Rhamnolipid Biosurfactant Research Articles

Biosurfactant rhamnolipid assisted microemulsification of bio-oil components in diesel

ABSTRACTThe use of model bio-oil from pyrolysis biomass as a fuel was improved by forming diesel microemulsion using rhamnolipid (RL) as the surfactant. After microemulsification, synthetic bio-oil components were solubilized in different positions of the microemulsion. Water and some hydrophilic substances were solubilized in the hydrophilic core of the microemulsion, glyoxal, and vanillin in the palisade layer, and guaiacol in the diesel continuous phase. The bio-oil components species and their solubilization positions in the microemulsion fuel system had considerable effect on properties of the fuel, e.g., degradation/combustion characteristics as determined by thermogravimetric analysis.

Decolorization and detoxification of water-insoluble Sudan dye by Shewanella putrefaciens CN32 co-cultured with Bacillus circulans BWL1061

Effluents loaded with various synthetic dyes are considered as a huge burden to the surrounding ecosystems. Sudan dyes are relatively difficult to decolorize due to its water-insolubility. In the present study, the strain Shewanella putrefaciens CN32 was firstly applied to decolorize Sudan dyes under the anaerobic condition, and the physicochemical parameters on the decolorization were optimized. The results demonstrated that the suitable decolorization condition was temperature 26 °C, initial pH 7.0–8.0 and NaCl concentrations 0–20 g/L. Electron competitive acceptors including nitrite, nitrate, dimethyl sulphoxide and oxygen could cause the significant inhibition to the decolorization of Sudan dyes. Biosurfactant rhamnolipid played a positive role in enhancing the decolorization of Sudan I. The co-culture of S. putrefaciens CN32 and Bacillus circulans BWL1061 is reported for the first time to accelerate the decolorization through improving the synergistic effect of enzymatic degradation and biological reductive effect. The highest decolorization of 90.23% to Sudan I was achieved within 108 h, suggesting that co-culture technique has a good potential in the treatment of dyeing wastewater. Furthermore, the microbial toxicity tests indicated that the toxicity of Sudan I to Escherichia coli BL21 and Bacillus subtilis 168 was obviously decreased after the decolorization.

Comparative study of various carbon sources on rhamnolipid production

This study aimed at comparing the effect of various carbon sources with a fixed nitrogen source for the syntheses of rhamnolipid biosurfactant using a strain of Pseudomonas aeruginosa. The carbon sources used were glycerol, glucose and waste cooking oil (WCO), for the benefit of utilising wastes. The characterized microbial strain was obtained from the Microbiology Department of Obafemi Awolowo University, Ile-Ife. It was grown on a surface culture before inoculation into a production culture. Each culture media were sterilized at 121 °C, 15 psi for 15 min and cooled before inoculation. Each procedure was carried out in duplicates and culture flasks incubated in a shaker for 7 days with 24-h monitoring. The growth of P. aeruginosa on the three carbon sources passed through the phases of formation of primary metabolites. The surface tensions of medium relative to water was reduced from 86.69 mNm−1 to 33.63 mNm−1, 36.44 mNm−1 and 18.02 mNm−1 for biosurfactant from use of glycerol, glucose and WCO as carbon sources respectively. Excellent emulsification index, E24, was obtained in the continuous media Heavy black oil and lubricating oil unlike in the other media: vegetable oil and kerosene. The FTIR spectra revealed that the glycerol- and glucose-based biosurfactants were di-substituted rhamnolipids with difference in the hydrophobic moieties. However, the biosurfactant formed with WCO was not a rhamnolipid but a lipopeptide.

The antibacterial activity of rhamnolipid biosurfactant is pH dependent

Rhamnolipid (RL) biosurfactants have been studied as agents to control the growth of food pathogens however, to be successful applied as antimicrobial agent in food, is important to determine the effect of environmental conditions on RL activity. Once pH is a determinant factor to the development of microorganisms in food, we investigated the antimicrobial activity of RL under different pH values. The antimicrobial activity of RL against the Gram-positive pathogens L. monocytogenes, B. cereus and S. aureus was pH dependent and favored at more acidic conditions while the Gram-negative Salmonella enterica and E. coli (EHEC) showed resistance at all pH levels studied. Bacillus cereus was the most sensitive bacteria showing MIC of 19.5 μg/mL and eradication of the population was observed after 30 min with 39.1 μg/mL of RL. The sensitivity to RL was associated with reduction on cell surface hydrophobicity and cytoplasmic membrane damage. Scanning Electron Microscopy images evidenced the cell damage promoted by RL on sensitive strains. The pH is an important factor to be considered on developing RL-based strategies to the control of food pathogens.

