Microbial enzymes and their exploitation in remediation of environmental contaminants

2021 ◽  
pp. 59-71
Author(s):  
Sandeep Kumar Singh ◽  
Manoj Kumar Singh ◽  
Vipin Kumar Singh ◽  
Arpan Modi ◽  
Pooja Jaiswal ◽  
...  
Keyword(s):  
Environmental Contaminants ◽  
Microbial Enzymes

Reductive Dehalogenation of Environmental Contaminants: A Critical Review

1989 ◽  
Vol 24 (2) ◽  
pp. 299-322 ◽  
Author(s):  
R. M. Baxter
Keyword(s):  
Hydrogen Atom ◽  
Aromatic Compounds ◽  
Reductive Dechlorination ◽  
Halogen Atom ◽  
Environmental Contaminants ◽  
Methanogenic Bacteria ◽  
Photochemical Reactions ◽  
Reductive Dehalogenation ◽  
Iron Porphyrins ◽  
Aliphatic Compounds

Abstract It is generally recognized that reductive processes are more important than oxidative ones in transforming, degrading and mineralizing many environmental contaminants. One process of particular importance is reductive dehalogenation, i.e., the replacement of a halogen atom (most commonly a chlorine atom) by a hydrogen atom. A number of different mechanisms are involved in these reactions. Photochemical reactions probably play a role in some instances. Aliphatic compounds such as chloroethanes, partly aliphatic compounds such as DDT, and alicyclic compounds such as hexachlorocyclohexane are readily dechlorinated in the laboratory by reaction with reduced iron porphyrins such as hematin. Many of these are also dechlorinated by cultures of certain microorganisms, probably by the same mechanism. Such compounds, with a few exceptions, have been found to undergo reductive dechlorination in the environment. Aromatic compounds such as halobenzenes, halophenols and halobenzoic acids appear not to react with reduced iron porphyrins. Some of these however undergo reductive dechlorination both in the environment and in the laboratory. The reaction is generally associated with methanogenic bacteria. There is evidence for the existence of a number of different dechlorinating enzymes specific for different isomers. Recently it has been found that many components of polychlorinated biphenyls (PCBs), long considered to be virtually totally resistant to environmental degradation, may be reductively dechlorinated both in the laboratory and in nature. These findings suggest that many environmental contaminants may prove to be less persistent than was previously feared.

Microbial enzymes used in prodrug activation for cancer therapy: Insights and future perspectives

2020 ◽  
Vol 21 ◽  
Author(s):  
Rakhi Dhankhar ◽  
Anubhuti Kawatra ◽  
Aparajita Mohanty ◽  
Pooja Gulati
Keyword(s):  
Purine Nucleoside Phosphorylase ◽  
Cytosine Deaminase ◽  
Therapeutic Index ◽  
Enzyme Prodrug Therapy ◽  
Prodrug Activation ◽  
Microbial Enzymes ◽  
High Productivity ◽  
Delivery Vector ◽  
Exogenous Enzymes ◽  
Activation Therapy

Abstract:: Enzyme prodrug therapy has gained momentum in the recent years due to their ability to improve therapeutic index (benefits versus toxic side-effects) and efficacy of chemotherapy in cancer treatment. Inactive prodrugs used in this system are converted into active anti-cancerous drugs by enzymes, specifically within the tumor cells. This therapy involves three components namely prodrug, enzyme and gene delivery vector. Past reports have clearly indicated that the choice of enzyme used, is the major determinant for the success of this therapy. Generally, enzymes from non-human sources are employed to avoid off-target toxicity. Exogenous enzymes also give a better control to the clinician regarding the calibration of treatment by site-specific initiation. Amongst these exo-enzymes, microbial enzymes are preferred due to their high productivity, stability and ease of manipulation. The present review focuses on the commonly used microbial enzymes particularly cytosine deaminase, nitroreductase, carboxypeptidase, purine nucleoside phosphorylase in prodrug activation therapy. Various aspects viz. source of the enzymes, types of cancer targeted, mode of action and efficacy of the enzyme/prodrug system, efficient vectors used and recent research developments of each of these enzymes are comprehensively elaborated. Further, the results of the clinical trials and various strategies to improve their clinical applicability are also discussed.

