Studies on reclamation of crude oil polluted soil by biosurfactant producing Pseudomonas aeruginosa (DKB1)

Recent advances and discoveries of microbial-based glycolipids: Prospective alternative for remediation activities

Surfactants have always been a prominent chemical that is useful in various sectors (e.g., cleaning agent production industry, textile industry and painting industry). This is due to the special ability of surfactants to reduce surface tension between two fluid surfaces (e.g., water and oil). However, the current society has long omitted the harmful effects of petroleum-based surfactants (e.g., health issues towards humans and reducing cleaning ability of water bodies) due to their usefulness in reducing surface tension. These harmful effects will significantly damage the environment and negatively affect human health. As such, there is an urgency to secure environmentally friendly alternatives such as glycolipids to reduce the effects of these synthetic surfactants. Glycolipids is a biomolecule that shares similar properties with surfactants that are naturally synthesized in the cell of living organisms, glycolipids are amphiphilic in nature and can form micelles when glycolipid molecules clump together, reducing surface tension between two surfaces as how a surfactant molecule is able to achieve. This review paper aims to provide a comprehensive study on the recent advances in bacteria cultivation for glycolipids production and current lab scale applications of glycolipids (e.g., medical and waste bioremediation). Studies have proven that glycolipids are effective anti-microbial agents, subsequently leading to an excellent anti-biofilm forming agent. Heavy metal and hydrocarbon contaminated soil can also be bioremediated via the use of glycolipids. The major hurdle in the commercialization of glycolipid production is that the cultivation stage and downstream extraction stage of the glycolipid production process induces a very high operating cost. This review provides several solutions to overcome this issue for glycolipid production for the commercialization of glycolipids (e.g., developing new cultivating and extraction techniques, using waste as cultivation medium for microbes and identifying new strains for glycolipid production). The contribution of this review aims to serve as a future guideline for researchers that are dealing with glycolipid biosurfactants by providing an in-depth review on the recent advances of glycolipid biosurfactants. By summarizing the points discussed as above, it is recommended that glycolipids can substitute synthetic surfactants as an environmentally friendly alternative.

Isolation, identification, and screening of biosurfactant-producing and hydrocarbon-degrading bacteria from oil and gas industrial waste

Qatar is one of the biggest oil and gas producers in the world, coupled with it is challenging environmental conditions (high average temperature: >40 °C, low annual rainfall: 46.71 mm, and high annual evaporation rate: 2200 mm) harbors diverse microbial communities that are novel and robust, with the potential to biodegrade hydrocarbons. In this study, we collected hydrocarbon contaminated sludge, wastewater and soil samples from oil and gas industries in Qatar. Twenty-six bacterial strains were isolated in the laboratory from these samples using high saline conditions and crude oil as the sole carbon source. A total of 15 different bacterial genera were identified in our study that have not been widely reported in the literature or studied for their usage in the biodegradation of hydrocarbons. Interestingly, some of the bacteria that were identified belonged to the same genus however, demonstrated variable growth rates and biosurfactant production. This indicates the possibility of niche specialization and specific evolution to acquire competitive traits for better survival. The most potent strain EXS14, identified as Marinobacter sp., showed the highest growth rate in the oil-containing medium as well as the highest biosurfactant production. When this strain was further tested for biodegradation of hydrocarbons, the results showed that it was able to degrade 90 to 100% of low and medium molecular weight hydrocarbons and 60 to 80% of high molecular weight (C35 to C50) hydrocarbons. This study offers many promising leads for future studies of microbial species and their application for the treatment of hydrocarbon contaminated wastewater and soil in the region and in other areas with similar environmental conditions.

Supramolecular bioamphiphile facilitated bioemulsification and concomitant treatment of recalcitrant hydrocarbons in petroleum refining industry oily waste

