Isolation and characterization of a biosurfactant from Deinococcus caeni PO5 using jackfruit seed powder as a substrate

Biosurfactant-producing bacteria were isolated from various sources in the south of Thailand. Isolates were screened for biosurfactant production using jackfruit seed powder (JSP) as a novel and promising substrate. The highest biosurfactant activity was obtained with a bacterial strain which was identified by 16S rRNA gene sequence analysis as Deinococcus caeni PO5. D. caeni PO5 was able to grow and reduce the surface tension of the culture supernatant from 67.0 to 25.0 mN/m after 87 h of cultivation when 40 g/l of JSP and 1 g/l of commercial monosodium glutamate were used as carbon and nitrogen sources, respectively. The biosurfactant obtained by ethyl acetate extraction showed high surface tension reduction (47.0 mN/m), a small critical micelle concentration value (8 mg/l), thermal and pH stability with respect to surface tension reduction and emulsification activity, and a high level of salt tolerance. Chemical characterization by biochemical testing, Fourier transform infrared spectroscopy, and mass spectra revealed that the obtained biosurfactant was a glycolipid-type biosurfactant. The obtained biosurfactant was capable of forming stable emulsions with various hydrocarbons and had the ability to enhance oil recovery, the solubility of polyaromatic hydrocarbons, heavy metal removal, and antimicrobial activity.     

Isolation and functional characterization of a biosurfactant produced by a new and promising strain of Oleomonas sagaranensis AT18

Biosurfactant-producing bacteria were isolated from mangrove sediment in southern Thailand. Isolates were screened for biosurfactant production by using the surface tension test. The highest reduction of surface tension was achieved with a bacterial strain which was identified by 16S rRNA gene sequencing as Oleomonas sagaranensis AT18. It has also been investigated using different carbon and nitrogen sources. It showed that the strain was able to grow and reduce the surface tension of the culture supernatant to 25?mN/m. In all 5.30?g of biosurfactant yield was obtained after 54?h of cultivation by using molasses and NaNO(3) as carbon and nitrogen sources, respectively. The biosurfactant recovery by chloroform:methanol extraction showed a small critical micelle concentration value (8?mg/l), thermal and pH stability with respect to surface tension reduction. It also showed emulsification activity and a high level of salt concentration. The biosurfactant obtained was confirmed as a glycolipid by using a biochemical test, FT-IR and mass spectra. The crude biosurfactant showed a broad spectrum of antimicrobial activity and also had the ability to emulsify oil and enhance PAHs solubility.     

Utilization of palm oil decanter cake as a novel substrate for biosurfactant production from a new and promising strain of Ochrobactrum anthropi 2/3

A biosurfactant-producing bacterium, isolate 2/3, was isolated from mangrove sediment in the south of Thailand. It was evaluated as a potential biosurfactant producer. The highest biosurfactant production (4.52 g/l) was obtained when the cells were grown on a minimal salt medium containing 25 % (v/v) palm oil decanter cake and 1 % (w/v) commercial monosodium glutamate as carbon and nitrogen sources, respectively. After microbial cultivation at 30 °C in an optimized medium for 96 h, the biosurfactant produced was found to reduce the surface tension of pure water to 25.0 mN/m with critical micelle concentrations of 8.0 mg/l. The stability of the biosurfactant at different salinities, pH and temperature and also its emulsifying activity was investigated. It is an effective surfactant at very low concentrations over a wide range of temperatures, pH and salt concentrations. The biosurfactant obtained was confirmed as a glycolipid type biosurfactant by using a biochemical test, fourier-transform infrared spectroscopy, MNR and mass spectrometry. The crude biosurfactant showed a broad spectrum of antimicrobial activity and also had the ability to emulsify oil and enhance polyaromatic hydrocarbons solubility.     

