Biosurfactant-producing Strain Research Articles

Isolation and Characterization of Biosurfactant-Producing Bacteria for Enhancing Oil Recovery

Biosurfactants produced by bacteria possess remarkable emulsification properties for crude oil, significantly enhancing oil mobility and recovery rates. This study aimed to isolate and screen biosurfactant-producing bacteria for oil enhancing recovery. A total of 93 bacterial strains were isolated from marine sediments, with three high-yield biosurfactant-producing strains identified: Pseudomonas aeruginosa N33, Bacillus paralicheniformis Nian2, and Stenotrophomonas nematodicola T10. The fermentation conditions, such as pH, carbon source, nitrogen source, and C/N ratio, were optimized to maximize the yield and activity of biosurfactants. Further evaluations were performed to assess the stability of the bio-surfactant activity and its emulsification properties. The results indicated that all three strains produced biosurfactants that retained their oil displacement activity in the presence of Na+ and Mg2+, but showed a significant reduction in their activities in the presence of Ca2+. The biosurfactants maintained their original activity after treatment at 120 °C for 3 h. Additionally, the biosurfactants produced by all three strains demonstrated excellent oil emulsification capabilities. Static oil-washing and dynamic displacement experiments revealed static oil recovery rates of 28.1%, 23.4%, and 7.1%, respectively, for N33, Nian2, and T10, and dynamic oil displacement recovery rates of 95.0%, 74.1%, and 69.0%, respectively. This research provides valuable microbial resources for enhancing oil recovery via microorganisms and lays a foundation for practical application.

Production and characterization of biosurfactants from lactic acid bacteria in Dadiah for strawberries edible coating

Biosurfactants are amphiphilic components applied in various fields, one of which is preserving agricultural products. Biosurfactants can be used as additives in edible coatings to prevent microbial adhesion by reducing surface tension on the fruit surface. They also play a role in increasing the moisture barrier and slowing down the physiological changes of fruit. Nonetheless, biosurfactants were often produced by non-GRAS bacteria. GRAS biosurfactant-producing bacteria are urgently needed for application in food products. This study aims to isolate and characterize biosurfactant-producing strains of lactic acid bacteria from Dadiah and evaluate their efficacy in reducing microbial adhesion on strawberries. From four selected isolates found in Dadiah, Lactiplantibacillus plantarum was the best candidate, producing biosurfactant with index emulsification (EI24) of 64.48 ± 0.37% with a CMC of 1 g/l. LC-MS and FT-IR characterized the biosurfactants as glycolipids. The rate of antibacterial and anti-adhesive tests on Escherichia coli ATCC 8739 were 18.79 ± 5.23% and 55.26 ± 0.02%, while on Staphylococcus aureus ATCC 6738 were 31.60 ± 2.63% and 74.63 ± 0.00% at a concentration of 3000 mg/l. However, no anti-fungal activity against Rhizopus stolonifer and Aspergillus niger was observed at the same concentration. Compared to SDS, biosurfactants demonstrated non-toxicity with an LC50 value of 2.94 x 108 mg/l. A combination of 1% chitosan reduced the number of fungal cells by 29.76 ± 3.25% on 125 mg/l biosurfactant and bacterial cells by 31.91 ± 5.06% on 1000 mg/l biosurfactant after 10 days, indicating their potential to reduce fruit spoilage and enhance microbial anti-adhesive properties of edible coatings.

Isolation, Screening and Identification of Biosurfactant Producing Strain Nocardiopsis dassonvillei var B2 From Oil Contaminated Soil.

