Maximum Biosurfactant Research Articles

Benchmarking of different microbes for their biosurfactants antifungal action against plant pathogens

The biotic stress caused by phytopathogens (bacteria, fungus, yeast and insect pests) is a primary factor in yield loss of plants. Biocontrol agents and their active compounds are used to manage such plant pathogens. Here, in our study, we screened four bacterial isolates identified as Bacillus cereus, B. anthracis, B. velezensis and Serratia marcescens after morphological, biochemical and molecular characterization (16s rDNA sequencing) for production of biosurfactant by foam forming activity, oil spreading tests and emulsification activity. Highest foam stability (75 min) and maximum emulsification activity E24% (75%) was observed by B. velezensis strain. Among all the four isolates, Bacillus velezensis strain produced maximum biosurfactant (0.349±0.004 g/50 mL). Biosurfactant of all the four bacterial isolates were checked for fungal inhibiton on PDA plate(s). Bacillus velezensis showed comparatively the highest percent inhibition 58.82, 88.15, 78.45,72.68, 83.96, 75.47, 68.07 and 88.44% against Colletotrichum falcatum, Fusarium oxysporum f sp. ciceri, Helminthosporium maydis, F. oxysporum f. sp. lycopersici, Aspergillus niger, Mucor sp., Helminthosporium oryzae and Rhizoctonia solani, respectively. Bacillus velezensis biosurfactant among all the four bacterial isolates was found to be most effective against the tested phytopathogens.

Biosurfactant Production by Bacillus amyloliquefaciens C11 and Streptomyces lavendulae C27 Isolated from a Biopurification System for Environmental Applications

Biosurfactant-producing bacteria can be found in contaminated environments such as biopurification systems (BPS) for pesticide treatments. A total of 18 isolates were screened to determine their ability to produce extracellular biosurfactants, using olive oil as the main carbon source. Out of the eighteen isolates, two strains (C11 and C27) were selected for biosurfactant production. The emulsification activities of the C11 and C27 strains using sunflower oil was 58.4 and 53.7%, respectively, and 46.6 and 48.0% using olive oil. Using molecular techniques and MALDI-TOF, the strains were identified as Bacillus amyloliquefaciens (C11) and Streptomyces lavendulae (C27). The submerged cultivation of the two selected strains was carried out in a 1 L stirred-tank bioreactor. The maximum biosurfactant production, indicated by the lowest surface tension measurement, was similar (46 and 45 mN/m) for both strains, independent of the fact that the biomass of the B. amyloliquefaciens C11 strain was 50% lower than the biomass of the S. lavendulae C27 strain. The partially purified biosurfactants produced by B. amyloliquefaciens C11 and S. lavendulae C27 were characterized as a lipopeptide and a glycolipid, respectively. These outcomes highlight the potential of the selected biosurfactant-producing microorganisms for improving pesticides’ bioavailability and therefore the degradational efficacy of BPS.

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.

Lab-scale bioremediation technology: Ex-situ bio-removal and biodegradation of waste cooking oil by Aspergillus flavus USM-AR1

Large amounts of waste cooking oil from residential areas can cause adverse effect on the environment if not disposed properly. Fungi have a higher tolerance to hydrocarbon toxicity due to their physiology and adaptation to the environment. Consequently, they can be employed in bioremediation to reduce waste oils release to the environment. This work aims to bio-remove and biodegrade the waste cooking oil using a newly isolated strain Aspergillus flavus USM-AR1, in stirred tank reactor (STR). The strain showed remarkable removal activity of waste cooking oil. The removal efficiency of waste cooking oil reached 97% on day 3 of cultivation. This was attained when the culture was agitated at 400 rpm, maintaining the Reynold’s number of that obtained in the shake flask culture. Fortuitously, the best dispersion of waste cooking oil was also obtained at 400 rpm. The highest cell surface hydrophobicity (MATH) at 76.42% was observed at day 3 of cultivation. The maximum biosurfactant and emulsification activity occurred at day 2 of cultivation, which were 43 mm and 44%, respectively. Cell surface hydrophobicity and biosurfactant produced by strain Aspergillus flavus USM-AR1 played an important role in bio-removal of waste cooking oil, making this strain a prospective candidate for treating waste cooking oil.