Fluorescent Nanotechnology: An Evolution in Optical Sensors

2020 ◽  
Vol 17 ◽  
Author(s):  
Dilawar Hassan ◽  
Hadi Bakhsh ◽  
Asif M. Khurram ◽  
Shakeel A. Bhutto ◽  
Nida S. Jalbani ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Sensors ◽  
Light Emission ◽  
Environmental Contaminants ◽  
Fluorescent Nanoparticles ◽  
Sensing Applications ◽  
Properties Of Materials ◽  
Optical Properties Of Materials ◽  
Fluorescent Nanomaterials

Background: The optical properties of nanomaterials have evolved enormously with the introduction of nanotechnology. The property of materials to absorb and/or emit specific wavelength has turned them into one of the most favourite candidates to be effectively utilized in different sensing applications e.g organic light emission diodes (OLEDs) sensors, gas sensors, biosensors and fluorescent sensors. These materials have been reported as a sensor in the field of tissue and cell imaging, cancer detection and detection of environmental contaminants etc. Fluorescent nanomaterials are heling in rapid and timely detection of various contaminants that greatly impact the quality of life and food, that is exposed to these contaminants. Later, all the contaminants have been investigated to be most perilous entities that momentously affect the life span of the animals and humans who use those foods which have been contaminated. Objective: In this review, we will discuss about various methods and approaches to synthesize the fluorescent nanoparticles and quantum dots (QDs) and their applications in various fields. The application will include the detection of various environmental contaminants and bio-medical applications. We will discuss the possible mode of action of the nanoparticles when used as sensor for the environmental contaminants as well as the surface modification of some fluorescent nanomaterials with anti-body and enzyme for specific detection in animal kingdom. We will also describe some RAMAN based sensors as well as some optical sensing-based nanosensors. Conclusion: Nanotechnology has enabled to play with the size, shape and morphology of materials in the nanoscale. The physical, chemical and optical properties of materials change dramatically when they are reduced to nanoscale. The optical properties can become choosy in terms of emission or absorption of wavelength in the size range and can result in production of very sensitive optical sensor. The results show that the use of fluorescent nanomaterials for the sensing purposes are helping a great deal in the sensing field.

scholarly journals The Role of the Human Microbiome in Chemical Toxicity

2019 ◽  
Vol 38 (4) ◽  
pp. 251-264 ◽  
Author(s):  
Jason M. Koontz ◽  
Blair C. R. Dancy ◽  
Cassandra L. Horton ◽  
Jonathan D. Stallings ◽  
Valerie T. DiVito ◽  
...  
Keyword(s):  
Health Outcomes ◽  
Human Microbiome ◽  
Chemical Exposure ◽  
Environmental Chemicals ◽  
Microbial Interactions ◽  
World Population ◽  
Toxic Exposure ◽  
Chemical Toxicity ◽  
Microbial Enzymes ◽  
Overwhelming Evidence

There is overwhelming evidence that the microbiome must be considered when evaluating the toxicity of chemicals. Disruption of the normal microbial flora is a known effect of toxic exposure, and these disruptions may lead to human health effects. In addition, the biotransformation of numerous compounds has been shown to be dependent on microbial enzymes, with the potential for different host health outcomes resulting from variations in the microbiome. Evidence suggests that such metabolism of environmental chemicals by enzymes from the host's microbiota can affect the toxicity of that chemical to the host. Chemical-microbial interactions can be categorized into two classes: Microbiome Modulation of Toxicity (MMT) and Toxicant Modulation of the Microbiome (TMM). MMT refers to transformation of a chemical by microbial enzymes or metabolites to modify the chemical in a way that makes it more or less toxic. TMM is a change in the microbiota that results from a chemical exposure. These changes span a large magnitude of effects and may vary from microbial gene regulation, to inhibition of a specific enzyme, to the death of the microbes. Certain microbiomes or microbiota may become associated with different health outcomes, such as resistance or susceptibility to exposure to certain toxic chemicals, the ability to recover following a chemical-induced injury, the presence of disease-associated phenotypes, and the effectiveness of immune responses. Future work in toxicology will require an understanding of how the microbiome interacts with toxicants to fully elucidate how a compound will affect a diverse, real-world population.

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