Petroleum and other oil manufacturing industries contribute to environmental pollution by releasing hazardous hydrocarbons. Biosurfactants offer a sustainable solution for mitigating oil pollution through emulsification processes, safeguarding agricultural soils, aquatic ecosystems, and human health. This study focuses on isolating, screening, and identifying actinomycetes producing biosurfactant from oil-polluted soil in the naval dockyard of Visakhapatnam. Biosurfactant production was successfully achieved utilizing Kim's medium, which was supplemented with olive oil serving as the carbon source. The evaluation involved preliminary identification tests, including oil displacement, Parafilm-M, and lipase activity assays, using sodium lauryl sulfate as the standard reference. Surface tension and emulsification index measurements were conducted, and the chemical composition of glycolipids and phospholipids was elucidated using phenol-sulfuric acid and phosphate assays. Glycolipids, specifically identified as rhamnolipids, were confirmed via cetyltrimethylammonium bromide (CTAB) testing and quantitatively analyzed using the orcinol method. The cell-free broth exhibited antagonistic activity against Gram-positive and negative bacilli.16S rRNA sequencing-based phylogenetic analysis was carried out by the NCIM, Pune, with the gene sequence being deposited in GenBank. Further characterization of isolate B2 included scanning electron microscopy (SEM) analysis, as well as physiological and biochemical assays. This study highlights the ability of Nocardiopsis dassonvillei var. B2, isolated from oil-polluted soil, to produce biosurfactants, specifically glycolipids identified as rhamnolipids. Our findings represent the first reported instance of biosurfactant production from isolate B2 originating from the naval dockyard in Visakhapatnam, Andhra Pradesh, India.

Application of Acinetobacter indicus to promote cigarette smoke particulate matter phytoremediation: removal efficiency and plant-microbe interactions.

Particulate matter (PM) is one of the most hazardous atmospheric pollutants. Several plant species show high potential to reduce air pollutants and are widely used as green belts to provide clean outdoor spaces for human well-being. However, high PM concentrations cause physiological changes and stress in plants. In this study, 11 species of Thai native perennial plants were exposed to PM generated from tobacco smoke. Wrightia religiosa (Teijsm. & Binn.) Benth. ex Kurz, Bauhinia purpurea DC. ex Walp. and Tectona grandis L.f. reduced PM effectively (which is in the typical range of 43.95 to 52.97%) compared to other plant species. In addition, the responses of perennial plants under PM stress at the proteomic level were also evaluated. Proteomic analysis of these three plant species showed that plants respond negatively to high PM concentrations, such as reducing several photosynthetic-related proteins and increasing plant stress response proteins. To improve PM phytoremediation efficiency and reduce plant stress from PM, perennial plant-microbe interactions were investigated. W. religiosa was inoculated with Acinetobacter indicus PS1, and high biosurfactant-producing strains clearly showed a higher PM removal efficiency than non-inoculated plants (9.48, 9.5 and 12.6% for PM1.0, PM2.5 and PM10, respectively). Inoculating W. religiosa with A. indicus PS1 maintained chlorophyll a and b concentrations. Moreover, the malondialdehyde (MDA) concentration of W. religiosa inoculated with A. indicus PS1 was lower than that of non-inoculated W. religiosa. The leaf wax content (µg/cm2) and biosurfactant (µg/cm2) of W. religiosa inoculated with A. indicus PS1 were also higher than those of non-inoculated W. religiosa. This study clearly showed that inoculating plants with A. indicus PS1 can help plants remediate PM and improve their PM stress response.

Isolation and Identification of Bacterial Biosurfactant Producing Strain from Soil and Evaluation of Their Antimicrobial Activity Mediated Zinc Oxide Nanoparticles