An efficient biosurfactant-producing and crude-oil emulsifying bacterium Bacillus methylotrophicus USTBa isolated from petroleum reservoir

An efficient biosurfactant-producing bacterium was isolated and cultured from petroleum reservoir in northeast China. Isolate was screened for biosurfactant production using haemolytic assay, Cetyl Trimethyl Ammonium Bromide agar plate assay (CTAB) and the qualitative oil-displacement test. Based on partial sequenced 16S rDNA analysis of isolate, USTBa, identified as Bacillus methylotrophicus with 100% identity. This bacterium was able to produce a type of biosurfactant with excessive foam-forming properties. The maximum biosurfactant production was obtained when the cells were grown on minimal salt medium containing 2% (v/v) crude-oil as the sole source of carbon at 35 °C and 180 rpm after 192 h. This strain had a high emulsification activity and biosurfactant production of 78% and 1.8 g/L respectively. The cell free broth containing biosurfactant could reduce the surface tension to 28 mN/m. Fourier transform infrared (FT-IR) spectrum of extracted biosurfactant indicates the presence of carboxyl, hydroxyl and methoxyl functional groups. Elemental analysis of the biosurfactant by Energy dispersive X-ray spectroscopy (EDS) reveals that the biosurfactant was anionic in nature. The strain USTBa represented as a potent biosurfactant-producer and could be useful in variety of biotechnological and industrial processes, particularly oil industry.     

Production and characterization of biosurfactant from marine bacterium Inquilinus limosus KB3 grown on low-cost raw materials

Inquilinus limosus strain KB3, isolated from marine sediment in the south of Thailand, was used to produce a biosurfactant from a mineral salts medium (MSM) with palm oil decanter cake (PODC) as a carbon source. It was found that cellular growth and biosurfactant production in MSM were greatly affected by the medium components. I. limosus KB3 was able to grow and to produce surfactant reducing the surface tension of medium to 28.2 mN/m and giving a crude surfactant concentration of 5.13 g/l after 54 h. The biosurfactant obtained was found to reduce the surface tension of pure water to 25.5 mN/m with the critical micelle concentration of 9 mg/l, and retained its properties during exposure to elevated temperatures (121 °C), high salinity (12 % NaCl), and a wide range of pH values. Chemical characterization by FT-IR, NMR, and ESI-MS revealed that the biosurfactant has a lipopeptide composition with molecular mass (m/z) of 1,032. The biosurfactant was capable of forming stable emulsions with various hydrocarbons and had the ability to enhance oil recovery, PAHs solubility, and antimicrobial activity.     

Screening and Evaluation of Biosurfactant-Producing Strains Isolated from Oilfield Wastewater

The six biosurfactant-producing strains, isolated from oilfield wastewater in Daqing oilfield, were screened. The production of biosurfactant was verified by measuring the diameter of the oil spreading, measuring the surface tension value and emulsifying capacity against xylene, n-pentane, kerosene and crude oil. The experimental result showed three strains (S2, S3, S6) had the better surface activity. Among the three strains, the best results were achieved when using S2 strain. The diameter of the oil spreading of the biosurfactant produced by S2 strain was 14 cm, its critical micelle concentration (CMC) was 21.8 mg/l and the interfacial tension between crude oil and biosurfactant solution produced by S2 strain reduced to 25.7 mN/m. The biosurfactant produced by S2 strain was capable of forming stable emulsions with various hydrocarbons, such as xylene, n-pentane, kerosene and crude oil. After S2 strain treatment, the reduction rate of oil viscosity was 51 % and oil freezing point reduced by 4 °C.     

Enhancement of stability of biosurfactant produced by <Emphasis Type="Italic">Candida lipolytica</Emphasis> using industrial residue as substrate

This work describes experimental results carried out on the fermentation of Candida lipolytica, which produced a new biosurfactant when grown on a vegetable oil refinery residue as substrate. The cell-free culture broth containing the biosurfactant formed stable emulsions with hydrophobic natural compounds. Emulsification properties of the biosurfactant were not affected by salinity; however, treatment at a higher temperature decreased the emulsification activity, indicating applications in oil recovery. The isolated biosurfactant corresponds to a yield of 4.5 g/l, and the surface tension of water was reduced from 71 to 32 mN/m. Preliminary chemical characterizations showed that the biosurfactant consisted of protein (50%), lipid (20%), and carbohydrate (8%).     