Application of a Dynamic Method for the Volumetric Mass Transfer Coefficient Determination in the Scale‐Up of Rhamnolipid Biosurfactant Production

AbstractBiosurfactants are widely used for industrial, agricultural, food, cosmetics, and pharmaceutical applications. However, much of the work on biosurfactant production is still in the laboratory stage. In addition, there is a lack of fundamental knowledge about the scale‐up of biosurfactant production. This article addresses this issue and describes dynamic methods for obtaining scalable data for aerobic fermenters. To achieve this objective, the present work aims to study the scale‐up of the rhamnolipid production process from 2.5 to 20 L of an aerated and agitated bioreactor. A similar scale‐up trend in both Pseudomonas aeruginosa growth and biosurfactant production under optimum conditions demonstrated that the scale‐up protocol based on the constant oxygen transfer coefficient is successfully implemented in this work. A maximum rhamnolipid production of 8.3 g L−1 was achieved after 1 week in the 20‐L fermenter, which was 10% better than that of the 2.5‐L fermenter at the same time period. This difference may be due to the change of aeration from 1.0 vvm (volume of air per volume of medium per minute) on the small scale to 2.0 vvm on the large scale. However, the comparable results obtained on both scales confirmed that the scale‐up protocol works for rhamnolipid production. Based on our results, we consider that this method is perhaps the most helpful tool for successful scale‐up of biosurfactant production and for the determination of the optimal conditions at the production scale. The results of this work will help the researchers to have a good prediction of scale‐up in this field.

Production of rhamnolipids by integrated foam adsorption in a bioreactor system

Biosurfactants offer environmental as well as health benefits over traditionally used chemical surfactants and heterologous production from engineered microorganisms has been demonstrated, offering containable as well as scalable production of these alternative chemicals. Low product titers and cost intensive downstream processing are the main hurdles for economical biosurfactant production at industrial scales. Increased biosurfactant concentrations are found in the liquid fraction of the foam formed during fermentation of producing microbes. Adsorption of biosurfactants from foam fractions in cultivations may offer a simple concentration and purification method which could enable their cost-effective production. Here, foam adsorption was applied as an in situ method for separation of the rhamnolipid biosurfactants during fermentation of Pseudomonas putida EM383. An integrated process was designed to capture the produced rhamnolipids on hydrophobic adsorbent in packed bed units while minimizing the impact of adsorption on the productivity of the system by recirculating cell-containing collapsed foam flow-through back into the reactor vessel. A stable rhamnolipid production by P. putida EM383 on glucose was performed coupled to this adsorption strategy for 82 h, after which no remaining rhamnolipids were found in the cultivation broth and 15.5 g of rhamnolipids could be eluted from the adsorbent. Rhamnolipid yield from glucose feed was 0.05 g g−1, when up to 2 g L−1 glucose pulse feeding was applied. After solvent evaporation, a product purity of 96% was obtained. The results indicate that the integrated adsorption method can be efficient for simultaneous production and recovery of rhamnolipid biosurfactants from microbial fermentations.

Novel insights into scalability of biosurfactant combined microwave disintegration of sludge at alkali pH for achieving profitable bioenergy recovery and net profit

In the present study, a novel alkali rhamnolipid combined microwave disintegration (ARMD) was employed to achieve net energy production, increased liquefaction and to increase the amenability of sludge towards biomethanation. Additionally, biosurfactant rhamnolipid under alkali conditions enhances the liquefaction at alkali pH of 10 with a maximal liquefaction of 55% with reduced energy consumption (1620 kJ/kg TS) than RMD (45.7% and 3240 kJ/kg TS specific energy) and MD (33.7% and 6480 kJ/kg TS specific energy). A higher biomethane production of 379 mL/g COD was achieved for ARMD when compared to RMD (329 mL/g COD) and MD (239 mL/g COD). The scalable studies imply that the ARMD demands input energy of −282.27 kWh. A net yield of (0.39 USD/ton) was probably achieved via novel ARMD technique indicating its suitability at large scale execution when compared to RMD (net cost −31.34 USD/ton) and MD (−84.23 net cost USD/ton), respectively.