Nanoparticle synthesis using biosurfactants is currently a popular and environmentally friendly method for improving both particle synthesis and stabilization. Zinc oxide nanoparticles (ZnO NPs) have found extensive applications in the field of biomedicine. The present study focused on isolating microorganisms that produce biosurfactants from soil contaminated with oil. The isolated microorganisms were identified through molecular identification of 16s r-RNA gene sequencing and characterization as Bacillus pseudomycoides. We determined biosurfactant production using various assays such as hemolysis assay, emulsification index, oil spreading tests, and drop-collapsing assays. This investigation confirms that isolated microorganisms possess biosurfactant properties. We utilized a biosurfactant extract from the B. pseudomycoides strain for the synthesis of ZnO NPs. Advanced techniques such as UV-vis spectroscopy, XRD, FTIR, SEM, and Edax were employed to ensure accurate characterization. Furthermore, the biosurfactant-mediated ZnO NPs effectively killed a few bacterial pathogens, such as Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia. They were also effective against fungal pathogens, such as Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum. This research highlights the impressive effectiveness of newly synthesized biosurfactant-mediated ZnO against clinical isolates. This research suggests that the biosurfactant extract from B. pseudomycoides could be used to make ZnO nanoparticles that could be useful for treating harmful infections.

Screening and Characterization of Biosurfactant-producing Strains in Contaminated Soil

Biosurfactant obtained from microorganisms isolated from different locations presents an alternative source to chemical surfactant, due to its structural and functional similarity, as well as its biodegradability properties. The goal of this work was to isolate biosurfactant-producing bacterial strains in seven sites with oil-contaminated soils, in district Lucknow, Uttar, India. Drop collapse assay, oil displacement method, emulsification activity and haemolytic assay were used to screen the total of 13 distinct colonies obtained from this study. Isolates GAR-1, TP-2, PET-1 & PET-3 were screened and evaluated to be more potent for biosurfactant production. The molecular identification of GAR-1, TP-2, PET-1 & PET-3 isolates were identified by 16S rRNA sequencing and characterized by FT-IR analysis. A total of 13 bacteria were isolated in the oil-contaminated soils, these four strains with high biosurfactant-production, identified as Bacillus paralicheniformis HRA-IU, B. velezensis NWR-20, Bacillus sp. HUR-IU and P. aeruginosa HUR-IA, respectively. The present study confirms that isolated microorganisms have biosurfactant property and screens the most potent biosurfactant (rhamnolipid) producing strain which is Bacillus sp. HUR-IU.

Screening of sustainable biosurfactant produced by indigenous bacteria isolated from Egyptian oil fields for microbial enhanced oil recovery

Microbial enhanced oil recovery (MEOR) stands out as an environmentally and economically significant approach utilizing microorganisms and their bio-products to reduce residual oil, and hence improve oil recovery. Due to the pollution that synthetic surfactants entail and their very expensive costs, there is a growing necessity for clean, eco-friendly alternatives. This research focuses on exploring the potential of producing biosurfactants by indigenous bacteria isolated from Egyptian Oil Fields. Five crude oil and formation water samples were collected from four Egyptian Oil Fields located in the Western Desert (WD). Nine bacterial strains were isolated and screened for biosurfactant production using different assays, followed by the extraction and purification of crude biosurfactants. The most promising biosurfactant-producing strains that showed their ability to produce effective biosurfactant according to biosurfactant screening assays were selected for further studies and identified through 16S rRNA gene sequencing. Furthermore, core-flooding micromodel experiments were conducted to evaluate the effectiveness of these extracted biosurfactants compared to a synthetic surfactant, Sodium Dodecyl Sulfate (SDS), in improving oil recovery. Results showed that the most promising biosurfactant-producing strains that exhibited notable performance and ability to produce effective biosurfactants were namely A-LB, C-LB2, and B-YM2. Therefore, they were selected for further studies and identified through 16S rRNA gene sequencing. 16S rRNA gene sequencing results showed that namely A-LB, C-LB2, and B-YM2 were identified as Bacillus massiliigabonensis, Pseudomonas nitritolerans, and Aninetobacter seohaensis, respectively. Finally, core flooding results showed that the biosurfactant produced by Bacillus massiliigabonensis demonstrated significant performance by recovering 69.96% of additional oil, whereas 68.11% and 63.34% of additional oil were recovered using biosurfactants produced by Pseudomonas nitritolerans, and Aninetobacter seohaensis, respectively. It was also noticed that the biosurfactant produced by Bacillus massiliigabonensis demonstrated significant potential in improving oil recovery compared to the synthetic surfactant (61.78%), it outperformed 8.18% more additional oil. These findings validate the effectiveness of the produced biosurfactants over synthetic surfactants emphasizing their potential as sustainable and cost-effective alternatives for enhanced oil recovery in Egyptian oil fields.

