain S1-4-2), P. balearica (Strain S1-4-1), Pseudomonas sp. (Strain S2-1), P. stutzeri (Strain R3-2), P. chloritidismutans (Strain K4-1), Achromobacter xylosoxidans (Strain K4-3), Acinetobacter radioresistens (Strain S1-2), Acinetobacter calcoaceticus (Strain K4-2) and Citrobacter freundii (Strain R3-1). The largest clear zone diameters for oil spreading method observed for P. balearica strain S1-4-1 (14 mm). Also, this strain has the best emulsification activity (100 %); surface hydrophobicity (BATH: 77 %) and reduction of surface tension (34.5 mN m-1). Thus, this strain selected as the best isolated strains. The results of this study confirmed that there is sufficient diversity of biosurfactant-producing bacteria in the Caspian Sea and the environmental problem can be resolved by application of these bacteria in petrochemical waste water.

Pseudomonas aeruginosa L10: A Hydrocarbon-Degrading, Biosurfactant-Producing, and Plant-Growth-Promoting Endophytic Bacterium Isolated From a Reed (Phragmites australis).

Bacterial endophytes with the capacity to degrade petroleum hydrocarbons and promote plant growth may facilitate phytoremediation for the removal of petroleum hydrocarbons from contaminated soils. A hydrocarbon-degrading, biosurfactant-producing, and plant-growth-promoting endophytic bacterium, Pseudomonas aeruginosa L10, was isolated from the roots of a reed, Phragmites australis, in the Yellow River Delta, Shandong, China. P. aeruginosa L10 efficiently degraded C10–C26 n-alkanes from diesel oil, as well as common polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, phenanthrene, and pyrene. In addition, P. aeruginosa L10 could produce biosurfactant, which was confirmed by the oil spreading method, and surface tension determination of inocula. Moreover, P. aeruginosa L10 had plant growth-stimulating attributes, including siderophore and indole-3-acetic acid (IAA) release, along with 1-aminocyclopropane-1-carboxylic (ACC) deaminase activity. To explore the mechanisms underlying the phenotypic traits of endophytic P. aeruginosa L10, we sequenced its complete genome. From the genome, we identified genes related to petroleum hydrocarbon degradation, such as putative genes encoding monooxygenase, dioxygenase, alcohol dehydrogenase, and aldehyde dehydrogenase. Genome annotation revealed that P. aeruginosa L10 contained a gene cluster involved in the biosynthesis of rhamnolipids, rhlABRI, which should be responsible for the observed biosurfactant activity. We also identified two clusters of genes involved in the biosynthesis of siderophore (pvcABCD and pchABCDREFG). The genome also harbored tryptophan biosynthetic genes (trpAB, trpDC, trpE, trpF, and trpG) that are responsible for IAA synthesis. Moreover, the genome contained the ACC deaminase gene essential for ACC deaminase activity. This study will facilitate applications of endophytic P. aeruginosa L10 to phytoremediation by advancing the understanding of hydrocarbon degradation, biosurfactant synthesis, and mutualistic interactions between endophytes and host plants.

Characterization of Biosurfactant Produced by Probiotic Bacteria Isolated from Human Breast Milk

Background: Breast milk is an important nutrient source for rapidly growing neonates since breastfeeding protects the newborn against some disease. This effect may be due to the useful and natural microflora of breast milk. Biosurfactants are unique amphipathic compounds produced by some microorganisms. The present study demonstrates the isolation and characterization of biosurfactant producing bacteria from human breast milk samples. Methods: The human breast milk samples were collected aseptically and then cultured in MRS agar media. The biosurfactant producing ability of the isolated strains was investigated by hemolytic assay, oil spreading method, drop collapse test and emulsification index assay. The screened isolates were identified by 16S rDNA gene sequencing analysis. In vitro antibacterial activities of biosurfactants against some Gram-positive and Gram negative bacteria were investigated by the agar disc diffusion method. This biosurfactant was characterized with Fourier transform infrared spectroscopy (FTIR). Results: In this study, 337 different colonies were isolated from 42 breast milk samples. The best isolates were identified as Pediococcus pentosaceus HM-1, Pediococcus pentosaceus HM-2 and Pediococcus pentosaceus HM-3 based on microscopic and 16S rDNA gene sequencing analysis. The biosurfactant extracted from screened strains exhibited a broad spectrum of antagonistic activity against some pathogenic bacteria. The results showed similarity to lipopeptide biosurfactants like surfactin. Conclusion: Bacterial strains isolated in this study could be valuable sources for novel biosurfactants. The Human breast milk could be a safe source for isolation of biosurfactant producing probiotic bacteria and for improve intestinal microflora of infants.

