Biosurfactant-mediated biodegradation of straight and methyl-branched alkanes by Pseudomonas aeruginosa ATCC 55925

Potential of Indigenous Strains Isolated from the Wastewater Treatment Plant of a Crude Oil Refinery

Contamination of the environment with crude oil or other fuels is an enormous disaster for all organisms. The microbial communities for bioremediation have been an effective tool for eliminating pollution. This study aimed to determine individual cultures’ and a strain mixture’s ability to utilize alkanes (single alkanes and crude oil). The proper study of pure cultures is necessary to design synergistically working consortia. The Acinetobacter venetianus ICP1 and Pseudomonas oleovorans ICTN13 strains isolated from a wastewater treatment plant of a crude oil refinery can grow in media containing various aromatic and aliphatic hydrocarbons. The genome of the strain ICP1 contains four genes encoding alkane hydroxylases, whose transcription depended on the length of the alkane in the media. We observed that the hydrophobic cells of the strain ICP1 adhered to hydrophobic substrates, and their biofilm formation increased the bioavailability and biodegradation of the hydrocarbons. Although strain ICTN13 also has one alkane hydroxylase-encoding gene, the growth of the strain in a minimal medium containing alkanes was weak. Importantly, the growth of the mixture of strains in the crude oil-containing medium was enhanced compared with that of the single strains, probably due to the specialization in the degradation of different hydrocarbon classes and co-production of biosurfactants.

Nature-Based Solutions for Restoring an Agricultural Area Contaminated by an Oil Spill

A feasibility study is presented for a bioremediation intervention to restore agricultural activity in a field hit by a diesel oil spill from an oil pipeline. The analysis of the real contaminated soil was conducted following two approaches. The first concerned the assessment of the biodegradative capacity of the indigenous microbial community through laboratory-scale experimentation with different treatments (natural attenuation, landfarming, landfarming + bioaugmentation). The second consisted of testing the effectiveness of phytoremediation with three plant species: Zea mays (corn), Lupinus albus (lupine) and Medicago sativa (alfalfa). With the first approach, after 180 days, the different treatments led to biodegradation percentages between 83 and 96% for linear hydrocarbons and between 76 and 83% for branched ones. In case of contamination by petroleum products, the main action of plants is to favor the degradation of hydrocarbons in the soil by stimulating microbial activity thanks to root exudates. The results obtained in this experiment confirm that the presence of plants favors a decrease in the hydrocarbon content, resulting in an improved degradation of up to 18% compared with non-vegetated soils. The addition of plant growth-promoting bacteria (PGPB) isolated from the contaminated soil also promoted the growth of the tested plants. In particular, an increase in biomass of over 50% was found for lupine. Finally, the metagenomic analysis of the contaminated soil allowed for evaluating the evolution of the composition of the microbial communities during the experimentation, with a focus on hydrocarbon- oxidizing bacteria.

Recent advancements in hydrocarbon bioremediation and future challenges: a review

Petrochemicals are important hydrocarbons, which are one of the major concerns when accidently escaped into the environment. On one hand, these cause soil and fresh water pollution on land due to their seepage and leakage from automobile and petrochemical industries. On the other hand, oil spills occur during the transport of crude oil or refined petroleum products in the oceans around the world. These hydrocarbon and petrochemical spills have not only posed a hazard to the environment and marine life, but also linked to numerous ailments like cancers and neural disorders. Therefore, it is very important to remove or degrade these pollutants before their hazardous effects deteriorate the environment. There are varieties of mechanical and chemical methods for removing hydrocarbons from polluted areas, but they are all ineffective and expensive. Bioremediation techniques provide an economical and eco-friendly mechanism for removing petrochemical and hydrocarbon residues from the affected sites. Bioremediation refers to the complete mineralization or transformation of complex organic pollutants into the simplest compounds by biological agents such as bacteria, fungi, etc. Many indigenous microbes present in nature are capable of detoxification of various hydrocarbons and their contaminants. This review presents an updated overview of recent advancements in various technologies used in the degradation and bioremediation of petroleum hydrocarbons, providing useful insights to manage such problems in an eco-friendly manner.

