**1. Introduction**

Acrylamide (CH2=CHCONH2) is a well-known bifunctional monomer, appearing as a white odorless flake-like crystal. It is soluble in water, methanol, ethanol, dimethyl ether, and acetone, but insoluble in benzene and heptane. Acrylamide is incompatible with acids, bases, oxidizing agents, irons and iron salts. It decomposes non-thermally to form ammonia while thermal decomposition produces carbon monoxide, carbon dioxide, and oxides of nitrogen [1].

As a commercial conjugated reactive molecule, acrylamide has been used worldwide for the synthesis of polyacrylamide and other polymers [2, 3]. It has also been used as a binding, thickening, or flocculating agent in grout, cement, sewage, wastewater treatment, pesticide formulation, cosmetics, sugar manufacturing, and to prevent soil erosion. Polymers of this compound have been used in ore processing, food packaging, plastic products, and in scientific and medical laboratories as solid support for the separation of proteins by electrophoresis [4]. Acrylamide monomer is also widely used as an alkylating agent for the selective modification of sulfhydryl proteins and in fluorescence studies of tryptophan residues in proteins. In 2002, there was an alarming report of the occurrence of acrylamide at high levels up to 3 mg/kg in plant-derived foods and thought to form during cooking allowing the formation of Maillard browning products [5]. Many reports have suggested that acrylamide seems to be found in foods that have been processed by heat-treatment methods other than boiling [6]. One possible pathway to the formation of acrylamide is via the Maillard reaction between amino acids, particularly asparagines, and reducing sugars at high temperatures [5, 6]. Some reports suggest acrylamide could form by acrolein (2-propenal, CH=CHCHO), a three-carbon aldehyde, by either the transformation of lipids or the degradation of amino acids, proteins and carbohy‐ drates [7-12].

Acrylamide could be absorbed through unbroken skin, mucous membranes, lungs, and the gastrointestinal tract. Human exposure to acrylamide is primarily occupational from dermal

© 2013 Charoenpanich; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. contact with the solid monomer and inhalation of dust and vapor. Although it is not toxic in polymer form, the monomer can cause peripheral neuropathy. Residual monomer in polymers is also of health concern [13]. Primary exposure occurs during the handling of monomers. Two acrylamide manufacturing factories showed breathing zone concentrations of 0.1 to 3.6 mg/m3 [1]. During normal operations, workers at another plant were exposed to not more than 0.3 mg/m3 . Aside from occupational exposure, probable exposure to the general public is through consumption of certain foods [14]. Another source of acrylamide exposure to the general public could be through drinking water treated with polyacrylamide flocculants [13]. Acrylamide may not be completely removed in many water treatment processes with some remaining after flocculation with polyacrylamides probably due to its water solubility and is not absorbed by sediment [15].

emulsion stabilizers, thickening agents for agricultural sprays, latex dispersions, textile printing paste, and water retention aids [25]. An aqueous 50% solution of acrylamide is used as acrylic copolymer dispersions in surface coatings and adhesives. In surface coatings, polymers are used as dispersants and binders to provide better pigment separation and flow. Surface coatings are used on home appliances and in the automotive trade [1, 26]. In addition, polyacrylamide has been used in both paper production process and treatment of mill wastewater [27]. Emulsions of polyacrylamide, calcium carbonate and clay are applied as a white coating in the manufacture of cardboard cartons [22]. These polymers are used as thickeners in soap and cosmetic preparations, and in skin care and hair grooming products, to impart a smooth after-feel and shine [22]. For oil drilling, liquid or powder partiallyhydrolyzed polyacrylamide is used as additives to water based drilling mud to provide a lubricating film and reduce friction at the drill bit, impart stability to shale and clay and increase viscosity [1, 22, 26]. Moreover, specialized gels comprised in part of acrylamide polymers are manufactured for use as lubricants in the textile dying components to which fabric or finished garments are added. The gel lubricates the cloth preventing it from clumping together and aids pigment dispersion during the dying process to ensure an even color [22, 28]. In leather processing, acrylamide is used as polymers impart a gloss or specific feel and suppleness to leather. The hide is most commonly placed in a drum with the polymer and various other constituents such as dyes, formaldehyde and pigments, then rolled for about two hours. The polymer can also be applied by brush or spray. There is no set formulation for the components of the mix and the proportion of acrylamide polymer is at the discretion of the operator seeking to obtain the properties required in the tanned product [29-30]. Another major application of acrylamide is to reduce herbicide drift during spray applications. The polymer increases the viscosity of the herbicide solution, allowing for more uniform spray applications, and also