Biosurfactant production and concomitant hydrocarbon degradation potentials of bacteria isolated from extreme and hydrocarbon contaminated environments

Amongst the total forty-seven bacterial isolates, eleven potent biosurfactant producing and concomitant hydrocarbon degraders were obtained after primary screening involving drop collapse method (DCM) and Oil-spreading method (OSM) followed by secondary screening comprising of Haemolytic assay (HA), Cetyl trimethyl ammonium bromide (CTAB) assay, Surface tension (ST), Emulsification index (E24) and Emulsification activity (EA). 16S-rRNA sequencing and phylogenetic analysis revealed the presence of Achromobacter, Bacillus, Citrobacter, Lysinibacillus, Ochrobactrum and Pseudomonas. Two genera, Achromobacter (PS1) (observed for the first time) and Bacillus (SLDB1) were found to be glycolipid producers as evident by TLC, FT-IR and GC–MS chromatograms. The surface tension values were 30.43mN/m and 31.10mN/m with (E24) of 69.90% and 65.23% respectively. Similarly the TLC, FT-IR and GC–MS results of the other two genera Ochrobactrum (GREW1) and Bacillus (SB2) confirmed them as lipopeptide biosurfactant producers with surface tension values of 31.14mN/m and 28.16mN/m and (E24) of 59.51% and 61.35% respectively. Qualitative 2,6-Dichlorophenol Indophenol (2,6-DCPIP) and quantitative methods for hydrocarbon degradation revealed that Achromobacter sp. (PS1) showed a maximum degradation (46.32%) of 2% (w/v) crude oil with 70.77% and 77.17% reduction in peak area of aliphatic and aromatic fractions respectively with simultaneous lowering of surface tension from 59.27mN/m (control) to 32.43mN/m in 7days. In case of Achromobacter sp. (PS1) and Bacillus sp. (SB2 and SLDB1), glucose supported biosurfactant production, whereas in Ochrobactrum sp. (GREW1) glucose along with 1% diesel enhanced biosurfactant production. This signifies the role of substrate in the nature of biosurfactants produced.

Optimization of biosurfactant production from Vibrio sp. BSM-30 isolated in tropical waters

The strain BSM-30 (Vibrio sp.), isolated from Chinese tropical waters, could be a biosurfactant producing bacteria according with results obtained by the oil spreading method. The culture conditions for biosurfactant production were tested respectively such as inoculation (2%,6%,10%,14% as setting), shaking speed(120 r/min,150 r/min,180 r/min as setting), temperature (25°C,30°C,35°C as setting), pH (7,8,9 as setting), salinity (1.5%, 2.5%, 3.0%, 4.5%, 5.5% as setting), which results showed that the best culture conditions for BS production were 10% inoculation quantity, 180 r/min, 25°C, pH 8, and 3.5% salinity. The optimization of carbon sources (20g/ of glucose, 20g/L of starch, 20g/L of paraffin oil 20g/L of diesel, 20g/L of oil as setting) and nitrogen sources (6g/L of NaNO3,7.1g/L of KNO3,5.6g/L of NH4NO3,9.3g/L of (NH4)2SO4, 4.2g/L of CO(NH2)2 as setting) were also tested, which results showed that the best nitrogen source and carbon source were (NH4) 2SO4 and soluble starch.

Comparison of Methods to Quantify Rhamnolipid and Optimization of Oil Spreading Method

Abstract A rapid and reliable method to quantify rhamnolipid is indispensable to study and evaluate rhamnolipid-producing bacteria. Five methods were attempted to quantify rhamnolipid in bacteria culture. The oil spreading method better predicted the rhamnolipid concentration and is simpler than the other methods. The potential influencing factors (temperature, pH, salinity, metals, bacterial cells, carbon sources) were investigated. The common substance in fermentation broth has little effect on oil spreading circle. An optimized protocol of the oil spreading method to quantify rhamnolipid was proposed. A positive linear correlation (R2 – 0.9908) was established between the diameter of the formed oil spreading circle and the concentration of rhamnolipid (100–800 mg L−1). Results of a large number of samples suggested that the oil spreading method is easy, rapid and reliable to analyze quantitatively rhamnolipids.

