Microbial surfactant-enhanced mineral oil recovery under laboratory conditions

Research advances in the identification of regulatory mechanisms of surfactin production by Bacillus: a review

Surfactin is a cyclic hexalipopeptide compound, nonribosomal synthesized by representatives of the Bacillus subtilis species complex which includes B. subtilis group and its closely related species, such as B. subtilis subsp subtilis, B. subtilis subsp spizizenii, B. subtilis subsp inaquosorum, B. atrophaeus, B. amyloliquefaciens, B. velezensis (Steinke mSystems 6: e00057, 2021) It functions as a biosurfactant and signaling molecule and has antibacterial, antiviral, antitumor, and plant disease resistance properties. The Bacillus lipopeptides play an important role in agriculture, oil recovery, cosmetics, food processing and pharmaceuticals, but the natural yield of surfactin synthesized by Bacillus is low. This paper reviews the regulatory pathways and mechanisms that affect surfactin synthesis and release, highlighting the regulatory genes involved in the transcription of the srfAA-AD operon. The several ways to enhance surfactin production, such as governing expression of the genes involved in synthesis and regulation of surfactin synthesis and transport, removal of competitive pathways, optimization of media, and fermentation conditions were commented. This review will provide a theoretical platform for the systematic genetic modification of high-yielding strains of surfactin.

New Trends in Biosurfactants: From Renewable Origin to Green Enhanced Oil Recovery Applications

Enhanced oil recovery (EOR) processes are technologies used in the oil and gas industry to maximize the extraction of residual oil from reservoirs after primary and secondary recovery methods have been carried out. The injection into the reservoir of surface-active substances capable of reducing the surface tension between oil and the rock surface should favor its extraction with significant economic repercussions. However, the most commonly used surfactants in EOR are derived from petroleum, and their use can have negative environmental impacts, such as toxicity and persistence in the environment. Biosurfactants on the other hand, are derived from renewable resources and are biodegradable, making them potentially more sustainable and environmentally friendly. The present review intends to offer an updated overview of the most significant results available in scientific literature on the potential application of biosurfactants in the context of EOR processes. Aspects such as production strategies, techniques for characterizing the mechanisms of action and the pros and cons of the application of biosurfactants as a principal method for EOR will be illustrated and discussed in detail. Optimized concepts such as the HLD in biosurfactant choice and design for EOR are also discussed. The scientific findings that are illustrated and reviewed in this paper show why general emphasis needs to be placed on the development and adoption of biosurfactants in EOR as a substantial contribution to a more sustainable and environmentally friendly oil and gas industry.

Potential Application of Biosurfactant-Producing Bacteria for Bioremediation of Oil Polluted Marine Intertidal Sediments

The removal of oil contaminants in marine intertidal sediments under cold climate is an urgent issue. Although the bioavailability of petroleum hydrocarbons decreases at low temperatures, biosurfactants can promote oil biodegradation. In this study, characteristics of biosurfactants produced by cold-adapted oil-degrading bacteria Planococcus sp. XW-1 were studied. Adding the XW-1 biosurfactant could effectively facilitate the solubility of phenanthrene, pyrene, diesel oil, and crude oil. The solubilization was limited by the number of rings and the molecular weight (WSRphenanthrene = 0.0234; WSRpyrene = 0.0165; WSRdiesel oil = 0.0027; WSRcrude oil = 0.0015). Additional biosurfactants significantly washed out crude oil adsorbed to the sand (reduction from 17.1%, 22.7% to 87.9% and 94.28% in 24 h). With the increase in particle size, the removal efficiency increased from 87.9% to 94.28%. After the addition of biosurfactant, the effect of degradation increased by 20% in 20 days. The results suggest that the biosurfactant-producing bacteria Planococcus sp. XW-1 is a promising candidate used in the in situ bioremediation of petroleum-contaminated intertidal sediment.

Prospects in the bioremediation of petroleum hydrocarbon contaminants from hypersaline environments: A review

Hypersaline environments are underappreciated and are frequently exposed to pollution from petroleum hydrocarbons. Unlike other environs, the high salinity conditions present are a deterrent to various remediation techniques. There is also production of hypersaline waters from oil-polluted ecosystems which contain toxic hydrophobic pollutants that are threat to public health, environmental protection, and sustainability. Currently, innovative advances are being proposed for the remediation of oil-contaminated hypersaline regions. Such advancements include the exploration and stimulation of native microbial communities capable of utilizing and degrading petroleum hydrocarbons. However, prevailing salinity in these environments is unfavourable for the growth of non-halophylic microorganisms, thus limiting effective bioremediation options. An in-depth understanding of the potentials of various remediation technologies of hydrocarbon-polluted hypersaline environments is lacking. Thus, we present an overview of petroleum hydrocarbon pollution in hypersaline ecosystems and discuss the challenges and prospects associated with several technologies that may be employed in remediation of hydrocarbon pollution in the presence of delimiting high salinities. The application of biological remediation technologies including the utilization of halophilic and halotolerant microorganisms is also discussed.