Metabolic engineering of Escherichia coli for efficient degradation of 4-fluorophenol

As a kind of refractory organic pollutant, 4-fluorophenol (4-FP) can be degraded by only a few microorganisms with low efficiency because of the great electron-withdrawing ability of fluorine atoms. So it is necessary to artificially construct engineered strain to improve the degradation efficiency and meet the requirements of pollutant degradation. In this study, four genes (fpdA2, fpdB, fpdC, and fpdD) for 4-FP degradation from Arthrobacter sp. strain IF1 were optimized and synthesized and then reconstructed into Escherichia coli by a multi-monocistronic vector to obtain recombinant BL-fpd that could degrade 4-FP efficiently. Under optimized induction conditions (inducing the strain by 2 g/L L-arabinose and 1 mM IPTG at 37 ℃), BL-fpd could completely degrade 2 mM 4-FP, 4-chlorophenol, 4-bromophenol, and 4-nitrophenol into β-ketoadipate, which could be further metabolized by the bacteria. FpdA2 showed the highest activity towards 4-bromophenol. The strain could completely degrade 1 mM 4-FP in industrial wastewater within 3 h. This study provided a promising strain for the degradation of 4-FP and some other 4-substituted phenols. The construction technologies of multi-monocistronic expression vector may also be used to construct other organic pollutants degrading bacteria.

Methanogenic Biodegradation of iso-Alkanes by Indigenous Microbes from Two Different Oil Sands Tailings Ponds

iso-Alkanes, a major fraction of the solvents used in bitumen extraction from oil sand ores, are slow to biodegrade in anaerobic tailings ponds. We investigated methanogenic biodegradation of iso-alkane mixtures comprising either three (2-methylbutane, 2-methylpentane, 3-methylpentane) or five (2-methylbutane, 2-methylpentane, 2-methylhexane, 2-methylheptane, 2-methyloctane) iso-alkanes representing paraffinic and naphtha solvents, respectively. Mature fine tailings (MFT) collected from two tailings ponds, having different residual solvents (paraffinic solvent in Canadian Natural Upgrading Limited (CNUL) and naphtha in Canadian Natural Resources Limited (CNRL)), were amended separately with the two mixtures and incubated in microcosms for ~1600 d. The indigenous microbes in CNUL MFT produced methane from the three-iso-alkane mixture after a lag of ~200 d, completely depleting 2-methylpentane while partially depleting 2-methylbutane and 3-methylpentane. CNRL MFT exhibited a similar degradation pattern for the three iso-alkanes after a lag phase of ~700 d, but required 1200 d before beginning to produce methane from the five-iso-alkane mixture, preferentially depleting components in the order of decreasing carbon chain length. Peptococcaceae members were key iso-alkane-degraders in both CNUL and CNRL MFT but were associated with different archaeal partners. Co-dominance of acetoclastic (Methanosaeta) and hydrogenotrophic (Methanolinea and Methanoregula) methanogens was observed in CNUL MFT during biodegradation of three-iso-alkanes whereas CNRL MFT was enriched in Methanoregula during biodegradation of three-iso-alkanes and in Methanosaeta with five-iso-alkanes. This study highlights the different responses of indigenous methanogenic microbial communities in different oil sands tailings ponds to iso-alkanes.

