Statistical approach to optimize production of biosurfactant by Pseudomonas aeruginosa 2297.
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ABSTRACT:
SUBMITTER: Kumar AP
PROVIDER: S-EPMC4327757 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The opportunistic human pathogen Pseudomonas aeruginosa produces a variety of virulence factors, including exotoxin A, elastase, alkaline protease, alginate, phospholipases, and extracellular rhamnolipids. The previously characterized rhlABR gene cluster encodes a regulatory protein (RhlR) and a rhamnosyltransferase (RhlAB), both of which are required for rhamnolipid synthesis. Another gene, rhII, has now been identified downstream of the rhlABR gene cluster. The putative RhlI protein shares significant sequence similarity with bacterial autoinducer synthetases of the LuxI type. A P. aeruginosa rhlI mutant strain carrying a disrupted rhlI gene was unable to produce rhamnolipids and lacked rhamnosyltransferase activity. Rhamnolipid synthesis was restored by introducing a wild-type rhlI gene into such strains or, alternatively, by adding either the cell-free spent supernatant from a P. aeruginosa wild-type strain or synthetic N-acylhomoserine lactones. Half-maximal induction of rhamnolipid synthesis in the rhlI mutant strain required 0.5 microM N-butyrylhomoserine lactone or 10 microM N-(3-oxohexanoyl)homoserine lactone. The P. aeruginosa rhlA promoter was active in the heterologous host Pseudomonas putida when both the rhlR and rhlI genes were present or when the rhlR gene alone was supplied together with synthetic N-acylhomoserine lactones. The RhlR-RhlI regulatory system was found to be essential for the production of elastase as well, and cross-communication between the RhlR-RhlI rhamnolipid regulatory system and the LasR-LasI elastase regulatory system was demonstrated.
| S-EPMC41530 | biostudies-other
Project description:Tea is an ancient non-alcoholic beverage plantation crop cultivated in the most part of Assam, India. Being a long-term monoculture, tea plants are prone to both biotic and abiotic stresses, and requires massive amounts of chemicals as fertilizers and pesticides to achieve worthy crop productivity. The rhizosphere bacteria with the abilities to produce phytohormone, secreting hydrolytic enzyme, biofilm formation, bio-control activity provides induced systemic resistance to plants against pathogens. Thus, plant growth promoting (PGP) rhizobacteria represents as an alternative candidate to chemical inputs for agriculture sector. Further, deciphering the secondary metabolites, including biosurfactant (BS) allow developing a better understanding of rhizobacterial strains. The acidic nature of tea rhizosphere is predominated by Bacillus followed by Pseudomonas that enhances crop biomass and yield through accelerating uptake of nutrients. In the present study, a strain Pseudomonas aeruginosa RTE4 isolated from tea rhizosphere soil collected from Rosekandy Tea Garden, Cachar, Assam was evaluated for various plant-growth promoting attributes. The strain RTE4 produces indole acetic acid (74.54 μg/ml), hydrolytic enzymes, and solubilize tri-calcium phosphate (46 μg/ml). Bio-control activity of RTE4 was recorded against two foliar fungal pathogens of tea (Corticium invisium and Fusarium solani) and a bacterial plant pathogen (Xanthomonas campestris). The strain RTE4 was positive for BS production in the preliminary screening. Detailed analytical characterization through TLC, FTIR, NMR, and LCMS techniques revealed that the strain RTE4 grown in M9 medium with glucose (2% w/v) produce di-rhamnolipid BS. This BS reduced surface tension of phosphate buffer saline from 71 to 31 mN/m with a critical micelle concentration of 80 mg/L. Purified BS of RTE4 showed minimum inhibitory concentration of 5, 10, and 20 mg/ml against X. campestris, F. solani and C. invisium, respectively. Capability of RTE4 BS to be employed as a biofungicide as compared to Carbendazim - commercially available fungicide is also tested. The strain RTE4 exhibits multiple PGP attributes along with production of di-rhamnolipid BS. This gives a possibility to produce di-rhamnolipid BS from RTE4 in large scale and explore its applications in fields as a biological alternative to chemical fertilizer.
| S-EPMC7403194 | biostudies-literature
Project description: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.
