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Soil Microbial Enzymes and Their Importance, Significance, and Industrial Applications
Published in Pankaj Bhatt, Industrial Applications of Microbial Enzymes, 2023
Hemant Dasila, Sarita Joshi, Sudipta Ramola
Oxygenases are enzymes that insert oxygen atoms into the substrates. Depending on the number of oxygen atoms used in the oxidation, oxygenases can be either monooxygenase (incorporate one oxygen atom into the substrate) or dioxygenase (incorporate two atoms of oxygen into the substrate). Monooxygenase first activates molecular oxygen by donating electrons to it, and then the oxygenation of the substrate occurs. During this process of activation, the formation of reactive oxygen intermediate takes place. The type of intermediate depends on the type of cofactor present in monooxygenase. Some monooxygenases obtain these electrons from the substrate, whereas others from external electron donors. Some of the monooxygenases that do not require any cofactors for their activity are ActVAorf6 monooxygenase from Streptomyces coelicolor A3(2) (Fetzner, 2002), tetracenomycin F1 monooxygenase (TcmH) from Streptomyces glauscens (Shen and Hutchinson, 1993), Rv0793 monooxygenase from Mycobacterium tuberculosis (Lemieux et al., 2005), and quinol monooxygenase (YgiN) from E. coli (Adams and Jia, 2005), whereas others require cofactors, such as heme, flavin, copper, and pterin, for their function.
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
Oxygenases have a broad substrate range and are active against a wide range of compounds. The introduction of O2 atoms into the organic molecule by oxygenase results in cleavage of the aromatic rings. Oxygenases act as biocatalysts in the bioremediation process and synthetic chemistry due to their high regioselectivity, stereoselectivity, and enantiospecificity of a wide range of substrates (Arora et al. 2010). The variety of pollutants that persists in the environment, including chlorinated compounds, halogen-containing herbicides, fungicides, and pesticides, are degraded by oxygenase (Sharma et al. 2018). Glyphosate oxidase isolated from bacterium Pseudomonas sp. LBr is involved in the bioremediation of pesticides; similarly, oxygenase produced by certain marine bacteria degrades organic pollutants (Scott et al. 2008; Sivaperumal et al. 2017). On the basis of oxygen molecules involved in the enzymatic reaction, oxygenases are classified into two subclasses: monooxygenase (catalyze the insertion of a single oxygen atom) and dioxygenase (catalyze the insertion of both oxygen atoms).
Global Environmental Issues and the Role of Nanobiotechnology for the Sustainable Environment
Published in Amit Kumar, Chhotu Ram, Nanobiotechnology for Green Environment, 2021
Chhotu Ram, Amit Kumar, Yilkal Bezie
The oxidoreductases perform humification of different phenolic compounds that are generated from the decomposition of lignin in the soil environment. Similarly, oxidoreductases can also detoxify toxic xenobiotic substances such as phenolic or anilinic compounds polymerization, copolymerization with other substrates, or binding to humic substances (Karigar and Rao, 2011; Park et al., 2006). Oxygenases are the oxidoreductases that perform the oxidation of reduced substances by utilizing oxygen from molecular oxygen and FAD/NADH, NADPH as a co-substrate. Oxygenases are categorized into two groups (monooxygenases and dioxygenases) based on the number of oxygen atoms used for oxygenation (Arora et al., 2009; Karigar and Rao, 2011). Mono-oxygenases incorporate one atom of oxygen into the substrate; whereas, dioxygenases add both atoms of oxygen to a substrate. Mono-oxygenases are grouped into flavin-dependent mono-oxygenases and P450 mono-oxygenases, based on the co-factor requirement (Arora et al., 2010) (Table 1.2). Dioxygenases are a multicomponent enzyme system that incorporates oxygen into the substrate. Dioxygenases primarily oxidize aromatic compounds and therefore are applicable in environmental remediation (Karigar and Rao, 2011).