Removal of Acrylamide by Microorganisms http://dx.doi.org/10.5772/56150 101

In worldwide usage, acrylamide is released into environment as waste during its production and in the manufacture of polyacrylamides and other polymers. Residual acrylamide concen‐ trations in 32 polyacrylamide flocculants approved for water treatment plants ranged from 0.5 to 600 ppm [13]. Acrylamide may remain in water after treatment [15] and after flocculation with polyacrylamides due to its high solubility and is not readily adsorbed by sediment [34]. Other sources of release to water are from acrylamide-based sewer grouting and recycling of wastepaper. Another important source of contamination is from acrylonitrile-acrylamide production which releases approximately 1 g acrylamide in each liter of effluent [35]. Some reports have indicated that polyacrylamide, in the presence of sunlight and glyphosate, photolytically degrades to acrylamide monomer and this is a direct introduction of acrylamide into agricultural areas [36-38]. The half-life of acrylamide monomer in rivers ranges from weeks to months [22]. However, one report indicates that polyacrylamide does not degrade to acrylamide monomer in the presence of sunlight and glyphosate. Additionally, glyphosate appears to interact with either the acrylamide monomer or polymer, decreasing the rate of monomer degradation [39]. The most important environmental contamination results from acrylamide use in soil grouting [13]. Half-life of acrylamide in aerobic soil increases with decreasing temperature [40]. Under aerobic conditions, acrylamide was readily degraded in

increases plant contact time [31-33].

Acrylamide is evidentially a neurogenic, terratogenic or carcinogenic toxicant in animals [16]. The neurotoxic properties of acrylamide have been studied for humans in relation to occupa‐ tional exposures and, experimentally, in laboratory animals. Understanding of acrylamideinduced neuropathies is quite advanced, a consequence of more than 30 years of research on the possible mechanisms of action [17]. The mechanism underlying the neurotoxic effects of acrylamide as with other toxins are interference with the kinesin-related motor proteins in nerve cells or with fusion proteins in the formation of vesicles at the nerve terminus and eventual cell death [18]. Neurotoxicity and resulting behavioral changes in acrylamideexposed laboratory animals can reduce reproductive fitness. Further, kinesin motor proteins are important in sperm motility, which could alter reproductive parameters. Effects on kinesin proteins could also explain some of the genotoxic effects on acrylamide. These proteins form the spindle fibers in the nucleus that function in the separation of chromosomes during cell division. This could explain the clastogenic effects of the chemical noted in a number of tests for genotoxicity and assays for germ cell damage [4].