Core flooding tests to investigate the effects of IFT reduction and wettability alteration on oil recovery during MEOR process in an Iranian oil reservoir

Microbial enhanced oil recovery (MEOR) refers to the process of using bacterial activities for more oil recovery from oil reservoirs mainly by interfacial tension reduction and wettability alteration mechanisms. Investigating the impact of these two mechanisms on enhanced oil recovery during MEOR process is the main objective of this work. Different analytical methods such as oil spreading and surface activity measurements were utilized to screen the biosurfactant-producing bacteria isolated from the brine of a specific oil reservoir located in the southwest of Iran. The isolates identified by 16S rDNA and biochemical analysis as Enterobacter cloacae (Persian Type Culture Collection (PTCC) 1798) and Enterobacter hormaechei (PTCC 1799) produce 1.53 g/l of biosurfactant. The produced biosurfactant caused substantial surface tension reduction of the growth medium and interfacial tension reduction between oil and brine to 31 and 3.2 mN/m from the original value of 72 and 29 mN/m, respectively. A novel set of core flooding tests, including in situ and ex situ scenarios, was designed to explore the potential of the isolated consortium as an agent for MEOR process. Besides, the individual effects of wettability alteration and IFT reduction on oil recovery efficiency by this process were investigated. The results show that the wettability alteration of the reservoir rock toward neutrally wet condition in the course of the adsorption of bacteria cells and biofilm formation are the dominant mechanisms on the improvement of oil recovery efficiency.     

Properties of the biosurfactant produced byBacillus licheniformis strain JF-2

Summary The activity of the biosurfactant produced byBacillus licheniformis strain JF-2 was quantified using a unit defined as the amount of the acid-precipitated biosurfactant that lowered the surface tension by 10 mN/m. One unit was equivalent to 37 g/ml of the acid-precipitated biosurfactant. Acid precipitation was very effective in the removal of the biosurfactant from the spent medium. Among the solvents tested methanol was the most efficient in extracting the surfactant activity from acid-precipitated material. Thin-layer chromatography of the acid-precipitated biosurfactant revealed four components, two of which contained a lipid moiety and one of which contained an amino group. The methanol-soluble fraction also contained these four components. Studies suggested that all four components were needed for full activity. The lowest interfacial tensions against octane were observed when NaCl concentrations were 50 g/l or greater. Calcium concentrations greater than 25 g/l significantly increased the interfacial tension     

Biosurfactant production by Pseudomonas aeruginosa A41 using palm oil as carbon source

Biosurfactant production by Pseudomonas aeruginosa A41, a strain isolated from seawater in the gulf of Thailand, was examined when grown in defined medium containing 2% vegetable oil or fatty acid as a carbon source in the presence of vitamins, trace elements and 0.4% NH(4)NO(3), at pH 7 and 30 degrees C with 200 rpm-shaking for 7 days. The yield of biosurfactant steadily increased even after a stationary phase. Under such conditions the surface tension of the medium was lowered from 55-70 mN/m to 27.8-30 mN/m with every carbon source tested. However, types of carbon sources were found to affect biosurfactant yield. The yields of rhamnolipid biosurfactant were 6.58 g/L, 2.91 g/L and 2.93 g/L determined as rhamnose content when olive oil, palm oil and coconut oil, respectively, were used as a carbon source. Among them, biosurfactant obtained from palm oil was the best in lowering surface tension of the medium. Increase in biosurfactant activities in terms of oil displacement test and rhamnose content were observed to be higher with shorter chain fatty acids than that of the longer chains (C12>C14>C16). In addition, we found that C18:2, highly unsaturated fatty acid, showed higher oil displacement activity and rhamnose content than that of C18:1. The optimal oil displacement activity was found at pH 7-9 and in the presence of 0.5-3% NaCl. The oil displacement activity was stable to temperatures up to 100 degrees C for 15 h. Surface tension reduction activity was relatively stable at pH 2-12 and 0-5% of NaCl. Emusification activity tested with various types of hydrocarbons and vegetable oils showed similarity of up to 60% stability. The partially purified biosurfactant via TLC and silica gel column chromatography gave three main peaks on HPLC with mass spectra of 527, 272, and 661 m/z respectively, corresponding to sodium-monorhamnodecanoate, hydroxyhexadecanoic acid and an unknown compound, respectively.     

