Biodegradation of diesel oil by a novel microbial consortium: comparison between co-inoculation with biosurfactant-producing strain and exogenously added biosurfactants

Common operational issues and possible solutions for sustainable biosurfactant production from lignocellulosic feedstock

Surfactants are compounds with high surface activity and emulsifying property. These compounds find application in food, medical, pharmaceutical, and petroleum industries, as well as in agriculture, bioremediation, cleaning, cosmetics, and personal care product formulations. Due to their widespread use and environmental persistence, ensuring biodegradability and sustainability is necessary so as not to harm the environment. Biosurfactants, i.e., surfactants of plant or microbial origin produced from lignocellulosic feedstock, perform better than their petrochemically derived counterparts on the scale of net-carbon-negativity. Although many biosurfactants are commercially available, their high cost of production justifies their application only in expensive pharmaceuticals and cosmetics. Besides, the annual number of new biosurfactant compounds reported is less, compared to that of chemical surfactants. Multiple operational issues persist in the biosurfactant value chain. In this review, we have categorized some of these issues based on their relative position in the value chain - hurdles occurring during planning, upstream processes, production stage, and downstream processes - alongside plausible solutions. Moreover, we have presented the available paths forward for this industry in terms of process development and integrated pretreatment, combining conventional tried-and-tested strategies, such as reactor designing and statistical optimization with cutting-edge technologies including metabolic modeling and artificial intelligence. The development of techno-economically feasible biosurfactant production processes would be instrumental in the complete substitution of petrochemical surfactants, rather than mere supplementation.

Biofilm formation in xenobiotic-degrading microorganisms

The increased presence of xenobiotics affects living organisms and the environment at large on a global scale. Microbial degradation is effective for the removal of xenobiotics from the ecosystem. In natural habitats, biofilms are formed by single or multiple populations attached to biotic/abiotic surfaces and interfaces. The attachment of microbial cells to these surfaces is possible via the matrix of extracellular polymeric substances (EPSs). However, the molecular machinery underlying the development of biofilms differs depending on the microbial species. Biofilms act as biocatalysts and degrade xenobiotic compounds, thereby removing them from the environment. Quorum sensing (QS) helps with biofilm formation and is linked to the development of biofilms in natural contaminated sites. To date, scant information is available about the biofilm-mediated degradation of toxic chemicals from the environment. Therefore, we review novel insights into the impact of microbial biofilms in xenobiotic contamination remediation, the regulation of biofilms in contaminated sites, and the implications for large-scale xenobiotic compound treatment.

New roles for Bacillus thuringiensis in the removal of environmental pollutants

For a long time, the well-known Gram-positive bacterium Bacillus thuringiensis (Bt) has been extensively studied and developed as a biological insecticide for Lepidoptera and Coleoptera pests due to its ability to secrete a large number of specific insecticidal proteins. In recent years, studies have found that Bt strains can also potentially biodegrade residual pollutants in the environment. Many researchers have isolated Bt strains from multiple sites polluted by exogenous compounds and characterized and identified their xenobiotic-degrading potential. Furthermore, its pathway for degradation was also investigated at molecular level, and a number of major genes/enzymes responsible for degradation have been explored. At present, a variety of xenobiotics involved in degradation in Bt have been reported, including inorganic pollutants (used in the field of heavy metal biosorption and recovery and precious metal recovery and regeneration), pesticides (chlorpyrifos, cypermethrin, 2,2-dichloropropionic acid, etc.), organic tin, petroleum and polycyclic aromatic hydrocarbons, reactive dyes (congo red, methyl orange, methyl blue, etc.), and ibuprofen, among others. In this paper, the biodegrading ability of Bt is reviewed according to the categories of related pollutants, so as to emphasize that Bt is a powerful agent for removing environmental pollutants.

Isolation and characterization of two glycolipopeptids biosurfactants produced by a Lactiplantibacillus plantarum OL5 strain isolated from green olive curing water

Microbial surfactants are natural amphiphilic compounds with high surface activities and emulsifying properties. Due to their structural diversity, low toxicity, biodegradability, and chemical stability in different conditions, these molecules are potential substitutes for chemical surfactants; their interest has grown significantly over the last decade. The current study focuses on the isolation, identification, and characterization of a lactic acid bacteria that produce two forms of biosurfactants. The OL5 strain was isolated from green olive fermentation and identified using MALDI/TOF and DNAr16S amplification. Emulsification activity and surface tension measurements were used to estimate biosurfactant production. The two biosurfactants derived from Lactiplantibacillus plantarum OL5 presented good emulsification powers in the presence of various oils. They were also shown to have the potential to reduce water surface tension from 69 mN/m to 34 mN/m and 37 mN/m within a critical micelle concentration (CMC) of 7 mg/ml and 1.8 mg/ml, respectively, for cell bound and extracellular biosurfactants. Thin layer chromatography (TLC) and FT-IR were used to analyze the composition of the two biosurfactants produced. the obtained data revealed that the two biomolecules consist of a mixture of carbohydrates, lipids and proteins. We demonstrated that they are two anionic biosurfactants with glycolipopeptide nature which are stable in extreme conditions of temperature, pH and salinity.

Formation and structural features of micelles formed by surfactin homologues

Surfactin, a group of cyclic lipopeptides produced by Bacillus subtilis, possesses surfactant properties and is a promising natural and biologically active compound. In this study, we present a comprehensive characterization of surfactin, including its production, chromatographic separation into pure homologues (C₁₂, C₁₃, C₁₄, C₁₅), and investigation of their physicochemical properties. We determined adsorption isotherms and interpreted them using the Gibbs adsorption equation, revealing that the C₁₅ homologue exhibited the strongest surface tension reduction (27.5 mN/m), while surface activity decreased with decreasing carbon chain length (32.2 mN/m for C₁₂). Critical micelle concentration (CMC) were also determined, showing a decrease in CMC values from 0.35 mM for C₁₂ to 0.08 mM for C₁₅. We employed dynamic light scattering (DLS), transmission electron microscopy (TEM), and density functional theory (DFT) calculations to estimate the size of micellar aggregates, which increased with longer carbon chains, ranging from 4.7 nm for C₁₂ to 5.7 nm for C₁₅. Furthermore, aggregation numbers were determined, revealing the number of molecules in a micelle. Contact angles and emulsification indexes (E₂₄) were measured to assess the functional properties of the homologues, showing that wettability increased with chain length up to C₁₄, which is intriguing as C₁₄ is the most abundant homologue. Our findings highlight the relationship between the structure and properties of surfactin, providing valuable insights for understanding its biological significance and potential applications in various industries. Moreover, the methodology developed in this study can be readily applied to other cyclic lipopeptides, facilitating a better understanding of their structure-properties relationship.

Optimization of textile effluent bacterial treatment and improvement of the process efficiency through SPB1 biosurfactant addition

The current work aims to optimize biological textile effluent treatment through the use of newly selected bacterial consortia composed of two strains: Citrobacter sedlakii RI11 and Aeromonas veronii GRI. We assessed the effect of SPB1 biosurfactant addition on color removal (CR). The process was optimized by a Box-Bhenken by examining the effect of pH, consortia density and biosurfactant value on treatment efficiency. Firstly, physicochemical analyses of the studied effluent revealed an alkaline pH along with a high content of suspended materials and large amounts of organic matter. Optimal CR and a chemical oxygen demand abatement of about 94 and 86% were obtained when treating the textile effluent at pH 5 with a total optical density of 0.4 and by incorporating 0.01% SPB1 biosurfactant. Additionally, an abolishment of phytotoxicity was registered after treatment optimization. The evaluations of the action mode of both selected bacteria during textile effluent treatment suggested the occurrence of biodegradation phenomena of dyes through enzymatic activities.