Isolation and Characterization of Glycolipid Biosurfactant Produced by Marine Bacterium Cobetia marina Strain F1 and Investigation of Antimicrobial and Anti-Biofilm Activity

The marine environment is a rich source of microorganisms producing bioactive compounds, like biosurfactant-producing bacteria that exhibit unique characteristics and functionalities. In this study, we examined glycolipid biosurfactants produced by bacteria that live commensally with marine organisms. We isolated a biosurfactant-producing strain identified as Cobetia marina strain F1, which displayed high hemolytic activity (27 mm), oil spreading ability (4 mm), emulsification index (40%), and decreasing surface tension to 31.3 (mN·m−1). Fourier transform infrared (FT-IR) spectroscopy revealed the glycolipid composition of the biosurfactant. Furthermore, elemental analysis utilizing CHNS and energy-dispersive X-ray spectroscopy (EDS) confirmed the biosurfactant contained carbon, hydrogen, nitrogen, sulfur, chlorine, potassium, oxygen, and additional elements. The critical micelle concentration (CMC) of the crude biosurfactant was determined to be 350 mg·L−1, at which concentration, a decrease in surface tension was observed when the biosurfactant was dissolved in distilled water. Given the presence of impurities in the biosurfactant composition, this observed CMC is considered acceptable. Furthermore, the biosurfactant exhibited significant antimicrobial activity against both Gram-positive and Gram-negative bacterial strains, with the largest zone of inhibition (ZOI) of 27 mm against Pseudomonas aeruginosa. This demonstrates the potential of the biosurfactant to serve as an alternative to novel antibiotic agents. The biosurfactant exhibited considerable inhibition of biofilm formation, disruption of preformed biofilms, and reduced enzymatic activity in bacterial cells following treatment. Moreover, the combination of the biosurfactant and F1 bacterial strain enhanced the degradation of crude oil by 86%, indicating its potential application in environmental remediation. These findings highlight the importance of investigating commensal strains capable to produce biosurfactants for applications in hydrocarbon remediation, overcoming antibiotic resistance, and biofilm disruption.

High mono-rhamnolipids production by a novel isolate Pseudomonas aeruginosa LP20 from oily sludge: characterization, optimization, and potential application.

This study aims to isolate microbial strains for producing mono-rhamnolipids with high proportion. Oily sludge is rich in petroleum and contains diverse biosurfactant-producing strains. A biosurfactant-producing strain LP20 was isolated from oily sludge, identified as Pseudomonas aeruginosa based on phylogenetic analysis of 16S rRNA. High-performance liquid chromatography-mass spectrometry results indicated that biosurfactants produced from LP20 were rhamnolipids, mainly containing Rha-C8-C10, Rha-C10-C10, Rha-Rha-C8-C10, Rha-Rha-C10-C10, Rha-C10-C12:1, and Rha-C10-C12. Interestingly, more mono-rhamnolipids were produced by strain LP20 with a relative abundance of 64.5%. Pseudomonas aeruginosa LP20 optimally produced rhamnolipids at a pH of 7.0 and a salinity of 0.1% using glycerol and nitrate. The culture medium for rhamnolipids by strain LP20 was optimized by response surface methodology. LP20 produced rhamnolipids up to 6.9 g L-1, increased by 116%. Rhamnolipids produced from LP20 decreased the water surface tension to 28.1 mN m-1 with a critical micelle concentration of 60 mg L-1. The produced rhamnolipids emulsified many hydrocarbons with EI24 values higher than 56% and showed antimicrobial activity against Staphylococcus aureus and Cladosporium sp. with inhibition rates 48.5% and 17.9%, respectively. Pseudomonas aeruginosa LP20 produced more proportion of mono-rhamnolipids, and the LP20 rhamnolipids exhibited favorable activities and promising potential in microbial-enhanced oil recovery, bioremediation, and agricultural biocontrol.