Attenuation of petroleum hydrocarbon fractions using rhizobacterial isolates possessing alkB, C23O, and nahR genes for degradation of n-alkane and aromatics
Published in Journal of Environmental Science and Health, Part A, 2021
Joseph E. Agbaji, Eucharia O. Nwaichi, Gideon O. Abu
Petroleum hydrocarbons undergo multiple pathways involving various enzymes during biodegradation.[16] Under aerobic conditions, the initial steps in the bacterial degradation of hydrocarbons rely on oxygenases (monooxygenases and dioxygenases). These oxygenases are membrane-bound, the cell must mix with their water-soluble substrates. Because the oxygenases are group-specific,[24] they catalyze the initial oxidation reactions of n-alkane and aromatic hydrocarbons to primary alcohols (monooxygenase reactions with hydroxylases) and trans-dihydrodiols (monooxygenase reactions) or cis-dihydrodiols (dioxygenase reactions). Furthermore, oxidation of the trans-dihydrodiols and the cis-dihydrodiols leads to the synthesis of catechols, which are substrates for other dioxygenases that catalyze enzymatic nick of the aromatic ring.[16] It follows that only a mixture of different microorganisms, possessing versatile catabolic genes can efficiently degrade crude oil and petroleum fractions.[19,25]
Evidence of p-nitrophenol Biodegradation and Study of Genomic Attributes from a Newly Isolated Aquatic Bacterium Pseudomonas Asiatica Strain PNPG3
Published in Soil and Sediment Contamination: An International Journal, 2022
Sk Aftabul Alam, Pradipta Saha
The aquatic bacterial strain PNPG3 could utilize PNP catabolically and could degrade 70% of 0.5 mM PNP within 48 h and 97% of the same within 60 h with concomitant release of nitrite (Figure 2). During the complete biodegradation of PNP 0.44 mM of nitrite was released within 60 h by the strain PNPG3 (Figure 2). Growth of the strain in the PNP-containing medium, PNP depletion with concomitant release of nitrite indicated that oxidative reaction takes place during the conversion of the parent compound and PNP is transformed to other intermediates. Similar growth and degradation characteristics were reported earlier. For example, Arthrobacter sp. SPG, the soil bacterium was reported to utilize 0.3 mM PNP as a sole source of carbon and nitrogen and 0.2 mM nitrite was released during this process (Arora 2012). Similar types of results were reported for Rhodococcus imtechensis RKJ300 (MTCC 7085 T), and Pseudomonas cepacia RKJ200 where nitrite was released during utilization of PNP as a sole source of carbon (Ghosh et al. 2010; Prakash, Chauhan, and Jain 1996). However, the aquatic PNP degrading bacterium – Nocardioides sp. NSP41 was able to degrade PNP cometabolically (Cho, Rhee, and Lee 2000); Citriococcus nitrophenolicus sp. PNP1 can degrade 0.7 mM of PNP (undefined medium yeast extract was added in the medium) (Nielsen, Kjeldsen, and Ingvorsen 2011). In general, for Pseudomonas, the pathway for biodegradation of all aromatic compounds may be divided into two parts the upper and the lower pathways. The most crucial enzyme in the upper pathway is oxygenase, which can be of two types mono and dioxygenase. While the lower pathway converges to 14 central pathways of catabolism with the beta-ketoadipate being the most common one through which all the toxic, chemically complex pollutant (and their intermediates) are converted to nontoxic, simple forms to enter into the TCA cycle for further metabolism (Medić and Karadžić 2022). Comparison of PNP biodegradation among different members within Pseudomonas revealed: co-metabolic biodegradation of 0.5 mM PNP within 12 h for Pseudomonas cepacia strain RKJ200 (Prakash, Chauhan, and Jain 1996); for Pseudomonas putida PNP1, catabolic degradation of 100 mg/L (Löser, Oubelli, and Hertel 1998); for Pseudomonas psudomallai ENB-10, co-metabolic biodegradation of 50 µg/L (Rehman et al. 2007); for Pseudomonas sp. WBC-3 catabolic degradation of 75 µM (Zhang et al. 2009a); for Pseudomonas putida DLL-E4 catabolic degradation of 0.5 mM (Shen et al. 2010). Thus, if we compare these, it seems that the biodegradation performance and efficiency of the strain PNPG3 is the best, so far reported. The correlation coefficient (r) between percent biodegradation and time was determined to be 0.9841 and the t-test value was p < .01, thereby indicating that the correlation was highly statistically significant.