OPTIMIZATION TRENDS IN TOTAL LIPOPEPTIDE PRODUCTION BY Bacillus velezensis 0G REVEALED A SUSTAINABLE SUBMERGED FERMENTATION METHOD USING SWEET POTATO PEELS

Bacillus velezensis are plant-growth promoting microorganisms. They produce an interesting class of cyclic peptides; surfactin, which have antifungal and surfactant properties. Lipopeptide of the surfactin family are very potent biosurfactants with important applications for environmental remediation and chemical industries. In the present work, the complex production of lipopeptide (mostly surfactins) by B. velezensis 0G, was evaluated under different growth conditions using factorial design 23 with central and axial points. All experiments were carried out based on sustainable submerged fermentation containing sweet potato peels. The response surface trends demonstrate a maximum biosurfactant production at inoculum volume of 32 mL; combined broth volume of 46 mL, and incubation time of 24h. These observations were based on the analysis of supernatant by HPLC.

Numerical Investigation on Low-Salinity Augmented Microbial Flooding within a Sandstone Core for Enhanced Oil Recovery under Nonisothermal and pH Gradient Conditions

Summary In an era of increasing energy demand, declining oil fields, and fluctuating crude oil prices globally, most oil companies are looking forward to implementing cost-effective and environmentally sustainable enhanced oil recovery (EOR) techniques such as low salinity waterflooding (LSWF) and microbial EOR (MEOR). The present study numerically investigates the combined influence of simultaneous LSWF and microbial flooding for in-situ MEOR in tertiary mode within a sandstone core under spatiotemporally varying pH and temperature conditions. The developed black oil model consists of five major coupled submodels: nonlinear heat transport model; ion transport coupled with multiple ion exchange (MIE) involving uncomplexed cations and anions; pH variation with salinity and temperature; coupled reactive transport of injected substrates, Pseudomonas putida and produced biosurfactants with microbial maximum specific growth rate varying with temperature, salinity, and pH; relative permeability and fractional flow curve variations owing to interfacial tension (IFT) reduction and wettability alteration (WA) by LSWF and biofilm deposition. The governing equations are solved using finite difference technique. Operator splitting and bisection methods are adopted to solve the MIE-transport model. The present model is found to be numerically stable and agree well with previously published experimental and analytical results. In the proposed MIE-transport mechanism, decreasing injection water (IW) salinity from 2.52 to 0.32 M causes enhanced Ca2+ desorption rendering rock surface toward more water-wet. Consequently, oil relative permeability (kro) increases with >55% reduction in water fractional flow (fw) at water saturation of 0.5 from the initial oil-wet condition. Further reducing IW salinity to 0.03 M causes Ca2+ adsorption shifting the surface wettability toward more oil-wet, thus increasing fw by 52%. Formation water (FW) salinity showed minor impact on WA with <5% decrease in fw when FW salinity is reduced from 3.15 to 1.05 M. During low-salinity augmented microbial flooding (LSAMF), biosurfactant production is enhanced by >63% on reducing IW salinity from 2.52 to 0.32 M with negligible increase on further reducing IW and FW salinities. This might be owing to limiting nonisothermal condition (40 to 55°C), dispersion, sorption, and microbial decay. During LSAMF, maximum biosurfactant production occurs at microbial maximum specific growth rate of 0.53 h-1, mean fluid velocity of 2.63×10-3 m h-1 and initial oil saturation of 0.6, thus resulting in significant WA, increase in kro by >20%, and corresponding fw reduction by >84%. Moreover, the EOR efficiency of LSAMF is marginally impacted even on increasing the minimum attainable IFT by two orders of magnitude from 10-3 to 10-1 mN m-1. Though pH increased from 8.0 to 8.9, it showed minor impact on microbial metabolism. Formation damage owing to bioplugging observed near injection point causing increase in fw by ~26% can be mitigated by adopting suitable well-stimulation strategies during the LSAMF run time. The present study is a novel attempt to show synergistic effect of LSAMF over LSWF in enhancing oil mobility and recovery at core scale by simultaneously addressing complex crude oil-brine-rock (COBR) chemistry and critical thermodynamic parameters that govern MEOR efficiency within a typical sandstone formation. The present model with relatively lower computational cost and running time improves the predictive capability to preselect potential field candidates for successful LSAMF implementation.