Characterization and performance of a new lipopeptide biosurfactant producing strain Bacillus Subtilis R1-2

Biosurfactants produced by native microorganisms have excellent surface activity and ideal environmental compatibility, and the mining of the biosurfactant-producing strains has become a key focus in the field of applied and environmental biotechnology. In this paper, we report a new lipopeptide-producing strain isolated from the production water of Daqing oilfield in China and identified as Bacillus Subtilis R1-2 based on 16S rRNA gene sequence analyses. A combination of ESI-MS and FT-IR analyses revealed that the strain R1-2 produced the surfactin family containing four members of the C12-surfactin, C13-surfactin, C14-surfactin and C15-surfactin, which is a representative family of the lipopeptide biosurfactants. The lipopeptide biosurfactant produced by the strain R1-2 exhibits excellent surface activity and good thermal stability over a temperature range between 20°C and 100°C and pH range between 3 and 14, and has a strong salt tolerance to NaCl concentration up to 140 g/L. In addition, the lipopeptide biosurfactant demonstrates significant properties in changing the contact angles of oil reservoir core slices from 86.2° to 39.0° and the wettability from strong oil-wet to strong water-wet, and therefore, resulted in a good oil removing ability with an efficiency of 64.84%, suggesting that the lipopeptide-producing strain R1-2 is promising in applications in environmental bioremediation and enhanced oil recovery.

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.

Structural and compositional diversity of biosurfactants produced by a novel strain of Sporosarcina luteola ME44 from oil reservoir.

The urealytically active microorganism Sporosarcina luteola induces the precipitation of metals, which has attracted attention in biomineralization, bioremediation, and industrial waste recycling. Herein, we report a novel biosurfactant-producing strain of S. luteola ME44 isolated from Chinese Oilfield. The structure, composition, and surface activity of the biosurfactants produced by S. luteola ME44 were investigated by using a combination of the high-performance liquid chromatography, time-of-flight mass spectrometry, and surface tensiometer. The biosurfactant extracted by strain ME44 was identified as surfactin with five variants and the yield was 1010±60mg⋅L-1 . This is the first report on the structural composition and surface activity of biosurfactants isolated from the S. luteola. It extended our knowledge about the role of the species S. luteola in the ecosystem of extreme natural environments such as oil reservoir. In addition, S. luteola ME44 showed bioprecipitation properties for metal ions Cd(II), Cu(II), Zn(II), and Ag(I), which indicated the application potential of S. luteola in the field of bioremediation.

Enhanced Solubilization and Biodegradation of HMW-PAHs in Water with a Pseudomonas mosselii-Released Biosurfactant.

The treatment and reuse of wastewater are crucial for the effective utilization and protection of global water resources. Polycyclic aromatic hydrocarbons (PAHs), as one of the most common organic pollutants in industrial wastewater, are difficult to remove due to their relatively low solubility and bioavailability in the water environment. However, biosurfactants with both hydrophilic and hydrophobic groups are effective in overcoming these difficulties. Therefore, a biosurfactant-producing strain Pseudomonas mosselii MP-6 was isolated in this study to enhance the bioavailability and biodegradation of PAHs, especially high-molecular-weight PAHs (HMW-PAHs). FTIR and LC-MS analysis showed that the MP-6 surfactant belongs to rhamnolipids, a type of biopolymer, which can reduce the water surface tension from 73.20 mN/m to 30.61 mN/m at a critical micelle concentration (CMC = 93.17 mg/L). The enhanced solubilization and biodegradation of PAHs, particularly HMW-PAHs (when MP-6 was introduced), were also demonstrated in experiments. Furthermore, comprehensive environmental stress tolerance tests were conducted to confirm the robustness of the MP-6 biosurfactant, which signifies the potential adaptability and applicability of this biosurfactant in diverse environmental remediation scenarios. The results of this study, therefore, have significant implications for future applications in the treatment of wastewater containing HMW-PAHs, such as coking wastewater.