Dealing with complex contamination: A novel approach with a combined bio-phytoremediation strategy and effective analytical techniques

Phytoremediation is a sustainable technology capable of efficiently removing low or moderate contamination. However, complex pollution conditions can drastically reduce efficiency, as plants can show themselves sensitive to organic contaminants, growing slowly and thus impairing metals' absorption. In cases where the action of indigenous bacteria degrading hydrocarbons and promoting plant growth is not sufficient, more sophisticated strategies are necessary. This investigation aims to evaluate the effectiveness of a train of technologies that sees advanced phytoremediation in combination with other biological approaches to remediate soil from a disused industrial area contaminated by N-containing compounds, alkyl aromatic hydrocarbons, copper, and nickel. In particular, a stepwise procedure was used with a pre-treatment (landfarming and bioaugmentation), significantly affecting the soil's fertility, increasing germinability up to 85%, and allowing the plants to extract the metals adequately. Furthermore, with EDTA as a mobilizing agent, nickel absorption has increased up to 36% in Helianthus annuus and up to 88% in Zea mays. For copper, an increase of up to 262% in Helianthus annuus and up to 202% in Zea Mays was obtained. Analysis through Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry highlighted the biodegradation of some of the N-containing compounds recording, after phytoremediation, a decrease of up to almost 90%. Metagenomic analysis of the soil showed a typical microbial population of oxidizing hydrocarbon strains with a prevalence of the Nocardiaceae family (43%). The results obtained appear to confirm the usefulness of the approach developed, and the employed cutting-edge analytical techniques allowed a top-notch characterization of the remediation scenario.

Synergetic degradation of waste oil by constructed bacterial consortium for rapid in-situ reduction of kitchen waste

Traditional composting of kitchen waste (KW) is cost- and time-intensive, requiring procedures of collection, transport and composing. Consequently, the direct in-situ reduction of KW via treatment at the point of collection is gaining increasing attention. However, high oil content of KW causes separation and degradation issues due to its low bioavailability and the hydrophobicity, and therefore greatly limiting the direct application of in-situ methods for mass reduction. To overcome this, a bacterial consortium of Pseudomonas putida and Bacillus amyloliquefaciens was constructed, which exhibited a synergistically improved oil degrading ability for lipase-catalyzed hydrolysis, fatty acids β-oxidation, biosurfactant production and surface tension reduction, and the degradation ratio reached 58.96% within 48 h when the initial KW oil concentration was 8.0%. The in-situ aerobic digestion of KW was further performed in a 20-L stirred-tank reactor, the content of KW oil (34.72 ± 2.05% of total solids, w/w) was rapidly decreased with a simultaneous increase in both lipase activity and in microbial cell numbers, and the degradation ratio reached 57.38%. The synergetic effect of the two strains including B. amyloliquefaciens and P. putida promoted the decomposition process of KW oil, which also paved the way for an efficient degradation strategy to support the application potential of in-situ microbial reduction of KW.

Bioaugmentation potential evaluation of a bacterial consortium composed of isolated Pseudomonas and Rhodococcus for degrading benzene, toluene and styrene in sludge and sewage

Bioaugmentation was conducted using a bacterial consortium of Pseudomonas putida SW-3 and Rhodococcus ruber SS-4, to test their ability to degrade benzene, toluene, and styrene (BTS). SW-3 and SS-4 were isolated from domestic sludge and sewage samples to establish a synthetic consortium with an optimized ratio of 2:1 to reach a degradation efficiency of 82.5-89.8% of BTS. The bacterial consortium was inoculated with sludge and sewage samples at a ratio of 2:1, resulting in a degradation efficiency of 97.9% and 92.7%, respectively, at a BTS concentration of 1800 mg·L^-1. Analysis of bacterial community structure following bioaugmentation indicated an increase in abundance of BTS-degrading bacteria, particularly Acinetobacter and Pseudoxanthomonas in sludge and Pseudomonas in sewage, enhancing the collective BTS degradation ability of the bacterial community. Principal component analysis demonstrated that a more balanced bacterial community structure was established following intervention. This indicated that the selected bacteria are excellent candidates for bioaugmentation.