Biosurfactant Production by Pseudomonas aeruginosa Strain LTR1 and its Application

On the circumstances of the growing market of biosurfactants all over the globe, the presented study focused on the characterization of biosurfactants produced by newly isolated and reported as biosurfactant producer strain Pseudomonas aeruginosa LTR1. Additionally, production media and physiological factors are optimized using a one factor at a time (OFAT) approach for maximum biosurfactant production. Its efficacy for antimicrobial and emulsification activities was determined. P. aeruginosa LTR1 utilized all the carbon sources provided, and a maximum of 9.5 g/L of biosurfactant was produced in soybean oil supplemented minimal salts medium (MSM). The critical micelle concentration (CMC) was determined as 12 mg/L and can reduce the surface tension of the medium from 72 mN/m to 31 mN/M. The biosurfactant was characterized by biochemical analysis and Fourier transform infrared spectroscopy (FTIR) and was not a protein in nature, possibly a glycolipid type of biosurfactant. It has shown the good emulsification activities for various hydrocarbon tested here. In addition, it acts as an antibiofilm agent with the minimum inhibitory concentration required for 50 % biofilms reduction was 30.95 µg/mL suggesting the antimicrobial potential. The biosurfactant produced by Pseudomonas aeruginosa strain LTR1 has shown good surface-active properties, good emulsification, and antimicrobial activities, demonstrating its potential for application in various areas like the oil industry, especially in tank cleaning, bioremediation of spills at sea or soil, and candidates as antimicrobial.

Effect of nutritional factors and growth conditions on biosurfactant production by Pseudomonas mendocina and Pseudomonas oleovorans isolated from oil contaminated soil in Jeddah city

Objectives: The current study aimed to investigate the impact of different nutritional factors and growth conditions on biosurfactant production by bacterial isolates (EMB16 and EMB21) isolated from oil-contaminated soil samples. Methods: Based on the used quantitative and qualitative screening method in current study, the selected bacterial isolates showed a high potential to produce biosurfactant. Results: By using 16S rRNA sequence analysis, the bacterial isolates EMB16 and EMB21 were found to be closely related to Pseudomonas mendocina and Pseudomonas oleovorans, respectively. The ultimate yields of biosurfactant (8.06±0.06 mg/ml) by Ps. mendocina EMB16 was with corn oil as a carbon source, urea as a nitrogen source, C/N ratio of 30, pH value of 7, and 2% inoculum size. For Ps. oleovorans EMB21, the maximum biosurfactant production (4.68±0.14mg/ml) was achieved by diesel oil as a carbon source, urea as a nitrogen source, C/N ratio of 30, pH of 7, and 5% size of inoculum. The best incubation period and temperature for the examined strains was 168 hrs. at 37℃. Conclusion: The results proved that Ps. mendocina EMB16 was the most efficient biosurfactant producer as it showed the greatest amount of biosurfactant concentration and lowestvalue of surface tension measurement with an emulsification index of 67±6%.

Production and characterisation of a biosurfactant based on Acinetobacter sp. V2 and its potential use for environmental applications

ABSTRACT Maximum biosurfactant production was achieved in an optimised process containing pH 8 and 30°C, with waste coconut oil and ammonium sulphate at carbon-to-nitrogen ratio of 1:7. The structural composition of Acinetobacter sp. V2 biosurfactant was polymeric, consisting of a protein complex and a fatty acid. This biosurfactant exhibited stability to different pH and temperature conditions. The emulsifying property was affected by changes in NaCl concentration. The V2 biosurfactant was effective in removing heavy metals present in acid mine drainage effluents and contaminated vegetables.

Optimization of process inputs for the synthesis of waste rice bran oil isolated Pseudomonas aeruginosa MTCC 424 biosurfactant using response surface methodology for oil recovery applications

In this current study, the process variables i.e., the concentration of RBO (2–4%), pH (4–10), and incubation time (4–11 days) for the preparation of rhamnolipid biosurfactant based on Pseudomonas aeruginosa MTCC 424 and rice bran oil (RBO) were analyzed using response surface methodology-central composite design (RSM-CCD). At 5.02% of RBO, 7.3 pH, and 9.5 days of incubation time, maximum biosurfactant production was achieved. The process parameter was strongly affected by RBO, followed by the marginal effect of time and pH of incubation. The optimized biosurfactant was further analyzed using various techniques viz. surface tension measurement, Fourier transform infrared spectroscopy (FTIR), emulsifying ability test and oil displacement technique. As compared to synthetic chemical surfactant, the lower critical micelle concentration (CMC) (28.5 mN/m), impressive oil-free zone displacement (17.26 ± 0.18 cm2) and benchmark emulsifying ability demonstrated the perfect use of the biosurfactant for oil recovery applications.