| S-EPMC8421616 | biostudies-literature
Project description:A mutant strain (65E12) of Pseudomonas aeruginosa that is unable to produce rhamnolipid biosurfactants and lacks rhamnosyltransferase activity was genetically complemented by using a P. aeruginosa PG201 wild-type gene library. A single complementing cosmid was isolated on the basis of surface tension measurements of subcultures of the transconjugants by using a sib selection strategy. The subcloning of the complementing cosmid clone yielded a 2-kb fragment capable of restoring rhamnolipid biosynthesis, rhamnosyltransferase activity, and utilization of hexadecane as a C source in mutant 65E12. The nucleotide sequence of the complementing 2-kb fragment was determined, and a single open reading frame (rhlR) of 723 bp specifying a putative 28-kDa protein (RhlR) was identified. Sequence homologies between the RhlR protein and some regulatory proteins such as LasR of P. aeruginosa, LuxR of Vibrio fischeri, RhiR of Rhizobium leguminosarum, and the putative activator 28-kDa UvrC of Escherichia coli suggest that the RhlR protein is a transcriptional activator. A putative target promoter which is regulated by the RhlR protein has been identified 2.5 kb upstream of the rhlR gene. Multiple plasmid-based rhlR gene copies had a stimulating effect on the growth of the P. aeruginosa wild-type strain in hexadecane-containing minimal medium, on rhamnolipid production, and on the production of pyocyanin chromophores. Disruption of the P. aeruginosa wild-type rhlR locus led to rhamnolipid-deficient mutant strains, thus confirming directly that this gene is necessary for rhamnolipid biosynthesis. Additionally, such PG201::'rhlR' mutant strains lacked elastase activity, indicating that the RhlR protein is a pleiotropic regulator.
| S-EPMC205310 | biostudies-other
Project description:The effect of low-concentrations of monorhamnolipid biosurfactant on transport of Pseudomonas aeruginosa ATCC 9027 in natural porous media (silica sand and a sandy soil) was studied with miscible-displacement experiments using artificial groundwater as the background solution. Transport of two types of cells was investigated, glucose- and hexadecane-grown cells with lower and higher cell surface hydrophobicity (CSH), respectively. The effect of hexadecane presence as a residual non-aqueous phase liquid (NAPLs) on transport was also examined. A clean-bed colloid deposition model was used to calculate deposition rate coefficients (k) for quantitative assessment. Significant cell retention was observed in the sand (81% and 82% for glucose- and hexadecane-grown cells, respectively). Addition of a low-concentration rhamnolipid solution enhanced cell transport, with 40 mg/L of rhamnolipid reducing retention to 50% and 60% for glucose- and hexadecane-grown cells, respectively. The k values for both glucose- and hexadecane-grown cells correlate linearly with rhamnolipid-dependent CSH represented as bacterial-adhesion-to-hydrocarbon rate of cells. Retention of cells by the soil was nearly complete (>99%). Addition of 40 mg/L rhamnolipid solution reduced retention to 95%. The presence of NAPLs in the sand increased the retention of hexadecane-grown cells with higher CSH. Transport of cells in the presence of the NAPL was enhanced by rhamnolipid at all concentrations tested, and the relative enhancement was greater than in was in the absence of NAPL. This study shows the importance of hydrophobic interaction on bacterial transport in natural porous media and the potential of using low-concentration rhamnolipid for facilitating the transport in subsurface for bioaugmentation efforts.
| S-EPMC5607479 | biostudies-literature
Project description:There has been growing interest in disrupting bacterial virulence mechanisms as a form of infectious disease control through the use of 'anti-infective' drugs. Pseudomonas aeruginosa is an opportunistic pathogen noted for its intrinsic antibiotic resistance that causes serious infections requiring new therapeutic options. In this study, an analysis of the P. aeruginosa PAO1 deduced proteome was performed to identify pathogen-associated proteins. A computational screening approach was then used to discover drug repurposing opportunities, i.e. identifying approved drugs that bind and potentially disrupt the pathogen-associated protein targets. The selective oestrogen receptor modulator raloxifene, a drug currently used in the prevention of osteoporosis and/or invasive breast cancer in post-menopausal women, was predicted from this screen to bind P. aeruginosa PhzB2. PhzB2 is involved in production of the blue pigment pyocyanin produced via the phenazine biosynthesis pathway. Pyocyanin is toxic to eukaryotic cells and has been shown to play a role in infection in a mouse model, making it an attractive target for anti-infective drug discovery. Raloxifene was found to strongly attenuate P. aeruginosa virulence in a Caenorhabditis elegans model of infection. Treatment of P. aeruginosa wild-type strains PAO1 and PA14 with raloxifene resulted in a dose-dependent reduction in pyocyanin production in vitro; pyocyanin production and virulence were also reduced for a phzB2 insertion mutant. These results suggest that raloxifene may be suitable for further development as a therapeutic for P. aeruginosa infection and that such already approved drugs may be computationally screened and potentially repurposed as novel anti-infective/anti-virulence agents.