Biosurfactant production prospects of a Gram-negative bacterium-Klebsiella pneumoniae ssp. ozaenae BK34

Increasing environmental concerns have brought natural surfactant produced by microorganisms into limelight due to their lesser toxicity, biodegradable nature, and retention of activity at extreme conditions. In the present investigation, the surfactant production perspective of capsulated Gram-negative bacilli Klebsiella pneumoniae ssp. ozaenae BK34 was explored. It was identified on the basis of PCR amplification of conserved region of 16SrRNA using species specific primers. Highest oil displacement and emulsification (E₂₄) index of 6.8 cm and 20% along with 4.38-fold increase in biomass were attained using olive oil (2% (v/v)) as substrate. Incorporation of urea at 0.5% (w/v) concentration increased the oil displacement, E₂₄ index, and drop diameter to 9.2 cm, 77.50%, and 0.80 cm, respectively, accompanied by 5.38-fold increase in biomass production. Biosurfactant level was recorded maximum at 30 °C as apparent from the oil displacement of 9.3 cm and E₂₄ index of 75%. Reduction in incubation temperature to 25 °C abated oil displacement (5.2 cm) and E₂₄ index (17.66%). Biosurfactant production was also appeared to be pH sensitive as shifting pH from 7.0 to 6.0 or 8.0 reduced the E₂₄ index from 75 to 35% and 25%, respectively. Inoculum of stationary phase bacterial biomass at the proportion of 0.05% (w/v) was found adequate in triggering maximum biosurfactant production while the log phase biomass delayed the production significantly. Acid precipitation method was able to yield 7 g/L biosurfactant at pH 2. The surfactant was allocated to glycolipopeptide class on the basis of FTIR spectroscopy.

The selective breeding and mutagenesis mechanism of high-yielding surfactin Bacillus subtilis strains with atmospheric and room temperature plasma

BACKGROUND

Surfactin, a good biological surfactant, is derived from the metabolites of microorganisms. However, the ability of natural strains to produce surfactin is low, and so the presented study aimed to use a novel mutagenesis technology to increase their yields.

RESULTS

Atmospheric and room temperature plasma (ARTP) was used to conduct mutation breeding of Bacillus subtilis CICC 10721, and a mutant strain M45 with a higher surfactin yield of 34.2% and a stable subculture was screened out. From the fermentation kinetics study, it was found that the maximum cell dry weight, maximum growth rate and surfactin synthesis parameters of the mutant strain M45 were all greater than that of the original strain. Scanning electron microscope and laser scanning confocal microscope observations showed that the spore morphology changed after ARTP treating, and the intracellular Ca²⁺ concentration of the mutant increased. Genome resequencing analysis showed that 66 single nucleotide poymorphism non-synonymous mutation sites occurred in M45, and the identification results of the fermentation broth extract from M45 showed that it is composed of C₁₂ -C₁₆ surfactin.

CONCLUSION

ARTP mutagenesis was found to change the morphology of bacteria, membrane permeability and genes related to the synthesis and secretion of surfactin. The present study provides a basis for industrial production of surfactin and an understanding of the mutagenesis mechanism. © 2021 Society of Chemical Industry.

Construction and Degradation Performance Study of Polycyclic Aromatic Hydrocarbons (PAHs) Degrading Bacterium Consortium

PAHs are widely distributed in the environment and pose a serious threat to ecological security and human health. The P&A (Pseudomonas aeruginosa and Alcaligenes faecalis) bacterium consortium obtained in this study comes from oily sludge and is reused for the degradation of PAHs mixture in oily sludge. Few articles pay attention to the PAHs mixture in oily sludge and reuse the bacterium consortium for its degradation. The PAHs solution degradation efficient of P&A bacterial consortium under different environmental conditions, bioaugmentations, and exogenous stimulations were studied by ultraviolet visible spectrophotometer and gas chromatography–mass spectrometry. The result shows that, after 8 days of degradation under 35 °C, pH 7, with 5% (volume percent) of the inoculation amount, the degradation rate of NAP, PHE, and PYR solution could higher than 90%, 80%, and 70%, respectively. The additional crude oil could further improve the NAP, PHE, and PYR degradation efficiency. The minimum inhibitory concentration of Cu2+, Zn2+, and Pb2+ to bacterium were 2.002, 17.388, and 9.435 mM, respectively. The addition of surfactants had negative or limited positive effect on the PAHs degradation rate. Furthermore, the average degradation rates of NAP, PHE, and PYR, in oily sludge of local petroleum polluted area by P&A bacterial consortium, could all reach above 80%. Based on gas chromatography–mass spectrometry test results before and after incubation, P&A bacterial consortium also provides more opportunities for other organic compounds’ degradation.

Low-cost production and application of lipopeptide for bioremediation and plant growth by Bacillus subtilis SNW3

At present time, every nation is absolutely concern about increasing agricultural production and bioremediation of petroleum-contaminated soil. Hence, with this intention in the current study potent natural surfactants characterized as lipopeptides were evaluated for low-cost production by Bacillus subtilis SNW3, previously isolated from the Fimkessar oil field, Chakwal Pakistan. The significant results were obtained by using substrates in combination (white beans powder (6% w/v) + waste frying oil (1.5% w/v) and (0.1% w/v) urea) with lipopeptides yield of about 1.17 g/L contributing 99% reduction in cost required for medium preparation. To the best of our knowledge, no single report is presently describing lipopeptide production by Bacillus subtilis using white beans powder as a culture medium. Additionally, produced lipopeptides display great physicochemical properties of surface tension reduction value (SFT = 28.8 mN/m), significant oil displacement activity (ODA = 4.9 cm), excessive emulsification ability (E24 = 69.8%), and attains critical micelle concentration (CMC) value at 0.58 mg/mL. Furthermore, biosurfactants produced exhibit excellent stability over an extensive range of pH (1-11), salinity (1-8%), temperature (20-121°C), and even after autoclaving. Subsequently, produced lipopeptides are proved suitable for bioremediation of crude oil (86%) and as potent plant growth-promoting agent that significantly (P < 0.05) increase seed germination and plant growth promotion of chili pepper, lettuce, tomato, and pea maximum at a concentration of (0.7 g/100 mL), showed as a potential agent for agriculture and bioremediation processes by lowering economic and environmental stress.