Evaluation of biosurfactant production potential of Lysinibacillus fusiformis MK559526 isolated from automobile-mechanic-workshop soil.

Biosurfactants are amphipathic biological compounds with surface active potential and are produced by many microorganisms.Biosurfactant production by Lysinibacillus fusiformis MK559526 isolated from automobile-mechanic-shop soil was investigated with a view to assessing itspotential for production and potential for optimization. Effects of carbon and nitrogen sources, pH, temperature and incubationperiods on biosurfactant production were evaluated with a view to optimizing the processes. Fourier Transform Infra-Red absorption peaks and Gaschromatography mass spectrometry were used to determine the functional groups of the chemical make-up and the chemical profile of the biosurfactantrespectively. Lysinibacillus fusiformis surfactant had emulsification index of 65.15 ± 0.35 %, oil displacement of 2.7 ± 0.26 mm, zone ofhaemolysis of 7.3 ± 0.16 mm and a positive drop collapse test. Optimized culture conditions for biosurfactant production: temperature, 35 ºC; pH, 7.0;starch solution, 40 g/L and urea, 1.5 g/L showed a reduction in surface tension to 28.46 ± 1.11 mN/m and increased emulsification index to 93.80 ± 0.41 %.Maximum biosurfactant production of 2.92 ± 0.04 g/L was obtained after 72 h. The biosurfactant contained peptides and fatty acids. The predominant fattyacid was 9-Octadecenoic acid (80.80%). The above results showing high emulsification potential and remarkable reduction in the surfacetension are good biosurfactant attributes. Consequently, Lysinibacillus fusiformis MK559526 is a good candidate for biosurfactant production.

Use of Natural Wastes for Biosurfactant (BS) and Bioemulsifier (BE) Production and their Applications – A Review

Commercial biosurfactant (BS) or bioemulsifier (BE) production requires high manufacturing cost and result difficulties in downstream processing and purification. This problem can be resolved by using low- cost natural substrates. Agro- industrial wastes as well as non-edible portions of fruits, vegetables, fish and meat contributes in high disposal and loss of nutritional biomass from the environment. These are readily available wastes which have tremendous potential to be reused as a substrate by microorganisms for efficient BS or BE production. Fruits, vegetables, fish, dairy and brewery wastes are rich sources of valuable nutrients which includes carbon, nitrogen, vitamins and other minerals. BS or BE produced using these substrates are stable in environment and show potential applications in many sectors of food industry, oil industry, agriculture, bioremediation, medicine and pharmaceutical industry. Yield of biosurfactant or bioemulsifier production can be increased by optimizing certain media parameters with the natural substrate concentrations. Growth parameters such as pH, temperature, salinity, carbon and nitrogen content have effect on stability of microorganism for maximum biosurfactant or bioemulsifier production. This review describes some recent developments and applications for the commercial biosurfactant or bioemulsifier production using cheap and unconventional natural wastes.

Optimization of biosurfactant production from Pseudomonas sp. CQ2 and its application for remediation of heavy metal contaminated soil

The present study was conducted to enhance the biosurfactant production yield of Pseudomonas sp. CQ2 isolated from the Chongqing oilfield (China). Besides, the capability of biosurfactant and underlying mechanism for remediation of heavy metal contaminated soil was also investigated. Our results suggested that maximum biosurfactant production (40.7 g/L) was attained at 35 °C by using soybean oil and ammonium nitrate as carbon and nitrogen sources with pH 7, rotational speed of 175 rpm and inoculation ratio of 3%). The removal efficiencies of 78.7, 65.7 and 56.9% for Cd, Cu and Pb respectively were achieved at optimized bioleaching conditions (pH: 11, soil/solution ratio: 30:1 and non-sterilized soil), comparative tests between common chemical surfactants (SDS, Tween-80) and biosurfactants demonstrated the larger removal capacity of biosurfactants. Through SEM-EDX, it was found that the granular material disappeared, the content of Cd, Cu and Pb decreased significantly, and the soil surface became smooth with hole formation after soil washing following bioleaching. ATR-FTIR results showed that the carboxyl functional groups in biosurfactants could chelate heavy metals. These results indicated that biosurfactants from Pseudomonas sp. CQ2 could effectively eliminate Cd, Cu, and Pb from soil.

