Aerobic Styrene Degradation

Kindergarten Phonics Worksheets

Under aerobic conditions, side-chain oxygenation of styrene seems to be the favored mechanism, since most microorganisms investigated in that respect were found to follow this degradation pathway (Hartmans et al. 1990 Cox et al. 1996 Itoh et al. 1996 Beltrametti et al. 1997 Panke et al. 1998 Velasco et al. 1998 Park et al. 2006b). In the first reaction step, styrene is oxygenated into styrene oxide by the action of a monooxygenase (Fig. 3.1). Styrene monooxygenases (SMOs) of bacteria are...

Aerobic Degradation of Alkanes

Aerobic alkane degraders activate alkane molecules using O2 as a reactant. The alkane-activating monooxygenase overcomes the low reactivity of the hydrocarbon by producing reactive oxygen species. Oxidation of methane leads to formation of CH4 CHjOH H2C 0 HCOOH CO Serine pathway Ribulose-P pathway Serine pathway Ribulose-P pathway Fig. 17.2 Aerobic pathways of methane oxidation (after Rojo 2009) methanol which is subsequently transformed to formaldehyde and then to formic acid (Fig. 17.2). This...

Aerobic Degradation of Dyes

Most common aerobic process is activated sludge process. Activated sludge is a process dealing with the treatment of sewage and dyes containing wastewaters (Beun et al. 1999). The combination of raw sewage (or industrial wastewater) and biological mass is commonly known as mixed liquor. In all activated sludge plants, once the sewage (or industrial wastewater) has received sufficient treatment, excess mixed liquor is discharged into settling tanks and the treated supernatant is run off to...

Aerobic Treatment

Conventional activated sludge treatment of wastes is often an effective and highly economic system for reducing organic pollutants in wastewater. A fair amount of research has been conducted assessing the viability of using activated sludge to treat textile effluents (Zissi et al. 1997). However, aerobic treatment of azo dye wastes has been proven ineffective in most cases, hence, a typical method of treatment is used today. Because aerobic microbes cannot reduce azo linkages, their ability to...

Anaerobic Degradation of nAlkanes

Apart from aerobic oxidation, anaerobic degradation also plays an important role in the recycling of hydrocarbons in the environment. Alkanes are also degraded through anaerobic process as reported by various workers (Callaghan et al. 2009 Higashioka et al. 2009). There are two known pathways of anaerobic n-alkanes degradation (Fig. 17.5). First pathway is the alkane addition to fumarate, and second is through putative pathways (So et al. 2003). Fumarate addition proceeds via terminal or...

Anaerobic Treatment

Anaerobic reduction of dyes using microbial sludges can be an effective and economic treatment process for removing color from dye house effluents. Previous studies have demonstrated the ability of anaerobic bacteria to reductively cleave Fig. 12.2 A schematic diagram (a) and photo (b) of a laboratory scale upflow anaerobic sludge blanket reactor (UASB) Fig. 12.2 A schematic diagram (a) and photo (b) of a laboratory scale upflow anaerobic sludge blanket reactor (UASB) the azo linkages in...

Application of Biological Bacterial Methods for Azo Dye Containing Wastewaters

A wide range of structurally diverse dyes is used in the textile industry in the same unit. Although there are many reports available on dye decolorization under aerobic conditions in the presence of either glucose and or yeast extract, most of these are limited to few specific dyes. On the other hand, decolorization in the absence of oxygen is non-specific. As compared to methanogenic consortia, anoxic decolorization requires high concentrations of co-substrates, such as yeast extract or...

Biodegradation of Polychlorinated Biphenyls

Polychlorinated biphenyls belong to persistent organic pollutants. Although their production was stopped long time ago, they still persist in the environment and represent a serious environmental problem. The aromatic ''doublering'' structure may be substituted with one to ten chlorine atoms. Although there are 209 individual compounds designated as congeners, but only 130 could be found in commercial PCB mixtures. The toxicity of such molecules is directly correlated to both number and...

Biodegradation of RDX and HMX under Aerobic Conditions

Several groups have studied aerobic metabolism of RDX and HMX and have demonstrated the potential for these energetic chemicals to be mineralized (Binks et al. 1995 Jones et al. 1995a, b Greer et al. 1997 Coleman et al. 1998 Tekoah and Abeliovich 1999 Sheremata and Hawari 2000). Binks et al. (1995) showed that Stenotrophomonas maltophilia can degrade RDX, but not HMX when the cyclic nitramine is used as a nitrogen source. Harkins et al. (1999) reported the formation of five nitroso derivatives...