糖脂类生物表面活性剂的特性及其对白腐真菌降解蒽的强化作用

【目的】对铜绿假单胞菌(Pseudomonas aeruginosa)所产生物表面活性剂的稳定性进行分析,考察该生物表面活性剂对乳白耙齿菌F17(Irpex lacteus F17)降解蒽的强化作用。【方法】采用三氯甲烷萃取的方法从铜绿假单胞菌的发酵液中提取生物表面活性剂,采用表/界面张力仪测定该生物表面活性剂在不同条件下的表面张力值,对其进行稳定性研究。在乳白耙齿菌F17降解蒽的过程中加入适量的生物表面活性剂,测定蒽的降解率,探讨其对蒽生物降解的强化作用。【结果】铜绿假单胞菌所产生物表面活性剂的临界胶束浓度为40 mg/L,在15-150°C及pH 6.0-13.0范围内表现出优良的稳定性,对盐浓度的耐受性也很高。在蒽的生物降解过程中,生物表面活性剂能极大地促进蒽的降解,在生物表面活性剂浓度为50 mg/L时,第15天蒽的降解率达到了82.9%。生物表面活性剂在接种乳白耙齿菌F17前1天加入培养基中,能更好地促进蒽的降解。与化学表面活性剂相比,生物表面活性剂对蒽降解的强化作用更显著。【结论】该生物表面活性剂性能优良、稳定性好,能够显著强化乳白耙齿菌F17对蒽的降解,具有良好的应用前景。     

Isolation of biosurfactant-producing <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> RS29 from oil-contaminated soil and evaluation of different nitrogen sources in biosurfactant production

An efficient biosurfactant-producing native Pseudomonas aeruginosa RS29 has been isolated from crude oil contaminated soil. Isolation was followed by optimization of different factors to achieve maximum production of biosurfactant in terms of surface tension reduction (STR) and emulsification index (E24). The isolated strain produced highest biosurfactant in the presence of glycerol after 48 h of incubation at 37.5°C, with pH range of 7–8 and at salinity <0.8% (w/v). The extent of STR and the E24 of medium with different nitrogen sources were investigated and found to be maximal for sodium nitrate (26.3 mN/m, E24?=?80%) and potassium nitrate (26.4 mN/m, E24?=?79%). The production of biomass by the designated strain was found to be maximal in ammonium-nitrate-containing medium as compared to the other nitrogen sources. A kinetic study revealed that biosurfactant production is positively correlated with growth of P. aeruginosa, and highest STR was achieved (27.0 mN/m) after 44 h of growth. The biosurfactant was produced as a primary metabolite and 6 g/L crude biosurfactant was extracted by chloroform:methanol (2:1). The critical micelle concentration of the biosurfactant was 90 mg/L. The absorption bands of the FTIR spectra confirmed the rhamnolipid nature of the biosurfactant. The biosurfactant was thermostable (up to 121°C for 15 min) and could withstand a wide range of pH (2–10) and NaCl concentration (2%–10% w/v). The extracted biosurfactant had good foaming and emulsifying activities and was of satisfactory quality in terms of stability (temperature, pH and salinity) and foaming activity.     

