Growth inhibition and stimulation of Shewanella oneidensis MR-1 by surfactants and calcium polysulfide

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.

Surfactant-enhanced mobilization of persistent organic pollutants: Potential for soil and sediment remediation and unintended consequences

This review aims to provide an overview of the sources and reactions of persistent organic pollutants (POPs) and surfactants in soil and sediments, the surfactant-enhanced solubilisation of POPs, and the unintended consequences of surfactant-induced remediation of soil and sediments contaminated with POPs. POPs include chemical compounds that are recalcitrant to natural degradation through photolytic, chemical, and biological processes in the environment. POPs are potentially toxic compounds mainly used in pesticides, solvents, pharmaceuticals, or industrial applications and pose a significant and persistent risk to the ecosystem and human health. Surfactants can serve as detergents, wetting and foaming compounds, emulsifiers, or dispersants, and have been used extensively to promote the solubilization of POPs and their subsequent removal from environmental matrices, including solid wastes, soil, and sediments. However, improper use of surfactants for remediation of POPs may lead to unintended consequences that include toxicity of surfactants to soil microorganisms and plants, and leaching of POPs, thereby resulting in groundwater contamination.

Investigation of factors affecting phytoremediation of multi-elements polluted calcareous soil using Taguchi optimization

Growing environmental concern regarding multi elements-contaminated soils reveals the necessity of paying more attention to environmentally friendly remediation techniques such as phytoremediation. A large number of factors influences phytoremediation of potentially toxic elements (PTEs) and investigation on a variety of these factors need appropriate statistical approaches such as "Taguchi optimization" which effectively decreases time and cost of experiments. In the present study, based on the Taguchi optimization method, the effects of several biological (plant type and mycorrhizal fungi (AMF)) and chemical (chelating agents, surfactants and organic acids) factors, on the phytoremediation of soils contaminated with zinc (Zn), lead (Pb), cadmium (Cd) and nickel (Ni) were investigated. The goal was to find out the most effective factors as well as the best level for each factor. The values of dry weights in roots and aerial parts of the studied plants were in orders of maize > sorghum > sunflower and sorghum > maize > sunflower, respectively. AMF was the main factor in increasing dry weight of shoots. Inoculation of AMF caused increases in root and shoot uptake of some PTEs. RESULTS: showed that phytoremediation of PTEs is element-dependent; as Zn showed the highest translocation factor (TF) and bioconcentration factor (BCF) values, while Ni showed the lowest ones and the intermediate values belonged to Pb and Cd. These results show the diverse distribution of elements in plant parts, as Zn and Ni were mostly accumulated in shoot and root, respectively. Although different factors caused impacts on phytoremediation criteria, the role of plant type in the phytoremediation of PTEs was at the first rank. Mean TF of PTEs in sunflower was 6.3 times that of maize. Sunflower showed high TF value for the four elements and translocated most of the PTEs from root to the aerial parts demonstrating phytoextraction as the main mechanism in this plant. Maize and sorghum, however, showed low TF and accumulated most of PTEs in their roots revealing phytostabilization as the main mechanism. In general, it can be concluded that plant type was the most influential factor in the phytoremediation of PTEs followed by EDTA and AMF. Taguchi optimization revealed the appropriateness and significance of different chemical and biological treatments on phytoremediation criteria of different elements.

Soil Bioremediation: Overview of Technologies and Trends

Petroleum hydrocarbons, heavy metals and agricultural pesticides have mutagenic, carcinogenic, immunotoxic and teratogenic effects and cause drastic changes in soil physicochemical and microbiological characteristics, thereby representing a serious danger to health and environment. Therefore, soil pollution urgently requires the application of a series of physicochemical and biological techniques and treatments to minimize the extent of damage. Among them, bioremediation has been shown to be an alternative that can offer an economically viable way to restore polluted areas. Due to the difficulty in choosing the best bioremediation technique for each type of pollutant and the paucity of literature on soil bioremediation enhanced by the use of specific additives, we reviewed the main in situ and ex situ methods, their current properties and applications. The first section discusses the characteristics of each class of pollutants in detail, while the second section presents current bioremediation technologies and their main uses, followed by a comparative analysis showing their respective advantages and disadvantages. Finally, we address the application of surfactants and biosurfactants as well as the main trends in the bioremediation of contaminated soils.

Chemical- and microbial-enhanced phytoremediation of cadmium-contaminated calcareous soil by maize

Phytoremediation is an appropriate technology used to remove pollutants from environment components. A greenhouse trial was conducted to test the hypothesis that application of surfactant levels and inoculation with Pseudomonas fluorescens bacterium and/or Piriformospora indica fungus enhances the phytoremediation of cadmium (Cd). Maize seeds were sown in Cd-polluted soil, and after 2 months Cd status in plant tissues and Cd phytoremediation criteria was determined. Results showed that application of surfactant increased root and shoot dry weight. Mean Cd uptake in roots and shoots increased following the application of 2 and 4 mmol kg−1 Tween 80, respectively. Application of 2 mmol kg−1 Tween 80 increased mean Cd uptake efficiency, while application of 4 mmol kg−1 Tween 80 increased phytoextraction and translocation efficiencies. Inoculation with P. indica and P. fluorescens was mostly effective in increasing Cd uptake and Cd phytoextraction efficiency, respectively. Co-inoculation with P. indica and P. fluorescens had no superiority to application of each inoculant alone. Since most of the Cd remained in roots, phytostabilization is probably the main mechanism controlling Cd phytoremediation by maize. According to the results, application of Tween 80 and inoculation with P. indica and P. fluorescens effectively enhanced phytoremediation of Cd-contaminated soil by maize.

