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Approaches for increasing bioremediation capabilities of plants and microorganisms towards heavy metals and radionuclides
Published in Rym Salah-Tazdaït, Djaber Tazdaït, Phyto and Microbial Remediation of Heavy Metals and Radionuclides in the Environment, 2022
Rym Salah-Tazdaït, Djaber Tazdaït
An alternative method is the use of genetically modified bacteria cells killed before they come into contact with the polluted matrix. Because DNA is stable in the environment, dead cells can transfer plasmids to other organisms. In addition, even if such cells obviously cannot multiply in the environment, they could release enzymes there or carry on their surface molecules capable of degrading or absorbing pollutants. However, their use would require developing effective methods of contacting the pollutant within the contaminated matrix and repeating them throughout the treatment. For the first time in the United States, a team from the University of Minnesota at St Paul used a recombinant strain of E. coli manipulated to overexpress an atrazine chlorohydrolase to decontaminate soil polluted by atrazine, a herbicide widely used in agriculture. Before their application to the surfaces to be treated, the bacteria had been killed by a chemical agent, glutaraldehyde. In eight weeks, the authors found a reduction in the concentration of atrazine by 77%. They consider this to be the minimum efficiency of their technique because it was applied in late fall when temperatures were already low enough. These authors also noted that the enzymatic activity was preserved for several months after treating the bacteria with glutaralde-hyde. This stability is undoubtedly one of the keys to the effectiveness of the treatment (Strong, McTavish, Sadowsky, and Wackett 2000, 91).
Role of Enzymes in the Bioremediation of Refractory Pollutants
Published in Maulin P. Shah, Removal of Refractory Pollutants from Wastewater Treatment Plants, 2021
Viresh R. Thamke, Ashvini U. Chaudhari, Kisan M. Kodam, Jyoti P. Jadhav
LinB has been characterized in Spingobium sp. And is effective against the β and γ isomers of lindane. The other enzyme coded by gene LinA (discussed in the Lyases section) is closely associated with the activity of LinB. It is effective against the product transformed by LinA and acts against various isoforms of lindane pesticide. This implies the use of multiple enzymes for the bioremediation of various pesticides and their isoforms. Several fungi, namely Trametes hirsutus, Phanerochaete chrysosporium, Phanerochaete sordia, and Cyathus bulleri, are able to degrade lindane and other pesticides (Singh et al. 2000). As mentioned above, hydrolases are highly promiscuous in nature; they are operational in catalyzing a plethora of organic compounds with varied functional groups. One of the most extensively studied chlorinated polycyclic hydrocarbon is Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-1,3,5-triazine)]. Atrazine chlorohydrolase (AtaA), first characterized in Pseudomonas, catalyzes the hydrolysis of carbon–halide bonds [Figure 28.5(D)].
Bioremediation of Pesticides with Microbes: Methods, Techniques and Practices
Published in Amitava Rakshit, Manoj Parihar, Binoy Sarkar, Harikesh B. Singh, Leonardo Fernandes Fraceto, Bioremediation Science From Theory to Practice, 2021
Rakesh Kumar Ghosh, Deb Prasad Ray, Ajoy Saha, Neethu Narayanan, Rashmita Behera, Debarati Bhaduri
Being economic and ecologically sustainable, bioremediation with microbes is always regarded as the most important option for pesticide decontamination However, various environmental factors may limit its application, particularly at the field level. The bioremediation technique at the lab scale may not succeed or fail at the field scale. The reason may be the difficulties in simulating the controlled laboratory condition to the field level. Several biotic and abiotic factors which control the microbes may also control the outcome of bioremediation experiment at field level. Another important factor is the bioavailability of pesticides, particularly persistent pesticides like DDT towards the microbes. Therefore, it is important to determine ways of increasing pesticide bioavailability. Table 3 lists some success stories where microbial bioremediation of pesticides was validated at the field level or mesocosm level. Strong et al. (2000) succeeded in 97% degradation of atrazine at the filed level by using recombinant E. coli overexpressing the atrazine chlorohydrolase gene derived from Pseudomonas sp. ADP. The addition of phosphate as a biostimulant increases the biodegradation of atrazine in soil plots. Sagarkar et al. (2013) carried out a mesocosm study (100 Kg soil) for biodegradation of atrazine herbicides and almost 90% atrazine degradation was observed with an atrazine degrading consortium comprising of 3 novel bacterial strains. John et al. (2018) used Klebsiella sp. isolated from pesticide-contaminated agricultural soil for in situ bioremediation of insecticide chlorpyrifos and demonstrated that the microbes can degrade the toxic chlorpyrifos into non-toxic products which increased the growth of soil microorganisms and dehydrogenase activity. Several field level studies for bioremediation of DDT contaminated site resulted in 68-95% removal of DDT.
Microalgae and bio-polymeric adsorbents: an integrative approach giving new directions to wastewater treatment
Published in International Journal of Phytoremediation, 2022
Palak Saket, Mrinal Kashyap, Kiran Bala, Abhijeet Joshi
The usage of pesticides has effectively increased the production of crops. Pesticides are of different categories depending on their structure and use. It includes different classes such as insecticides, fungicides, rodenticides and herbicides (Younes and Galal-Gorchev 2000). Chemically they are classified as organophosphorus, organochlorines, carbamates and pyrethroids (Castelo-Grande et al.2010). Organochlorine and organophosphate pesticides are reported to be most hazardous because of their extensive application and they can remain in the environment for more than three decades (Castelo-Grande et al.2010; Lari et al.2014). Endosulfan is one of the dominant pesticides of this group, which can cause severe neurotoxicity in humans and animals (Coats 1990). These are massively distributed in water, soil, air and agricultural products, causing a tremendous potential threat to the environment. A study reported that 0.3% of pesticide applied goes to the targeted pest while the rest remains in the environment (Pimentel 1995). Agriculture persons/farmers are more prone to pesticides exposure leading to health issues and environmental hazards living in nearby areas of farms (Wesseling et al.2001). Micro-algal cells are able to utilize these pesticides as nutrients and convert them into carbon dioxide and water. This process follows reaction pathways that can be oxidation, hydroxylation, deamination and dehalogenation (Huang et al.2018). This involves an enzymatic process used by microalgae to convert the more toxic pollutant into less toxic ones (De Souza et al.1996; Cooper et al.2010). Atrazine degradation into carbon dioxide and amines occur by a series of dechlorination and dehydrochlorination with enzymes AtzA (Atrazine Chlorohydrolase) and AtzB (Hydroxyatrazine N-ethylaminohydrolase), respectively (De Souza et al.1996). Abiotic factors such as aeration and sunlight assist in pesticide reduction (Hultberg et al.2016). Chemical and physical properties of pesticides like molecular weight, functional group, and toxicity level affect the degradation efficiency (Hussein et al.2017). Microalgae have lipids molecules in the cell membrane, which are associated with the removal of lipophilic contaminants. 68.2% degradation of 0.5mg/L of lindane, a lipophilic pesticide, has been shown by Nostoc oculata (Pérez-Legaspi et al.2016) (Table 1). A consortium of bacteria and algae also show great promise in pilot-scale treatment of pesticides in water (McLellan et al.2019). Researchers have shown that organophosphate pesticides affect health in various ways like genetic damage, disrupted hormonal activity, human breast carcinoma, etc. (Daneshvar et al.2007; Ibrahim et al.2014). A larger population is getting affected by pesticides because agriculture is the basic need of every country to develop. Microalgae is highly capable of the removal of various pesticides. Indigenous species of microalgae need to be isolated and used for the study of treatment efficiency for different pesticides.