Laboratory production and characterization of a new biosurfactant from <Emphasis Type="Italic">Candida glabrata</Emphasis> UCP1002 cultivated in vegetable fat waste applied to the removal of hydrophobic contaminant

Biosurfactant production by Candida glabrata was studied using vegetable fat waste as substrate. A factorial design was initially carried out to investigate the effects and interactions of waste, yeast extract and glucose on the surface tension after 144 h cultivation. Maximum surface tension reduction was achieved with vegetable fat waste at 5% and yeast extract at 0.2%. The biosurfactant containing cell-free broth retained its surface-active properties after incubation at high temperatures, at a wide range of pH values and salt concentrations. Comparison between three solvent systems for surfactant recovery showed that ethyl acetate extracted both crude extracellular and intracellular biosurfactant with high product recovery. The isolated extracellular biosurfactant showed a CMC of 1% and the surface tension at that point was 24 mN m⁻¹. Preliminary chemical composition revealed the presence of carbohydrates, proteins and lipids. The application of the crude biosurfactant to a soil–water-hydrophobic contaminant system was investigated and the apparent critical micelle concentration was determined at 7% of the broth, although the best oil removal (92.6%) had been obtained with 10% of the cell-free broth. The cost of application of the biosurfactant in soils was estimated based on the cost of a commercial biosurfactant.     

Crude biosurfactant from thermophilic Alcaligenes faecalis: Feasibility in petro-spill bioremediation

The thermophilic bacterium Alcaligenes faecalis isolated from the crude oil contaminated soil of Upper Assam, India. The isolated bacterium was first screened for the ability to produce biosurfactant. The strain growing at 42 °C could produce higher amount of biosurfactant in medium supplemented with 2% (v/v) diesel as sole source of carbon and energy. Biochemical characterizations including FT-IR and MS studies suggested the biosurfactant to be glycolipid. Tensiometric studies revealed that the biosurfactant produced by the bacterial strain could decrease the surface tension (??) at air-water interface from 71.6 to 32.3 mNm⁻¹ after 96 h of growth on hydrocarbon and possessed a low critical micelle concentration (CMC) value of approximately 38 mgl⁻¹, indicating high surface activity. The culture supernatant containing the biosurfactant was found to be functionally stable at varying pH (2-12), temperature (100 and 121 °C) and salinity (1-6% NaCl, w/v) conditions. Both the culture broth and the cell free supernatant exhibited high emulsifying activity against the different hydrocarbons and the crude oil components. The increase in cell surface hydrophobicity and glycolipid production by the strain suggested the existence of biosurfactant enhanced interfacial uptake of the hydrocarbons. Moreover, the partially purified biosurfactant exhibited antimicrobial activity by inhibiting the growth of several bacterial and fungal species. The strain represented a new class of biosurfactant producers and could be a potential candidate for the production of glycolipid biosurfactant which could be useful in a variety of biotechnological and industrial processes, particularly in the oil industry.     

Isolation and characterization of biosurfactant production under extreme environmental conditions by alkali-halo-thermophilic bacteria from Saudi Arabia

Twenty three morphologically distinct microbial colonies were isolated from soil and sea water samples, which were collected from Jeddah region, Saudi Arabia for screening of the most potent biosurfactant strains. The isolated bacteria were selected by using different methods as drop collapse test, oil displacement test, blue agar test, blood hemolysis test, emulsification activity and surface tension. The results showed that the ability of Virgibacillus salarius to grow and reduce surface tension under a wide range of pH, salinities and temperatures gives bacteria isolate an advantage in many applications such as pharmaceutical, cosmetics, food industries and bioremediation in marine environment. The biosurfactant production by V. salarius decreased surface tension and emulsifying activity (30 mN/m and 80%, respectively). In addition to reducing the production cost of biosurfactants by tested several plant-derived oils such as jatropha oil, castor oils, jojoba oil, canola oil and cottonseed oil. In this respect the feasibility to reusing old frying oil of sunflower for production rhamnolipids and sophorolipids, their use that lead to solve many ecological and industrial problems.     