Application of alkyl polyglycosides for enhanced bioremediation of petroleum hydrocarbon-contaminated soil using Sphingomonas changbaiensis and Pseudomonas stutzeri

Bioremediation is considered a cost-effective and environmentally sound method for degradation of petroleum hydrocarbons in contaminated soils. This study investigated the effects of biosurfactant alkyl polyglycosides (APG) on enhanced biodegradation of petroleum hydrocarbon-contaminated soils using Sphingomonas changbaiensis and Pseudomonas stutzeri and explored the mechanism responsible for the enhanced petroleum hydrocarbon degradation. To accomplish this, the following treatments were evaluated: (1) bioaugmentation with Sphingomonas changbaiensis; (2) bioaugmentation with Pseudomonas stutzeri; (3) a combination of Sphingomonas changbaiensis and APG; and (4) a combination of Pseudomonas stutzeri and APG. The results showed that the degradation rates of total petroleum hydrocarbons (TPH) in contaminated soil samples bioaugmented with S. changbaiensis and P. stutzeri for 30 days were 39.2 ± 1.9% and 47.2 ± 1.2%, respectively. The addition of biosurfactant APG enhanced the bioremediation processes and improved the biodegradation rates. The biodegradation rate at 1.5 g/kg APG in soil samples bioaugmented with S. changbaiensis was 52.1 ± 2.0%, while the rate at 1.5 g/kg APG in soil samples bioaugmented with P. stutzeri was 59.0 ± 1.8%. The half-life decreased from 39.7 d to 24.5 d and from 29.6 to 20.1 d when the dosage of APG was 1.5 g/kg in contaminated soil samples bioaugmented with S. changbaiensis and P. stutzeri, respectively. Mechanism studies showed that the addition of APG can increase the TPH solubility, promote the sorption of TPH onto microbial cells and subsequent trans-membrane transport by APG-induced structural changes, stimulate microbial activities and participate in the co-metabolism. Therefore, the combination of bioaugmentation and APG is an effective method for remediation of petroleum hydrocarbon-contaminated soil.

Kerosene tolerance in Achromobacter and Pseudomonas species

Purpose

The aim of the present study was to investigate the tolerance of five new Achromobacter and Pseudomonas strains to kerosene and to establish if the production of several secondary metabolites increases or not when these bacteria were grown in the presence of kerosene. The biodegradation of kerosene by isolated bacteria was also investigated in this study.

Methods

Five Proteobacteria were isolated from different samples polluted with petroleum and petroleum products. Based on their morphological, biochemical, and molecular characteristics, isolated bacteria were identified as Achromobacter spanius IBBPo18 and IBBPo21, Pseudomonas putida IBBPo19, and Pseudomonas aeruginosa IBBPo20 and IBBPo22.

Results

All these bacteria were able to tolerate and degrade kerosene. Higher tolerance to kerosene and degradation rates were observed for P. aeruginosa IBBPo20 and IBBPo22, compared with that observed for A. spanius IBBPo18 and IBBPo21, and P. putida IBBPo19. All these bacteria were able to produce several secondary metabolites, such as surfactants and pigments. Glycolipid surfactants produced by P. aeruginosa IBBPo20 and IBBPo22, A. spanius IBBPo18 and IBBPo21, and P. putida IBBPo19 have a very good emulsification activity, and their activity increased when they were grown in the presence of kerosene. The production of rhamnolipid surfactants by P. aeruginosa IBBPo20 and IBBPo22 was confirmed by detection of rhlAB gene involved in their biosynthesis. Pyocyanin and pyoverdin pigments were produced only by P. aeruginosa IBBPo20 and IBBPo22, while carotenoid pigments were produced by all the isolated bacteria. Significant changes in pigments production were observed when P. aeruginosa IBBPo20 and IBBPo22, A. spanius IBBPo18 and IBBPo21, and P. putida IBBPo19 were grown in the presence of kerosene.