Unexplored Brazilian oceanic island host high salt tolerant biosurfactant-producing bacterial strains.

We aimed to isolate biosurfactant-producing bacteria in high salt conditions from uncontaminated soils on the Brazilian oceanic island, Trindade. Blood agar medium was used for the isolation of presumptive biosurfactant-producing bacteria. Confirmation and measurements of biosurfactant production were made using an oil-spreading method. The isolates were identified by fatty acid profiles and partial 16S rRNA gene sequence analysis. A total of 14 isolates obtained from the 12 soil samples were found to produce biosurfactants. Among them, two isolates stood out as being able to produce biosurfactant that is increasingly active in solutions containing up to 175 g L(-1) NaCl. These high salt tolerant biosurfactant producers are affiliated to different species of the genus Bacillus. Soil organic matter showed positive correlation with the number of biosurfactant-producing bacteria isolated from our different sampling sites. The applied approach successfully recovered and identified biosurfactant-producing bacteria from non-contaminated soils. Due to the elevated salt tolerance, as well as their capacity to produce biosurfactants, these isolates are promising for environmental biotechnological applications, especially in the oil production chain.

ISOLATION AND ANTIMICROBIAL ACTIVITY OF RHAMNOLIPID (BIOSURFACTANT) FROM OIL-CONTAMINATED SOIL SAMPLE USING HUMIC-ACID SALTS-VITAMIN AGAR

In this study, actinomycetes were isolated from the soil sample contaminated with petroleum oil in Naval Dockyard near Visakhapatnam. The isolate was identified as Streptomyces coelicoflavus comprising 16S rDNA sequence. Ten isolates of soil actinomycetes were initially screened in humic acid-salts vitamin agar plates. Soil organic matter is generally rich in humic acid and fluvic acid. Humic acid is an important ingredient for the extraction of biosurfactant producing actinomycetes. In the present study, humic acid substances used for screening of biosurfactant producing Actinomycetes were extracted by using soil organic matter. Humic substances were extracted by treating this organic soil with alkalis like dilute sodium hydroxide. The ten isolates were further grown in Kim’s medium, containing olive oil as the sole source of carbon, for extracellular biosurfactant activity by oil spreading method. Out of these ten, only three isolates namely, NDYS-1, NDYS-3, NDYS-4, showed promising biosurfactant activity compared to the standard, sodium laryl sulphate. These three promising isolates were further screened for their biosurfactant activity by using Para film–M method, Emulsification index and Phenol H2SO4. Out of these three, only NDYS-4 showed maximum biosurfactant activity for the above tests. The result showed that the extracellular surface active agent produced by the isolate NDYS-4 was Rhamnolipid in nature, and was further confirmed by orcinol assay taking L-rhamnose as standard. Then crude extract obtained from this isolate was used in contact bioautography for antibacterial activity. It was observed that as the antibacterial activity increased, the biosurfactant activity also increased and vice versa.

Aquatic model for engine oil degradation by rhamnolipid producing Nocardiopsis VITSISB.

The present study was focused on isolation, screening, characterization and application of biosurfactant producing marine actinobacteria. Twenty actinobacteria were isolated from marine water sample and were primarily screened for biosurfactant production using hemolytic activity method. Among the 20 isolates, six showed positive result for hemolytic activity and those were taken for further secondary screening tests such as oil collapse method, oil spreading method and emulsification method. From the results of secondary screening analysis, two isolates (SIS-3 and SIS-20) were selected and further used to carry out biosurfactant characterization test such as pH, density, surface tension and viscosity determination. Comparing biosurfactant characterization results, SIS-3 was chosen for further analysis and application. FT-IR and GC–MS were carried out for analysis of biosurfactant from isolate SIS-3 and the compound detected was rhamnolipid. The isolate (SIS-3) was identified as Nocardiopsis using 16S rRNA gene sequencing and named as ‘Nocardiopsis VITSISB’ (KC958579) which was further applied for immobilizing whole cells for engine oil degradation by constructing an aquatic model and using natural products such as soybean meal, sugarcane juice as nutrient source. The oil was efficiently degraded by rhamnolipid producing Nocardiopsis VITSISB (KC958579) within 25 days which indicated that the strain can act as a natural candidate for the bioremediation of oil spill in ocean.