Enhanced biodegradation of n-hexane from the air stream using rhamnolipid in a biofilter packed with a mixture of compost, scoria, sugar beet pulp and poplar tree skin

Biofiltration of n-hexane vapors with and without using rhamnolipid biosurfactant was investigated on a laboratory scale biofilter packed with compost, scoria, sugar beet pulp, and poplar tree skin at empty bed residence times (EBRT) of 30, 60 and 120s for a period of 131 days. Acclimation of microorganism in the biofilter was achieved in 31 days with an average n-hexane concentration of 0.269 gm −3 and EBRTs of 120s. The results demonstrated that average removal efficiencies (RE) for the corresponding EBRT with n-hexane loading rates (IL) of 6.7–137 gm −3 h −1 were 18.7 ± 1.67%, 28.9 ± 4.06% and 46.8 ± 8.2% without biosurfactant. While, the average REs in presence of the biosurfactant were 23.98 ± 4.08%, 42.4 ± 9.7% and 85.13 ± 10.44% at EBRTs of 30, 60 and 120s, respectively. About 53% of n-hexane removal was related to the segment 1 of the biofilter, where the bacterial and fungi population of its biofilm was 2 × 10 15 and 1.3 × 10 9 CFU g −1 (dry weight), respectively, which was significantly more than the other segments. For all the tested inlet concentrations, the RE was significantly increased by increasing EBRT and decreasing IL of n-hexane. The results of this study confirm the efficiency enhancement of rhamnolipid in biofiltration of hydrophobic compounds such as n-hexane from air streams. • Biofiltration of n-hexane vapors was investigated in the presence and absence of rhamnolipid biosurfactant. • Removal efficiency of n-hexane increased from 46 to 86% in the presence of rhamnolipid. • About 53% of n-hexane removal was related to the segment 1 of the biofilter. • Increasing the biofiltration of hydrophilic compounds by rhamnolipid.

Oil recovery from tank bottom sludge using rhamnolipids

Oil sludge has become a major impediment to the development of the petroleum and petrochemical industries with the growth of oil production worldwide. In this research, rhamnolipid biosurfactant produced by Pseudomonas aeruginosa was used to recover oil from oil tank bottom sludge. The optimum value of the fermentation broth (with rhamnolipid biosurfactant concentration of 5.4 g/L) addition was a volume fraction of 2% (v/v). Optimal temperature (65 °C), liquid/solid ratio (3:1), washing time (3 h), and agitation intensity (300 rpm) for oil recovery were determined. Wastewater from oil recovery was flocculated with 400 mg/L polyaluminum chloride for reuse. The moisture of the recovered oil was (0.42 ± 0.12) %, which could directly enter into the refinery process. The solid particles in the oil sludge exhibited a porous structure that adsorbed a significant amount of oil and increased the difficulty of oil recovery. Results showed that the fermentation broth of P. aeruginosa can be used to recover oil from oil sludge and has potential industrial applications.

TREATMENT OF WASTEWATER WITH HIGH FAT CONTENT EMPLOYING AN ENZYME POOL AND BIOSURFACTANT: TECHNICAL AND ECONOMIC FEASIBILITY

ABSTRACT The combination of 0.5% weight per volume (w/v) crude enzyme consortia produced by solid state fermentation with Penicillium brevicompactum and 27 milligrams per liter (mg/L) of rhamnolipid biosurfactant produced by submerged fermentation with Pseudomonas aeruginosa was employed to pretreat wastewater from a poultry slaughterhouse in bench upflow anaerobic sludge blanket (UASB) bioreactors. One bioreactor was fed with untreated wastewater (Control) and another with pretreated wastewater (Test). Under an organic loading rate of 11 kg COD/m3.d, the Test bioreactor showed higher specific methane production (67.8 mL CH4 (STP)/g COD removed), higher chemical oxygen demand (COD) (91.2%), and oil and grease (O&G) (95.8%) removal than the Control bioreactor, which produced 36.1 - 16.9 mL CH4 (STP)/g COD removed with 72.5% COD removal and 48% O&G removal. The Control bioreactor experienced five clogging episodes due to the accumulation of fat on the surface, while the Test bioreactor operated without operational problems. The scum of the Control bioreactor contained more than 10 times higher quantities of fat than the Test bioreactor. The economic analysis indicated that such alternative technology has lower costs than conventional technology.