Conclusion

Due to their ability to tolerate and degrade kerosene, and also to produce several secondary metabolites, the isolated bacteria could be used in the bioremediation of kerosene-polluted environments.

Effective bioremediation of a petroleum-polluted saline soil by a surfactant-producing Pseudomonas aeruginosa consortium

Bacteria able to produce biosurfactants can use petroleum-based hydrocarbons as a carbon source. Herein, four biosurfactant-producing Pseudomonas aeruginosa strains, isolated from oil-contaminated saline soil, were combined to form a bacterial consortium. The inoculation of the consortium to contaminated soil alleviated the adverse effects of salinity on biodegradation and increased the rate of degradation of petroleum hydrocarbon approximately 30% compared to the rate achieved in non-treated soil. In saline condition, treatment of polluted soil with the consortium led to a significant boost in the activity of dehydrogenase (approximately 2-fold). A lettuce seedling bioassay showed that, following the treatment, the soil's level of phytotoxicity was reduced up to 30% compared to non-treated soil. Treatment with an appropriate bacterial consortium can represent an effective means of reducing the adverse effects of salinity on the microbial degradation of petroleum and thus provides enhancement in the efficiency of microbial remediation of oil-contaminated saline soils.

A comprehensive multi-omics approach uncovers adaptations for growth and survival of Pseudomonas aeruginosa on n-alkanes

Background

Examination of complex biological systems has long been achieved through methodical investigation of the system’s individual components. While informative, this strategy often leads to inappropriate conclusions about the system as a whole. With the advent of high-throughput “omic” technologies, however, researchers can now simultaneously analyze an entire system at the level of molecule (DNA, RNA, protein, metabolite) and process (transcription, translation, enzyme catalysis). This strategy reduces the likelihood of improper conclusions, provides a framework for elucidation of genotype-phenotype relationships, and brings finer resolution to comparative genomic experiments. Here, we apply a multi-omic approach to analyze the gene expression profiles of two closely related Pseudomonas aeruginosa strains grown in n-alkanes or glycerol.

Results

The environmental P. aeruginosa isolate ATCC 33988 consumed medium-length (C₁₀–C₁₆) n-alkanes more rapidly than the laboratory strain PAO1, despite high genome sequence identity (average nucleotide identity >99%). Our data shows that ATCC 33988 induces a characteristic set of genes at the transcriptional, translational and post-translational levels during growth on alkanes, many of which differ from those expressed by PAO1. Of particular interest was the lack of expression from the rhl operon of the quorum sensing (QS) system, resulting in no measurable rhamnolipid production by ATCC 33988. Further examination showed that ATCC 33988 lacked the entire lasI/lasR arm of the QS response. Instead of promoting expression of QS genes, ATCC 33988 up-regulates a small subset of its genome, including operons responsible for specific alkaline proteases and sphingosine metabolism.

Conclusion

This work represents the first time results from RNA-seq, microarray, ribosome footprinting, proteomics, and small molecule LC-MS experiments have been integrated to compare gene expression in bacteria. Together, these data provide insights as to why strain ATCC 33988 is better adapted for growth and survival on n-alkanes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3708-4) contains supplementary material, which is available to authorized users.

Response of Rhodococcus erythropolis strain IBBPo1 to toxic organic solvents

Recently, there has been a lot of interest in the utilization of rhodococci in the bioremediation of petroleum contaminated environments. This study investigates the response of Rhodococcus erythropolis IBB_Po1 cells to 1% organic solvents (alkanes, aromatics). A combination of microbiology, biochemical, and molecular approaches were used to examine cell adaptation mechanisms likely to be pursued by this strain after 1% organic solvent exposure. R. erythropolis IBB_Po1 was found to utilize 1% alkanes (cyclohexane, n-hexane, n-decane) and aromatics (toluene, styrene, ethylbenzene) as the sole carbon source. Modifications in cell viability, cell morphology, membrane permeability, lipid profile, carotenoid pigments profile and 16S rRNA gene were revealed in R. erythropolis IBB_Po1 cells grown 1 and 24 h on minimal medium in the presence of 1% alkanes (cyclohexane, n-hexane, n-decane) and aromatics (toluene, styrene, ethylbenzene). Due to its environmental origin and its metabolic potential, R. erythropolis IBB_Po1 is an excellent candidate for the bioremediation of soils contaminated with crude oils and other toxic compounds. Moreover, the carotenoid pigments produced by this nonpathogenic Gram-positive bacterium have a variety of other potential applications.