Biosurfactant-producing strains in enhancing solubilization and biodegradation of petroleum hydrocarbons in groundwater

Three biosurfactant-producing strains designated as BS-1, BS-3, and BS-4 were screened out from crude oil-contaminated soil using a combination of surface tension measurement and oil spreading method. Thin layer chromatography and infrared analysis indicated that the biosurfactants produced by the three strains were lipopeptide, glycolipid, and phospholipid. The enhancement of solubilization and biodegradation of petroleum hydrocarbons in groundwater employing biosurfactant-producing strains was investigated. The three strain mixtures led to more solubilization of petroleum hydrocarbons in groundwater, and the solubilization rate was 10.5 mg l−1. The combination of biosurfactant-producing strains and petroleum-degrading strains exhibited a higher biodegradation efficiency of 85.4 % than the petroleum-degrading strains (71.2 %). Biodegradation was enhanced the greatest with biosurfactant-producing strains and petroleum-degrading strains in a ratio of 1:1. Fluorescence microscopy images illustrate that the oil dispersed into smaller droplets and emulsified in the presence of biosurfactant-producing strains, which attached to the oil. Thus, the biodegradation of petroleum hydrocarbons in groundwater was enhanced.

Biosurfactan Production by <i>Bacillus</i> sp. Isolated from Petroleum Contaminated Soils of Sirri Island

Problem statement: Biosurfactants are active surface components produced by some bacteria and fungi. These molecules reduce surface and interfacial tension in aqueous solutions and hydrocarbon mixtures. The most important application of biosurfactants is in oil industry to enhance oil quality and facilitate oil extraction. The aim of this study was to isolate biosurfactant producing bacteria and optimize the conditions like temperature and pH for maximum biosurfactant production. Approach: Samples were collected from 8 selected points of oil contaminated soils in Sirri Island-Iran. Primary screening tests including hemolytic activity, Drop collapse technique and Oil Spreading method were preformed and species with the best results were picked for complementary screening tests like emulsification activity, foaming and surface tension measurement. Results: Totally, 160 bacteria species were isolated. During primary and complementary screening tests, 59 species showed hemolytic activity, 46 had drop collapsing ability and 18 species showed positive results in emulsification, foaming and surface tension reduction. Finally, two Bacillus sp. were found to be able to reduce surface tension more than 30 mNm-1. Conclusion: Two strains with a high amount of biosurfactant production and emulsification ability were resulted from the present study. According to the high potential of Bacillus sp. especially for Microbial Enhanced Oil Recovery (MEOR) and Bioremediation of oil contamination we can hope that further study of the isolates characteristics and looking for new local strains can play an important role in their application in oil industry.

Comparative approach for detection of biosurfactant-producing bacteria isolated from Ahvaz petroleum excavation areas in south of Iran

The current study was undertaken to compare four analytical methods including drop collapse, oil spreading, surface tension (SFT) measurements, and blood agar lysis tests for detection of biosurfactant-producing bacteria. Among 32 biosurfactant-producing bacteria isolated from Ahvaz oil fields, in south of Iran, 16 isolates (50%) exhibited highest biosurfactant production. Eleven isolates (MASH.1 to MASH.11) demonstrated a reduction in surface tension from 65 mN/m to less than 41 mN/m. The results showed that about 91% of these highly biosurfactant producers had the same response levels of “++++” and “+++” in the case of both SFT and oil spreading methods. Among these, seven isolates had the haemolysis diameter less than 1 cm or between 1 and 2 cm on blood agar. As 64% of the best biosurfactant producers did not completely lyses blood, the ability of biosurfactant-producers for haemolysis may not always be trustworthy. According to our data, there is a good consistency between oil spreading technique and surface tension. As a conclusion, oil spreading method is the fastest, simplest and most consistent analytical method to be suggested for accurate measurements of biosurfactant producers.