Bioremediation of real-time petroleum refining industry oily waste (PRIOW) is a major challenge due to the poor emulsification potential and oil sludge disintegration efficiency of conventional bioamphiphile molecules. The present study was focused on the design of a covalently engineered supramolecular bioamphiphile complex (SUBC) rich in hydrophobic amino acids for proficient emulsification of hydrocarbons followed by the concomitant degradation of total petroleum hydrocarbons (TPH) in PRIOW using the hydrocarbonoclastic microbial bio-formulation system. The synthesis of SUBC was carried out by pH regulated microbial biosynthesis process and the yield was obtained to be 450.8 mg/g of petroleum oil sludge. The FT-IR and XPS analyses of SUBC revealed the anchoring of hydrophilic moieties of monomeric bioamphiphilic molecules, resulting in the formation of SUBC via covalent interaction. The SUBC was found to be lipoprotein in nature. The maximum loading capacity of SUBC onto surface modified rice hull (SMRH) was achieved to be 45.25 mg/g SMRH at the optimized conditions using RSM-CCD design. The SUBC anchored SMRH was confirmed using SEM, FT-IR, XRD and TGA analyses. The adsorption isotherm models of SUBC onto SMRH were performed. The integrated approach of SUBC-SMRH and hydrocarbonoclastic microbial bio-formulation system, emulsified oil from PRIOW by 92.86 ± 2.26% within 24 h and degraded TPH by 89.25 ± 1.75% within 4 days at the optimum dosage ratio of SUBC-SMRH (0.25 g): PRIOW (1 g): mass of microbial-assisted biocarrier material (0.05 g). The TPH degradation was confirmed by SARA fractional analysis, FT-IR, ¹H NMR and GC-MS analyses. The study suggested that the application of covalently engineered SUBC has resulted in the accelerated degradation of real-time PRIOW in a very short duration without any secondary sludge generation. Thus, the SUBC integrated approach can be considered to effectively manage the hydrocarbon contaminants from petroleum refining industries under optimal conditions.

Recent advances of biosurfactant for waste and pollution bioremediation: Substitutions of petroleum-based surfactants

Biosurfactant is one of the emerging compounds in the industrial sector that behaves similarly with their synthetic counterparts, as they can reduce surface and interfacial tension between two fluids. Their unique properties also enable biosurfactant molecules to be able to clump together to form micelles that can capture targeted molecules within a solution. Biosurfactants are compared with synthetic surfactants on various applications for which the results shows that biosurfactants are fully capable of replacing synthetic surfactants in applications including enhanced oil recovery and wastewater treatment applications. Biosurfactants are able to be used in different applications as well since they are less toxic than synthetic surfactants. These applications include bioremediation on oil spills in the marine environment and bioremediation for contaminated soil and water, as well as a different approach on the pharmaceutical applications. The future of biosurfactants in the pharmaceutical industry and petroleum industry as well as challenges faced for implementing biosurfactants into large-scale applications are also discussed at the end of this review.

Pseudomonas in environmental bioremediation of hydrocarbons and phenolic compounds- key catabolic degradation enzymes and new analytical platforms for comprehensive investigation

Pollution of the environment with petroleum hydrocarbons and phenolic compounds is one of the biggest problems in the age of industrialization and high technology. Species of the genus Pseudomonas, present in almost all hydrocarbon-contaminated areas, play a particular role in biodegradation of these xenobiotics, as the genus has the potential to decompose various hydrocarbons and phenolic compounds, using them as its only source of carbon. Plasticity of carbon metabolism is one of the adaptive strategies used by Pseudomonas to survive exposure to toxic organic compounds, so a good knowledge of its mechanisms of degradation enables the development of new strategies for the treatment of pollutants in the environment. The capacity of microorganisms to metabolize aromatic compounds has contributed to the evolutionally conserved oxygenases. Regardless of the differences in structure and complexity between mono- and polycyclic aromatic hydrocarbons, all these compounds are thermodynamically stable and chemically inert, so for their decomposition, ring activation by oxygenases is crucial. Genus Pseudomonas uses several upper and lower metabolic pathways to transform and degrade hydrocarbons, phenolic compounds, and petroleum hydrocarbons. Data obtained from newly developed omics analytical platforms have enormous potential not only to facilitate our understanding of processes at the molecular level but also enable us to instigate and monitor complex biodegradations by Pseudomonas. Biotechnological application of aromatic metabolic pathways in Pseudomonas to bioremediation of environments polluted with crude oil, biovalorization of lignin for production of bioplastics, biofuel, and bio-based chemicals, as well as Pseudomonas-assisted phytoremediation are also considered.