Bioengineering for the Microbial Degradation of Petroleum Hydrocarbon Contaminants

Petroleum hydrocarbons are relatively recalcitrant compounds, and as contaminants, they are one of the most serious environmental problems. n-Alkanes are important constituents of petroleum hydrocarbons. Advances in synthetic biology and metabolic engineering strategies have made n-alkane biodegradation more designable and maneuverable for solving environmental pollution problems. In the microbial degradation of n-alkanes, more and more degradation pathways, related genes, microbes, and alkane hydroxylases have been discovered, which provide a theoretical basis for the further construction of degrading strains and microbial communities. In this review, the current advances in the microbial degradation of n-alkanes under aerobic condition are summarized in four aspects, including the biodegradation pathways and related genes, alkane hydroxylases, engineered microbial chassis, and microbial community. Especially, the microbial communities of “Alkane-degrader and Alkane-degrader” and “Alkane-degrader and Helper” provide new ideas for the degradation of petroleum hydrocarbons. Surfactant producers and nitrogen providers as a “Helper” are discussed in depth. This review will be helpful to further achieve bioremediation of oil-polluted environments rapidly.

Soil treatment using a biosurfactant producing bacterial consortium in rice fields contaminated with oily sludge- a sustainable approach

A consortium of two biosurfactant-producing bacteria (Bacillus pumilus KS2 and Bacillus cereus R2) was developed to remediate petroleum hydrocarbon-contaminated paddy soil. Soil samples from a heavily contaminated rice field near Assam's Lakwa oilfield were collected and placed in earthen pots for treatment. After each month of incubation, 50 g of soil from each earthen pot was collected, and the soil TPH (ppm) in each sample was determined. The extracted TPH samples were analysed by Gas chromatography-mass spectrometry (GC-MS) to confirm microbial degradation. The soil samples were examined for changes in pH, conductivity, total organic content (TOC), water holding capacity, and total nitrogen content in addition to TPH degradation. An increasing trend in TPH degradation was observed with each passing month. After six months of treatment, the sample with the lowest initial TPH concentration (1735 ppm) had the highest degradation (91.24%), while the soil with the highest amount of TPH (5780 ppm) had the lowest degradation (74.35%). A wide range of aliphatic hydrocarbons found in soil samples was degraded by the bacterial consortium. The soil samples contained eight different low- and high-molecular-weight PAHs. Some were fully mineralized, while others were significantly reduced. With the decrease in the TPH level in the polluted soil, a significant improvement in the soil's physicochemical qualities (such as pH, electrical conductivity, total organic content, and water-holding capacity) was observed.

Bioremediation of Petroleum-Contaminated Soils with Biosurfactant-Producing Degraders Isolated from the Native Desert Soils

A crude oil spill in 2014 resulted in extensive soil contamination of the hyper arid Evrona Nature Reserve in Israel's Negev Desert. The contaminated soils became highly hydrophobic, threatening the existence of plants in the habitat. We hypothesized that bioaugmenting the soil with indigenous biosurfactant-producing, hydrocarbon-degrading bacteria (HDB) would accelerate the reduction in the soil's hydrophobicity. We aimed to isolate and characterize biosurfactant-producing HDBs from the desert-contaminated soil and test if they can be used for augmenting the soil. Twelve hydrocarbon-degrading strains were isolated, identified as Pseudomonas, and classified as biosurfactants "producing" and "nonproducing". Inoculating 10⁹ CFU/g of "producing" strains into the polluted soil resulted in a 99.2% reduction in soil hydrophobicity within seven days. At the same time, nonproducing strains reduced hydrophobicity by only 17%, while no change was observed in the untreated control. The microbial community in the inoculated soil was dominated by the introduced strains over 28 days, pointing to their persistence. Rhamnolipid biosynthesis gene rhlAB remained persistent in soil inoculated with biosurfactants, indicating in situ production. We propose that the success of the treatment is due to the use of inoculum enriched from the polluted soil.

Coconut oil and fermented palm wine biodiesel production for oil spill cleanup: experimental, numerical, and hybrid metaheuristic modeling approaches

This paper for the first time synthesizes novel biodiesel experimentally using low-cost feedstocks of coconut oil, caustic soda, and fermented palm wine contaminated by microorganisms. The alkaline catalyzed transesterification method was used for biodiesel production with minimal glycerol. The produced biodiesel was biodegradable and effective in cleaning a shoreline oil spill experiment verified by our developed oil spill radial numerical simulator. For the first time, an adaptive neuro-fuzzy inference system (ANFIS) was hybridized with invasive weed optimization (IWO), imperialist competitive algorithm (ICA), and shuffled complex evolution (SCE-UA) to predict biodiesel yield (BY) using obtained Monte Carlo simulation datasets from the biodiesel experimental seed data. The test results indicated ANFIS-IWO (MSE = 0.0628) as the best model and also when compared to the benchmarked ANFIS genetic algorithm (MSE = 0.0639). Additionally, ANFIS-IWO (RMSE = 0.54705) was tested on another coconut biodiesel data in the literature and it outperformed both response surface methodology (RMSE = 0.72739) and artificial neural network (RMSE = 0.68615) models used. The hybridized models proved to be robust for biodiesel yield modeling in addition to the produced biodiesel serving as an environmentally acceptable and cost-effective alternative for shoreline bioremediation.

Degradation characteristics of crude oil by a consortium of bacteria in the existence of chlorophenol

In order to enhance the degradation effect of microorganisms on crude oil in the existence of chlorophenol compounds, oil-degrading bacteria C4 (Alcaligenes faecails), C5 (Bacillus sp.) and 2,4-dichlorophenol (2,4-DCP) degrading bacteria L3 (Bacillus marisflavi), L4 (Bacillus aquimaris) were isolated to construct a highly efficient consortium named (C4C5 + L3L4). When the compound bacteria agent combination by V_C4: V_C5: V_L3: V_L4 = 1:2:2:1, the crude oil degradation efficiency of 7 days was stable at 50.63% ~ 55.43% under different conditions. Degradation mechanism was analyzed by FTIR, GC-MS and IC technology and the following conclusions showed that in the system of adding consortium (C4C5 + L3L4), the heavy components were converted into saturated and unsaturated components. The bacterial consortium could first degrade medium and long chain alkanes into short chain hydrocarbons and then further degrade. And the dechlorination efficiency of 2,4-DCP in the degradation system reached 73.83%. The results suggested that the potential applicability and effectiveness of the selected bacteria consortium for the remediation of oil-contaminated water or soil with the existence of chlorophenol compound.

Bioremediation of Soil from Petroleum Contamination

Petroleum is the most common global fossil fuel. It is a complex multi-component system mainly composed of various hydrocarbons such as alkanes, cycloalkanes, mono-, bi- and polyaromatic compounds, resins and asphaltenes. In spite of humanity’s need for petroleum, it negatively affects the environment due to its toxicity. The ecological problem is especially serious at petroleum mining sites or during petroleum transportation. Since it is not possible to replace petroleum with less toxic fuel, ways to reduce the toxic impact of petroleum hydrocarbons on the environment need to be developed. This review addresses bioremediation, a biological approach to petroleum degradation, which is mainly performed by microbes. The pathways of degradation of alkanes, alkenes and aromatic hydrocarbons are presented in detail. The effects of temperature, aeration and the presence of biogenic elements on microbial degradation of petroleum are discussed. Plant–microbe interactions involved with the bioremediation of petroleum-polluted soils are specifically addressed. The data presented in this review point to the great potential of bioremediation practices for cleaning soils of petroleum.