Enhanced petroleum removal with a novel biosurfactant producer consortium isolated from drilling cuttings of offshore Akçakoca-5 in the Black Sea

Staphylococcus capitis, Achromobacter marplatensis (dominant strain), Enterobacter cloacae, Ochrobactrum anthropi, Bacillus velezensis, and Bacillus subtilis strains were isolated from drilling cutting samples. The potent biosurfactant-producing strains: S. capitis (A) &A. marplatensis (B) and non-biosurfactant-producing strains: E. cloacae (C) &O. anthropi (G) strains were combined (1:1) as AB, AC, AG, BC, BG, CG. The degradation efficiency of consortium AB was 90%, while that of consortia AC, BG and CG were 85%. Biosurfactant-producing strains belong to potent consortium AB facilitate petroleum uptake and biodegradation by increasing the solubility and surface area of substrate through emulsification activity. The physiological conditions of petroleum removal (92.5%) by potent consortium AB were optimized as: 1 g/L yeast extract, 1% petroleum, 3% NaCl at pH:7.0, 30 °C, 150 rpm for 7 days. GC/MS analysis revealed that the consortium AB not only degraded the short- and medium-chain n-alkane fractions, but also removed the long-chain n-alkanes. The biosurfactant produced (0.5 g/L) by potent consortium AB was purified by silica gel 60 chromatography, further characterized by its lipopeptide structure with TLC, FT-IR, and SEM analyses. A new halotolerant consortium AB will make a significant contribution to MEOR applications in marine ecosystem.

A new biosurfactant-producing strain, Fictibacillus nanhaiensis ME46, isolated from an oil field in China

ABSTRACT The genus Fictibacillus contains twelve species significant in the synthesis of cellulose-degrading enzymes and phenylalanine dehydrogenase, isolated mainly from marine sedimentary environments. Here, we report a new biosurfactant-producing strain, Fictibacillus nanhaiensis ME46, isolated from Daqing oil field in China. The biosurfactant extracted from Strain ME46 was determined as surfactin, one of the representative families of lipopeptide biosurfactants. The yield of the surfactin produced by strain ME46 was 0.62 g·L−1 as determined by high-performance liquid chromatography, and the critical micelle concentration (CMC) of the surfactin was estimated to be about 68 mg·L−1 and the surface tension at CMC was 35.1 mN·m−1. This study extended our knowledge about the role of the species Fictibacillus nanhaiensis in the ecosystem of natural environments such as the oil field.

Improving Rhamnolipids Biosynthesis in Pseudomonas sp. L01 through Atmospheric and Room-Temperature Plasma (ARTP) Mutagenesis.

Biosurfactants have significant applications in various industries, including microbial-enhanced oil recovery (MEOR). While the state-of-the-art genetic approaches can generate high-yield strains for biosurfactant production in fermenters, there remains a critical challenge in enhancing biosurfactant-producing strains for use in natural environments with minimal ecological risks. The objectives of this work are enhancing the strain's capacity for rhamnolipids production and exploring the genetic mechanisms for its improvement. In this study, we employed atmospheric and room-temperature plasma (ARTP) mutagenesis to enhance the biosynthesis of rhamnolipids in Pseudomonas sp. L01, a biosurfactant-producing strain isolated from petroleum-contaminated soil. Following ARTP treatment, we identified 13 high-yield mutants, with the highest yield of 3.45 ± 0.09 g/L, representing a 2.7-fold increase compared to the parent strain. To determine the genetic mechanisms behind the enhanced rhamnolipids biosynthesis, we sequenced the genomes of the strain L01 and five high-yield mutants. A comparative genomic analysis suggested that mutations in genes related to the synthesis of lipopolysaccharides (LPS) and the transport of rhamnolipids may contribute to the improved biosynthesis. To the best of our knowledge, this is the first instance of utilizing the ARTP approach to improve rhamnolipid production in Pseudomonas strains. Our study provides valuable insights into the enhancement of biosurfactant-producing strains and the regulatory mechanisms of rhamnolipids biosynthesis.