Plant-Derived Saponins: A Review of Their Surfactant Properties and Applications

In response to increasing natural surfactant demand and environmental concerns, natural plant-based surfactants have been replacing synthetic ones. Saponins belong to a class of plant metabolites with surfactant properties that are widely distributed in nature. They are eco-friendly because of their natural origin and biodegradable. To date, many plant-based saponins have been investigated for their surface activity. An overview of saponins with a particular focus on their surface-active properties is presented in this article. For this purpose, works published in the past few decades, which report better surfactant relevant properties of saponins than synthetic ones, were extensively studied. The investigations on the potential surfactant application of saponins are also documented. Moreover, some biological activities of saponins such as antimicrobial activity, antidiabetic activity, adjuvant potentials, anticancer activity, and others are reported. Plants rich in saponins are widely distributed in nature, offering great potential for the replacement of toxic synthetic surfactants in a variety of modern commercial products and these saponins exhibit excellent surface and biological activities. New opportunities and challenges associated with the development of saponin-based commercial formulations in the future are also discussed in detail.

Nanobubbles activate anaerobic growth and metabolism of Pseudomonas aeruginosa

The effect of nanobubbles on anaerobic growth and metabolism of Pseudomonas aeruginosa was investigated. P. aeruginosa grew earlier in the culture medium containing nanobubbles and the bacterial cell concentration in that culture medium was increased a few times higher compared to the medium without nanobubbles under anaerobic condition. Both gas and protein, which are the metabolites of P. aeruginosa, were remarkably produced in the culture medium containing nanobubbles whereas those metabolites were little detected in the medium without nanobubbles, indicating nanobubbles activated anaerobic growth and metabolism of P. aeruginosa. The carbon dioxide nanobubbles came to be positively charged by adsorbing cations and delivered ferrous ions, one of the trace essential elements for bacterial growth, to the microbial cells, which activated the growth and metabolism of P. aeruginosa. The oxygen nanobubbles activated the activities of P. aeruginosa as an oxygen source.

Genetic engineering of the precursor supply pathway for the overproduction of the nC14-surfactin isoform with promising MEOR applications

Background

Surfactin, a representative biosurfactant of lipopeptide mainly produced by Bacillus subtilis, consists of a cyclic heptapeptide linked to a β-hydroxy fatty acid chain. The functional activity of surfactin is closely related to the length and isomerism of the fatty acid chain.

Results

In this study, the fatty acid precursor supply pathway in Bacillus subtilis 168 for surfactin production was strengthened through two steps. Firstly, pathways competing for the precursors were eliminated with inactivation of pps and pks. Secondly, the plant medium-chain acyl-carrier protein (ACP) thioesterase (BTE) from Umbellularia californica was overexpressed. As a result, the surfactin titer after 24 h of cultivation improved by 34%, and the production rate increased from 0.112 to 0.177 g/L/h. The isoforms identified by RP-HPLC and GC–MS showed that the proportion of nC₁₄-surfactin increased 6.4 times compared to the control strain. A comparison of further properties revealed that the product with more nC₁₄-surfactin had higher surface activity and better performance in oil-washing. Finally, the product with more nC₁₄-surfactin isoform had a higher hydrocarbon-emulsification index, and it increased the water-wettability of the oil-saturated silicate surface.

Conclusion

The obtained results identified that enhancing the supply of fatty acid precursor is very essential for the synthesis of surfactin. At the same time, this study also proved that thioesterase BTE can promote the production of nC₁₄-surfactin and experimentally demonstrated its higher surface activity and better performance in oil-washing. These results are of great significance for the MEOR application of surfactin.

Graphic abstract

Biosurfactant Production Using Mutant Strains of Pseudomonas aeruginosa and Bacillus subtilis from Agro-industrial Wastes

Purpose: Biosurfactants are applied in drug formulations to improve drug solubility and in some cases, treat diseases. This study is focused on generating, extracting, purifying and then characterizing biosurfactants from bacterial isolates of palm oil wastes and abattoir soil origins. Methods: Eight bacteria were isolated from the soil and sludge samples, out of which four (50%) were found to produce biosurfactants. Bacillus subtilis (37.5%) and Pseudomonas aeruginosa (50%) were isolated and identified from these samples using mineral salt medium, nutrient agar and Cetrimide agar. Mutant isolates of B. subtilis BS3 and P. aeruginosa PS2 were used to produce biosurfactants using mineral salt medium as enrichment medium and extraction was done using membrane filter. Results: The mutant strains B. subtilis BS3 and P. aeruginosa PS2 generated biosurfactants that displayed significant solubility and dissolution properties by enhancing the percentage solubility of piroxicam to 62.86 and 54.29% respectively, and achieved 51.71 and 48.71% dissolution of the drug in 0.1N HCl. Conclusion: From the results obtained, the produced biosurfactants could serve as a better alternative to conventional surfactants. Notably, the study indicated that the biosurfactant produced by mutant strain of B. subtilis produced more potent activities (surface tension reduction ability, high emulsification) than those of P. aeruginosa.