Efficient chromium removal from aqueous solutions by precipitate flotation using rhamnolipid biosurfactants

Efficient chromium removal from aqueous solutions by precipitate flotation using rhamnolipid biosurfactants

Synergistic Effect of Saponin and Rhamnolipid Biosurfactants Systems on Foam Behavior

AbstractIn this study, the synergistic effect of saponin and rhamnolipid biosurfactant on foam properties at an air-water interface was investigated. In order to reach the optimum hydrophilic lipophilic balance (HLB) value, samples of 2 wt% of rhamnolipid and saponin biosurfactants with different HLB values (9.6, 10, 10.4, 10.8, 11.2, 11.6, and 12) in 5 ml of DI water were prepared. Results showed that the optimum HLB value of the microemulsion system was 10.8 for the mixture of 84% rhamnolipid and 16% saponin. At that optimum HLB value and a total surfactant concentration of 2 wt%, the maximum foaming ability and foam stability of the mixed system was 48 mm and 72 min respectively. During the experiment, it was observed that at optimum HLB value the foaming ability of the system increased by increasing the concentration of rhamnolipid and saponin. Comparing the foaming ability and foam stability of biosurfactant system with the properties of SDS, Tween80 and Span80 showed that the biosurfactants have a good foaming ability. The CMC value of the biosurfactant mixtures at the optimum HLB value was lower than that of other synthetic surfactants. The results show that, the biosurfactant mixtures had a synergistic effect on foaming ability and foam stability compared to the individual biosurfactants and synthetic surfactants. Therefore, the mixture of rhamnolipid and saponin is proposed as a potential alternative for detergent, cosmetic and petroleum industry.

Removal of zinc and cadmium ions from contaminated soils with rhamnolipid biosurfactant produced by Pseudomonas aeruginosa S7PS5

A soil treatment process using froth flotation technique involving anionic biosurfactant (rhamnolipids) using Sodium sulfide was studied. The supernatant produced by the strain Pseudomonas aeruginosa S7PS5 was tested for biosurfactants production, HPLC analysis showed the presence of L-rhamnosyl- β- hydroxydecanoyl- β-hydroxydecanoate (RL1) and L-rhamnosyl L-rhamnosyl- β-hydroxydecanoyl-β- hydroxydecanoate (RL2). The influence of the collector (rhamnolipid), pulp pH, a chemical activation step (sulfidization) and process time on metal removal efficiency has been investigated to recover Zn and Cd ions from a contaminated soil. An effective CMC of 35 mg/L was obtained. A perfect Zn and Cd removal efficiency was made at pH = 12 and 4 mg/g of Na 2 S during the first 5 min of soil washing process, then a longer flotation time ( > 5 min) caused mechanical entrainment of Zn and Cd. Keywords: Biosurfactants, flotation, Pseudomonas aeruginosa , rhamnolipids, soil washing

Application of biosurfactant for enhancement of bioremediation process of crude oil contaminated soil

In the present study, a biosurfactant produced by Pseudomonas aeruginosa SR17 was utilized to evaluate its efficiency in enhancement of bioremediation of oil contaminated soil. The degradation of total petroleum hydrocarbon (TPH) on application of rhamnolipid biosurfactant at 1.5 g L−1 was found to be 86.1% and 80.5% in two soil samples containing 6800 ppm and 8500 ppm TPH respectively. The efficiency of biosurfactant was also compared with a frequently used synthetic surfactant, sodium dodecyl sulphate (SDS) that resulted in 70.8% and 68.1% degradation of TPH from the same contaminated soil samples. GC-MS based analysis showed the presence of poly aromatic hydrocarbons (PAHs) namely indene, chamazulene, naphthalene, phenanthrene, anthracene, fluorene, floranthene, benz(b)fluorene and benz(d)anthracene in the soil samples. Rhamnolipid treatment eliminated 3 PAHs namely floranthene, benz(b)fluorene, and benz(d)anthracene completely within six months and the remaining PAHs were depleted up to 60–80%, within the same period. The efficient degradation of PAHs and other components of TPH on application of the biosurfactant were attributed to enhanced heterotrophic bacterial population. It was also found that the degradation of oil contaminants led to alteration of certain vital physico-chemical properties of the soil.