Biodegradation of RDX and HMX under Anaerobic Conditions

Biod gradation of RDX and HMX under anaerobic condition has been extensively studied (McCormick et al. 1981 Hawari et al. 2000a Adrian and Arnett 2004 Bhatt et al. 2005). Anaerobic reduction of RDX and HMX can be achieved in several different ways. RDX biodegradation under anaerobic conditions was first reported by McCormick et al. (1981), who proposed RDX biodegradation by reduction of the RDX nitro (-NO2) groups to nitroso (-NO) groups to produce (MNX) hexahydro-...

Biotransformation Pathways of RDX

Metabolic pathways involved in the biodegradation of the cyclic nitramines RDX and HMX have been reviewed (Hawari et al. 2000a Crocker et al. 2006). The potential degradation routes known for RDX are presented in Fig. 9.2. Three mechanisms for the transformation of RDX have been proposed two-electron reduction, single-electron reduction denitration, and direct enzymatic cleavage. Path A Reduction of RDX to nitroso derivatives before ring cleavage (McCormick et al, 1981) Path B Reduction of RDX...

Chemistry of TNT

Unlike toluene which is metabolized through oxidation pathway for its methyl group, 2,4,6-TNT is more resistant to oxidative reaction, because p electrons from the aromatic ring of TNT are removed by the electronegative nitro groups. Therefore, the aromatic ring of TNT has electrophilic property. The detail explanation has been schemed in Fig. 8.1. Basically, methyl group is an electron-releasing substituent, therefore, p electrons from the aromatic ring of toluene increase. The carbon atom of...

Chlorinated Insecticides

Lindane (y isomer of hexachlorocyclohexane) was a widely used pesticide in the past and an estimated 600,000 tons of lindane were produced globally between 1950 and 2000. There is a global ban on the use of lindane now because of its environmental persistence as a pollutant. P. chrysosporium, cultured under ligninolytic conditions, was reported to partially mineralize lindane in liquid cultures and in a corncob-amended soils inoculated with P. chrysosporium (Bumpus et al. 1985 Kennedy et al....

Conclusion On Xenobiotics In The Environment

The degradation of polymers was at first expected to be catalyzed solely by extracellular enzymes, given the assumption that macromolecules are never incorporated into cells, but this was disproved by the periplasmic degradation of PEG and PVA, as described above. These are surely incorporated into the periplasm through the outer membranes of Sphingomonads and are metabolized by periplasmic enzymes, although the mechanism of macromolecule uptake has not been well characterized. Many enzymes...

Cytochrome P450 Monooxygenase

These enzymes are heme proteins and catalyze the hydrocarbons using NAD(P)H as cofactor. They usually consist of two components hydroxylase and reductase (Sono et al. 1996). These enzymes are usually membrane-bound and have a multi-component nature (Ayala and Torres 2004). The molecular mechanisms of oxygen activation for some metalloenzymes are well investigated. Heme-oxygenases, such as CYP, hydroxylate inert hydrocarbon substrates by using a high-valent oxoiron(IV) porphyrin p-cation-radical...

Degradation of Chloroorganic Pollutants by White Rot Fungi

Ligno-cellulosic plant biomass is the most abundant renewable organic resource on earth and contains cellulose, hemicellulose, and lignin polymers as its key components. Lignin, the most abundant aromatic polymer in the biosphere, is a highly complex, three dimensional, branched, recalcitrant polymer. Because of its recalcitrance, biodegradation of lignin is the rate-limiting step in the degradation of lignocellulosic biomass and thus lignin plays a pivotal role in global carbon cycling....

Degradation of Hmw Pahs and Substrate Interaction Effects

In the environment, PAHs exist as complex mixtures along with a multitude of other compounds, such as, in creosote and coal tar. In this scenario, one compound may affect the rate and extent of degradation of another compound, e.g., through increasing the biomass growth, competitive inhibition and co metabolism. These effects are referred as substrate interaction effects. As observed by various researchers, the net result could be an increase in the rate of biodegradation as a result of...