Application of biosurfactant surfactin as a pH-switchable biodemulsifier for efficient oil recovery from waste crude oil

Efficient oil separation is the most desirable, but still challenging solution for the waste crude oil problem. This study developed biosurfactant surfactin as a novel pH-switchable biodemulsifier for efficient oil separation. As found, surfactin demulsification achieved a quite well oil separation ratio of over 95% on model emulsions after 20 min at 50 °C. The validity of this demulsification process should be mainly based on the readily lost stabilization ability of surfactin in emulsions triggered by acid addition. Then, surfactin (0.2 g/L) treatment with the aid of ethanol (2%) to improve its distribution could recover over 95% of oil from waste crude oil. After treated by surfactin, the separated oil phase contains tiny water (less than 0.5%) and thus can be reused for resource recycling to reach a compromised balance between satisfying the strict environmental regulations and decreasing the high treatment costs. Hence, in consideration of high demulsification efficiency, environmental-friendly properties and cost-efficiency, surfactin has a great potential for industrial applications for oil recovery from waste crude oil which is a severe problem presents in most of the petroleum-related factories.

Oil reservoir simulating bioreactors: tools for understanding petroleum microbiology

Various aspects of the oil fields in terms of microbial activity (souring, biocorrosion, etc.) and oil production (polymer flooding, etc.) have been evaluated through a variety of experiments. The primary step to study these properties in the laboratory requires the construction and operation of up-flow oil reservoir simulating bioreactors (ORSBs) in real time. Souring by reduction of sulfate to sulfide is a major contributor in enhancing corrosion of metal infrastructure used for oil production and processing. Whether the injection of biocides prevents or remediates reservoir souring can be addressed by flooding up-flow ORSBs. The potential of biopolymers/biosurfactants produced by different microbial strains have also been investigated for the role in maintaining additional oil recovery using ORSB. Additionally, key issues of polymer behavior during flooding of reservoirs could be understood during laboratory studies by monitoring the in situ porous medium rheology. Besides, the change in various ORSB parameters helps in adjudging the effect of different biosurfactants/biopolymers in enhancing oil recovery. Parameters such as permeability reduction, adsorption, interaction with porous matrix, and formation damage can be evaluated using ORSB. The analysis of earlier studies indicated that running bioreactors for longer duration of time can help in drawing conclusion with sharpness and less ambiguity. The current review discusses the construction and application of various types of ORSBs including the experimental studies employing ORSBs.

Evaluation of rhamnolipid production by a halotolerant novel strain of Pseudomonas aeruginosa

This work was aimed to evaluate six qualitative and quantitative methods (hemolytic activity, cetyltrimethylammonium bromide agar plate method, oil spread method, drop collapse method, surface tension measurement and emulsification index) to study biosurfactant production by sixty-nine bacterial isolates which were obtained from petroleum crude contaminated soil and water samples. Among all isolates, Pseudomonas aeruginosa NCIM 5514 was evaluated as the most potent isolate producing rhamnolipid. Effectiveness of growth medium pH, inoculum size and concentration of NaCl on surface active properties and biomass & rhamnolipid production in fermentation medium were studied. Highest surface activity was obtained at 1% (v/v) inoculum at initial pH of the medium 7.2, which resulted 4.389 ± 0.019 and 3.146 ± 0.087 g/l biomass and rhamnolipid, respectively. Notable surface activity of rhamnolipid produced by P. aeruginosa NCIM 5514 makes it feasible to be used for industrial application.

Hyperthermophilic Clostridium sp. N-4 produced a glycoprotein biosurfactant that enhanced recovery of residual oil at 96 °C in lab studies

Biosurfactant producing hypethermophilic microorganisms are essentially required for Microbial Enhanced Oil Recovery (MEOR) from high temperature oil reservoirs (above 90 °C). In the present study, biosurfactant producing Clostridium sp. N-4, optimally growing at 96 °C was isolated from a high temperature oil reservoir. Effect of pH, temperature and salinity on production and activity of N-4 biosurfactant was investigated. Biosurfactant produced by N-4 was partially purified by acid precipitation, characterized using FT-IR spectroscopy; and evaluated for its ability to enhance oil recovery in sand pack studies. The strain N-4 produced biosurfactant over a wide range of pH (5.0-9.0) and salinity (0-13%) at high temperature (80-100 °C) and optimally at pH 7, 96 °C and 4% salinity. N-4 biosurfactant was active at 37-101 °C; pH, 5-10 and salinity of 0-12 % (w/v). N-4 biosurfactant, characterized as glycoprotein reduced the surface tension of water by 32 ± 0.4 mN/m at critical micelle concentration of 100 μg/ml. N-4 biosurfactant mobilized 17.15% of residual oil saturation in sand pack studies. Similarly, the strain N-4 also recovered 36.92% of the residual oil in sand pack studies under the conditions mimicking the environment of depleted high temperature oil reservoir. Thus, the biosurfactant producing Clostridium sp. N-4 was identified as a suitable agent for enhanced oil recovery from high temperature oil reservoirs.