Pseudomonas rhizophila S211, a New Plant Growth-Promoting Rhizobacterium with Potential in Pesticide-Bioremediation.

A number of Pseudomonas strains function as inoculants for biocontrol, biofertilization, and phytostimulation, avoiding the use of pesticides and chemical fertilizers. Here, we present a new metabolically versatile plant growth-promoting rhizobacterium, Pseudomonas rhizophila S211, isolated from a pesticide contaminated artichoke field that shows biofertilization, biocontrol and bioremediation potentialities. The S211 genome was sequenced, annotated and key genomic elements related to plant growth promotion and biosurfactant (BS) synthesis were elucidated. S211 genome comprises 5,948,515 bp with 60.4% G+C content, 5306 coding genes and 215 RNA genes. The genome sequence analysis confirmed the presence of genes involved in plant-growth promoting and remediation activities such as the synthesis of ACC deaminase, putative dioxygenases, auxin, pyroverdin, exopolysaccharide levan and rhamnolipid BS. BS production by P. rhizophila S211 grown on olive mill wastewater based media was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum BS production yield (720.80 ± 55.90 mg/L) were: 0.5% (v/v) inoculum size, 15% (v/v) olive oil mill wastewater (OMWW) and 40°C incubation temperature at pH 6.0 for 8 days incubation period. Biochemical and structural characterization of S211 BS by chromatography and spectroscopy studies suggested the glycolipid nature of the BS. P. rhizophila rhamnolipid was stable over a wide range of temperature (40–90°C), pH (6–10), and salt concentration (up to 300 mM NaCl). Due to its low-cost production, emulsification activities and high performance in solubilization enhancement of chemical pesticides, the indigenous BS-producing PGPR S211 could be used as a promising agent for environmental bioremediation of pesticide-contaminated agricultural soils.

Rhamnolipid as new bio-agent for cleaning of ultrafiltration membrane fouled by whey.

In this work, rhamnolipid biosurfactant as an eco-friendly and biodegradable cleaning agent was produced by Pseudomonas aeruginosa bacteria and was used to evaluate the chemical cleaning efficiency of whey fouled ultrafiltration membranes. Thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR) confirmed the successful synthesis of rhamnolipid. The produced rhamnolipid was compared to chemical cleaners including sodium hydroxide (NaOH), sodium dodecyl sulfate (SDS) and Tween 20. Ultrafiltration membranes used for fouling and cleaning analysis were prepared using phase inversion via immersion precipitation technique. For studying the fouling mechanisms, Hermia's model adapted to cross-flow was used. From the fouling mechanism experiments, it was found that the complete blocking and cake formation were the dominant fouling mechanisms. The highest values of cleaning efficiency were achieved using rhamnolipid and NaOH as cleaning agents with the flux recovery of 100%, but with considering the low concentration of the rhamnolipid used in the cleaning solution compared to NaOH (0.3 versus 4 g/L for NaOH), its application is preferred.

Enhanced utilization of fluorene by Paenibacillus sp. PRNK-6: Effect of rhamnolipid biosurfactant and synthetic surfactants

The present investigation was to study the effect of different non-ionic surfactants (Tween-80, Tween-60, Tween-40, Tween-20, Triton X-100) and a rhamnolipid biosurfactant on the degradation of fluorene by Paenibacillus sp. PRNK-6. An enhancement in the growth, as well as fluorene utilization by this strain were observed in the presence of biosurfactant and non-ionic surfactants except Tween-20 and Triton X-100. Triton X-100 and Tween-20 were toxic to this bacterium. The strain PRNK-6 utilized 75% of fluorene (280mg/L) in 24h in an unamended condition. On the other hand, the complete utilization of higher concentration fluorene (320mg/L) by this strain was noticed when the medium was amended with Tween-80 (1.5% v/v) within 24h of incubation. Whereas, 90.6%, 96.5% and 96.7% of fluorene (280mg/L) was utilized when amended with Tween-60 (3.5% v/v), Tween-40 (3% v/v) and biosurfactant (25mg/L) respectively. Biosurfactant promoted the fluorene degradation potential of PRNK-6 as 96.2% of 320mg/L fluorene was degraded within 24h. Further, the added tween series surfactants and a biosurfactant have increased the cell surface hydrophobicity of the PRNK-6. Thus correlating with the enhanced degradation of the fluorene.

