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...

Azo Dye Decolorization Under Methanogenic Conditions

Anaerobic methanogenesis, from complex organic compounds, requires the coordinated participation of many different trophic groups of bacteria, which include acidogenic, acetogenic and methanogenic bacteria (Kasper and Wuhrmann 1978). It has been widely reported that azo dyes are gratuitously reduced by anaerobic sludges, anaerobic sediments and anaerobic enrichment cultures (Brown and Hamburger 1987 Weber and Wolfe 1987 Chung et al. 1992 Manu and Choudhary 2003). Dye decolorization, under...

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-...

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...

Co

Atrazine is a commonly used triazine herbicide and is degraded by a number of white rot fungi (Masaphy et al. 1993 Mougin et al. 1994 Entry et al. 1996 Bending et al. 2002 Nwachukwu and Osuji 2007). Degradation of atrazine by Pleurotus pulmonarius and P. chrysosporium leads to the accumulation of the N-dealkylated products deethylatrazine, deisopropylatrazine, deethyl-deisopropy-latrazine and hydroxyisopropylatrazine (the latter produced only by P. pulmonarius). Atrazine oxidation by these two...

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...

Conclusions

Despite of an extensive industrial usage of styrene which brings about significant anthropogenic releases in the environment, the ecological threat of this hydrocarbon is considerably limited due to its high volatility, its distinct chemical reactivity, and a pronounced susceptibility against biological transformations. In mammals and human, these transformations involve an initial cytochrome P450-mediated oxygenation yielding a mutagenic epoxide which, as a proven carcinogen, causes the most...

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 Four Ring PAHs

Of the four ring PAHs, degradation of fluoranthene, pyrene, chrysene, and benzo(a)anthracene has been investigated to varying degree. Fluoranthene, a non-alternant PAH containing a five carbon aromatic ring, is observed to be metabolized by a variety of bacteria, and pathways describing its biodegradation have been proposed. 7.2.1.1 Degradation of Fluoranthene by Bacteria In 1990, two independent groups of researcher reported the isolation of a single organism capable of utilizing fluoranthene...

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...

Direct Interfacial Uptake

In direct interfacial uptake, bacteria attach itself to the surface of the NAPL droplets which are larger in size compared to the bacterial cell. Substrate uptake takes place at the point of contact through diffusion. CSH plays an important role in direct uptake. Microorganisms capable of direct uptake can modify their cell surface outer membrane to enhance CSH. In this case, substrate uptake does not depend on the dissolution rate. Some microorganisms have surface structures such as, fimbriae...

Fate of Aromatic Amines Under Aerobic Conditions

General degradation pathways for benzene and naphthyl amines under aerobic conditions involve the participation of either mono or dioxygenases (specific hydroxylases) leading to the formation of dihydroxyaromatic compounds (Bayley and Barbour 1984). The dihydroxylated compounds are subsequently dearoma-tized by the cleavage of aromatic ring, which is catalysed by specific dioxygen-ases. Ring cleavage can occur either at ortho or meta position to the hydroxyl groups, leading to the formation of...

Freshwater

Levels of different PAHs in freshwater are very heterogeneous. For example, Wang et al. (2009) found in the Three Gorges Reservoir (Yangtze River) levels of total PAHs between 13.8 and 97.2 ng L-1. Fernandes et al. (1997) found PAH level in the Seine River and its estuary, ranging from 4 to 36 ng L-1. Countway et al. (2003) carried out a study in the York River and its estuary, and obtained levels of PAHs between 2.09 and 122.85 ng L-1 (with the salinity in these points around 13). Smith et al....

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,...

Identifying and Quantifying In situ Biodegradation of Explosives

While identifying the potential of indigenous bacteria to biodegrade a compound is relatively simple, gaining evidence that biodegradation is actually occurring and further, quantifying its extent in complex environments is intrinsically difficult. Thus, studies on degradation potential, pathway identification, and rate quantification of explosives biodegradation under controlled laboratory conditions are frequently carried out. A few studies have been also aimed at characterizing the microbial...