Microbial originated surfactants with multiple applications: a comprehensive review

Microbial synthesized surfactants are used in contaminated soil bioremediation processes and have multiple applications in various industries. These compounds minimize the negative influences in soil via absorption by detoxifying the toxic metals or compounds. Further, applications of biosurfactants are detected in treating chronic diseases or synthetic drugs alternatives in current periods. Various surfactant molecules can provide many benefits due to their diversities in structural and functional groups. These compounds showed a wide array of applications in multiple sectors such as biomedical or pharmaceutical fields. Agricultural, food processing, laundry, or other sectors. Many microbial systems or plant cells are utilized in biosurfactant production as confirmed by biochemical analysis of genome sequencing tools. Biosurfactant compounds can alter drug transport across the cell membrane. Different nature of biosurfactant compounds exhibited their antifungal, antibacterial, antiviral activities, or antiadhesive coating agents used in reduction of many hospital infections. These distinct properties of biosurfactants pushed their broad spectrum applications in biomedical, agriculture sectors and bioremediation tasks. Additionally, many strains of fungi or bacteria are utilized for biosurfactant synthesis involved in the detoxification of soil/other components of the environment. In these reviews, authors explained various biosurfactants molecules and their mode of actions. Also, applications of microbial originated biosurfactants along with their process technologies are described. Future perspectives of biosurfactants and their scope are also critically explained so that this review paper can be used as a showcase for production and application of biosurfactants.

Characterization of two novel strains of Pseudomonas aeruginosa on biodegradation of crude oil and its enzyme activities

Crude oil contaminant is one of the major problem to environment and its removal process considered as most challenging tool currently across the world. In this degradation study, crude oil hydrocarbons are degraded on various pH optimization conditions (pH 2, 4,6,7,8 and 10) by using two biosurfactant producing bacterial strains Pseudomonas aeruginosa PP3 and Pseudomonas aeruginosa PP4. During crude oil biodegradation, degradative enzymes alkane hydroxylase and alcohol dehydrogenase were examined and found to be higher in PP4 than PP3. Biodegradation efficiency (BE) of crude oil by both PP3 and PP4 were analysed by gas chromatography mass spectroscopy (GCMS). Based on strain PP3, the highest BE was observed in pH 2 and pH 4 were found to be 62% and 69% than pH 6, 7, 8 and 10 (47%, 47%, 49% and 45%). It reveals that PP3 was survived effectively in acidic condition and utilized the crude oil hydrocarbons. In contrast, the highest BE of PP4 was observed in pH 7 (78%) than pH4 (68%) and pH's 2, 6, 8 and 10 (52%, 52%, 43% and 53%) respectively. FTIR spectra results revealed that the presence of different functional group of hydrocarbons (OH, -CH₃, CO, C-H) in crude oil. GCMS results confirmed that both strains PP3 and PP4 were survived in acidic condition and utilized the crude oil hydrocarbons as sole carbon sources. This is the first observation on biodegradation of crude oil by the novel strains of Pseudomonas aeruginosa in acidic condition with higher BE. Overall, the extracellular enzymes and surface active compounds (biosurfactant) produced by bacterial strains were played a key role in crude oil biodegradation process.

Crude oil exploration in Africa: socio-economic implications, environmental impacts, and mitigation strategies

Crude oil exploration is a source of significant revenue in Africa via trade and investment since its discovery in the mid-19th Century. Crude oil has bolstered the continent's economy and improved the wellbeing of the citizenry. Historically, Africa has suffered from conflicts due to uneven redistribution of crude oil revenue and severe environmental pollution. Advancements in geophysical survey techniques, such as magnetic and gravity methods, to seismic methods, have made the commercial exploration of crude oil possible for some other countries in Africa apart from Nigeria, Angola, Algeria, Libya, and Egypt. The occurrence of organic-rich, oil-prone Type I, II, and mixed II/III kerogens in sedimentary basins and entrapment within reservoir rocks with intrinsic petrophysical properties are majorly responsible for the large deposits of hydrocarbon in Africa. The unethical practices by some multinational oil corporations have resulted in social movements against them by host communities and human rights groups. The unscrupulous diversion of public funds, award of oil blocks, and production rights to certain individuals have impaired economic growth in Africa. The over-dependence on crude oil revenues has caused the economic recession in oil-producing countries due to plummeting oil prices and global pandemic. Most host communities of crude oil deposits suffer from a lack of infrastructure, arable soils, clean water, and their functioning capabilities are violated by crude oil exploratory activities, without adequate compensations and remedial actions taken by oil companies and the government. Thus, this review examines crude oil exploration in Africa and provides insight into the environmental and socio-economic implications of crude oil exploration in Africa. Furthermore, this report highlights some recommendations that may ensure ethical and sustainable practices toward minimizing negative impacts and improving the quality of life in affected communities.