Rational strain improvement for surfactin production: enhancing the yield and generating novel structures

Surfactin, one of the most powerful microbial surfactants, is a lipopeptide-type biosurfactant which combines interesting physicochemical properties and biological activities. However, the high cost caused by its low productivity largely limits the commercial application of surfactin. Hence, many engineered bacterium have also been used to enhance surfactin biosynthesis. This review briefly summarizes the mechanism of surfactin biosynthesis, highlighting the synthesis pathway of N-terminally attached fatty acids, and outlines the main genetic engineering strategies for improving the yield and generating novel structures of surfactin, including promoter engineering, enhancing efflux systems, modifying the transcriptional regulatory genes of surfactin synthase (srfA), genomics and transcriptomics analysis, non ribosomal peptide synthetase (NRPS) domain and combinatorial biosynthesis. Finally, we discuss the future prospects of the research on surfactin.

Biosurfactant-Producing Capability and Prediction of Functional Genes Potentially Beneficial to Microbial Enhanced Oil Recovery in Indigenous Bacterial Communities of an Onshore Oil Reservoir

Microbial enhanced oil recovery (MEOR) is a bio-based technology with economic and environmental benefits. The success of MEOR depends greatly on the types and characteristics of indigenous microbes. The aim of this study was to evaluate the feasibility of applying MEOR at Mae Soon Reservoir, an onshore oil reservoir experiencing a decline in its production rate. We investigated the capability of the reservoir's bacteria to produce biosurfactants, and evaluated the potentials of uncultured indigenous bacteria to support MEOR by means of prediction of MEOR-related functional genes, based on a set of metagenomic 16s rRNA gene data. The biosurfactant-producing bacteria isolated from the oil-bearing sandstones from the reservoir belonged to one species: Bacillus licheniformis, with one having the ability to decrease surface tension from 72 to 32 mN/m. Gene sequences responsible for biosurfactant (licA3), lipase (lipP1) and catechol 2,3-dioxygenase (C23O) were detected in these isolates. The latter two, and other genes encoding MEOR-related functional proteins such as enoyl-CoA hydratase and alkane 1-monooxygenase, were predicted in the bacterial communities residing the reservoir's sandstones. Exposure of these sandstones to nutrients, consisting of KNO₃ and NaH₂PO₄, resulted in an increase in the proportions of some predicted functional genes. These results indicated the potentials of MEOR application at Mae Soon site. Using the approaches demonstrated in this study would also assist evaluation of the feasibility of applying MEOR in oil reservoirs, which may be enhanced by an appropriate nutrient treatment.

Experimental Investigations of Behaviour of Biosurfactants in Brine Solutions Relevant to Hydrocarbon Reservoirs

In this study, we investigated the behaviour of rhamnolipid and Greenzyme in brine solutions relevant to hydrocarbon reservoir. Prior to this work, several studies only reported the behaviour of the biosurfactants dissolved in sodium chloride solutions of varied salinity. The results of this study are relevant to the application of the biosurfactants in enhanced oil recovery, during which the compounds are injected into reservoir saturated with formation water, typically of high salinity and complex composition. Surface tension and conductivity methods were used to determine the critical micelle concentrations of the biosurfactants, Gibbs surface excess concentrations and standard free energy at water-air interface. The results show that rhamnolipid and Greenzyme could reduce the surface tension of water from 72.1 ± 0.2 mN/m to 34.7 ± 0.4 mN/m and 47.1 ± 0.1 mN/m respectively. They were also found to be stable in high salinity and high temperature with rhamnolipid being sensitive to brine salinity, composition and pH while Greenzyme showed tolerance for high salinity. Furthermore, the Gibbs standard free energy of micellisation shows that rhamnolipid and Greenzyme have the tendency to spontaneously form micelles with rhamnolipid showing more surface adsorption. However from maximal Gibbs surface excess concentration calculations, Greenzyme monomers tend to favour aggregation more than that of rhamnolipid.

Sustainable biosurfactant produced by Serratia marcescens UCP 1549 and its suitability for agricultural and marine bioremediation applications

BACKGROUND

Biosurfactants are surface-active agents produced by microorganisms that have higher efficiency and stability, lower toxicity and higher biocompatibility and biodegradability than chemical surfactants. Despite its properties and potential application in a wide range of environmental and industrial processes, biosurfactants are still not cost-competitive when compared to their synthetic counterparts. Cost effective technologies and renewable raw substrates as agro-industrial and regional waste from northeast of Brazil as cassava flour wastewater, supplemented with lactose and corn oil are mainly the chemically media for growing microorganism and in turn the production of the biosurfactant of quality. This study aimed to obtained biosurfactant by Serratia marcescens UCP 1549 containing cassava flour wastewater (CWW), by application of a full-factorial design, as sustainable practices in puts the production process in promising formulation medium. The characterization of the biomolecule was carried out, as well as the determination of its stability and toxicity for cabbage seeds. In addition, its ability to stimulate seed germination for agriculture application and oil spill bioremediation were investigated.

RESULTS

Serratia marcescens showed higher reduction of surface tension (25.92 mN/m) in the new medium containing 0.2% lactose, 6% cassava flour wastewater and 5% corn waste oil, after 72 h of fermentation at 28 °C and 150 rpm. The substrate cassava flour wastewater showed a promising source of nutrients for biosurfactant production. The isolate biosurfactant exhibited a CMC of 1.5% (w/v) and showed an anionic and polymeric structure, confirmed by infrared spectra. The biomolecule demonstrated high stability under different temperatures, salinity and pH values and non-toxicity against to cabbage seeds. Thus, exploring biosurfactant their potential role in seeds germinations and the promotion and agricultural applications was investigated. In addition, the effectiveness of biosurfactant for removal burned motor oil adsorbed in sand was verified.