Influence of Environmental Conditions on the Fungal Biodegradation of Non Oxygenated Mono Aromatic Compounds

For most microorganisms, environmental conditions, such as pH, temperature, relative humidity, moisture content of the ecosystem, play a key role on the activity of fungal species degrading mono-aromatic compounds. Interestingly, all fungi isolated so far on alkylbenzenes and other related non-oxygenated benzene-compounds are mesophilic organisms. Their optimal temperature is generally around 30 C. Toluene biodegradation by Exophiala oligospermia and Paecilomyces variotii at different...

Initial Denitration Followed by Ring Cleavage

Anaerobic denitration of HMX as a result of a single-electron transfer, followed by ring cleavage and MEDINA formation, was detected by resting cells of C. bifermentans strains HAW-1 and HAW-EB21 (Zhao et al. 2004a, b). NDAB was not detected in this study. Bhushan et al. (2003 a) studied the transformation pathway of HMX with the metallo-flavo enzyme xanthine oxidase. Based on the detected products, they proposed that HMX undergoes a single denitration step. They observed this step under...

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...

Limitations in Degradation of PAHs in Soil

Many microorganisms are metabolically capable of mineralizing or partially transforming PAHs in the environment. Some fungi can produce extracellular enzymes, but for most of the bacteria, the pollutants must cross the cell membrane to get direct access to the enzymes or at least attach to the membrane bound enzymes. With the exception of some bacterial species that can attach directly to the interface between the organic and aqueous phase, in general for degradation to Table 7.2 Rate and...

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 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...

Reductive Pathway of Nitro Groups

TNT is commonly biotransformed by converting nitro groups into nitroso, hydroxylamino and amino groups (Hawari et al. 2000 Esteve-NUnez et al. 2001 Snellinx et al. 2002), as shown in Fig. 8.2. Thus, because of its high electron deficiency, initial microbial transformations of TNT are characterized by reductive rather than by oxidative reactions (Barrows et al. 1996). In several bacterial species, the major reduction metabolites from TNT are hydroxylamino-dinitrotoluenes HADNTs...

References

Aitken MD, Stringfellow WT, Nagel RD, Kazunga C, Chen SH (1998) Characteristics of phenanthrene-degrading bacteria isolated from soils contaminated with polycyclic aromatic hydrocarbons. Can J Microbiol 44 743-752 Atlas RM (1981) Microbial degradation of petroleum hydrocarbons, an environmental perspective. Microbiol Rev 45 180-209 Atlas RM (1984) Petroleum microbiology. Macmillan, New York Bartha R, Atlas RM (1977) The microbiology of aquatic oil spills. Adv Appl Microbiol 22 225266 Batts BD,...

Sequential Reduction Pathway

In contrast to TNT, sequential reduction of RDX occurs mostly under anaerobic conditions, as initially presented by McCormick et al. (1981). This pathway proceeds through reduction of the nitro groups to nitroso derivatives by subsequent two-electron transfer steps, followed by accumulation of (MNX), (DNX), and (TNX) derivatives. Again in contrast to TNT, the nitroso derivatives do not tend to undergo further reduction to stable detectable product. Although this degradation pathway leads to the...

Structure and Properties of RDX and HMX

(RDX) and (HMX) are two widely used cyclic nitramine explosives. The nitramines are the most recently introduced class of organic nitrate explosives. RDX (Research Department Explosive) and HMX (High Melting Explosive) are the most prominent members of this class. RDX and HMX are considered to be oligomers, (CH2NNO2)n n 3 or 4, respectively of the same repeating structural moiety, CH2NNO2. HMX is a big ring molecule, same as RDX but with an extra CH2NNO2 unit (Fig. 9.1). Research Department...

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 Regulatory System of the Sty Operon

The two-component regulatory system StyS StyR of the sty-operon from the strains Pseudomonas putida CA-3, Pseudomonas sp. Y2, and Pseudomonas fluo-rescens ST was investigated in detail (Velasco et al. 1998 Santos et al. 2000 O'Leary et al. 2001, 2002a Leoni et al. 2003). With respect to the conserved operon organization among pseudomonads (Fig. 3.3a, b), the described features of this regulatory system are supposed to occur and interact similarly in all functional sty-operons of pseudomonads....

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...