Distillery and curd whey wastes as viable alternative sources for biosurfactant production

Biosurfactant production from synthetic medium and industrial waste, viz. distillery and whey wastes was investigated by using an oily sludge isolate Pseudomonas aeruginosa strain BS2. In synthetic medium separately supplemented with glucose and hexadecane as water-soluble and -insoluble carbon sources, respectively, strain BS2 reduced the surface tension of the fermentation broth from 57 to 27 mN/m. The culture produced biosurfactant during the stationary growth phase and its yield was 0.97 g/l. The culture utilized distillery and whey wastes for its growth, as maximum cell counts reached to 54 × 10⁸ and 64 × 10⁹ c.f.u./ml from an initial inoculum size of 1 × 0⁵ c.f.u./ml, respectively, within 48 h of incubation and in these wastes the yields of biosurfactant obtained were 0.91 and 0.92 g/l, respectively. In synthetic medium, distillery and whey wastes, strain BS2 produced a crystalline biosurfactant which belonged to the category of secondary metabolites and its maximum production occurred after the onset of nitrogen-limiting conditions. After recovering biosurfactant from the fermented waste, the chemical oxygen demand (COD) of distillery and whey wastes was significantly reduced by 81 and 87%, respectively. Total acids, nitrogen and phosphate levels in distillery waste were reduced by 90, 92 and 92%, respectively, while in case of whey waste the concentration of these nutrients was reduced by 88, 95 and 93%, respectively. The isolated biosurfactant possessed potent surface active properties, as it effectively reduced the surface tension of water from 72 to 27 mN/m and formed 100% stable emulsions of a variety of water-insoluble compounds such as hydrocarbons, viz. hexadecane, crude oil, kerosene and oily sludge and pesticides, viz. dichlorodiphenyltrichloroethane (DDT) and benzene hexachloride (BHC). The effectiveness of biosurfactant was also evident from its low critical micellar concentration (CMC) which was 0.028 mg/ml.     

Production and partial characterization of biosurfactant produced by Streptomyces sp. R1

The present study focused on developing a wild-type actinomycete isolate as a model for a non-pathogenic filamentous producer of biosurfactants. A total of 33 actinomycetes isolates were screened and their extracellular biosurfactants production was evaluated using olive oil as the main substrate. Out of 33 isolates, 32 showed positive results in the oil spreading technique (OST). All isolates showed good emulsification activity (E₂₄) ranging from 84.1 to 95.8%. Based on OST and E₂₄ values, isolate R1 was selected for further investigation in biosurfactant production in an agitated submerged fermentation. Phenotypic and genotypic analyses tentatively identified isolate R1 as a member of the Streptomyces genus. A submerged cultivation of Streptomyces sp. R1 was carried out in a 3-L stirred-tank bioreactor. The influence of impeller tip speed on volumetric oxygen transfer coefficient (k _L a), growth, cell morphology and biosurfactant production was observed. It was found that the maximum biosurfactant production, indicated by the lowest surface tension measurement (40.5 ± 0.05 dynes/cm) was obtained at highest k _L a value (50.94 h⁻¹) regardless of agitation speed. The partially purified biosurfactant was obtained at a concentration of 7.19 g L⁻¹, characterized as a lipopeptide biosurfactant and was found to be stable over a wide range of temperature (20–121 °C), pH (2–12) and salinity [5–20% (w/v) of NaCl].