Bioremediation of petroleum contaminated soil through biosurfactant and Pseudomonas sp. SA3 amended design treatments

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Potent PGP strain Pseudomonas sp SA3 was isolated from oil contaminated zone.

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PGPR strain SA3 produce biosurfactant under petroleum stress.

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Biosurfactant and strain SA3 amended treatments were developed.

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Amended treatments effects the plant growth and pigments.

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Treatment are efficient in reclamation of petroleum contaminated soil.

Toxicity of agricultural soil due to petroleum contamination has become a serious issue in recent times. Petrol oil exhibits toxic effects in agricultural crops due to the presence of various hazardous hydrocarbons. The degradation of petroleum hydrocarbon has been widely studied by the researchers that signify the requirement of effective treatments for the detoxification of petroleum contaminated soil and their reuse for growing crops. Hence, with this intention in the present study secondary metabolites “biosurfactant” (natural surfactant) along with the potent plant growth promoting (PGP) bacterial strain Pseudomonas sp. SA3 was used in the designed treatments for growing agricultural crop. The biosurfactant produced by the strain has the emulsification capacity of 43% and surface tension reduction ability to 34.5 mN/m whereas the plant growth promoting traits demonstrates 93.46 µg/mL phosphate solubilisation ability, siderophores (iron chelating compound) production upto 69.41% units and 81.41 µg/mL indole acetic acid  (IAA) production ability. Further, the results of the design treatments signifies that treatments amended with the strain SA3 and biosurfactant is effective in the management of petroleum contaminated soil indicating treatment EX 5 (1 kg soil + 1 L water + Pseudomonas sp. SA3 + 300 mL crude biosurfactant), as an efficient treatment in increment of phytochemical constituents and 10–15% enhancement in growth parameters as compared to negative control. Hence, the developed treatments can be efficaciously used for the management of petroleum contaminated soil for agronomy.

Enhanced biodegradation of hydrophobic organic pollutants by the bacterial consortium: Impact of enzymes and biosurfactants

Hydrocarbons and their derivative compounds are recalcitrant in nature and causing adverse impacts to the environment and are classified as important pollutants. Removal of these pollutants from the atmosphere is a challenging process. Hydrophobic organic pollutants (HOPs) including crude oil, diesel, dotriacontane (C₃₂), and tetracontane (C₄₀) are subjected to the biodegradation study by using a bacterial consortium consist of Bacillus subtilis, Pseudomonas stutzeri, and Acinetobacter baumannii. The impact of pH and temperature on the biodegradation process was monitored. During the HOPs biodegradation, the impact of hydrocarbon-degrading extracellular enzymes such as alcohol dehydrogenase, alkane hydroxylase, and lipase was examined, and found average activity about 47.2, 44.3, and 51.8 μmol/mg^-1, respectively. Additionally, other enzymes such as catechol 1,2 dioxygenase and catechol 2,3 dioxygenase were found as 118 and 112 μmol/mg^-1 Enzyme as an average range in all the HOPs degradation, respectively. Also, the impact of the extracellular polymeric substance and proteins were elucidated during the biodegradation of HOPs with the average range of 116.90, 54.98 mg/L^-1 respectively. The impact of biosurfactants on the degradation of different types of HOPs is elucidated. Very slight changes in the pH were also noticed during the biodegradation study. Biodegradation efficiency was calculated as 90, 84, 76, and 72% for crude oil, diesel, C_32, and C₄₀, respectively. Changes in the major functional groups (CH, C-O-C, CO, =CH₂, CH₂, CH₃) were confirmed by FTIR analysis and intermediated metabolites were identified by GCMS analysis. The surface-active molecules along with the enzymes played a crucial role in the biodegradation process.

Impact of kerosene pollution on ground vegetation of southern taiga in the Amur Region, Russia

