Enzymatic degradation of Congo Red by turnip (Brassica rapa) peroxidase.

Pas de DOI. Info bibliogr : http://www.znaturforsch.com/ac/v67c/67c0429.pdfInternational audienceThe enzyme peroxidase is known for its capacity to remove phenolic compounds and aromatic amines from aqueous solutions and also to decolourize textile effluents. This study aims at evaluating the potential of a turnip (Brassica rapa) peroxidase (TP) preparation in the discolouration of textile azo dyes and effluents. An azo dye, Congo Red (CR), was used as a model pollutant for treatment by the enzyme. The effects of various operating conditions like pH value, temperature, initial dye and hydrogen peroxide concentrations, contact time, and enzyme concentration were evaluated. The optimal conditions for maximal colour removal were at pH 2.0, 40 degrees C, 50 mM hydrogen peroxide, 50 mg/l CR dye, and TP activity of 0.45 U/ml within 10 min of incubation time. Analysis of the by-products from the enzymatic treatment by UV-Vis and IR spectroscopy showed no residual compounds in the aqueous phase and a precipitate of polymeric nature

New Insight into the Influence of Rhamnolipid Bio-Surfactant on the Carbonate Rock/Water/Oil Interaction at Elevated Temperature

Tertiary recovery is directly dependent on the alteration in wettability and interfacial tension (IFT), hence releasing the trapped oil from rock pore spaces. Bio-surfactant water flooding to mobilise residual oil in reservoirs is a new and developing prospect that can be used more often in future due to its environmentally friendly nature and economic advantages. In this work, the impact of rhamnolipids as water soluble bio-surfactant solutions on the interfacial activities of saline water and the wettability of carbonate rock are studied at elevated temperature. The effectiveness of the bio-surfactant as a rock wettability modifier is analysed in the presence of different salinities, in particular SO42− ions. The reason for the focus on SO42− is its high affinity towards calcite surfaces, and hence its ability to intervene strongly on bio-surfactant performance. To achieve the objectives of this study, the oil-wet calcite samples at elevated temperature were put through a washing process that included bio-surfactant solutions in seawater at various concentrations of sodium sulphate ions, where the measurement of the contact angles of each sample after treatment and the IFT between the oil model and the washing solutions were taken. The obtained results illustrated that bio-surfactants (rhamnolipids) with incremental concentrations of SO42− ions in sea water (up to three times higher than the original ion concentration) can lower the IFT, and assessed changing the rocks towards greater water-wettability. This study reveals that the alteration of SO42− ions had a greater impact on the wettability alteration, whereas rhamnolipids were better at reducing the IFT between the oil phase and the aqueous phase. This study also looked at temperatures of 50 °C and 70 °C, which demonstrated undesired influences on the wettability and IFT. Bio-surfactants at high temperature showed less interfacial activity, thus indicating that rhamnolipids are not active at high temperatures, while the addition of SO42− shows a continuous decrease in the contact angle and IFT measurements at high temperature

Novel Application of Cyclolipopeptide Amphisin: Feasibility Study as Additive to Remediate Polycyclic Aromatic Hydrocarbon (PAH) Contaminated Sediments

To decontaminate dredged harbor sediments by bioremediation or electromigration processes, adding biosurfactants could enhance the bioavailability or mobility of contaminants in an aqueous phase. Pure amphisin from Pseudomonas fluorescens DSS73 displays increased effectiveness in releasing polycyclic aromatic hydrocarbons (PAHs) strongly adsorbed to sediments when compared to a synthetic anionic surfactant. Amphisin production by the bacteria in the natural environment was also considered. DSS73’s growth is weakened by three model PAHs above saturation, but amphisin is still produced. Estuarine water feeding the dredged material disposal site of a Norman harbor (France) allows both P. fluorescens DSS73 growth and amphisin production

Cost effective technologies and renewable substrates for biosurfactants’ production

Diverse types of microbial surface-active amphiphilic molecules are produced by a range of microbial communities. The extraordinary properties of biosurfactant / bioemulsifier (BS/BE) as surface active products allows them to have key roles in various field of applications such as bioremediation, biodegradation, enhanced oil recovery, pharmaceutics, food processing among many others. This leads to a vast number of potential applications of these BS/BE in different industrial sectors. Despite the huge number of reports and patents describing BS and BE applications and advantages, commercialization of these compounds remain difficult, costly and to a large extent irregular. This is mainly due to the usage of chemically synthesized media for growing producing microorganism and in turn the production of preferred quality products. It is important to note that although a number of developments have taken place in the field of biosurfactant industries, large scale production remains economically challenging for many types of these products. This is mainly due to the huge monetary difference between the investment and achievable productivity from the commercial point of view. This review discusses low cost, renewable raw substrates and fermentation technology in BS/BE production processes and their role in reducing the production cost

Rhamnolipids: diversity of structures, microbial origins and roles

Rhamnolipids are glycolipidic biosurfactants produced by various bacterial species. They were initially found as exoproducts of the opportunistic pathogen Pseudomonas aeruginosa and described as a mixture of four congeners: α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-Rha-C10-C10), α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β-hydroxydecanoate (Rha-Rha-C10), as well as their mono-rhamnolipid congeners Rha-C10-C10 and Rha-C10. The development of more sensitive analytical techniques has lead to the further discovery of a wide diversity of rhamnolipid congeners and homologues (about 60) that are produced at different concentrations by various Pseudomonas species and by bacteria belonging to other families, classes, or even phyla. For example, various Burkholderia species have been shown to produce rhamnolipids that have longer alkyl chains than those produced by P. aeruginosa. In P. aeruginosa, three genes, carried on two distinct operons, code for the enzymes responsible for the final steps of rhamnolipid synthesis: one operon carries the rhlAB genes and the other rhlC. Genes highly similar to rhlA, rhlB, and rhlC have also been found in various Burkholderia species but grouped within one putative operon, and they have been shown to be required for rhamnolipid production as well. The exact physiological function of these secondary metabolites is still unclear. Most identified activities are derived from the surface activity, wetting ability, detergency, and other amphipathic-related properties of these molecules. Indeed, rhamnolipids promote the uptake and biodegradation of poorly soluble substrates, act as immune modulators and virulence factors, have antimicrobial activities, and are involved in surface motility and in bacterial biofilm development