Microbial biofilms: Recent advances and progress in environmental bioremediation

Microbial biofilms are formed by adherence of the bacteria through their secreted polymer matrices. The major constituents of the polymer matrices are extracellular DNAs, proteins, polysaccharides. Biofilms have exhibited a promising role in the area of bioremediation. These activities can be further improved by tuning the parameters like quorum sensing, characteristics of the adhesion surface, and other environmental factors. Organic pollutants have created a global concern because of their long-term toxicity on human, marine, and animal life. These contaminants are not easily degradable and continue to prevail in the environment for an extended period. Biofilms are being used for the remediation of different pollutants, among which organic pollutants have been of significance. The bioremediation of organic contaminants using biofilms is an eco-friendly, cheap, and green process. However, the development of this technology demands knowledge on the mechanism of action of the microbes to form the biofilm, types of specific bacteria or fungi responsible for the degradation of a particular organic compound, and the mechanistic role of the biofilm in the degradation of the pollutants. This review puts forth a comprehensive summary of the role of microbial biofilms in the bioremediation of different environment-threatening organic pollutants.

Microbial associations for bioremediation. What does "microbial consortia" mean?

Microbial associations arise as useful tools in several biotechnological processes. Among them, bioremediation of contaminated environments usually takes advantage of these microbial associations. Despite being frequently used, these associations are indicated using a variety of expressions, showing a lack of consensus by specialists in the field. The main idea of this work is to analyze the variety of microbial associations referred to as "microbial consortia" (MC) in the context of pollutants biodegradation and bioremediation. To do that, we summarize the origin of the term pointing out the features that an MC is expected to meet, according to the opinion of several authors. An analysis of related bibliography was done seeking criteria to rationalize and classify MC in the context of bioremediation. We identify that the microbe's origin and the level of human intervention are usually considered as a category to classify them as natural microbial consortia (NMC), artificial microbial consortia (AMC), and synthetic microbial consortia (SMC). In this sense, NMC are those associations composed by microorganisms obtained from a single source while AMC members come from different sources. SMC are a class of AMC in which microbial composition is defined to accomplish a certain specific task. We propose that the effective or potential existence of the interaction among MC members in the source material should be considered as a category in the classification as well, in combination with the origin of the source and level of intervention. Cross-kingdom MC and new developments were also considered. Finally, the existence of grey zones in the limits between each proposed microbial consortia category is addressed. KEY POINTS: • Microbial consortia for bioremediation can be obtained through different methods. • The use of the term "microbial consortia" is unclear in the specialized literature. • We propose a simplified classification for microbial consortia for bioremediation.

Interspecies Interactions of the 2,6-Dichlorobenzamide Degrading Aminobacter sp. MSH1 with Resident Sand Filter Bacteria: Indications for Mutual Cooperative Interactions That Improve BAM Mineralization Activity

Bioaugmentation often involves an invasion process requiring the establishment and activity of a foreign microbe in the resident community of the target environment. Interactions with resident micro-organisms, either antagonistic or cooperative, are believed to impact invasion. However, few studies have examined the variability of interactions between an invader and resident species of its target environment, and none of them considered a bioremediation context. Aminobacter sp. MSH1 mineralizing the groundwater micropollutant 2,6-dichlorobenzamide (BAM), is proposed for bioaugmentation of sand filters used in drinking water production to avert BAM contamination. We examined the nature of the interactions between MSH1 and 13 sand filter resident bacteria in dual and triple species assemblies in sand microcosms. The residents affected MSH1-mediated BAM mineralization without always impacting MSH1 cell densities, indicating effects on cell physiology rather than on cell number. Exploitative competition explained most of the effects (70%), but indications of interference competition were also found. Two residents improved BAM mineralization in dual species assemblies, apparently in a mutual cooperation, and overruled negative effects by others in triple species systems. The results suggest that sand filter communities contain species that increase MSH1 fitness. This opens doors for assisting bioaugmentation through co-inoculation with "helper" bacteria originating from and adapted to the target environment.

Insights into the biodegradation of diesel oil and changes in bacterial communities in diesel-contaminated soil as a consequence of various soil amendments

Soil amendment is a promising strategy to enhance biodegradation capacity of indigenous bacteria. To assess the consequences of various soil amendments before large-scale implementation, a microcosm study was employed to investigate the effects of nutrients (TN), surfactants (TS), oxidants (TO), biochar (TB), and zero-valent iron nanoparticles (nZVI; TNP) on diesel degradation, bacterial communities, and community-level physiological profiles (CLPPs) of legacy field contaminated soil. The results showed that the TN, TB, TNP, TS, and TO, reduced 75.8%, 63.9%, 62.8%, 49.3%, and 40.1% of total petroleum hydrocarbons (TPH), respectively, within 120 days, while control (TW) reduced only 33.8%. In all soil amendments, TPH reduction was positively correlated with oxidation-reduction potential and heterotrophic and TPH-degrading bacteria, while negatively correlated with total nitrogen and available phosphate. Furthermore, in TW, TB, and TNP microcosms, TPH reduction showed positive association with pH, whereas in TN, TS, and TO, TPH reduction was negatively associated with pH. The bacterial diversity was reduced in all treatments as a function of the soil amendment and remediation time: the enriched potential TPH-degrading bacteria were Dyella, Paraburkholderia, Clavibacter, Arthrobacter, Rhodanobacter, Methylobacterium, and Pandoraea. The average well colour development (AWCD) values in CLPPs were higher in TB, sustained and improved in TN, and markedly lower in TNP, TS, and TO microcosms. Overall, these data demonstrate that nutrients and biochar amendments may be helpful in boosting biodegradation, increasing diesel-degrading bacteria, and improving soil physiological functions. In conclusion, diesel degradation efficiency and bacterial communities are widely affected by both type and duration of soil amendments.

Surface properties and heavy metals chelation of lipopeptides biosurfactants produced from date flour by Bacillus subtilis ZNI5: optimized production for application in bioremediation

The present study summarizes the valorization of date flour by the production of lipopeptide biosurfactant (BioS) by Bacillus subtilis ZNI5 (MW091416). A Taguchi design permitted the formulation of a medium composed only of 6% date flour and 0.5% yeast extract within 2 days of incubation at 150 rpm with a maximal surface tension (ST) reduction of about 27.8 mN/m. The characterization of the lipopeptide shows a CMC value of about 400 mg/L with a minimal ST of 30 mN/m and an ability to disperse oil to about 80 mm at 800 mg/L. Having reduced phytotoxicity, the ZNI5 BioS and ZNI5 strain were assayed for Copper and Cobalt chelation and biosorption. The improvement of the germination index of radish seeds irrigated by the treated contaminated water showed the great potential application of ZNI5 lipopeptide in the bioremediation of heavy metals.

Biodiversity and oil degradation capacity of oil-degrading bacteria isolated from deep-sea hydrothermal sediments of the South Mid-Atlantic Ridge

Studies have reported that various hydrocarbons and hydrocarbon-degrading bacteria are found in global deep-sea hydrothermal regions. However, little is known about degradation characteristics of culturable hydrocarbon-degrading bacteria from these regions. We speculate that these bacteria can be used as resources for the bioremediation of oil pollution. In this study, six oil-degrading consortia were obtained from the hydrothermal region of the Southern Mid-Atlantic Ridge through room-temperature enrichment experiments. The dominant oil-degrading bacteria belonged to Nitratireductor, Pseudonocardia, Brevundimonas and Acinetobacter. More varieties of hydrocarbon-degrading bacteria were obtained from sediments (preserved at 4 °C) near hydrothermal vents. Most strains had the ability to degrade high molecular weight petroleum components. In addition, Pseudonocardia was shown to exhibit a high degradation ability for phytane and pristine for the first time. This study may provide new insights into the community structure and biodiversity of culturable oil-degrading bacteria in deep-sea hydrothermal regions.