Biosurfactant production and engine oil degradation by marine halotolerant Bacillus licheniformis LRK1

Abstract In this study, a halotolerant marine bacterium Bacillus licheniformis LRK1 was studied to check its biosurfactant production potential. In substrate utilization study, the isolate was able to utilize 58 substrates out of 95 substrates studied. Biosurfactant production by the isolate was studied using various screening methods. It showed Emulsification Index (EI24) of 70% and 31.43% reduction in surface tension. Column purified biosurfactant was analyzed by Thin Layer Chromatography (TLC) and Fourier-transform Infrared Spectroscopy (FTIR) which confirmed the nature of the produced biosurfactant as lipopeptide. The maximum biosurfactant production was achieved at neutral pH, incubation temperature of 35 ± 2 °C and salinity concentration of 3% w/v. The gravimetric method showed 24.23% degradation of engine oil by the isolate after 21 days of incubation. The degradation was further confirmed by Gas Chromatography (GC) and High-performance Thin Layer Chromatography (HPTLC) analysis. This indicates that strain possesses great potential in the field of bioremediation of oil pollution in the marine environment.

Optimization of biosurfactant production from chemically mutated strain of Bacillus subtilis using waste automobile oil as low-cost substrate

In this study, we have evaluated biosurfactant production potential of locally isolated strain of Bacillus subtilis (accession # KX788864) using waste automobile oil as cost-effective substrate with waste-to-value nexus. The wild strain of B. subtilis yielded 2.1 g/L biosurfactant, showed 42% emulsification index, and 38.27 cm2 of total oil displacement. The ethidium bromide (EtBr) mutagenesis was performed by exposing native B. subtilis strain with varying concentrations of EtBr (50, 100, 150 and 200 µg/10 mL) for different time intervals of 30, 60 and 90 min. Significantly higher yield (4.2 g/L) was attained from B. subtilis MS1 exposed to EtBr (50 µg/10 mL) for 60 min confirming the positive effect of mutagenesis. The mutated strain (B. subtilis MS1) showed improved emulsification index (50.53%) and oil displacement (49.32 cm2). Fourier-transform infrared (FTIR) spectroscopy analysis of biosurfactant produced from mutated strain (B. subtilis MS1) confirmed the lipopeptide nature of biosurfactant due to the existence of amide, amine and phospholipids functional groups. The maximum surfactant yielding mutant was proceeded for optimization using response surface methodology (RSM) technique and the interaction effect of different parameters was studied that allow biosurfactant hyperproduction. After optimization, maximum biosurfactant (4.7 g/L) was obtained at pH 7, temperature 35 °C, inoculum size 3 mL and an overall incubation of 120 h. In conclusion, the economical production of biosurfactant, along with novel functional properties (i.e., oil/hydrocarbon recovery and emulsification properties), this research may be valuable for numerous bioremediation and industrial biotechnological applications.

Improved Biosurfactant Production by Enterobacter cloacae B14, Stability Studies, and its Antimicrobial Activity.

This work aimed to optimize carbon and nitrogen sources for the growth of Enterobacter cloacae B14 and its biosurfactant (BS) production via One-Variable-At-a-Time (OVAT) method. The BS stability under a range of pH and temperatures was assessed. Antimicrobial activity against Gram-positive and Gram-negative pathogens was determined by the agar well diffusion method. The results showed that the optimum carbon and nitrogen sources for BS production were maltose and yeast extract, respectively, with a maximum BS yield of (39.8 ± 5.2) mg BS/g biomass. The highest emulsification activity (E24) was 79%, which is significantly higher than in the previous studies. We found that B14 BS can withstand a wide range of pH values from 2 to10. It could also function under a range of temperatures from 30–37°C. Thin Layer Chromatography (TLC) and Fourier Transform Infrared Spectrometry (FTIR) analysis confirmed that B14 BS is a glycolipid-like compound, which is rarely found in Enterobacter spp. Cell-free broth showed inhibition against various pathogens, preferable to Gram-positive ones. It had better antimicrobial activity against Bacillus subtilis than a commonly-used antibiotic, tetracycline. Furthermore, B14 broth could inhibit the growth of a tetracycline-resistant Serratia marcescens. Our results showed promising B14 BS applications not only for bioremediation but also for the production of antimicrobial products.

Process parameters for biosurfactant production using yeast Meyerozyma guilliermondii YK32.