Isolation and screening of Bacillus subtilis MJ01 for MEOR application: biosurfactant characterization, production optimization and wetting effect on carbonate surfaces

Abstract The bacterial strain MJ01 was isolated from stock tank water of one of the Iranian south oil field production facilities. The 16S rRNA gene of isolate, MJ01, showed 99% similarity to Bacillus subtilis. The results revealed that biosurfactant produced by this strain was lipopeptide-like surfactin based on FTIR analysis. Critical micelle concentration of produced surfactin in distilled water was 0.06 g/l. Wettability study showed that at zero salinity surfactin can change original oil-wet state to water-wet state, but in seawater salinity it cannot modify the wettability significantly. To utilize this biosurfactant in ex situ MEOR process, economical and reservoir engineering technical parameters were considered to introduce a new optimization strategy using the response surface methodology. Comparing the result of this optimization strategy with the previous optimization research works was shown that significant save in use of nutrients is possible by using this medium. Furthermore, using this method leads to less formation damage due to the incompatibility of injecting fluid and formation brine, and less formation damage due to the bioplugging

Phenol removal by a sequential combined fenton-enzymatic process

International audienceA two-stage process for the treatment of phenol by Fenton reaction coupled with enzymatic polymerization was investigated. The study was conducted on synthetic and industrial wastewaters containing phenol. The pretreatment of this effluent was carried out by the Fenton's reaction followed by enzymatic treatment with immobilized turnip peroxidase. Results showed that enzymatic treatment was an efficient complementary process to eliminate toxic compounds that were generated by the Fenton radical oxidation. Both processes were performed under optimal conditions, starting from a concentrated phenol solution of 100 mg L-1 which was pretreated by the Fenton reaction during 120 minutes at pH 3 and 40°C, in the presence of iron(II) (5 mg L-1) and hydrogen peroxide 9mM. Phenol concentration after the Fenton treatment decreased to 40 mg L-1. Other compounds such as hydroquinone, catechol and benzoquinone were also present. Residual phenol, catechol and hydroquinone were eliminated by the immobilized turnip peroxidase treatment at pH 7 and 40°C, during 165 minutes by adding H2O2 (10.6 mM) and 5 U of immobilized peroxidase. Benzoquinone was eliminated by coagulation-precipitation with chitosan (4g L-1). The global phenol removal by the combined process was 99.7% with almost total elimination of catechol, hydroquinone and benzoquinone. The application of the combined treatment to a pharmaceutical effluent containing initially 56 mg L-1 of phenol was also successful. More than 99.3% of phenol was eliminated after 120 and 165 minutes of Fenton and enzymatic processes, consecutively; and more than 72% decrease in COD and 66.7% in BOD5 were obtained

Degradation of disperse dye from textile effluent by free and immobilized Cucurbita pepo peroxidase

Disperse dyes constitute the largest group of dyes used in local textile industry. This work evaluates the potential of the Cucurbita peroxidase(C-peroxidase) extracted from courgette in the decolourization of disperse dye in free and immobilized form. The optimal conditions for immobilization of C-peroxidase in Ca-alginate were identified. The immobilization was optimized at 2%(w/v) of sodium alginate and 0.2 M of calcium chloride. After optimization of treatment parameters, the results indicate that at pH 2, dye concentration: 80 mg/L(for FCP) and 180 mg/L(for ICP), H2O2 dose: 0,02M (for FCP) and 0,12M(for ICP), the decolourization by free and immobilized C-peroxidase were 72.02% and 69.71 % respectively. The degradation pathway and the metabolic products formed after the degradation were also predicted using UV–vis spectroscopy analysis

Production of a biosurfactant by Pseudomonas fluorescens - Solubilizing and wetting capacity

International audienceProduction of biosurfactant by free and alginate entrapped cells of Pseudomonas fluorescens Migula 1895-DSMZ was investigated using olive oil as the sole carbon and energy source. Diffusional limitations in alginate beads affected the kinetic of biosurfactant production when compared to that obtained with free cells culture. Nevertheless, the emulsion stability was improved and fewer by-products interfered with the biosurfactant activity. After separation by acetone precipitation, the biosurfactant showed a rhamnolipid-type in nature, and had a good foaming and emulsifying activities. The critical micellar concentration (CMC) was found to be 290 mg l-1. The product exhibited a positive effect to alkaline pH and demonstrated a high level of tolerance to ionic strength. Above the CMC, naphthalene solubility was deeply affected by biosurfactant concentration, pH and salinity. A quantitative estimation of the effectiveness of the solubility process was obtained by calculating the weight solubilization ratio (WSR). The WSR decreased from 0.63 to 0.015 for increasing biosurfactant concentration up to 1.5 g L-1, alkaline pH or high salinity; and reached an almost constant value for 4.0 g L-1 of biosurfactant irrespective of the pH and the salinity. In all cases the solubility of naphthalene in water was enhanced by the biosurfactant addition, showing its potential for application in bioremediation of polycyclic aromatic hydrocarbons (PAH) contamination in extreme environments