Isolation and characterization of different bacterial strains for bioremediation of n-alkanes and polycyclic aromatic hydrocarbons

Crude oil is a common environmental pollutant composed of a large number of both aromatic and aliphatic hydrocarbons. Biodegradation is carried out by microbial communities that are important in determining the fate of pollutants in the environment. The intrinsic biodegradability of the hydrocarbons and the distribution in the environment of competent degrading microorganisms are crucial information for the implementation of bioremediation processes. In the present study, the biodegradation capacities of various bacteria toward aliphatic and aromatic hydrocarbons were determined. The purpose of the study was to isolate and characterize hydrocarbon-degrading bacteria from contaminated soil of a refinery in Arzew, Algeria. A collection of 150 bacterial strains was obtained; the bacterial isolates were identified by 16S rRNA gene sequencing and their ability to degrade hydrocarbon compounds characterized. The isolated strains were mainly affiliated to the Gamma-Proteobacteria class. Among them, Pseudomonas spp. had the ability to metabolize high molecular weight hydrocarbon compounds such as pristane (C19) at 35.11 % by strain LGM22 and benzo[a] pyrene (C20) at 33.93 % by strain LGM11. Some strains were able to grow on all the hydrocarbons tested including octadecane, squalene, phenanthrene, and pyrene. Some strains were specialized degrading only few substrates. In contrast, the strain LGM2 designated as Pseudomonas sp. was found able to degrade both linear and branched alkanes as well as low and high poly-aromatic hydrocarbons (PAHs). The alkB gene involved in alkane degradation was detected in LGM2 and other Pseudomonas-related isolates. The capabilities of the isolated bacterial strains to degrade alkanes and PAHs should be of great practical significance in bioremediation of oil-contaminated environments.

Biosurfactant activity, heavy metal tolerance and characterization of Joostella strain A8 from the Mediterranean polychaete Megalomma claparedei (Gravier, 1906)

The effect of heavy metals on the activity of biosurfactants produced by Joostella strain A8 from the polychaete Megalomma claparedei was investigated. Biosurfactant activity was first improved by evaluating the influence of abiotic parameters. Higher E(24) indices were achieved at 25 °C in mineral salt medium supplemented with 2 % glucose, 3 % sodium chloride (w/v) and 0.1 % ammonium chloride (w/v). Considerable surface tension reduction was never recorded. Heavy metal tolerance was preliminarily assayed by plate diffusion method resulting in the order of toxicity Cd > Cu > Zn. The activity of biosurfactants was then evaluated in the presence of heavy metals at different concentrations in liquid cultures that were incubated under optimal conditions for biosurfactant activity. The production of stable emulsions resulted generally higher in the presence of metals. These findings suggest that biosurfactant production could represent a bacterial adaptive strategy to defend cells from a stress condition derived from heavy metals in the bulk environment.

A Comprehensive Review of Aliphatic Hydrocarbon Biodegradation by Bacteria

Hydrocarbons are relatively recalcitrant compounds and are classified as high-priority pollutants. However, these compounds are slowly degraded by a large variety of microorganisms. Bacteria are able to degrade aliphatic saturated and unsaturated hydrocarbons via both aerobic and anaerobic pathways. Branched hydrocarbons and cyclic hydrocarbons are also degraded by bacteria. The aerobic bacteria use different types of oxygenases, including monooxygenase, cytochrome-dependent oxygenase and dioxygenase, to insert one or two atoms of oxygen into their targets. Anaerobic bacteria, on the other hand, employ a variety of simple organic and inorganic molecules, including sulphate, nitrate, carbonate and metals, for hydrocarbon oxidation.