## **2. Release of acrylamide in environment**

Acrylamide is a synthetic monomer with a broad spectrum of industrial applications, mainly as a precursor in the production of several polymers, such as polyacrylamide [1, 19]. High molecular weight polymers can be modified to develop nonionic, anionic, or cationic proper‐ ties for specific uses [1, 20]. Various grades of acrylamide are available with the industrial grade typically with a purity of 98 to 99%. Acrylamide for laboratory use ranges from routine to pure, the former for electrophoresis, the latter for molecular applications [21]. The largest demand for acrylamide polymers in industry is for flocculation of unwanted chemical substances in water arising from mining activities, pulp and paper processing, sewage treatment, and other industrial processes. Applications are based on the principles of colloidal suspensions and used to clean up liquids, particularly aqueous media, either for disposal or human consump‐ tion [20, 22-23]. Acrylamide is also used as a chemical intermediate in the production of *N*methylol acrylamide and *N*-butoxy acrylamide and as a superabsorbent in disposable diapers, medical, and agricultural products [24]. Small amounts of acrylamide are also used in sugar beet juice clarification, adhesives, binders for seed coatings and foundry sand, printing ink emulsion stabilizers, thickening agents for agricultural sprays, latex dispersions, textile printing paste, and water retention aids [25]. An aqueous 50% solution of acrylamide is used as acrylic copolymer dispersions in surface coatings and adhesives. In surface coatings, polymers are used as dispersants and binders to provide better pigment separation and flow. Surface coatings are used on home appliances and in the automotive trade [1, 26]. In addition, polyacrylamide has been used in both paper production process and treatment of mill wastewater [27]. Emulsions of polyacrylamide, calcium carbonate and clay are applied as a white coating in the manufacture of cardboard cartons [22]. These polymers are used as thickeners in soap and cosmetic preparations, and in skin care and hair grooming products, to impart a smooth after-feel and shine [22]. For oil drilling, liquid or powder partiallyhydrolyzed polyacrylamide is used as additives to water based drilling mud to provide a lubricating film and reduce friction at the drill bit, impart stability to shale and clay and increase viscosity [1, 22, 26]. Moreover, specialized gels comprised in part of acrylamide polymers are manufactured for use as lubricants in the textile dying components to which fabric or finished garments are added. The gel lubricates the cloth preventing it from clumping together and aids pigment dispersion during the dying process to ensure an even color [22, 28]. In leather processing, acrylamide is used as polymers impart a gloss or specific feel and suppleness to leather. The hide is most commonly placed in a drum with the polymer and various other constituents such as dyes, formaldehyde and pigments, then rolled for about two hours. The polymer can also be applied by brush or spray. There is no set formulation for the components of the mix and the proportion of acrylamide polymer is at the discretion of the operator seeking to obtain the properties required in the tanned product [29-30]. Another major application of acrylamide is to reduce herbicide drift during spray applications. The polymer increases the viscosity of the herbicide solution, allowing for more uniform spray applications, and also increases plant contact time [31-33].

contact with the solid monomer and inhalation of dust and vapor. Although it is not toxic in polymer form, the monomer can cause peripheral neuropathy. Residual monomer in polymers is also of health concern [13]. Primary exposure occurs during the handling of monomers. Two acrylamide manufacturing factories showed breathing zone concentrations of 0.1 to 3.6 mg/m3 [1]. During normal operations, workers at another plant were exposed to not more than

through consumption of certain foods [14]. Another source of acrylamide exposure to the general public could be through drinking water treated with polyacrylamide flocculants [13]. Acrylamide may not be completely removed in many water treatment processes with some remaining after flocculation with polyacrylamides probably due to its water solubility and is

Acrylamide is evidentially a neurogenic, terratogenic or carcinogenic toxicant in animals [16]. The neurotoxic properties of acrylamide have been studied for humans in relation to occupa‐ tional exposures and, experimentally, in laboratory animals. Understanding of acrylamideinduced neuropathies is quite advanced, a consequence of more than 30 years of research on the possible mechanisms of action [17]. The mechanism underlying the neurotoxic effects of acrylamide as with other toxins are interference with the kinesin-related motor proteins in nerve cells or with fusion proteins in the formation of vesicles at the nerve terminus and eventual cell death [18]. Neurotoxicity and resulting behavioral changes in acrylamideexposed laboratory animals can reduce reproductive fitness. Further, kinesin motor proteins are important in sperm motility, which could alter reproductive parameters. Effects on kinesin proteins could also explain some of the genotoxic effects on acrylamide. These proteins form the spindle fibers in the nucleus that function in the separation of chromosomes during cell division. This could explain the clastogenic effects of the chemical noted in a number of tests