| S-EPMC5511546 | biostudies-literature
Project description:BACKGROUND:Rhamnolipids are the most extensively studied biosurfactants and has been successfully used in various areas from bioremediation to industrial fields. Rhamnolipids structural composition decide their physicochemical properties. Different physicochemical properties influence their application potential. Rhamnolipids can be produced at both aerobic conditions and anaerobic conditions by Pseudomonas aeruginosa. This study aims to evaluate the oxygen effects on the rhamnolipids yield, structural composition, physicochemical properties and the rhl-genes expression in P. aeruginosa SG. Results will guide researchers to regulate microbial cells to synthesize rhamnolipids with different activity according to diverse application requirements. RESULTS:Quantitative real-time PCR analysis revealed that rhlAB genes were down-regulated under anaerobic conditions. Therefore, strain P. aeruginosa SG anaerobically produced less rhamnolipids (0.68 g/L) than that (11.65 g/L) under aerobic conditions when grown in media containing glycerol and nitrate. HPLC-MS analysis showed that aerobically produced rhamnolipids mainly contained Rha-C8-C10, Rha-Rha-C10-C12:1 and Rha-Rha-C8-C10; anaerobically produced rhamnolipids mainly contained Rha-C10-C12 and Rha-C10-C10. Anaerobically produced rhamnolipids contained more mono-rhamnolipids (94.7%) than that (54.8%) in aerobically produced rhamnolipids. rhlC gene was also down-regulated under anaerobic conditions, catalyzing less mono-rhamnolipids to form di-rhamnolipids. Aerobically produced rhamnolipids decreased air-water surface tension (ST) from 72.2 to 27.9 mN/m with critical micelle concentration (CMC) of 60 mg/L; anaerobically produced rhamnolipids reduced ST to 33.1 mN/m with CMC of 80 mg/L. Anaerobically produced rhamnolipids emulsified crude oil with EI24 = 80.3%, and aerobically produced rhamnolipids emulsified crude oil with EI24 = 62.3%. Both two rhamnolipids products retained surface activity (ST < 35.0 mN/m) and emulsifying activity (EI24 > 60.0%) under temperatures (4-121 °C), pH values (4-10) and NaCl concentrations less than 90 g/L. CONCLUSIONS:Oxygen affected the rhl-genes expression in P. aeruginosa, thus altering the rhamnolipids yield, structural composition and physicochemical properties. Rhamnolipids produced at aerobic or anaerobic conditions was structurally distinct. Two rhamnolipids products had different application potential in diverse biotechnologies. Although both rhamnolipids products were thermo-stable and halo-tolerant, aerobically produced rhamnolipids possessed better surface activity, implying its well wetting activity and desorption property; anaerobically produced rhamnolipids exhibited better emulsifying activity, indicating its applicability for enhanced oil recovery and bioremediation of petroleum pollution.