Microbially produced biosurfactants are fast catching up due to their environment-friendly approach over chemical surfactants. But their commercial production is restricted due to poor economy of the production process which could be improved by using high yielding microbial strains and optimizing the process parameters. The present research was directed to optimize the biosurfactant production monitored in terms of oil displacement and emulsification (E24) index, using a promising yeast Meyerozyma guilliermondii YK32. Maximum oil displacement equaling 7.5 cm was obtained with olive oil at 8% (v/v) concentration as carbon source under shaking conditions (150 rpm). Diesel being a complex hydrocarbon was not utilized easily by yeast and showed poor biosurfactant production. Yeast extract at 1.5% (w/v) concentration yielded maximum biosurfactant as evident from maximum oil displacement and E24 index equal to 8.1 cm and 52.6%, respectively. Sodium chloride at the rate of 3% (w/v) supported maximum oil displacement (8.8 cm) using the production broth containing optimized carbon and nitrogen sources. Any increase beyond this level negatively influenced the biosurfactant production. The yield was at its maximum at 30 °C as a shift in temperature either to 35 °C or 25 °C decreased the oil displacement from 8.8 to 5.2 or 7.6 cm, respectively. At 40 °C, oil displacement was decreased to 2.5 cm. Biosurfactant production appeared to be sensitive to varying pH as evident from the E24 index as high as 67.3% at pH 6.0 as compared with 60.2%, 60.1%, and 52.4% at pH 5.0, 5.5, and 7.0, respectively. Yeast biomass yield equivalent to 10.3 g/L and 8.3 g/L was recorded at pH 6 and 7, respectively, during the production process. Elimination of shaking reduced the E24 index from 67.3 to 34.8% under optimized conditions.

Biodegradation process of crude oil and bioemulsifier activity by a bacterial consortium culture

This study reports the analysis of biosurfactant production by a bacterial consortium culture (CC) during biodegradation of crude oil. The ability of CC (5% v/v), grown in Minimal Medium (MM) added with 1% (v/v) Tapis crude oil, to produce biosurfactant under different incubation times (0, 2, 4, 6 and 8 week) was investigated. Biosurfactant activity was estimated by water surface tension changes and emulsification index (E24). Maximum biosurfactant production was observed at 2 weeks incubation period, after which the yield gradually decreased. The biosurfactant produced by the CC significantly decreased the surface tension of water from 72 dynes/cm to 52 dynes/cm (p < 0.05) at week 4. Emulsification test indicated that this biosurfactant effectively emulsified the crude oil with an emulsification index (E24) of 85% (p < 0.05). This is significantly better (p < 0.05) when compared to other chemical surfactants tested namely SDS (53.3%), Tween-20 (50.8%) and Triton X-100 (55%). These results indicate the capability of CC to produce biosurfactant during crude oil degradation and this can be exploited for enhanced bioremediation in oil contaminated areas.

STATISTICAL OPTIMIZATION OF MEDIUM COMPONENTS FOR BIOSURFACTANT PRODUCTION BY ACHROMOBACTER XYLOS GSR21

Introduction: Biosurfactants have picked up an impressive consideration as of late due to their potential uses in an expansive scope of use territories, including environmental remediation, agriculture, biofilm formation, quorum sensing, textile, pharmaceuticals, cosmetics, and the food, oil, and petrochemical industries. Aim: In the present study, optimization of the critical medium components for biosurfactant production by Achromobacter xylos strain GSR21 using statistical experimental design was studied. Materials and Methods: Response surface methodology (RSM) was employed to determine the optimal level of the four medium variables (agar powder, yeast extract, FeSO47H2O, and KH2PO4). Central composite design of RSM was applied to study the four variables at five levels, and biosurfactant concentration was measured as a response. Results: Regression coefficients were calculated by regression analysis and the model equation was determined. R2 value for biosurfactant (g/L) was calculated as 72%, and it indicates that the model was well fitted with the experimental results. Surface plots were made, and the maximum biosurfactant production (A. xylos strain GSR21) (10.20 g/L) was predicted at the optimized values of agar powder 90 g/L, yeast extract 5 g/L, FeSO47H2O 0.05 g/L, and KH2PO4 0.15 g/L. The obtained mathematical model was verified by performing the experiment with the predicted optimized values, and the yield of bio-surfactant was found to be 9.69 g/L. Validation of the predicted model was fitted 96.9% with the experimental results conducted at the optimum conditions. Conclusion: Results of this statistical analysis showed that agar powder and yeast extract had found significant medium components for biosurfactant (A. xylos GSR21) production.

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.