Factors Affecting the Penetration of Niosome into the Skin, Their Laboratory Measurements and Dependency to the Niosome Composition: A Review

Skin, the most significant protective organ in the body, may face serious problems, including cancer, infectious diseases, etc., requiring different drugs for the treatment. However, most of these drugs have poor chemical and physical stability, and insufficient penetration through the skin layers. In recent years, with the development of nanotechnology, it has been possible to load a variety of drugs into nanocarriers, to effectively targeted drug delivery. The unique structure of niosome presents an effective novel drug delivery system with the ability to load both hydrophilic and lipophilic drugs, having many potential therapeutic applications including skin treatment. However, surveying and discussing these recent, rapidly growing reported studies, along with their theoretical principals, are required for the full understanding and exploring the great potential of this approach in skin diseases and cosmetic treatments. To this aim, an emphasis has been given to the factors affecting the penetration of niosome into the skin and their laboratory measurements and dependency on the niosome composition. In sum, longer tail surfactants for storing hydrophobic drugs and intracellular passing and surfactants with a large head group for penetrating hydrophilic drugs are more suitable. Cholesterol and oleic acid are commonly used lipids to gain more stability and permeability, respectively. The ionic component in the niosome interrupts cellular connectivity, thus making it more permeable, but it may cause relative cell toxicity. Herbal oils have been used in the structure to make the nanoparticles elastic and allow them to pass through pores without changing the size of the particles.

Cyclic siloxane biosurfactant-producing Bacillus cereus BS14 biocontrols charcoal rot pathogen Macrophomina phaseolina and induces growth promotion in Vigna mungo L

Rhizobacteria are vital component of soil-plant interfaces which helps in plant growth responses and disease management. Precisely, the role of biosurfactant production by rhizobacteria in biocontrol mechanisms is underscored. The current study explores the destructive effect of a biosurfactant-producing bacterium Bacillus cereus BS14 on fungal growth under in vitro experiments and showed in vivo reduction of disease severity in pulse crop Vigna mungo. In this study, B. cereus BS14 was observed as plant growth-promoting rhizobacterium (PGPR) based on abilities of production of phytohormone and HCN, phosphate solubilization and biocontrol of Macrophomina phaseolina. The purified biosurfactant from BS14 inhibited the fungal growth by arresting radially growing mycelia. Scanning electron microscope (SEM) study revealed deformities at cellular level in the mycelia of M. phaseolina. The biosurfactant of Bacillus BS14 was identified as cyclic siloxane in GC-MS spectroscopy and FT-IR spectroscopy analyses. In the pot trial studies, B. cereus BS14 proved its efficiency for the growth promotion of Vigna mungo and significantly reduced disease severity index. The present study concludes that biosurfactant of rhizobacterial origin and rhizobacteria can serve for biological control, improvement in crop production and agricultural sustainability. In future, it can be developed as biological control and biofertilizer formulations for legume crops, and commercialized for routine farming practices.

Valorization of date juice by the production of lipopeptide biosurfactants by a Bacillus mojavensis BI2 strain: bioprocess optimization by response surface methodology and study of surface activities

Lipopeptides biosurfactants (BioS) are natural surface-active compounds produced by a variety of microorganisms. They have great interest in environmental, biomedical and agro-industrial fields. However their large-scale application and production is limited by the cost of culture media and the low yield of production. Therefore, the improvement of the production yields and the development of efficient and cost-effective bioprocess became of a great interest. In this aim, we applied the response surface method to optimize an economic BioS production by a newly isolated strain Bacillus mojavensis BI2 on date Juice called "Luegmi" as unique carbon and nitrogen source. Using a Box-Bhenken design, we studied the effect of three independent variables on lipopeptide production; Leugmi concentration, Na₂HPO₄ and incubation time. The results of this study showed that Leugmi concentration at 25%, Na₂HPO₄ at 0.1% and incubation time of 24 h were optimal conditions for BioS  production, with a maximum Surface Tension (ST) decreasing capacity of 55% corresponding to 27 mN/m and an Oil Dispersing Activity (ODA) of 30 cm² corresponding to a diameter of 6 cm. Preliminary characterization of the BioS produced on Luegmi by UV-Spectra and Thin Layer Chromatography showed its lipopeptide nature. Physic-chemical characterization of the produced lipopeptide on Leugmi showed its great surface activities and stabilities at different pH, temperature and salts concentration. The results of this study suggested that Leugmi, an agricultural byproducts can be used as a low-cost substrate to enhance the yield of lipopeptide BioS with great surface activities for potential environmental application.

Effect of consortium bioaugmentation and biostimulation on remediation efficiency and bacterial diversity of diesel-contaminated aged soil

This study aimed to evaluate the effects of consortium bioaugmentation (CB) and various biostimulation options on the remediation efficiency and bacterial diversity of diesel-contaminated aged soil. The bacterial consortium was prepared using strains D-46, D-99, D134-1, MSM-2-10-13, and Oil-4, isolated from oil-contaminated soil. The effects of CB and biostimulation were evaluated in various soil microcosms: CT (water), T1 (CB only), T2 (CB + NH₄NO₃ and KH₂PO_4, nutrients), T3 (CB + activated charcoal, AC), T4 (CB + nutrients + AC), T5 (AC + water), T6 (CB + nutrients + zero-valent iron nanoparticles, nZVI), T7 (CB + nutrients + AC + nZVI), T8 (CB + activated peroxidase, oxidant), T9 (AC + nZVI), and T10 (CB + nZVI + AC + oxidant). Preliminary evaluation of the bacterial consortium revealed 81.9% diesel degradation in liquid media. After 60 days of treatment, T6 demonstrated the highest total petroleum hydrocarbon (TPH) degradation (99.0%), followed by T1 (97.4%), T2 (97.9%), T4 (96.0%), T7 (96.0%), T8 (94.8%), T3 (93.6%), and T10 (86.2%). The lowest TPH degradation was found in T5 (24.2%), T9 (17.2%), and CT (11.7%). Application of CB and biostimulation to the soil microcosms decreased bacterial diversity, leading to selective enrichment of bacterial communities. T2, T6, and T10 contained Firmicutes (50.06%), Proteobacteria (64.69%), and Actinobacteria (54.36%) as the predominant phyla, respectively. The initial soil exhibited the lowest metabolic activity, which improved after treatment. The study results indicated that biostimulation alone is inadequate for remediation of contaminated soil that lacks indigenous oil degraders, suggesting the need for a holistic approach that includes both CB and biostimulation. Graphical Abstract.