Degradation of alkane hydrocarbons by Priestia megaterium ZS16 and sediments consortia with special reference to toxicity and oxidative stress induced by the sediments in the vicinity of an oil refinery

Petroleum hydrocarbon is a critical ecological issue with impact on ecosystems through bioaccumulation. It poses significant risks to human health. Due to the extent of alkane hydrocarbon pollution in some environments, biosurfactants are considered as a new multifunctional technology for the efficient removal of petroleum-based contaminants. To this end, Yamuna river sediments were collected at different sites in the vicinity of Mathura oil refinery, UP (India). They were analysed by atomic absorption spectrophotometry and gas chromatography-mass spectrometry (GC-MS) for heavy metals and organic pollutants. Heptadecane, nonadecane, oleic acid ester and phthalic acid were detected. In total 107 bacteria were isolated from the sediments and screened for biosurfactant production. The most efficient biosurfactant producing strain was tested for its capability to degrade hexadecane efficiently at different time intervals (0 h, 7 d, 14 d and 21 d). FT-IR analysis defined the biosurfactant as lipopeptide. 16S rRNA gene sequencing identified the bacterium as Priestia megaterium. The strain lacks resistance to common antibiotics thus making it an important candidate for remediation. The microbial consortia present in the sediments were also investigated for their capability to degrade C16, C17 and C18 alkane hydrocarbons. By using gas chromatography-mass spectrophotometry the metabolites were identified as 1-docosanol, dodecanoic acid, 7-hexadecenal, (Z)-, hexadecanoic acid, docosanoic acid, 1-hexacosanal, 9-octadecenoic acid, 3-octanone, Z,Z-6,28-heptatriactontadien-2-one, heptacosyl pentafluoropropionate, 1,30-triacontanediol and decyl octadecyl ester. Oxidative stress in Vigna radiata L. roots was observed by using Confocal Laser Scanning Microscopy. A strong reduction in seed germination and radicle and plumule length was observed when Vigna radiata L. was treated with different concentrations of sediment extracts, possibly due to the toxic effects of the pollutants in the river sediments. Thus, this study is significant since it considers the toxicological effects of hydrocarbons and to degrade them in an environmentally friendly manner.

Antifungal Activity of Rhamnolipid Biosurfactant Produced by Pseudomonas aeruginosa A4 against Plant Pathogenic Fungi

Biosurfactants have been shown to have a variety of other agricultural applications. Antimicrobial activity is a desirable property in a variety of biosurfactants. Several biosurfactants produced from bacteria have antibacterial activity against plant diseases, making them a promising biocontrol molecule for ensuring agricultural sustainability in the long run. The purpose of this research was to characterize biosurfactant produced at different carbon source by biosurfactant-producing bacterial strains isolated from contaminated soapstock sediment, as well as its antifungal properties. Biosurfactant-producing bacteria were isolated from soapstock-contaminated soil which bacteria were selected by using drop collapse and oil displacement tests. Twelve isolates reduced surface tension of culture broth from 50 to 31 - 43 mN/m. According to 16S rRNA sequence analysis, these isolates belong to 8 different genera (Acinetobacter, Citrobacter, Enterobacter, Klebsiella, Pantoea, Pseudomonas, Stenotrophomonas and Xanthomonas). The supernatant of Pseudomonas aeruginosa A4 grown in MSM supplemented with soapstock was the most effective biosurfactant against Aspergillus flavus F2, Aspergillus niger F14, Cunninghamella bertholletiae F1 and Rhizopus oryzae F5, inhibiting mycelium growth by 54, 61 59 and 50 %, respectively. The extract substance inhibited spore germination against A. flavus F2 and R. oryzae F5 with a minimum inhibitory concentration of 2.75 mg/mL. TLC, FT-IR, ESI-MS and GC-MS analysis demonstrated that the mono-rhamnolipids and di-rhamnolipids had the same 3-hydroxy fatty acid composition of C8, C10 and C12. Overall, the biosurfactant-producing strains identified in this investigation show promise for future development and application in cost-effective industrial-scale biotechnological processes.
 HIGHLIGHTS
 