Fungal Biodegradation of Endocrine Disrupting Compounds

Endocrine-disrupting compounds (EDCs) are a group of environmental pollutants known for their negative influence, particularly on aquatic organisms. EDCs tend to accumulate in aquatic organisms and also get adsorbed by sediments and on particles in the aquatic environment. These compounds mimic or antagonize the effects of endogenous hormones and hence, alter the synthesis and metabolism of natural hormones, or modify hormone receptor levels, disrupting endocrine and reproductive functions...

Fungal Decolorization and Degradation of Synthetic Dyes

Inefficiencies in industrial dyeing processes result in large amounts of synthetic dyes being directly lost to the wastewaters and consequently to the water environment. The amount of dye lost is dependent on the chemical structure of the dye and varies from 2 loss (basic dyes) to 50 loss (reactive dyes). Synthetic dyes represent a group of structurally different chemicals and are normally divided into azo, nitro, nitroso, diarylmethane, triarylsmethane, xanthene, anthraquinoid, acridine,...

Introduction

Styrene, the simplest representative of alkenylbenzenes, is one of the most important monomers produced by the chemical industry today. The compound shows a distinct toxicological behavior and is classified as a possible carcinogen due to its metabolism in human via a highly mutagenic epoxide. Considerable amounts of styrene are released by emissions and effluents during production and usage in polymer manufacture and by deposition of industrial wastes. A high chemical reactivity as well as its...

Mechanism of Azo Dye Reduction

The azo bond (-N N-) cleavage involves a transfer of four-electrons which proceeds through two stages at the azo linkage. Two electrons are transferred to the azo dye in each stage, which acts as final electron acceptor. The reduction may involve different mechanisms, such as enzymatic (Zimmermann et al. 1982, 1984 Rafii et al. 1990 Haug et al. 1991 Suzuki et al. 2001 Maier et al. 2004), involvement of low molecular weight redox mediators (Van der zee and Cervantes 2009), chemical reduction by...

Metabolism of PAH Compounds

PAHs with two to three fused aromatic rings are considered as low molecular weight (LMWPAHs) such as, naphthalene, anthracene and phenanthrene, whereas those with four and more fused rings are high molecular weight (HMWPAHs) that include chrysene, fluoranthene and pyrene, etc. (Igwo-Ezikpe et al. 2010). Isolation of highly efficient PAHs (containing four aromatic rings), degrading bacterium is the pioneering study that opened the possibility of PAH biodegradation (Heitkamp and Cerniglia 1988)....

Microbial Degradation of Polychlorophenols

Polychlorophenols are major environmental pollutants, and their degradation by microorganisms has been extensively studied for the purpose of bioremediation. Three different metabolic pathways for aerobic degradation of polychlorophenols have been completely worked out, revealing the metabolic diversity for these structurally similar compounds. Substituted quinols, rather than catechols, are key metabolic intermediates of polychlorophenol biodegradation. Substituted quinols and quinones are...

Polyamino acids and Polyamides

The degradation of poly(amino acid)s and polyamides was reviewed by Obst and Steinb chel (2004). In nature, proteins and poly(amino acid)s exist as two different types of amino acid polymers. The most critical differences are (i) that the former is a random polymerization of 20 amino acids and the latter a polymer of a single amino acid, and (ii) the synthesis of proteins is ribosome-dependent and forms an a-amino-a-carboxyl peptide linkage while that of poly(amino acid)s is...

Polyurethane Degradation

Research has been initiated to elucidate whether additives to the chemical structure of PU could decrease biodegradation. Kanavel et al. (1966) observed that sulfur-cured polyester and polyether PU had some fungal inertness. However, they noted that even with fungicides added to the sulfur- and peroxide-cured PU, fungal growth still occurred on the polyester PU and most fungicides had adverse effects on the formulations. Kanavel et al. (1966) also recognized the need for physical testing of the...

Polyurethane Degradation by Pseudomonas

Three Pseuomonads have been isolated for their ability to utilize a polyester PU as the sole carbon and energy source. Interestingly, three species of bacteria produce different PUase activities that are inhibited by serine hydrolase inhibitors. These data suggest that either esterase and or protease activities are involved in the degradation of Impranil (Fig. 14.4). Growth of Comamonas acidovorans on colloidal polyester-polyurethane resulted in the growth parameters for Ks and imax of 0.3 mg...