Stabilizing Effects on a Cd Polluted Coastal Wetland Soil using Calcium Polysulphide

In this study, different dosages of calcium polysulphide (CaS_x) were used as an amendment to investigate effects on the immobilizing of Cd in a wetland soil by pot experiment. In addition to chemical analysis (pH and bioavailable Cd concentration), changes in soil enzyme activities, microbial carbon utilization capacity, metabolic and community diversity were examined to assess dynamic impacts on soil environmental quality and toxicity of Cd resulting from ameliorant dosing. Soil pH increased immediately upon CaS_x amendment compared to the unamended control (CK), and then declined slowly to a level lower than CK. Diethylenetriamine pentaacetic acid (DTPA) extractable Cd concentration was determined to characterize the bioavailability of Cd in the soil. The CaS_x dose-dependent effect observed that with increasing CaS_x dosage, the immobilizing efficiency decreased. Soil urease and catalase activity assays and Biolog EcoPlate assay indicated that early stage addition of CaS_x significantly inhibited soil microbial activities. However, mid and late stage time periods showed the inhibition effects were alleviated, and the microbial activities could be recovered in 1% and 2% CaS_x treatments. Moreover, with increasing incubation time, microbial community diversity and richness were significantly recovered in 1% and 2% CaS_x treatments compared to the CK. No considerable changes were observed in the 5% CaS_x treatment. Conclusively, the 1% CaS_x amendment was an efficient and safe dosage for the stabilization of Cd contaminated wetland soil. This study contributes to the development of in situ remediation ameliorants and technologies for heavy metal polluted wetland soils.

Calcium polysulphide, its applications and emerging risk of environmental pollution-a review article

Easy availability, preparation technique, and economic value make calcium polysulphide (CaS _x ) a very useful inorganic chemical for various field and industrial applications. In this article, disparate applications of CaS _x solution have been reviewed to suggest potential and future consolidation. This article also encompasses the physiochemical properties and production of CaS _x solution, with critical appraisal on research focusing on CaS _x application in agriculture industries and removal of potentially toxic elements (PTEs) from the environment. The kinetics of CaS _x , technical issues associated with optimization of its dosage and environmental fate is also discussed in detail. This study covers almost all of the peer-reviewed research that has been performed since 1914. Some of the critiques in this article include the lack of integration between the exposure effect and the efficiency of treatment method, effects of oxidizing environments on the long-term performance of CaS _x solution, and kinetics of CaS _x solution with the PTEs. The working model of CaS _x with PTEs is still system dependent, and therefore cannot be used with other applications. The kinetics of CaS _x is described in detail with various phase stoichiometric reactions. Environmental fate is discussed based on applications, government reports, peer-reviewed articles and kinetics of CaS _x , which provides a clear picture of emerging contaminants in the environment in relation to the insect resistance and ecotoxicology. Real time, lab based research articles are needed to identify toxicity limits of CaS _x in environment in order to describe its effective permissible limit in environmental system. This review article provides a risk assessment of environmental pollution by CaS _x based on its physicochemical characteristic, stoichiometry, kinetics, field, and industrial applications.

Use of surfactants for the remediation of contaminated soils: a review

Due to the great harm caused by soil contamination, there is an increasing interest to apply surfactants to the remediation of a variety of contaminated soils worldwide. This review article summarizes the findings of recent literatures regarding remediation of contaminated soils/sites using surfactants as an enhancing agent. For the surfactant-based remedial technologies, the adsorption behaviors of surfactants onto soil, the solubilizing capability of surfactants, and the toxicity and biocompatibility of surfactants are important considerations. Surfactants can enhance desorption of pollutants from soil, and promote bioremediation of organics by increasing bioavailability of pollutants. The removal of heavy metals and radionuclides from soils involves the mechanisms of dissolution, surfactant-associated complexation, and ionic exchange. In addition to the conventional ionic and nonionic surfactants, gemini surfactants and biosurfactants are also applied to soil remediation due to their benign features like lower critical micelle concentration (CMC) values and better biocompatibility. Mixed surfactant systems and combined use of surfactants with other additives are often adopted to improve the overall performance of soil washing solution for decontamination. Worldwide the field studies and full-scale remediation using surfactant-based technologies are yet limited, however, the already known cases reveal the good prospect of applying surfactant-based technologies to soil remediation.

Synthesis and properties of quaternary ammonium surfactants containing a methoxy benzyl substitute

m-MDRA-n exhibit high surface activity, excellent adsorptive and bacterial properties, thermodynamic functions of micellization for m-MDRA-n were researched.