Acrylamide is a synthetic monomer with a broad spectrum of industrial applications, mainly as a precursor in the production of several polymers, such as polyacrylamide [1, 19]. High molecular weight polymers can be modified to develop nonionic, anionic, or cationic proper‐ ties for specific uses [1, 20]. Various grades of acrylamide are available with the industrial grade typically with a purity of 98 to 99%. Acrylamide for laboratory use ranges from routine to pure, the former for electrophoresis, the latter for molecular applications [21]. The largest demand for acrylamide polymers in industry is for flocculation of unwanted chemical substances in water arising from mining activities, pulp and paper processing, sewage treatment, and other industrial processes. Applications are based on the principles of colloidal suspensions and used to clean up liquids, particularly aqueous media, either for disposal or human consump‐ tion [20, 22-23]. Acrylamide is also used as a chemical intermediate in the production of *N*methylol acrylamide and *N*-butoxy acrylamide and as a superabsorbent in disposable diapers, medical, and agricultural products [24]. Small amounts of acrylamide are also used in sugar beet juice clarification, adhesives, binders for seed coatings and foundry sand, printing ink

. Aside from occupational exposure, probable exposure to the general public is

0.3 mg/m3

not absorbed by sediment [15].

100 Applied Bioremediation - Active and Passive Approaches

for genotoxicity and assays for germ cell damage [4].

**2. Release of acrylamide in environment**

In worldwide usage, acrylamide is released into environment as waste during its production and in the manufacture of polyacrylamides and other polymers. Residual acrylamide concen‐ trations in 32 polyacrylamide flocculants approved for water treatment plants ranged from 0.5 to 600 ppm [13]. Acrylamide may remain in water after treatment [15] and after flocculation with polyacrylamides due to its high solubility and is not readily adsorbed by sediment [34]. Other sources of release to water are from acrylamide-based sewer grouting and recycling of wastepaper. Another important source of contamination is from acrylonitrile-acrylamide production which releases approximately 1 g acrylamide in each liter of effluent [35]. Some reports have indicated that polyacrylamide, in the presence of sunlight and glyphosate, photolytically degrades to acrylamide monomer and this is a direct introduction of acrylamide into agricultural areas [36-38]. The half-life of acrylamide monomer in rivers ranges from weeks to months [22]. However, one report indicates that polyacrylamide does not degrade to acrylamide monomer in the presence of sunlight and glyphosate. Additionally, glyphosate appears to interact with either the acrylamide monomer or polymer, decreasing the rate of monomer degradation [39]. The most important environmental contamination results from acrylamide use in soil grouting [13]. Half-life of acrylamide in aerobic soil increases with decreasing temperature [40]. Under aerobic conditions, acrylamide was readily degraded in fresh water by bacteria with a half-life of 55-70 h, after acclimatization for 33-50 h [41]. Acrylamide has been shown to remain slightly longer in estuarine or salt than fresh water [15].

intermediate [46, 56]. For example, *R. rhodochrous* J1 changed acrylonitrile to acrylamide and subsequently to acrylic acid [47] and *R. erythropolis* utilized either 2-arylpropionamides or acrylamide to form acrylic acid and ammonia [64]. In China, *Nocardia* sp. 163, a soil derived bacterium from Taishan Mountain harboring the highest nitrile hydratase activity on acrylo‐ nitrile was also used frequently for bioconversion of acrylamide [65]. Another prominent example is *Rhodococcus* sp. AJ270 which is a powerful and robust nitrile hydratase/amidasecontaining microorganism isolated by Guo et al [66]. An aliphatic amidase (amidohydrolase) has been found to be the responsive enzyme for the deamidation of acrylamide to acrylic acid

Removal of Acrylamide by Microorganisms http://dx.doi.org/10.5772/56150 103

In 1990, Shanker and his colleagues isolated an acrylamide-degrading bacterium, *Pseudomo‐ nas* sp., from soil using an enrichment method. This bacterium degraded high concentration of acrylamide (4 g/l) to acrylic acid and ammonia. An amidase was also found to be the relevant enzyme for the hydrolysis of acrylamide and other short chain aliphatic amides like formamide and acetamide but not on acrylamide analogues, methacrylamide and *N, N*-methylene