     

Physicochemical and structural characterization of biosurfactant produced by <Emphasis Type="Italic">Pleurotus djamor</Emphasis> in solid-state fermentation

Biosurfactants are amphiphilic compounds produced by several microorganisms that reduce the surface tension. Low toxicity, optimal activity in extreme conditions, biodegradability and production from several wastes are main advantages of biosurfactants as compared to synthetic surfactants. Production of biosurfactant by a white rot fungus Pleurotus djamor on sunflower seed shell in solid-state fermentation was determined by emulsification indexes, oil spreading activity and surface tension (28.82 ± 0.3mN/m) measurement. The critical micelle concentration was detected as 0.964 ± 0.09 mg/mL. Also, the chemical and physicochemical properties of the biosurfactant produced were investigated. Considering the results of the chemical contents analysis, HPLC, FT-IR and ¹H-NMR, it can be concluded that the produced biosurfactant has a complex structure. Besides, resistance of its activity to environmental factors such as temperature, pH and salt concentration, as well as its thermal stability, were investigated. Additionally, the produced biosurfactant formed stabile emulsions with different hydrocarbons. Lastly, the performance of removing waste frying oil from contaminated sand of produced biosurfactant was detected as 76.57 ± 6%. Owing to its high emulsification capacity, low surface tension and critical micelle concentration, the biosurfactant, shows great potential for use in hydrocarbon removal applications.     

Isolation and characterization of a biosurfactant‐producing Fusarium sp. BS‐8 from oil contaminated soil

This study reports characterization of a biosurfactant‐producing fungal isolate from oil contaminated soil of Missa Keswal oil field, Pakistan. It was identified as Fusarium sp. BS‐8 on the basis of macroscopic and microscopic morphology, and 18S rDNA gene sequence homology. The biosurfactant‐producing capability of the fungal isolates was screened using oil displacement activity, emulsification index assay, and surface tension (SFT) measurement. The optimization of operational parameters and culture conditions resulted in maximum biosurfactant production using 9% (v/v) inoculum at 30°C, pH 7.0, using sucrose and yeast extract, as carbon and nitrogen sources, respectively. A C:N ratio of 0.9:0.1 (w/w) was found to be optimum for growth and biosurfactant production. At optimal conditions, it attained lowest SFT (i.e., 32 mN m^?1) with a critical micelle concentration of ≥ 1.2 mg mL^?1. During 5 L shake flask fermentation experiments, the biosurfactant productivity was 1.21 g L^?1 pure biosurfactant having significant emulsifying index (E₂₄, 70%) and oil‐displacing activity (16 mm). Thin layer chromatography and Fourier transform infrared spectrometric analyses indicated a lipopeptide type of the biosurfactant. The Fusarium sp. BS‐8 has substantial potential of biosurfactant production, yet it needs to be fully characterized with possibility of relatively new class of biosurfactants. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1065–1075, 2014     

Rhamnolipid production using Shewanella seohaensis BS18 and evaluation of its efficiency along with phytoremediation and bioaugmentation for bioremediation of hydrocarbon contaminated soils

Abstract

This study reports the combined use of a rhamnolipid type biosurfactant (BS) along with phytoremediation and bioaugmentation (BA) for bioremediation of hydrocarbon-contaminated soils. Bacterial isolates obtained from hydrocarbon contaminated soil were screened for rhamnolipid production and isolate BS18, identified as Shewanella seohaensis, was selected for bioremediation experiments. Growth of BS18 in mineral salt medium (MSM) with diesel oil as the carbon source showed a maximum biomass of 8.2?g L^?1, rhamnolipid production of 2.2?mg g^?1 cell dry weight, surface tension reduction of 28.6?mN/m and emulsification potential (EI₂₄%) of 65.6. Characterization of rhamnolipid based on Fourier transmittance infrared (FTIR) analysis confirmed the presence of OH, CH₂/CH₃, C=O, and COO stretching vibrations, respectively, which are distinctive features of rhamnolipid type BSs. In bioremediation experiments, the lowest hydrocarbon concentration of 2.1?mg g^?1 of soil for non-sterilized soil and 4.3?mg g^?1 of soil for sterilized soil was recorded in the combined application of rhamnolipid, phytoremediation, and BA. This treatment also yielded the highest hydrocarbon degrading bacterial population (6.4 Log Cfu g^?1 of soil), highest plant biomass (8.3?g dry weight plant^?1), and the highest hydrocarbon uptake (512.3?mg Kg^?1 of plant).