CONCLUSIONS

The use of medium containing CWW not only reduces the cost of process of biosurfactant production, but also the environmental pollution due to the inappropriate disposal of this residue. This fact, added to the high stability and non-toxicity of the biosurfactant produced by S. marcescens UCP 1549, confirms its high environmental compatibility, make it a sustainable biocompound that can be replace chemical surfactants in diverse industries. In addition, the effectiveness of biosurfactant for stimulate seed germination and removing burned motor oil from sand, suggests its suitability for agriculture and bioremediation applications.

Recovery of contaminated marine environments by biosurfactant-enhanced bioremediation

The need to remediate areas contaminated by petroleum products has led to the development of novel technologies for treating such contaminants in a non-conventional manner, that is, without the use of chemical or physical methods. Biosurfactants are amphipathic biomolecules produced by microorganisms that can be used in bioremediation processes in environments contaminated by petroleum products due to their excellent tensioactive properties. The aim of the present study was to produce a biosurfactant from Pseudomonas aeruginosa UCP 0992 cultivated in 0.5% corn steep liquor and 4.0% vegetable oil residue in a 1.2-L bioreactor employing a central composite rotatable design to optimize the cultivation conditions for maximum yield. The best results were achieved with aeration rate of 1.0 vvm and 3.0% inoculum at 225 rpm for 120 h, resulting in a surface tension of 26.5 mN/m and a biosurfactant yield of 26 g/L. Kinetic and static assays were then performed with the biosurfactant for the removal of motor oil adsorbed to sand, with removal rates around 90% and 80%, respectively, after 24 h. Oil degradation experiments with the bacterium and the combination of the bacterium and biosurfactant were also conducted to simulate the bioremediation process in sand and seawater samples (duration: 75 and 30 days, respectively). In both cases, oil degradation rates were higher than 90% in the presence of the biosurfactant and the producing species, indicating the potential of the biomolecule as an adjuvant in petroleum decontamination processes in the marine environment.

Dynamics of a microbial community during an effective boost MEOR trial using high-throughput sequencing

Using 454 pyrosequencing of 16S rRNA gene amplicons, microbial communities in samples of injection water and production water during a serial microbial enhanced oil recovery (MEOR) field trial in a water flooded high pour point oil reservoir were determined. There was a close microbial community compositional relationship between the injection water and the successful first round MEOR processed oil reservoir which was indicated by the result of 43 shared dominant operational taxonomic units detected in both the injection water and the production water. Alterations of microbial community after the injection of boost nutrients showed that microbes giving positive responses were mainly those belonging to the genera of Comamonas, Brevundimonas, Azospirillum, Achromobacter, Pseudomonas, and Hyphomonas, which were detected both in the injection water and in the production water and usually detected in oil reservoir environments or associated with hydrocarbon degradation. Additionally, microbes only dominant in the production waters were significantly inhibited with a sharp decline in their relative abundance. Based on these findings, a suggestion of re-optimization of the boost nutrients, targetting the microbes co-existing in the injection water and the oil reservoir and having survival ability in both surface and subsurface environments, rather than simple repeats for the subsequent in situ MEOR applications was proposed.

Biosurfactant surfactin with pH-regulated emulsification activity for efficient oil separation when used as emulsifier

In the present study, the pH-regulated emulsification activity of surfactin was studied and its potential application in oil separation towards enhanced oil recovery (EOR) was investigated. As demonstrated, surfactin can stabilize emulsions quite well beyond pH 7.4. An oil emulsification ratio of about 98% was obtained at pH 11.0; while this emulsification activity was rapidly and completely lost when pH decreased to below 3.0, having an oil separation ratio of over 98%. This pH-sensitive property is probably due to surfactin dissolution-precipitation induced by the ionization-protonation of a carboxyl group in its structure under alkaline or acidic conditions. This property allows oil emulsification or oil separation to be readily achieved via simple pH adjustments when surfactin is used as an emulsifier. Furthermore, surfactin sustained its activity after demulsification and can be readily reused many times. The above obtained results indicated surfactin-based EOR processes have great application feasibility.

Production, characterization, and antifungal activity of a biosurfactant produced by Rhodotorula babjevae YS3

Background

Sophorolipids are one of the most promising glycolipid biosurfactants and have been successfully employed in bioremediation and various other industrial sectors. They have also been described to exhibit antimicrobial activity against different bacterial species. Nevertheless, previous literature pertaining to the antifungal activity of sophorolipids are limited indicating the need for further research to explore novel strains with wide antimicrobial activity. A novel yeast strain, Rhodotorula babjevae YS3, was recently isolated from an agricultural field in Assam, Northeast India. This study was primarily emphasized at the characterization and subsequent evaluation of antifungal activity of the sophorolipid biosurfactant produced by R. babjevae YS3.

Results

The growth kinetics and biosurfactant production by R. babjevae YS3 was evaluated by cultivation in Bushnell-Haas medium containing glucose (10% w/v) as the sole carbon source. A reduction in the surface tension of the culture medium from 70 to 32.6 mN/m was observed after 24 h. The yield of crude biosurfactant was recorded to be 19.0 g/l which might further increase after optimization of the growth parameters. The biosurfactant was characterized to be a heterogeneous sophorolipid (SL) with both lactonic and acidic forms after TLC, FTIR and LC–MS analyses. The SL exhibited excellent oil spreading and emulsifying activity against crude oil at 38.46 mm² and 100% respectively. The CMC was observed to be 130 mg/l. The stability of the SL was evaluated over a wide range of pH (2–10), salinity (2–10% NaCl) and temperature (at 120 °C for time intervals of 30 up to 120 min). The SL was found to retain surface-active properties under the extreme conditions. Additionally, the SL exhibited promising antifungal activity against a considerably broad group of pathogenic fungi viz. Colletotrichum gloeosporioides, Fusarium verticilliodes, Fusarium oxysporum f. sp. pisi, Corynespora cassiicola, and Trichophyton rubrum.

