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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
Dioxygenase degrades aromatic pollutants by adding two atoms of an oxygen molecule in the ring [Figure 1(D)]. The aromatic dioxygenases are classified according to their mode of action as aromatic ring hydroxylation dioxygenase (ARHDs) and aromatic ring cleavage dioxygenase (ARCDs). The ARHDs degrade aromatic compounds by adding two molecules of oxygen into the ring, whereas ARCDs break aromatic rings of compounds. The catechol dioxygenases that are found in the soil bacteria cause the biotransformation of aromatic precursors into aliphatic products (Muthukamalam et al. 2017). Toluene dioxygenase (TOD) catalyzes the first reaction in the degradation of toluene. This multi-component enzyme system acts on the broad substrate and behaves as monooxygenase and dioxygenase. TOD also has the ability to catalyze sulfoxidation reactions and convert ethyl phenyl sulfide, methyl phenyl sulfide, methyl p-nitrophenyl sulfide, and p-methoxymethyl sulfide into their respective sulfoxides. TOD also detoxifies polychlorinated hydrocarbons, chlorotoluenes, and BTEX residues very effectively (Scott et al. 2008).
Fundamentals and Modeling Aspects of Bioventing
Published in Subhas K. Sikdar, Robert L. Irvine, Fundamentals and Applications, 2017
C. M. Tellez, A. Aguilar-Aguila, R. G. Arnold, R. Z. Guzman
A recombinant Escherichia coli containing the genes encoding for toluene dioxygenase was constructed to overcome inhibition by the inducer (Zylstra et al., 1989). Although it did not require the presence of toluene as inducer, the degradation rates were lower than with the P. putida strain from which the genes were cloned, possibly because of differences in cytotoxic effects between P. putida and E. coli.
Zinc and copper supplements enhance trichloroethylene removal by Pseudomonas plecoglossicida in water
Published in Environmental Technology, 2022
Lan Qiu, Keng Seng Lok, Qihong Lu, Hua Zhong, Xiaoyuan Guo, Hojae Shim
Figure 1 shows a synchronised removal of toluene and TCE. Toluene was rapidly utilised in the first day with a faster removal rate than TCE, and the organism achieved the highest cell density accordingly. After that, most substrate was consumed and its removal rate was slow and the cell growth entered a stationary phase while the removal of TCE was maintained almost steady during the remaining days. Toluene was used as the sole carbon source for growth and provided the energy for the metabolic activities of P. plecoglossicida, and the functional enzyme involved in the catabolism has been reported to be the toluene dioxygenase [45]. As shown in Figure 2, toluene is converted into 3-methylcatechol which was detected and confirmed by LC-MS and the subsequent degradation products were predicted to be 2-hydroxy-6-oxohepta-2,4-dienoic acid and acetic acid [46,47]. Simultaneously, TCE was co-metabolically removed by the isolate, and the TCE co-metabolic bacteria have been reported to primarily epoxidate the carbon–carbon double bond to chloroethene epoxides, catalysed by the toluene mono- or dioxygenase [37,48]. The chloroethene epoxides might be further hydrolysed spontaneously into glyoxylic acid which can be further mineralised to Cl−, CO2 and water (Figure 2) [37].
Removal of tetrachloroethene from polluted air by activated sludge
Published in Environmental Technology, 2019
Agnieszka Tabernacka, Ewa Zborowska, Katarzyna Pogoda, Marcin Żołądek
Enzymes associated with cometabolic aerobic biotransformation of TCE and PCE (non-specific oxygenases) are induced in the presence of growth substrates, such as methane, butane, propane, propylene, phenol, toluene and ammonia. The biodegradation process is initiated by a specific monooxygenase (toluene, phenol or methane), or toluene dioxygenase. Bacteria which degrade TCE and PCE belong to the genera: Burkholderia (Burkholderia cepacia), Methylomonas (Methylomonas methanica), Methylosinus (Methylosinus trichosporium), Pseudomonas (Pseudomonas butanavora, Pseudomonas putida, Pseudomonas mendocina), Mycobacterium (Mycobacterium vaccae), Xanthobacter, Ralstonia (Ralstonia eutropha) and Nitrosomonas (Nitrosomonas europaea) [8–12]. Unfortunately, addition of growth substrates causes additional loading of the technological system.
Toluene biodegradation in the vadose zone of a poplar phytoremediation system identified using metagenomics and toluene-specific stable carbon isotope analysis
Published in International Journal of Phytoremediation, 2019
Michael BenIsrael, Philipp Wanner, Ramon Aravena, Beth L. Parker, Elizabeth A. Haack, David T. Tsao, Kari E. Dunfield
Total bacteria and toluene-degrading bacterial populations were assessed by quantifying genes and transcripts (cDNA) in the metagenomic samples using previously published primers. The 335f/769r primer set was used to quantify the V3–V4 regions of the bacterial 16S rRNA gene to estimate total bacterial abundance (Dorn-In et al. 2015). Aerobic degradation pathways were targeted using toluene dioxygenase (TOD), ring-hydroxylating monooxygenase (RMO), and phenol hydroxylase (PHE) primers (Baldwin et al. 2003). Anaerobic pathways were targeted using the 7772f/8543r primer set that target benzyl succinate synthase alpha subunit (bssA)-related genes encoding fumarate-adding enzymes (von Netzer et al. 2013). All qPCR reactions were carried out on a CFX96™ Real-Time PCR Detection System (Bio-Rad Laboratories Inc.) and conformed to MIQE guidelines (Bustin et al. 2009). Full details on primers used and reaction conditions can be found in the Supporting Information.