Advances in applications of rhamnolipids biosurfactant in environmental remediation: A review.

The objective of this review is to provide a comprehensive overview of the advances in the applications of rhamnolipids biosurfactants in soil and ground water remediation for removal of petroleum hydrocarbon and heavy metal contaminants. The properties of rhamnolipids associated with the contaminant removal, that is, solubilization, emulsification, dispersion, foaming, wetting, complexation, and the ability to modify bacterial cell surface properties, were reviewed in the first place. Then current remediation technologies with integration of rhamnolipid were summarized, and the effects and mechanisms for rhamnolipid to facilitate contaminant removal for these technologies were discussed. Finally rhamnolipid-based methods for remediation of the sites co-contaminated by petroleum hydrocarbons and heavy metals were presented and discussed. The review is expected to enhance our understanding on environmental aspects of rhamnolipid and provide some important information to guide the extending use of this fascinating chemical in remediation applications.

Evaluation of Antibiotics Ampicillin and Ciprofloxacin and Biosurfactant Rhamnolipid Effect on Hydrophobicity and Electron Donors and Recipients in Urinary and Fecal <i>Escherichia Coli</i>

Adhesion is the first and most important stage in pathogenesis after bacteria enters to the body. Attachment of bacteria in medicine, industry, agriculture, waste decomposition, shipbuilding, etc. is important. Hydrophobicity and electron donor- electron acceptor characteristic are more important factors in bacterial adhesion. This study tries examining effect of biosurfactant rhamnolipid and two antibiotics ampicillin and ciprofloxacin on E. coli cell surface hydrophobicity and electron donor- electron acceptor characteristic by MATS method in terms of sample type and antibiotic resistance. Isolated bacteria from urine samples has a more antibiotic resistance to ampicillin. The results indicate that rhamnolipid makes increase in hydrophobicity and electron donor characteristic and in opposite ciprofloxacin makes increase electron acceptor and in opposite and decrease hydrophobicity. Also, hydrophobicity and electron donor- electron acceptor characteristic were different in sensitive and resistant to antibiotics strains. This study results showed since the hydrophobicity and electronic exchange are important factors involved in attachment of bacteria to inanimate surfaces and inner surfaces of the body, we can inhibit bacterial binding to it and help to reduce the incidence of antibiotic resistance by change these surfaces. The effect of antibiotics and rhamnolipid on some effective characteristic in adhesion cannot be ignored, despite the difference in their impact.

Determination of optimal parameters of rhamnolipid biosurfactant production: An agent for emulsification of heavy crude oil

ABSTRACTIn oil and petroleum industries, emulsification process is important to transfer and upgrade heavy oil. Rhamnolipids are the essential molecules of biosurfactants that used for this goal and they are often produced from various types of Pseudomonas aeroginosa bacteria. In this research, rhamnolipid biosurfactant produced from Pseudomonas aeroginosa ATCC 9027. The goal of this study was to optimize the effective parameters in production of rhamnolipid in order to reach the minimum water droplet size using Taguchi method. The evaluated parameters include incubation temperature, RPM of incubation, C/N ratio and pH of aqueous phase. Response parameters were yield, cost and water droplet size in water in oil (w/o) microemulsion. The results illustrated that the temperature of incubation and pH of the aqueous phase were the most effective factors in the production of rhamnolipid. Optimum operation condition including yield, cost and water droplet size, were 5.2 ± 0.1 g/l, 2.4 ± 0.14 $/g and 70 ± 5%, respectively. Dynamic light scattering (DLS) analysis was used for determination of water droplet size. Also the emulsification index (E24) of (w/o) emulsion was 98% ± 4. The results of this study could reduce the cost of rhamnolipid production for the applications in oil industries.