Conclusions

The study reports, for the first time, the biosurfactant producing ability of R. babjevae, a relatively lesser studied yeast. The persistent surface active properties of the sophorolipid in extreme conditions advocates its applicability in diverse environmental and industrial sectors. Further, antifungal activities against plant and human pathogens opens up possibilities for development of efficient and eco-friendly antifungal agents with agricultural and biomedical applications.

Agro-Industrial Wastes for Production of Biosurfactant by Bacillus subtilis ANR 88 and Its Application in Synthesis of Silver and Gold Nanoparticles

Biosurfactants, surface-active amphiphilic compounds, despite having a wide range of applications, have a high cost of production, which severely restricts their use. For cheaper production of biosurfactant, we investigated the potential of the indigenously isolated biosurfactant producing organism, Bacillus subtilis ANR 88, to grow on different cheap carbon sources (molasses, whey, and extracts of potato peels, orange peels, banana peels, and bagasse). We found that, B. subtilis ANR 88 used significant amounts of total sugar to produce cell biomass and biosurfactant. The biosurfactant production in minimal medium containing glucose as sole source of carbon was 0.207 g/l and the same with molasses as carbon source was 0.241 g/l. With whey as carbon source, isolate failed to produce biosurfactant. Amongst the extracts of the agro-wastes, the extracts of bagasse and orange peels gave 0.127 and 0.089 g/l of biosurfactant respectively. One-variable-at-a-time (OVAT) studies carried out to optimize the production of biosurfactant by B. subtilis ANR 88 resulted into maximum biosurfactant yield of 0.513 g/l in medium: molasses 4%, ammonium ferric citrate 0.25%, pH 7. Plackett–Burman design based statistical method for optimization increased the production of biosurfactant to 0.746 g/l, which is 3.6-fold of that produced on glucose. The biosurfactant produced by B. subtilis ANR 88 was analyzed by Fourier Transform Infrared Spectroscopy (FT-IR); it showed that the biosurfactant contained alkyl as well as peptide groups. The biosurfactant of B. subtilis ANR 88 was found effective in the synthesis of silver as well as gold nanoparticles in the total absence of conventional chemical reducing agents. Interestingly, nanoparticles produced were almost uniform in their size and shapes i.e., spherical silver (4–18 nm) and hexagonal gold nanoparticles (40–60 nm), as evident in TEM images.

Towards the development of an effective in vivo wound healing agent from Bacillus sp. derived biosurfactant using Catla catla fish fat

The aim of the present study was to investigate the excisional wound healing activity of a biosurfactant isolated fromBacillus stratosphericussp.

Carbon spectrum utilization by an indigenous strain of Pseudomonas aeruginosa NCIM 5514: Production, characterization and surface active properties of biosurfactant

The present research work was undertaken with a mandate to study carbon spectrum utilization and structural characterization of biosurfactant produced by indigenous Pseudomonas aeruginosa NCIM 5514, which showed unique properties to utilize a large number of carbon sources effectively for production of biosurfactant, although glucose was the best carbon substrate. In Bushnell-Hass medium supplemented with glucose (1%, w/v), 3.178±0.071g/l biosurfactant was produced by this isolate in 96h. The biosurfactant produced showed surface tension and emulsification activity values from 29.14±0.05 to 62.29±0.13mN/m and 88.50±1.96 to 15.40±0.91%, respectively. Toluene showed highest emulsification activity followed by kerosene. However, kerosene exhibited emulsion stability for 30days. Biosurfactant was characterized as a mixture of di-rhamnolipid (Rha-Rha-C₁₀-C_14:1) and mono-rhamnolipid (Rha-C₈-C₁₀) by FTIR, ESI-MS and LC-MS techniques. High biosurfactant yield opens up doors for the isolate to find utility in various industries.

Core Flood study for enhanced oil recovery through ex-situ bioaugmentation with thermo- and halo-tolerant rhamnolipid produced by Pseudomonas aeruginosa NCIM 5514

The aim of this work was to study the Microbial Enhanced Oil Recovery (MEOR) employing core field model ex-situ bioaugmenting a thermo- and halo-tolerant rhamnolipid produced by Pseudomonas aeruginosa. Thin Layer Chromatography (TLC) revealed that the biosurfactant produced was rhamnolipid type. Nuclear Magnetic Resonance analysis showed that the purified rhamnolipids comprised two principal rhamnolipid homologues, i.e., Rha-Rha-C10-C14:1 and Rha-C8-C10. The rhamnolipid was stable under wide range of temperature (4°C, 30-100°C), pH (2.0-10.0) and NaCl concentration (0-18%, w/v). Core Flood model was designed for oil recovery operations using rhamnolipid. The oil recovery enhancement over Residual Oil Saturation was 8.82% through ex-situ bioaugmentation with rhamnolipid. The thermal stability of rhamnolipid shows promising scope for its application at conditions where high temperatures prevail in oil recovery processes, whereas its halo-tolerant nature increases its application in marine environment.