Reconstruction and evaluation of oil-degrading consortia isolated from sediments of hydrothermal vents in the South Mid-Atlantic Ridge

In this study, sediments were collected from two different sites in the deep-sea hydrothermal region of the South Atlantic Ocean. Two microbial enrichment cultures (H7S and H11S), which were enriched from the sediments collected at two sample sites, could effectively degrade petroleum hydrocarbons. The bacterial diversity was analyzed by high-throughput sequencing method. The petroleum degradation ability were evaluated by gas chromatography–mass spectrometry and gravimetric analysis. We found that the dominant oil-degrading bacteria of enrichment cultures from the deep-sea hydrothermal area belonged to the genera Pseudomonas, Nitratireductor, Acinetobacter, and Brevundimonas. After a 14-day degradation experiment, the enrichment culture H11S, which was obtained near a hydrothermal vent, exhibited a higher degradation efficiency for alkanes (95%) and polycyclic aromatic hydrocarbons (88%) than the enrichment culture H7S. Interestingly, pristane and phytane as biomarkers were degraded up to 90% and 91% respectively by the enrichment culture H11S, and six culturable oil-degrading bacterial strains were isolated. Acinetobacter junii strain H11S-25, Nitratireductor sp. strain H11S-31 and Pseudomonas sp. strain H11S-28 were used at a density ratio of 95:4:1 to construct high-efficiency oil-degrading consortium H. After a three-day biodegradation experiment, consortium H showed high degradation efficiencies of 74.2% and 65.7% for total alkanes and PAHs, respectively. The degradation efficiency of biomarkers such as pristane and high-molecular-weight polycyclic aromatic hydrocarbons (such as CHR) reached 84.5% and 80.48%, respectively. The findings of this study indicate that the microorganisms in the deep-sea hydrothermal area are potential resources for degrading petroleum hydrocarbons. Consortium H, which was artificially constructed, showed a highly efficient oil-degrading capacity and has significant application prospects in oil pollution bioremediation.

Microbial biofilm ecology, in silico study of quorum sensing receptor-ligand interactions and biofilm mediated bioremediation

Biofilms are structured microbial communities of single or multiple populations in which microbial cells adhere to a surface and get embedded in extracellular polymeric substances (EPS). This review attempts to explain biofilm architecture, development phases, and forces that drive bacteria to promote biofilm mode of growth. Bacterial chemical communication, also known as Quorum sensing (QS), which involves the production, detection, and response to small molecules called autoinducers, is highlighted. The review also provides a brief outline of interspecies and intraspecies cell-cell communication. Additionally, we have performed docking studies using Discovery Studio 4.0, which has enabled our understanding of the prominent interactions between autoinducers and their receptors in different bacterial species while also scoring their interaction energies. Receptors, such as LuxN (Phosphoreceiver domain and RecA domain), LuxP, and LuxR, interacted with their ligands (AI-1, AI-2, and AHL) with a CDocker interaction energy of - 31.6083 kcal/mole; - 34.5821 kcal/mole, - 48.2226 kcal/mole and - 41.5885 kcal/mole, respectively. Since biofilms are ideal for the remediation of contaminants due to their high microbial biomass and their potential to immobilize pollutants, this article also provides an overview of biofilm-mediated bioremediation.

Functional Gene Diversity of Selected Indigenous Hydrocarbon-Degrading Bacteria in Aged Crude Oil

Crude oil pollution has consistently deteriorated all environmental compartments through the cycle of activities of the oil and gas industries. However, there is a growing need to identify microbes with catabolic potentials to degrade these pollutants. This research was conducted to identify bacteria with functional degradative genes. A crude oil-polluted soil sample was obtained from an aged spill site at Imo River, Ebubu, Komkom community, Nigeria. Bacteria isolates were obtained and screened for hydrocarbon degradation potential by turbidometry assay. Plasmid and chromosomal DNA of the potential degraders were further screened for the presence of selected catabolic genes (C230, Alma, Alkb, nahAC, and PAHRHD_(GP)) and identified by molecular typing. Sixteen (16) out of the fifty (50) isolates obtained showed biodegradation activity in a liquid broth medium at varying levels. Bacillus cereus showed highest potential for this assay with an optical density of 2.450 @ 600 nm wavelength. Diverse catabolic genes resident in plasmids and chromosomes of the isolates and, in some cases, both plasmid and chromosomes of the same organism were observed. The C230 gene was resident in >50% of the microbial population tested, while other genes occurred in lower proportions with the least observed in nahAC and PAHRHD. These organisms can serve as potential bioremediation agents.

Evaluation of seven chemical pesticides by mixed microbial culture (PCS-1): Degradation ability, microbial community, and Medicago sativa phytotoxicity

Environmental problems caused by the large-scale use of chemical pesticides are becoming more and more serious, and the removal of chemical pesticides from the ecological environment by microbial degradation has attracted wide attention. In this study, using enrichment screening with seven chemical pesticides as the sole carbon source, a mixed microbial culture (PCS-1) was obtained from the continuous cropping of strawberry fields. The microbial community composition, degradation ability, and detoxification effect of PCS-1 was determined for the seven pesticides. Inoculation with PCS-1 showed significant degradation of and tolerance to the seven pesticides. Microbial community composition analysis indicated that Pseudomonas, Enterobacter, Aspergillus, and Rhodotorula were the dominant genera for the degradation of the seven pesticides by PCS-1. The concentration of the seven pesticides was 10 mg L^-1 in hydroponic and soil culture experiments. The fresh weight, plant height, and root length of PCS-1-inoculated alfalfa (Medicago sativa) significantly increased compared with those of non-PCS-1-inoculated M. sativa. PCS-1 not only effectively degraded the residual content of the seven pesticides in water and soil but also reduced the pesticide residues in the roots, stems, and leaves of M. sativa. This study shows that PCS-1 may be important in environmental remediation involving the seven pesticides.

Bio-removal of tetracycline antibiotics under the consortium with probiotics Bacillus clausii T and Bacillus amyloliquefaciens producing biosurfactants

The contamination of the aquatic environments by tetracycline antibiotics (TCs) is an increasingly pressing issue. Here, we used the addition of exogenous surfactants and in situ biosynthesis of biosurfactants to remove tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC), and their mixtures using the co-culture of probiotic Bacillus clausii T and Bacillus amyloliquefaciens HM618 producing surfactin. The addition of exogenous biosurfactants to remove TCs was superior to nonionic surfactants. The maximal bio-removal efficiencies for OTC and CTC among mixed antibiotics under the co-culture of B. clausii T and B. amyloliquefaciens HM618 were 76.6% and 88.9%, respectively, which were both better than the efficiency of the pure culture of B. clausii T. TCs were removed mainly through biotransformation rather than absorption and hydrolysis. The removal efficiency was in the order CTC > OTC > TC. The co-culture of B. clausii T and B. amyloliquefaciens HM618 alleviated the cytotoxicity of OTC and CTC. The toxicity of the biotransformation products was lower than that of the parent compounds. Demethylation, hydroxylation, and dehydration are likely the major mechanisms of TC biotransformation. These results illustrate the potential of using surfactants in the bioremediation of tetracycline antibiotics, and provide new avenues for further exploration of the bioremediation of antibiotics pollution.

Effect of competition between petroleum-degrading bacteria and indigenous compost microorganisms on the efficiency of petroleum sludge bioremediation: Field application of mineral-based culture in the composting process

The effect of competition between isolated petroleum-degrading bacteria (PDB) and indigenous compost microorganisms (ICM) on the efficiency of composting process in bioremediation of petroleum waste sludge (PWS) was investigated. After isolating two native PDB (Acinetobacter radioresistens strain KA5 and Enterobacter hormaechei strain KA6) from PWS, their ability for growth and crude oil degradation was examined in the mineral-based culture (MBC). Then, the PDB isolate were inoculated into the composting experiments and operated for 12 weeks. The results showed that the PDB degraded 21.65-68.73% of crude oil (1-5%) in the MBC after 7 days. The PDB removed 84.30% of total petroleum hydrocarbon (TPHs) in the composting bioreactor containing the initial TPH level of 20 g kg^-1. Removal of petroleum hydrocarbons (PHCs) in the composting experiments proceeded according to the first-order kinetics. The computed values of degradation rate constants and half-lives showed a better performance of the PDB than ICM for TPHs removal. This finding suggests that simultaneous application of the PDB and ICM in the composting reactors resulted in a decline in the effectiveness of the PDB which is due to competition between them. The study also verified that the capability of PDB in degrading PHCs can be successfully scaled-up from MBC to composting process.