The present study is the field experiment on kerosene pollution impact on southern taiga plant communities. Experimental sites were located in a mixed forest, a deciduous forest, a sedge fen and a wet meadow within the Amur Region of the Russian Far East. Kerosene loads from 1 to 500 g/kg of soil were applied to 50 × 50 cm plots in three replications and their effects on number of species and projective cover of ground vegetation were analysed in 1.5 months and 1 year after exposure. Statistical analyses of data included Student's t-test, Friedman ANOVA and correlation coefficient (r). Phylogenetic analysis was carried out for herbaceous plants on experimental plots. The highest susceptibility to kerosene pollution was found in the mixed forest, where the edificator species (Pteridium aquilinum subsp. pinetorum) was significantly suppressed by the kerosene load of only 1 g/kg of soil. Wetland communities regenerated faster than ground vegetation of forests, especially, in tests with high (>25 g/kg) kerosene loads. The wet meadow community was the most resistant to kerosene pollution, i.e., despite significant decreases in projective cover and number of species after exposure to kerosene loads of 5 and 25 g/kg in the first season, it had the highest regeneration success in the next season. In our study, the kerosene load of 25 g/kg of soil was the threshold level of pollution, above which there were significant structural changes in the studied plant communities. Depending on their abilities to resist kerosene pollution and to regenerate in the next year, dominant species of the studied plant communities were arranged in the following ascending order: Pteridium aquilinum ssp. pinetorum, Convallaria keiskei < Carex cespitosa, Calamagrostis purpurea < Lespedeza bicolor < Vaccinium uliginosum.

Investigation on spectral and biomedical characterization of rhamnolipid from a marine associated bacterium Pseudomonas aeruginosa (DKB1)

Bio-surfactants are a principal group of significant molecules obtained from the microbial sources expressed with distinctive characteristics like biodegradation of hydrocarbons and also have different biomedical properties. The present investigation aims to assess the biomedical properties of synthesized bio-surfactant, rhamnolipid from Pseudomonas aeruginosa (DKB1) under in vitro conditions. The candidate bacterium P. aeruginosa (DKB1) was isolated from oil-polluted fishing harbors of Kanyakumari coast. Initially, the bio-surfactant production by this candidate strain was confirmed by oil displacement assay, hemolytic assay, drop collapse assay and emulsification index. Further, the production of bio-surfactant was achieved through submerged fermentation process using Bushnell-Haas mineral salts medium supplemented with 2% olive oil. The yield of the bio-surfactant was attained as 2.4 g/l and confirmed as rhamnolipid through blue agar plate assay; further, the extracted rhamnolipid was purified and characterized through standard procedures. In stability studies, the rhamnolipid could withstand up to pH 12, temperature 100 °C and 15% of NaCl concentration. The biomedical application of rhamnolipid (30 μg ml^-1) was determined by antibacterial, antioxidant and cytotoxic studies. It exhibited a maximum growth inhibition against Bacillus subtilis (26 mm) with the MIC value of 8 μg ml^-1. In antioxidant test, rhamnolipid expressed significant (P < 0.0001) inhibition of total reducing power (44.11%), DPPH activity (61.60%), hydroxyl radical (83.30%) and nitric oxide (51.86%) scavenging ability at 100 μg ml^-1with the respective IC50 values of 130.50, 77.18, 52.08 and 95.43 μg ml^-1. The anticancer activity of the rhamnolipid was assessed with the help of MTT test against MCF-7, HT-29 and E-143 cancer cell lines individually, and the viability of the cells was observed, respectively, as 10.24, 17.66 and 13.50% at 250 μg ml^-1concentration with the respective IC50 values of 140.2, 81.02 and 138.9 μg ml^-1. From the results, it could be concluded that the rhamnolipid produced by P. aeruginosa (DKB1) isolated from oil-polluted area has effective biomedical properties.

Exploring the effects of microalgal biomass on the oil behavior in a sand-water system

This study focused on the impact of microalgal biomass on the oil behavior in a sand-water system. The microalgal biomass was characterized, and the interaction between microalgal biomass and oil was analyzed through Fourier transform infrared (FTIR) spectroscopy. The effects of different conditions including microalgal biomass dose, pH, temperature, and salinity on the oil behavior were investigated. A two-level factorial analysis was also used to further explore the interactions of these conditions. The microalgal biomass was found to be the most influential parameter for the residual crude oil on sand. Higher microalgal biomass dose resulted in less residual oil on sand. The remaining oil decreased with increasing solution pH from 4 to 7, and an increase of remaining oil was observed when the pH was further increased above 7. In addition, temperature and salinity could affect the removal of crude oil in the presence of microalgal biomass. Increasing the temperature could result in less residual oil on sand and there was higher oil removal at the high salinity. The effects of microalgal biomass on the oil behavior could also be impacted by environmental conditions. The results of this study indicate that the presence of algae in the oiled shoreline can be considered in the comprehensive evaluation of spill risk and prediction of oil fate.