 Biosurfactant producing bacteria were isolated from soapstock contaminated soil
 The supernatant of Pseudomonas aeruginosa A4 grown in MSM supplemented with soapstock was the most effective biosurfactant against plant pathogenic fungi
 Biosurfactant from Pseudomonas aeruginosa A4 was identified as rhamnolipid comprising of both mono and di-rhamnolipid congeners
 
 GRAPHICAL ABSTRACT

The release of petroleum hydrocarbons from a saline-sodic soil by the new biosurfactant-producing strain of Bacillus sp.

Adsorption of old-aged petroleum hydrocarbons to the soil solid phase, which causes biosurfactant loss of performance, is among the limiting factors for the remediation of the saline-sodic soils contaminated with petroleum. Therefore, to find a functional biosurfactant in oil-contaminated saline-sodic soils, the efficiency of 39 bacteria isolated from petroleum-contaminated soils was evaluated. The strains were cultured in the Bushnell–Haas medium, and the produced biosurfactants and bioemulsifiers in this medium were extracted using chloroform/methanol and ethyl acetate extraction methods, respectively. Their partial purification was performed by column chromatography, and eventually, their performance in releasing TPH from the contaminated soil was evaluated. The soil test results revealed that the highest TPH releases due to the effects of the biosurfactants and bioemulsifier produced from SHA302, SH21, and SH72 isolates were 42.4% ± 0.2, 21.6% ± 0.15 and 24.3% ± 0.91, respectively. Based on the 16S rRNA gene sequence, the SHA302 strain showed 93.98% phylogenetic similarity with Bacillus pumilus strain ATCC 7061. The Fourier transform infrared spectroscopy and thin-layer chromatography results proved that the biosurfactants produced by isolates SHA302, SH21 and SH72 showed lipopeptide, glycolipoprotein and glycoprotein natures, respectively. The performance of the biosurfactant produced by SHA302 isolate indicated that it could be used as a good candidate for releasing TPH from saline-sodic soils with old contamination and facilitating the degradation of hydrocarbons.

Single-Cell-Based High-Throughput Cultivation and Functional Characterization of Biosurfactant-Producing Bacteria from Soil and Oilfield-Produced Water.

Biosurfactants are a group of surface-active compounds that can be produced by diverse microorganisms. They have been widely used in various industrial fields. Reducing production costs, improving efficiency, and collecting more diverse producing strains have become major challenges in the biosurfactant industry. These challenges could be overcome by screening for more diverse and efficient biosurfactant-producing strains. The conventional methods for the isolation and functional characterization of microorganisms are laborious and biased toward fast-growing or strongly competitive microorganisms. Here, we established a high-throughput approach of single-cell-based cultivation and functional characterization of biosurfactant-producing bacteria (SCCBB). This approach combines single-cell cultivation with the detection of optical distortions. Using this approach, we isolated 431 strains with biosurfactant production potential from petroleum-contaminated soil and oilfield-produced water. The surfactant production capabilities of the strains were subsequently validated using surface tension measurements, TLC, and CMC measurements. To investigate the industrial production potential, we optimized the production conditions of a representative glycolipids-producing strain, Pseudomonas sp. L01, using response surface methodology (RSM). Optimal conditions yielded a crude biosurfactant yield of 8.43 g/L in a flask. Our work provides a high-throughput approach to the isolation and screening of biosurfactant-producing bacteria, as well as other functional bacteria in a wide range of fields.