Biosurfactant: A new frontier for greener technology and environmental sustainability

Petroleum hydrocarbons, oil, heavy metals pollution is becoming additional severe problem due to the growing call for crude oil and crude oil products related products in several fields of application. Such pollution have fascinated much considerations and attractions as it leads to ecological damages in both marines, aquatic and terrestrial ecosystems. Thus, different techniques including chemical surfactants and complex technologies have been proposed for their clean up from the environment, which in turn has detrimental effects on the environment. As of late, biosurfactant compounds have added much deliberation since they are considered as a reasonable option and eco-accommodating materials for remediation technology. The present society is confronting a few difficulties of usage, authorizing ecological protection and environmental change for the next generations. Biosurfactants hold the special property of minimizing and reducing the interfacial tension of liquids. Such features endure biosurfactants to afford a major part in emulsification, de-emulsification, biodegradability, foam formation, washing performance, surface activity, and detergent formulation, which have potential applications in the diverse industrial set-up. Conversations on cost-effective technologies, renewable materials, novel synthesis, downstream, upstream, emerging characterization techniques, molecular, and genetical engineering are substantial to produce biosurfactant of quality and quantity. Therefore, greater attention is being paid to biosurfactant production by identifying their environmental, and biotechnological applications. Be that as it may, the extravagant cost drew in with biosurfactants biotechnological synthesis and recovery can hamper their application in those areas. Notwithstanding these costs, biosurfactants can be used as these parts shows outstandingly high benefits that can at present beat the expenses incurred in the initial purification and downstream processes. Biosurfactant production by microorganisms is relatively considered one of the crucial know-how for improvement, growth, advancement, and environmental sustainability of the 21st century. There is a developing conversation around environmental safety and the significant role that biosurfactants will progressively play soon, for instance, the use of renewable by-products as substrates, potential reduction, re-use and recycling of waste and waste products. The review confers the usefulness of biosurfactants in the removal of environmental contaminants and, consequently, expanding environmental safety and drive towards greener technology.

Biodegradation of high concentrations of petroleum compounds by using indigenous bacteria isolated from petroleum hydrocarbons-rich sludge: Effective scale-up from liquid medium to composting process

The scale-up of petroleum hydrocarbons-rich sludge (PHRS) bioremediation from liquid medium to a composting method bioaugmentated with two indigenous bacteria, capable of degrading high levels of crude oil, was surveyed. After isolating the strains (Sphingomonas olei strain KA1 and Acinetobacter radioresistens strain KA2) and determining their biomass production, emulsification index (E₂₄), bacterial adhesion to hydrocarbon (BATH), and crude oil degradation in liquid medium, they were inoculated into the composting experiments. In liquid medium, the removal rate of crude oil were 67.25, 70.86, 61.77, 42.13, and 27.92%, respectively for the initial oil levels of 1, 2, 3, 4, and 5% after 7 days. Degradation of 10, 20, 30, 40 and 50 g kg^-1 concentrations of total petroleum hydrocarbons (TPH) were also calculated to be 91.24, 87.23, 84.69, 74.08, and 60.14%, respectively after a composting duration of 12 weeks. The values of the rate constants (k) and half-lives (t_1/2) of petroleum hydrocarbons degradation were 0.083-0.212 day^-1 and 3.27-8.35 days for the first-order and 0.003-0.089 g kg^-1day^-1 and 1.12-6.67 days for the second-order model, respectively. This study verified the suitability of the isolated strains for PHRS bioremediation. Successful scale-up of PHRS bioremediation from a liquid medium to a composting process for degrading high amounts of TPH was also confirmed.

Development of a bacterial consortium comprising oil-degraders and diazotrophic bacteria for elimination of exogenous nitrogen requirement in bioremediation of diesel-contaminated soil

The purpose of this study was to develop an effective bacterial consortium and determine their ability to overcome nitrogen limitation for the enhanced remediation of diesel-contaminated soils. Towards this, various bacterial consortia were constructed using oil-degrading and nitrogen-fixing microbes. The diesel removal efficiency of various developed consortia was evaluated by delivering the bacterial consortia to the diesel-contaminated soils. The consortium Acinetobacter sp. K-6 + Rhodococcus sp. Y2-2 + NH₄NO₃ resulted in the highest removal (85.3%) of diesel from the contaminated soil. The consortium containing two different oil-degrading microbes (K-6 + Y2-2) and one nitrogen-fixing microbe Azotobacter vinelandii KCTC 2426 removed 83.1% of the diesel from the soil after 40 days of treatment. The total nitrogen content analysis revealed higher amounts of nitrogen in soil treated with the nitrogen-fixing microbe when compared with that of the soil supplemented with exogenous inorganic nitrogen. The findings in this present study reveal that the consortium containing the nitrogen-fixing microbe degraded similar amounts of diesel to that degraded by the consortium supplemented with exogenous inorganic nitrogen. This suggests that the developed consortium K-6 + Y2-2 + KCTC 2426 compensated for the nitrogen limitation and eliminated the need for exogenous nitrogen in bioremediation of diesel-contaminated soils.

Isolation, identification, and characterization of diesel-oil-degrading bacterial strains indigenous to Changqing oil field, China

In the present study, 12 indigenous diesel-oil-degrading bacteria were isolated from the petroleum-contaminated soils of the Changqing oil field (Xi'an, China). Measurement of the diesel-oil degradation rates of these strains by the gravimetric method revealed that they ranged from 42% to 66% within 2 weeks. The highest degradation rates were observed from strains CQ8-1 (66%), CQ8-2 (62.6%), and CQ11 (59%), which were identified as Bacillus thuringiensis, Ochrobactrum anthropi, and Bordetella bronchialis, respectively, based on their 16S rDNA sequences. Moreover, the physiological and biochemical properties of these three strains were analyzed by Gram staining, catalase, oxidase, and Voges-Proskauer tests. Transmission electron microscopy showed that all three strains were rod shaped with flagella. Gas chromatography and mass spectrometric analyses indicated that medium- and long-chain n-alkanes in diesel oil (C11-C29) were degraded to different degrees by B. thuringiensis, O. anthropi, and B. bronchialis, and the degradation rates gradually decreased as the carbon numbers increased. Overall, the results of this study indicate strains CQ8-1, CQ8-2, and CQ11 might be useful for environmentally friendly and cost-effective bioremediation of oil-contaminated soils.