| S-EPMC5844106 | biostudies-literature
Project description:In this study, we sought to investigate the production and optimization of biosurfactants by soil fungi isolated from petroleum oil-contaminated soil in Saudi Arabia. Forty-four fungal isolates were isolated from ten petroleum oil-contaminated soil samples. All isolates were identified using the internal transcribed spacer (ITS) region, and biosurfactant screening showed that thirty-nine of the isolates were positive. Aspergillus niger SA1 was the highest biosurfactant producer, demonstrating surface tension, drop collapsing, oil displacement, and an emulsification index (E24) of 35.8 mN/m, 0.55 cm, 6.7 cm, and 70%, respectively. This isolate was therefore selected for biosurfactant optimization using the Fit Group model. The biosurfactant yield was increased 1.22 times higher than in the nonoptimized medium (8.02 g/l) under conditions of pH 6, temperature 35°C, waste frying oil (5.5 g), agitation rate of 200 rpm, and an incubation period of 7 days. Model significance and fitness analysis had an RMSE score of 0.852 and a p-value of 0.0016. The biosurfactant activities were surface tension (35.8 mN/m), drop collapsing (0.7 cm), oil displacement (4.5 cm), and E24 (65.0%). The time course of biosurfactant production was a growth-associated phase. The main outputs of the mathematical model for biomass yield were Yx/s (1.18), and μmax (0.0306) for biosurfactant yield was Yp/s (1.87) and Yp/x (2.51); for waste frying oil consumption the So was 55 g/l, and Ke was 2.56. To verify the model's accuracy, percentage errors between biomass and biosurfactant yields were determined by experimental work and calculated using model equations. The average error of biomass yield was 2.68%, and the average error percentage of biosurfactant yield was 3.39%.
| S-EPMC10580895 | biostudies-literature
Project description:Heavy vacuum gas oil (HVGO) is a complex and viscous hydrocarbon stream that is produced as the bottom side product from the vacuum distillation units in petroleum refineries. HVGO is conventionally treated with thermochemical process, which is costly and environmentally polluting. Here, we investigate two petroleum biotechnology applications, namely valorization and bioupgrading, as green approaches for valorization and upgrading of HVGO. The Pseudomonas aeruginosa AK6U strain grew on 20% v/v of HVGO as a sole carbon and sulfur source. It produced rhamnolipid biosurfactants in a growth-associated mode with a maximum crude biosurfactants yield of 10.1 g l-1 , which reduced the surface tension of the cell-free culture supernatant to 30.6 mN m-1 within 1 week of incubation. The rarely occurring dirhamnolipid Rha-Rha-C12 -C12 dominated the congeners' profile of the biosurfactants produced from HVGO. Heavy vacuum gas oil was recovered from the cultures and abiotic controls and the maltene fraction was extracted for further analysis. Fractional distillation (SimDist) of the biotreated maltene fraction showed a relative decrease in the high-boiling heavy fuel fraction (BP 426-565 °C) concomitant with increase in the lighter distillate diesel fraction (BP 315-426 °C). Analysis of the maltene fraction revealed compositional changes. The number-average (Mn) and weight-average (Mw) molecular weights, as well as the absolute number of hydrocarbons and sulfur heterocycles were higher in the biotreated maltene fraction of HVGO. These findings suggest that HVGO can be potentially exploited as a carbon-rich substrate for production of the high-value biosurfactants by P. aeruginosa AK6U and to concomitantly improve/upgrade its chemical composition.
| S-EPMC5658591 | biostudies-literature
Project description:Rhamnolipids are extensively studied biosurfactants due to their potential in many industrial applications, eco-friendly production and properties. However, their availability for broader application is severely limited by their production costs, therefore the optimization of efficacy of their cultivation gains significance as well as the information regarding the physio-chemical properties of rhamnolipids resulting from various cultivation strategies. In this work, the bioprocess design focused on optimization of the rhamnolipid yield of Pseudomonas aeruginosa DBM 3774 utilizing the response surface methodology (RSM). Six carbon sources were investigated for their effect on the rhamnolipid production. The RSM prediction improved the total rhamnolipid yield from 2.2 to 13.5 g/L and the rhamnolipid productivity from 11.6 to 45.3 mg/L/h. A significant effect of the carbon source type, concentration and the C/N ratio on the composition of the rhamnolipid congeners has been demonstrated for cultivation of P. aeruginosa DBM 3774 in batch cultivation. Especially, changes in presence of saturated fatty acid in the rhamnolipid congeners, ranging from 18.8% of unsaturated fatty acids (carbon source glycerol; 40 g/L) to 0% (sodium citrate 20 g/L) were observed. This demonstrates possibilities of model based systems as basis in cultivation of industrially important compounds like biosurfactants rhamnolipids and the importance of detailed study of interconnection between cultivation conditions and rhamnolipid mixture composition and properties.
| S-EPMC9321515 | biostudies-literature