Polyvinyl Alcohol

Historically, PVA has been produced on an industrial scale by the hydrolysis of poly(vinyl acetate), since a vinyl alcohol monomer cannot exist due to tautomerization into acetoaldehyde. PVA are widely used due to its excellent physico-chemical properties, especially for fabric and paper sizing, fiber coating, adhesives, emulsion polymerization, films for packing and farming, and the production of poly(vinyl butyral). Maximum production of PVA amounted to about 1,250 kt in 2007 the top volume...

Production of Biosurfactants and PAH Uptake

Production of biosurfactant is another mechanism adopted by certain bacterial species to degrade complex petroleum hydrocarbons. Like chemical surfactants, biosurfactants are amphiphilic molecules having both hydrophilic and hydropho-bic regions which help them in attachment to different surfaces. Biosurfactants are categorized into groups based on their MW (Ron and Rosenberg 2002). LMW surfactants are typically glycolipids where the carbohydrate group is attached to long chain alkyl acids or...

Recombinant Bacteria for Alkane Degradation

Due to multi-component nature, recombinant production of CYP450 is difficult, but CYP BM-3 is readily expressed in E. coli (Peter et al. 2003). Rothen et al. (1998) constructed a plasmid with gene coding for the three enzymes alkane hydroxylase, alcohol dehydrogenase and aldehyde dehydrogenase simultaneously. The plasmid was inserted into an E. coli strain unable to Table 17.1 Different enzymes involved in alkane degradation (van Beilen et al. 2003) Cytochrome P450 (CYP153) monooxygenase...

Reduction of the Nitro Group

The most common degradation pathway for TNT proceeds along the sequential reduction of the nitro groups. Following sequential steps of two-electron transfers, the corresponding mononitroso, monohydroxylamino and monoamino derivatives 2-aminodinitrotoluene 4-aminodinitrotoluene (2-ADNT) (4-ADNT) Deaminationand formation of nitrogen free metabolites 2-aminodinitrotoluene 4-aminodinitrotoluene (2-ADNT) (4-ADNT) Bamberger rearrangement and formation nhoh of phenolic amine derivate Fig. 5.2...

References

Achtnich C, Sieglen U, Knackmuss H-J, Lenke H (1999) Irreversible binding of biologically reduced 2,4,6-trinitrotoluene to soil. Environ Toxicol Chem 18 2416-2423 Adrian NR, Arnett CM (2004) Anaerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Acetobacterium malicum strain HAAP-1 isolated from a methanogenic mixed culture. Curr Microbiol 48 332-340 Adrian NR, Arnett CM (2007) Anaerobic biotransformation of explosives in aquifer slurries amended with ethanol and propylene...

Structure of PAHs

The polynuclear aromatic hydrocarbons are composed of two or more aromatic (benzene) rings which are fused together in a linear, angular or cluster arrangement when a pair of carbon atoms is shared between them (Dhote et al. 2010). PAHs toxicity is quite structurally dependent, with isomers (PAHs with the same formula and number of rings) varying from non-toxic to extremely toxic. Thus, highly carcinogenic PAHs may be small or large. The PAH compound, benzo a pyrene (BAP), was notable as the...

Styrene Oxide Hydrolases and Styrene Oxide Isomerases

As mentioned before, epoxide hydrolases (EHs) can be involved in styrene metabolism (Fig. 3.1). More frequently, these enzymes play a role in the detoxification process of xenobiotics with epoxide-like structures, especially in mammalians. EHs are enantioselective and show a broad substrate spectrum. Styrene oxide is a model substrate for this enzyme class and most representatives convert solely one enantiomer of racemic styrene oxide into a chiral phenylethan-1,2-diol. Thus, EHs can be used to...

The Gene Cluster styABCDE of the Upper Styrene Degradation Pathway

The number and arrangement of genes within the styABCD(E) clusters of pseudomonads reflect the necessity and sequence of encoded enzymes, respectively, Fig. 3.3 Comparison of the organization of a the styABCDE-operon from Pseudomonas sp. Y2, b other (incomplete) styrene-catabolic gene clusters from pseudomonads, and c the genetic location of flavin monooxygenases with ( hypothetical) function as styrene monooxygenases. The upper pathway of styrene degradation by side-chain oxygenation is shown...