Enhancement of Paenibacillus sp. D9 Lipopeptide Biosurfactant Production Through the Optimization of Medium Composition and Its Application for Biodegradation of Hydrophobic Pollutants

Interests in biosurfactant in industrial and environmental applications have increased considerably in recent years, owing to their potential benefits over synthetic counterparts. The present study aimed at analyzing the stability and oil removal efficiency of a new lipopeptide biosurfactant produced by Paenibacillus sp. D9 and its feasibility of its use in biotechnological applications. Paenibacillus sp. D9 was evaluated for optimal growth conditions and improved production yield of lipopeptide biosurfactant with variations in different substrate parameters such as carbon (C), nitrogen (N), C:N: ratio, metal supplements, pH, and temperature. Enhanced biosurfactant production was observed when using diesel fuel and ammonium sulfate as carbon and nitrogen source respectively. The maximum biosurfactant yield of 4.11 g/L by Paenibacillus sp. D9 occurred at a C/N ratio of 3:1, at pH 7.0, 30 °C, 4.0 mM MgSO₄, and 1.5% inoculum size. The D9 biosurfactant was found to retain surface-active properties under the extreme conditions such as high thermal, acidic, alkaline, and salt concentration. The ability to emulsify further emphasizes its potential usage in biotechnological application. Additionally, the lipopeptide biosurfactant exhibited good performance in the degradation of highly toxic substances when compared with chemical surfactant, which proposes its probable application in biodegradation, microbial-enhanced oil recovery or bioremediation. Furthermore, the biosurfactants were effective in a test to stimulate the solubilization of hydrophobic pollutants in both liquid environments removing 49.1 to 65.1% diesel fuel including hydrophobic pollutants. The study highlights the usefulness of optimization of culture parameters and their effects on biosurfactant production, high stability, improved desorption, and solubilization of hydrophobic pollutants.

Biodegradation of pyraclostrobin by two microbial communities from Hawaiian soils and metabolic mechanism

Pyraclostrobin has been widely and long-termly applicated to agricultural fields. The removal of pyraclostrobin from ecological environment has received wide attention. In this study, using sequential enrichments with pyraclostrobin as a sole carbon source, two microbial communities (HI2 and HI6) capable of catabolizing pyraclostrobin were obtained from Hawaiian soils. The microfloras analysis indicated that only Proteobacteria and Bacteroides could survive in HI2-soil after acclimatization, whereas the number of Proteobacteria in HI6-soil accounted for more than 99%. The percentages of Pseudomonas in the HI2 and HI6 microfloras were 69.3% and 59.3%, respectively. More than 99% of pyraclostrobin (C₀ = 100 mg L^-1) was degraded by the HI2 and HI6 microorganisms within five days. A unique metabolite was identified by high performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS/MS). A metabolic pathway involving carbamate hydrolysis was proposed. The tertiary amine group of pyraclostrobin was hydrolyzed to primary amine group with the decarboxylation, which facilitated pyraclostrobin detoxification because carboxylester was an important functional group. The metabolic mechanism suggested that Pseudomonas expressing carboxylesterase might be able to degrade carbamate chemicals. Therefore, Pseudomonas might be an ideal candidate for expression and cloning of carbamate-degrading gene in genomics studies. The current study would have important implications in detoxification and bioremediation of carbamates through the CN bond cleavage of methyl carbamate.

Synthesis and characterization of stabilized oxygen-releasing CaO2 nanoparticles for bioremediation

Bioremediation is one of the general methods to treat pollutants in soil, sediment, and groundwater. However, the low concentration and restricted dispersion of dissolved oxygen (DO) in these areas have limited the efficiency of remediation especially for microorganisms that require oxygen to grow. Calcium peroxide (CaO₂) is one of the oxygen-releasing compounds and has been applied to magnify the remediation efficacy of polluting areas. In this study, CaO₂ nanoparticles (NPs) were synthesized and evaluated by wet chemistry methods as well as dry and wet grinding processes. The characteristics of CaO₂ particles and NPs were analyzed and compared by dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and X-ray powder diffraction. Our results showed that wet-grinded CaO₂ NPs had an average particle size of around 110 nm and were more stable compared to other particles from aggregation and sedimentation tests. In addition, we also observed that CaO₂ NPs had better DO characteristics and patterns; these NPs generated higher DO levels than their non-grinded form. Accordingly, our results suggested that wet-grinding CaO₂ particles to nanoscale could benefit their usage in bioremediation.

Microbial diversity and activity of an aged soil contaminated by polycyclic aromatic hydrocarbons

In-depth understanding of indigenous microbial assemblages resulted from aged contamination by polycyclic aromatic hydrocarbons (PAHs) is of vital importance in successful in situ bioremediation treatments. Soil samples of three boreholes were collected at 12 different vertical depths. Overall, the dominating three-ring PAHs (76.2%) were closely related to distribution patterns of soil dehydrogenase activity, microbial cell numbers, and Shannon biodiversity index (H') of indigenous microorganisms. High-molecular-weight PAHs tend to yield more diverse communities. Results from 16S rRNA analysis indicated that possible functional groups of PAH degradation include three species in Bacillus cereus group, Bacillus sp. SA Ant14, Nocardioides sp., and Ralstonia pickettii. Principal component analysis indicates significant positive correlations between the content of high-molecular-weight PAHs and the distribution of Bacillus weihenstephanensis KBAB4 and Nocardioides sp. The species B. cereus 03BB102, Bacillus thuringiensis, B. weihenstephanensis KBAB4, and Nocardioides sp. were recognized as main PAH degraders and thus recommended to be utilized in further bioremediation applications. The vertical distribution characteristics of PAHs in soil profiles (1-12 m) and the internal relationship between the transport mechanisms of PAHs and the response of soil biological properties help further understand the microbial diversity and activity in an aged site.

Resistance of aerobic microorganisms and soil enzyme response to soil contamination with Ekodiesel Ultra fuel

This study determined the susceptibility of cultured soil microorganisms to the effects of Ekodiesel Ultra fuel (DO), to the enzymatic activity of soil and to soil contamination with PAHs. Studies into the effects of any type of oil products on reactions taking place in soil are necessary as particular fuels not only differ in the chemical composition of oil products but also in the composition of various fuel improvers and antimicrobial fuel additives. The subjects of the study included loamy sand and sandy loam which, in their natural state, have been classified into the soil subtype 3.1.1 Endocalcaric Cambisols. The soil was contaminated with the DO in amounts of 0, 5 and 10 cm³ kg^-1. Differences were noted in the resistance of particular groups or genera of microorganisms to DO contamination in loamy sand (LS) and sandy loam (SL). In loamy sand and sandy loam, the most resistant microorganisms were oligotrophic spore-forming bacteria. The resistance of microorganisms to DO contamination was greater in LS than in SL. It decreased with the duration of exposure of microorganisms to the effects of DO. The factor of impact (IF_DO) on the activity of particular enzymes varied. For dehydrogenases, urease, arylsulphatase and β-glucosidase, it had negative values, while for catalase, it had positive values and was close to 0 for acid phosphatase and alkaline phosphatase. However, in both soils, the noted index of biochemical activity of soil (BA) decreased with the increase in DO contamination. In addition, a positive correlation occurred between the degree of soil contamination and its PAH content.

Enhancement of Surfactin and Fengycin Production by Bacillus mojavensis A21: Application for Diesel Biodegradation

This work concerns the study of the enhancement of surfactin and fengycin production by B. mojavensis A21 and application of the produced product in diesel biodegradation. The influences of the culture medium and cells immobilization were studied. The highest lipopeptides production was achieved after 72 hours of incubation in a culture medium containing 30 g/L glucose as carbon source and a combination of yeast extract (1 g/L) and glutamic acid (5 g/L) as nitrogen sources with initial pH 7.0 at 30°C and 90% volumetric aeration. The study of primary metabolites production showed mainly the production of acetoin, with a maximum production after 24 h of strain growth. The use of immobilized cells seemed to be a promising method for improving lipopeptides productivity. In fact, the synthesis of both lipopeptides, mainly fengycin, was greatly enhanced by the immobilization of A21 cells. An increase of diesel degradation capacity of approximately 20, 27, and 40% in the presence of 0.5, 1, and 2 g/L of produced lipopeptides, respectively, was observed. Considering these properties, B. mojavensis A21 strain producing a lipopeptide mixture, containing both surfactin and fengycin, may be considered as a potential candidate for future use in bioremediation and crop protection.