Transcriptional profiling suggests that multiple metabolic adaptations are required for effective proliferation of Pseudomonas aeruginosa in jet fuel

Fuel is a harsh environment for microbial growth. However, some bacteria can grow well due to their adaptive mechanisms. Our goal was to characterize the adaptations required for Pseudomonas aeruginosa proliferation in fuel. We have used DNA-microarrays and RT-PCR to characterize the transcriptional response of P. aeruginosa to fuel. Transcriptomics revealed that genes essential for medium- and long-chain n-alkane degradation including alkB1 and alkB2 were transcriptionally induced. Gas chromatography confirmed that P. aeruginosa possesses pathways to degrade different length n-alkanes, favoring the use of n-C11-18. Furthermore, a gamut of synergistic metabolic pathways, including porins, efflux pumps, biofilm formation, and iron transport, were transcriptionally regulated. Bioassays confirmed that efflux pumps and biofilm formation were required for growth in jet fuel. Furthermore, cell homeostasis appeared to be carefully maintained by the regulation of porins and efflux pumps. The Mex RND efflux pumps were required for fuel tolerance; blockage of these pumps precluded growth in fuel. This study provides a global understanding of the multiple metabolic adaptations required by bacteria for survival and proliferation in fuel-containing environments. This information can be applied to improve the fuel bioremediation properties of bacteria.

Biosurfactant production by marine bacterial isolates from the Venezuelan Atlantic Front

Our purpose was to detect, isolate and characterize tensioactive agents with or without emulsifying activity from marine bacterial strains present in seawater and sediment samples from the Venezuelan Atlantic Front. Biosurfactants found in cell-free supernatants from all cultures presented high surface activity as they were able to reduce the water surface tension from 72 dynes cm(-1) to values between 41.7 and 33.9 dynes cm(-1). However, high indirect CMC values were registered for the most of these compounds (51.4%-56.1% v/v). Culture supernatants from S3 and S29 strains showed highest emulsifying activity in the dispersion assay with diesel oil (absorbance 1.06 and 1.18, respectively), while supernatant from the S10 strain induced the most stable oil-in-water emulsions with 16° and 25°API crude oils. Only culture supernatant from S3 strain was able to produce stable oil-in water emulsions with diesel oil and both type of crude oils.

Production of microbial surfactants from oily sludge-contaminated soil by Bacillus subtilis DSVP23

The indigenous microbial community utilizing aliphatic, aromatic, and polar components from the oily sludge as sole source of carbon and energy was selected from the soil samples of Ankleshwar, India for biosurfactant production. Evaluation of biosurfactant production was done using screening assays such as surface tension reduction, hemolytic activity, emulsification activity, drop-collapse assay, and cell surface hydrophobicity studies. Maximum biosurfactant (6.9 g/l) production was achieved after 5 days of growth from Bacillus subtilis DSVP23 which was identified by 16S RNA technique (NCBI GenBank accession no. EU679368). Composition of biosurfactant showed it to be lipopeptide in nature with 15.2% protein content and 18.0% lipid content. Functional group analysis was also done by using Fourier transform infrared spectroscopy which showed it to be a protein-bound lipid thereby imparting them special properties. Analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometric and nuclear magnetic resonance revealed that the major constituents of lipopeptide are leucine and isoleucine. Gas chromatographic analysis data indicated that oily sludge components of chain length C₁₂-C₃₀ and aromatic hydrocarbons were degraded effectively by B. subtilis DSVP23 after 5 days of incubation. These results collectively points toward the importance of B. subtilis DSVP23 as a potential candidate for bioremediation studies.