Biodegradation of Petroleum Hydrocarbons in Petroleum Transporting Storage Tanks

Biodegradation of diesel hydrocarbon by B. cereus ACE4 and S. marcescens ACE2 was confirmed by GC-MS, NMR and FT-IR analyses in petroleum transporting pipeline, India (Rajasekar et al. 2007b, e). From GC-MS analysis, it was observed that the control system consisted of n-alkanes (Ci0-C20), branched alkanes, naphthalene derivatives, substituted naphthalenes and iso preniod alkanes (pristane, phytane) (Fig. 13.8a). The inoculated S. marcescens ACE2 degraded almost all the n-alkanes (C10-C20) and...

Microbial Degradation of Xenobiotic Polymers

What does ''biodegradability of polymers'' mean The first criterion for biodegradation is enzymatic processing. In particular, hydrolyzable polymers such as polyesters and polyamides are enzymatically degraded into monomers (depoly-merization process) that can easily enter central metabolic processes unless they are xenobiotic compounds. Most monomers are naturally occurring compounds, such as organic acids, alcohols glycols, and amide compounds. Proteases, lipases, and esterases originating...

Biodegradation of Non Oxygenated Mono Aromatic Compounds

Until the end of the past century, the biodegradation of non-oxygenated mono-aromatic compounds seemed to be an unusual capability of fungi (Kennes and Veiga 2004). The first isolated report suggesting minimal growth of a fungal strain on benzene compounds appeared in 1973 (Cofone et al. 1973). However, not enough evidence was obtained at that time to conclude that growth of the Cladosporium resinae strain was possible on benzene. Another report appeared several years later (Fedorak and...

Chlorinated Pharmaceutical and Personal Care Products

An expanding array of substances called 'Endocrine-disrupting compounds' (EDC) include chemicals of natural and anthropogenic origin. EDCs are widely distributed in the environment. They constitute a potential health risk to humans and aquatic life. Only a couple of EDCs are covered here. Triclosan is one such synthetic antimicrobial compound that is present in a wide range of health care products, such as tooth-paste, deodorant sticks and soaps. It has been detected in various environmental...

Microbial Degradation of Alkanes

Due to lack of functional groups as well as very low water solubility, aliphatic hydrocarbons exhibit both, low chemical reactivity and bioavailability for microorganisms. However, some microorganisms possess the metabolic capacity to use these compounds as carbon and energy sources for their growth (Berthe-Corti and Fetzner 2002). A number of microbes including bacteria, fungi and yeasts have been reported to degrade alkanes using them as the source of carbon and energy (van Beilen et al. 2003...

Role of Microbes in Petroleum Hydrocarbon Degradation

Xenobiotics

Twenty-one years after ZoBell's (1946) classic review, the super tanker Torrey Canyon sank in the English Channel. With this incident, attention of the scientific community was dramatically focused on problems of oil pollution. After this event, several studies were initiated to study the fate of oil pollution. Several studies were also initiated on the fate of petroleum in varied ecosystems. Biodegradation of petroleum products in natural ecosystem is no doubt a complex issue. The degradation...

Polyethers

Poly(alkylene glycol)s have a common structural formula HO R-O nH R CH2CH2 for PEG, CH3CHCH2 for polypropylene glycol (PPG), a polymer of 1,2-propylene oxide, (CH2)4 for polytetramethylene glycol (PTMG), and C2H5(CHCH2) for polybutylene oxide (PBO), a polymer of 1,2-butylene oxide , where n represents the average range of units. The physical properties of PEGs vary from viscous liquids to waxy solids based on their molecular sizes, although every PEG from oligomers up to polymers with a...

PAHs Degrading Organisms

The PAH-degrading microorganisms could be algae, bacteria and fungi. It involves breakdown of organic compounds through biotransformation into less complex metabolites, and through mineralization into inorganic minerals, H2O, CO2 (aerobic) or CH4 (anaerobic) (Haritash and Kaushik 2009) Schematic metabolic pathways to degrade PAHs of these microorganisms are shown in the Fig. 10.1. In aerobic pathways, the main strategy of microorganisms to degrade aromatic pollutants is to use a range of...