Bacterial degradation of crude oil using solid formulations of bacillus strains isolated from oil-contaminated soil towards microbial enhanced oil recovery application

Microbial enhanced oil recovery has played a major role in enhancing crude oil recovery from depleted oil reservoirs to solve stagnant petroleum production.

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.

Production and characterisation of glycolipid biosurfactant by Halomonas sp. MB-30 for potential application in enhanced oil recovery

Biosurfactant-producing Halomonas sp. MB-30 was isolated from a marine sponge Callyspongia diffusa, and its potency in crude oil recovery from sand pack column was investigated. The biosurfactant produced by the strain MB-30 reduced the surface tension to 30 mN m(-1) in both glucose and hydrocarbon-supplemented minimal media. The critical micelle concentration of biosurfactant obtained from glucose-based medium was at 0.25 mg ml(-1) at critical micelle dilution 1:10. The chemical structure of glycolipid biosurfactant was characterised by infrared spectroscopy and proton magnetic resonance spectroscopy. The emulsification activity of MB-30 biosurfactant was tested with different hydrocarbons, and 93.1 % emulsification activity was exhibited with crude oil followed by kerosene (86.6 %). The formed emulsion was stable for up to 1 month. To identify the effectiveness of biosurfactant for enhanced oil recovery in extreme environments, the interactive effect of pH, temperature and salinity on emulsion stability with crude oil and kerosene was evaluated. The stable emulsion was formed at and above pH 7, temperature >80 °C and NaCl concentration up to 10 % in response surface central composite orthogonal design model. The partially purified biosurfactant recovered 62 % of residual crude oil from sand pack column. Thus, the stable emulsifying biosurfactant produced by Halomonas sp. MB-30 could be used for in situ biosurfactant-mediated enhanced oil recovery process and hydrocarbon bioremediation in extreme environments.

Biosurfactant-producing and oil-degrading Bacillus subtilis strains enhance oil recovery in laboratory sand-pack columns

Microbial Enhanced Oil Recovery (MEOR) technology uses microorganisms and their metabolites to retrieve unrecoverable oil from mature reservoirs. In situ stimulation of biosurfactant-producing and oil-degrading microorganisms reduces the capillary forces retaining the oil inside the reservoir and decreases its viscosity, thus promoting oil flow and consequently production. In this work, a sand-pack column model was designed to simulate oil recovery operations and evaluate mobilization of residual oil by the selected microorganisms. Four different hydrocarbon mixtures and three Bacillus subtilis strains isolated from crude oil samples were used. Additional oil recoveries ranged from 6 to 24% depending on the hydrocarbon mixture and microorganism used. Biosurfactant production was observed with all the microorganisms and hydrocarbon mixtures studied. The oils recovered after incubation with B. subtilis isolates showed a reduction in the percentage of long-chain n-alkanes and lower viscosity when compared with the original oils. The results obtained suggest that stimulation of the selected B. subtilis strains in situ can contribute to mobilize entrapped oil in mature reservoirs.

Biosurfactant production by Bacillus subtilis B30 and its application in enhancing oil recovery

The fermentative production of biosurfactants by Bacillus subtilis strain B30 and the evaluation of biosurfactant based enhanced oil recovery using core-flood were investigated. Different carbon sources (glucose, sucrose, starch, date molasses, cane molasses) were tested to determine the optimal biosurfactant production. The isolate B30 produced a biosurfactant that could reduce the surface tension and interfacial tension to 26.63±0.45 mN/m and 3.79±0.27 mN/m, respectively in less than 12h in both glucose or date molasses based media. A crude biosurfactant concentration of 0.3-0.5 g/l and critical micelle dilution (CMD) values of 1:8 were observed. The biosurfactants gave stable emulsions with wide range of hydrocarbons including light and heavy crude oil. The biosurfactants were partially purified and identified as a mixture of lipopeptides similar to surfactin, using high performance thin layer chromatography and Fourier transform infrared spectroscopy. The biosurfactants were stable over wide range of pH, salinity and temperatures. The crude biosurfactant preparation enhanced light oil recovery by 17-26% and heavy oil recovery by 31% in core-flood studies. The results are indicative of the potential of the strain for the development of ex situ microbial enhanced oil recovery processes using glucose or date molasses based minimal media.

Production of a Lipopeptide Biosurfactant by a Novel Bacillus sp. and Its Applicability to Enhanced Oil Recovery

Biosurfactants are surface-active compounds derived from varied microbial sources including bacteria and fungi. They are secreted extracellularly and have a wide range of exciting properties for bioremediation purposes. They also have vast applications in the food and medicine industry. With an objective of isolating microorganisms for enhanced oil recovery (EOR) operations, the study involved screening of organisms from an oil-contaminated site. Morphological, biochemical, and 16S rRNA analysis of the most promising candidate revealed it to be Bacillus siamensis, which has been associated with biosurfactant production, for the first time. Initial fermentation studies using mineral salt medium supplemented with crude oil resulted in a maximum biosurfactant yield of 0.64 g/L and reduction of surface tension to 36.1 mN/m at 96 h. Characterization studies were done using thin layer chromatography and Fourier transform infrared spectroscopy. FTIR spectra indicated the presence of carbonyl groups, alkyl bonds, and C–H and N–H stretching vibrations, typical of peptides. The extracted biosurfactant was stable at extreme temperatures, pH, and salinity. Its applicability to EOR was further verified by conducting sand pack column studies that yielded up to 60% oil recovery.