Many aerobic microorganisms utilize acrylamide as their sole source of carbon and ener‐ gy including *Pseudomonas* sp. and *Xanthomonas maltophilia*. Nawaz and his team found amidase in cell free extracts of these species and suggested it was involved in acrylamide degradation [49]. This is consistent with their earlier conclusion of acrylamide degrada‐ tion by *Rhodococcus* sp. [50]. Later, the denitrifying bacteria, *Pseudomonas stutzeri* was found to use acrylamide as substrate in the acrylonitrile–butadiene–styrene resin waste‐ water treatment system. The strain could remove acrylamide at concentrations below 440 mg/l under aerobic conditions [52]. Acclimation of microorganisms is believed to enhance acrylamide biodegradation. Complete degradation of acrylamide at 10–20 ppm in river water occurred in about 12 days with non-acclimated microorganisms, but in only 2 days with acclimation [3]. In 2009, scientists in Malaysia reported two acrylamide-degrading bacteria, *Bacillus cereus* DRY135 and *Pseudomonas* sp. DRYJ7. Acrylic acid was also detect‐ ed as a metabolite in the degradation [53-54]. *Aspergillus oryzae* KBN 1010 has been the

In domestic wastewater in Thailand, four novel acrylamide-degrading bacteria (*Enterobacter aerogenes*, *Kluyvera georgiana*, *Klebsiella pneumoniae*, and *Enterococcus faecalis*) were isolated. *E. aerogenes* and *K. georgiana* showed degradation potential of acrylamide up to 5000 ppm at the mesophilic temperatures and could degrade other aliphatic amides especially short to medium-chain length but not amide derivatives [60-61]. Removal of acrylamide and ammo‐ nium nitrogen from industrial wastewater by *E. aerogenes* was generally higher than that by

Degradation of acrylamide under anaerobic conditions has been rarely described. Recently a new strain of *Rhodopseudomonas palustris* was found capable of using acrylamide under photoheterotrophic conditions but grew poorly under anaerobic dark or aerobic conditions. A study of acrylamide metabolism by nuclear magnetic resonance showed the rapid deami‐ dation of acrylamide to acrylate and further to propionate [57]. More recently, the denitrifying

and ammonia [50, 59, 62, 64-67].

only fungi documented as an acrylamide degrader [63].

mixed cultures of microorganisms [68].

bisacrylamide [48].

Acrylamide releases to land and water from 1987 to 1993 totaled over 18.16 tons of which about 85 percent was to water, according to Toxic Chemical Release Inventory of the U.S. Environ‐ mental Protection Agency (EPA) [40]. These releases were primarily from plastic industries which use acrylamide as a monomer. In 1992, discharges of acrylamide, reported to the Toxic Chemical Release Inventory by certain US industries included 12.71 tons to the atmosphere, 4.54 tones to surface water, 1,906.8 tones to underground injection sites, and 0.44 tones to land [4]. In an EPA study of five industrial sites that produce acrylamide and polyacrylamide, acrylamide (1.5 ppm) was found in only one sample downstream from a polyacrylamide producer and no acrylamide was detected in soil or air samples [13]. Concentrations of 0.3 ppb to 5 ppm acrylamide have been detected in terrestrial and aquatic ecosystems near industrial areas that use acrylamide and/or polyacrylamides [42-43]. Cases of human poisoning have been documented from water contaminated with acrylamide from sewer grouting. The acrylamide monomer was found to remain stable for more than 2 months in tap water [22]. Atmospheric levels around six US plants were found on an average of < 0.2 μg/m3 (0.007 ppb) in either vapor or particulate form [15]. The vapor phase chemical should react with photo‐ chemically produced hydroxyl radicals (half-life 6.6 h) and be washed out by rain [15].