Biosurfactants during in situ bioremediation: factors that influence the production and challenges in evalution

Research on the influence of biosurfactants on the efficiency of in situ bioremediation of contaminated soil is continuously growing. Despite the constant progress in understanding the mechanisms involved in the effects of biosurfactants, there are still many factors that are not sufficiently elucidated. There is a lack of research on autochthonous or exogenous microbial metabolism when biostimulation or bioaugmentation is carried out to produce biosurfactants at contaminated sites. In addition, studies on the application of techniques that measure the biosurfactants produced in situ are needed. This is important because, although the positive influence of biosurfactants is often reported, there are also studies where no effect or negative effects have been observed. This review aimed to examine some studies on factors that can improve the production of biosurfactants in soils during in situ bioremediation. Moreover, this work reviews the methodologies that can be used for measuring the production of these biocomposts. We reviewed studies on the potential of biosurfactants to improve the bioremediation of hydrocarbons, as well as the limitations of methods for the production of these biomolecules by microorganisms in soil.

Efficient phytoremediation of organic contaminants in soils using plant-endophyte partnerships

Soil pollution with organic contaminants is one of the most intractable environmental problems today, posing serious threats to humans and the environment. Innovative strategies for remediating organic-contaminated soils are critically needed. Phytoremediation, based on the synergistic actions of plants and their associated microorganisms, has been recognized as a powerful in situ approach to soil remediation. Suitable combinations of plants and their associated endophytes can improve plant growth and enhance the biodegradation of organic contaminants in the rhizosphere and/or endosphere, dramatically expediting the removal of organic pollutants from soils. However, for phytoremediation to become a more widely accepted and predictable alternative, a thorough understanding of plant-endophyte interactions is needed. Many studies have recently been conducted on the mechanisms of endophyte-assisted phytoremediation of organic contaminants in soils. In this review, we highlight the superiority of organic pollutant-degrading endophytes for practical applications in phytoremediation, summarize alternative strategies for improving phytoremediation, discuss the fundamental mechanisms of endophyte-assisted phytoremediation, and present updated information regarding the advances, challenges, and new directions in the field of endophyte-assisted phytoremediation technology.

Hydrocarbons biodegradation by activated sludge bacteria in the presence of natural and synthetic surfactants

Fuels, such as diesel oil, can have a substantial impact on the microbial equilibrium of activated sludge and have a negative influence on work of wastewater treatment plant. The primary objective of the research was to examine the possibility of using the surfactants to improve pollutants biodegradation by bacteria from activated sludge. The results showed that the addition of rhamnolipids allows to increase the hydrocarbon biodegradation from 47% up to 75% in the cultures inoculated with the consortium. The saponins increased the degradation of diesel oil by the two isolated strains: from 27% to 43% for Alcaligenes sp. and from 44% to 64% for Pseudomonas sp. The addition of surfactants to the cultures growth with diesel oil caused a significant decrease of the surface charge for Alcaligenes strain in the presence of saponins, but not in other cases. The obtained results revealed the potential of natural surfactants to support hydrocarbon biodegradation in wastewater treatment plants.

Development of an Efficient Bacterial Consortium for the Potential Remediation of Hydrocarbons from Contaminated Sites

The intrinsic biodegradability of hydrocarbons and the distribution of proficient degrading microorganisms in the environment are very crucial for the implementation of bioremediation practices. Among others, one of the most favorable methods that can enhance the effectiveness of bioremediation of hydrocarbon-contaminated environment is the application of biosurfactant producing microbes. In the present study, the biodegradation capacities of native bacterial consortia toward total petroleum hydrocarbons (TPH) with special emphasis to poly aromatic hydrocarbons were determined. The purpose of the study was to isolate TPH degrading bacterial strains from various petroleum contaminated soil of Assam, India and develop a robust bacterial consortium for bioremediation of crude oil of this native land. From a total of 23 bacterial isolates obtained from three different hydrocarbons contaminated samples five isolates, namely KS2, PG1, PG5, R1, and R2 were selected as efficient crude oil degraders with respect to their growth on crude oil enriched samples. Isolates KS2, PG1, and R2 are biosurfactant producers and PG5, R1 are non-producers. Fourteen different consortia were designed involving both biosurfactant producing and non-producing isolates. Consortium 10, which comprises two Bacillus strains namely, Bacillus pumilus KS2 and B. cereus R2 (identified by 16s rRNA sequencing) has shown the best result in the desired degradation of crude oil. The consortium showed degradation up to 84.15% of TPH after 5 weeks of incubation, as revealed from gravimetric analysis. FTIR (Fourier transform infrared) and GCMS (Gas chromatography-mass spectrometer) analyses were correlated with gravimetric data which reveals that the consortium has removed a wide range of petroleum hydrocarbons in comparison with abiotic control including different aliphatic and aromatic hydrocarbons.

A Combinatorial Algorithm for Microbial Consortia Synthetic Design

Synthetic biology has boomed since the early 2000s when it started being shown that it was possible to efficiently synthetize compounds of interest in a much more rapid and effective way by using other organisms than those naturally producing them. However, to thus engineer a single organism, often a microbe, to optimise one or a collection of metabolic tasks may lead to difficulties when attempting to obtain a production system that is efficient, or to avoid toxic effects for the recruited microorganism. The idea of using instead a microbial consortium has thus started being developed in the last decade. This was motivated by the fact that such consortia may perform more complicated functions than could single populations and be more robust to environmental fluctuations. Success is however not always guaranteed. In particular, establishing which consortium is best for the production of a given compound or set thereof remains a great challenge. This is the problem we address in this paper. We thus introduce an initial model and a method that enable to propose a consortium to synthetically produce compounds that are either exogenous to it, or are endogenous but where interaction among the species in the consortium could improve the production line.

Improvement of methyl orange dye biotreatment by a novel isolated strain, Aeromonas veronii GRI, by SPB1 biosurfactant addition

Aeromonas veronii GRI (KF964486), isolated from acclimated textile effluent after selective enrichment on azo dye, was assessed for methyl orange biodegradation potency. Results suggested the potential of this bacterium for use in effective treatment of azo-dye-contaminated wastewaters under static conditions at neutral and alkaline pH value, characteristic of typical textile effluents. The strain could tolerate higher doses of dyes as it was able to decolorize up to 1000 mg/l. When used as microbial surfactant to enhance methyl orange biodecolorization, Bacillus subtilis SPB1-derived lipopeptide accelerated the decolorization rate and maximized slightly the decolorization efficiency at an optimal concentration of about 0.025%. In order to enhance the process efficiency, a Taguchi design was conducted. Phytotoxicity bioassay using sesame and radish seeds were carried out to assess the biotreatment effectiveness. The bacterium was able to effectively decolorize the azo dye when inoculated with an initial optical density of about 0.5 with 0.25% sucrose, 0.125% yeast extract, 0.01% SPB1 biosurfactant, and when conducting an agitation phase of about 24 h after static incubation. Germination potency showed an increase toward the nonoptimized conditions indicating an improvement of the biotreatment. When comparing with synthetic surfactants, a drastic decrease and an inhibition of orange methyl decolorization were observed in the presence of CTAB and SDS. The nonionic surfactant Tween 80 had a positive effect on methyl orange biodecolorization. Also, studies ensured that methyl orange removal by this strain could be due to endocellular enzymatic activities. To conclude, the addition of SPB1 bioemulsifier reduced energy costs by reducing effective decolorization period, biosurfactant stimulated bacterial decolorization method may provide highly efficient, inexpensive, and time-saving procedure in treatment of textile effluents.