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Chapter 2

LITERATURE REVIEW

2.1 Acrylamide

Acrylamide with chemical expression C3H5NO is an organic compound. Synonyms for acrylamide are acrylamide monomer, acrylic amide, propenamide, 2- propenamide, acrilamida ( DOT Spanish ) , acrylamide ( DOT French ) , acrylamide solution, acrylic acid amide ( 50 % ) , acrylic amide ( 50 % ) , ethylene carboxamide, ethylenecarboxamide, propenamide ( 50 % ) , propenoic acid, amide, RCRA Waste Number U007, UN 2074, and vinyl amide ( Ware, 1989 ) . Acrylamide is a chemical that normally used in industry to fix polymeric stuff that used in many merchandises in modern-day life known as polyacrylamide. Acrylamide can be present in either monomer ( individual unit ) or polymer ( multiple units that joined together by chemical bonds ) ( The Merck Index, 1996 ) . The polymeric signifier of acrylamide called polyacrylamide, known to be non toxic ( Friedman et al. , 2003 ) , while the individual unit substance is toxic and cause harm to the cardinal nervous system, carcinogen in research lab animate beings, bring forthing an go uping central/peripheral axonopathy and besides suspected to be carcinogen in worlds.

2.1.1 Physical and chemical belongingss of Acrylamide

Acrylamide can happen both in crystalline solid and liquid signifier. It is colourless to white solid monomer, free fluxing crystal that is soluble in H2O, dimethyl quintessence, ethyl alcohol, methyl alcohol, but is indissoluble in heptane and benzine. The solubility of acrylamide in H2O at 30oC is 2155 g/L. The molecular weight of acrylamide is 71.08 Da, runing point of 84.5oC and 125oC boiling point at 25 mmHg ( European Commission, 2002 ) .

The crystalline acrylamide monomer is available as pellets of 98 % and 95 % pureness. The specific gravitation of acrylamide is 1.122 at 30 & A ; deg ; C. The 50 % aqueous signifier is form for applications in which H2O can be tolerated. The monomer readily polymerizes at the runing point or under ultraviolet visible radiation ( NICNAS, 2002 ) . Solid acrylamide is stable at room temperature, but it may polymerise violently when melted or in contact with oxidising agents. Commercial acrylamide monomer contains residuary degrees of propenonitrile ( 1 to 100 mg/ kilogram ) ( IARC 1986 ) . Table 1 shows the sum-up of physico-chemical belongingss of acrylamide while Figure 1 shows chemical constructions of polyacrylamide and polyacrylamide.

2.1.2 Uses of Acrylamide and Polyacrylamide

Since the last century, the usage of acrylamide has increased. Acrylamide is widely use in many industrial applications every bit good as for chemical and environmental intents. It is known that the chief usage of acrylamide is in the production of high molecular weight polyacrylamide. Polyacrylamide is an of import polymer to bring forth assorted compounds with different physical and chemical belongingss suited for industrial needed. It is estimated that about 99.9 % of acrylamide is used in the production of polyacrylamide in Europe Union ( European Commission, 2002 ) . In the paper fabrication industry, polyacrylamide plays an of import portion as binders and keeping supports for fibers and to retain pigments on paper fibers. In United Kingdom, about 12,000 dozenss of polyacrylamide is used in the paper production industry yearly.

The physical belongingss of polyacrylamides are decided by copolymerising with a assortment of different vinylic monomers. Polyacrylamide can be manufactured as cationic, non-ionic, or anionic polymer. Both cationic and anionic polyacrylamides are produced by the procedure of copolymerisation of acrylamide. Cationic polyacrylamides are utile for flocculation of sewerage sludge and assorted industrial wastes, every bit good as keeping AIDSs in the paper industry ( Barvenik, 1994 ) .

Large measures of acrylamide are used in the production of polyacrylamide gel as a grouting agent to stabilise mineshafts in the excavation industry, tunnels, and dikes to increase the strength and to curtail the flow of H2O through a construction ( Mona et al. , 2001 ) . In the excavation procedure, polyacrylamides are used as flocculants to divide solids from aqueous solutions. It is besides used in the disposal of industrial wastes and in the cleaning of H2O supplies ( European Commission, 2002 ) . Polyacrylamide allow more concentrated sludge when they are used as sludge conditioning or dewatering agent than inorganic coagulators. When polyacrylamide is used in drinkable H2O intervention, it must non transcend of 0.05 % of its monomer ; nevertheless there are polyacrylamides incorporating 0.1-5 % of monomer used as industrial coagulators ( Croll et al. , 1974 ) . The rule of the curdling procedure is when the polymers bind with the atoms, it will organize heavy sums that rapidly settle out of solution and leave clear supernatant ( Barvenik, 1994 ) . The most effective polymer is the 1 that have high molecular weight cationic polyacrylamide ( 1.5 X106 g mol-1 ) as it obtains a high exclusion efficiency % with dose every bit low as 64 mg L-1 ( Arifin et al. , 2004 ) .

Acrylamide besides used to diminish dirt eroding, and this portion has received rise of attending in recent old ages. The most extensively published is in furrow irrigation systems, in which polyacrylamides is added to the irrigation H2O to hedge eroding of the furrows ( Lentsz et al. , 1992 ) . Polyacrylamide adds to the irrigation H2O will cut down up to 94 % of furrow eroding. Polyacrylamide has been shown to cut down eroding when introduced through a sprinkler irrigation system ( Byornberg and Aase, 2000 ; Green et al. , 2000 ) .

Smaller measures of acrylamides are formulated in cosmetics and soap readyings as thickenings. It is besides usage in dental fixtures, preshave lotions, and hair preparing readyings. This compound besides use as lasting imperativeness cloths, in molecular biological science applications, photographic emulsions, and nutrient processing industry ; in the production of diazo compounds ; and for gel chromatography and cataphoresis ( Sittig, 1985 ; IARC, 1986 ) . In the fabric industry, acrylamide polymer, polyacrylamides are used to size and shrink-proof stuff and as H2O repellants. Home contraptions, edifice stuffs, and automotive parts are coated with acrylamide rosins and thermosetting acrylics.

Polyacrylamide gel is used as a medium for hydroponically adult harvests, and as a binder of bone cements ( European Commission, 2002 ) . Hydroponics is a conventional method in gardening technique. This technique allows harvests to turn faster and more consistent in quality than conventionally adult green goods. This is because ; polyacrylamide that used in this technique is basically inert and has high ability to absorb H2O to provide for the harvests and capable of keeping wet.

There is no specific informations sing the use of acrylamide and polyacrylamide in Malaysia ; nevertheless, several industries in Malaysia usage polyacrylamide. The industries that use the most polyacrylamide are in waste H2O intervention, paper, and mush processing. For the golf class in Malaysia, polyacrylamide was used to toughen the foundation of the unreal lakes. These cause the taint of belowground H2O supplies and hence do several toxic condition and upsets of the cardinal nervous system. Chatterjee ( 1993 ) has reported that many golf player, caddies, every bit good as local peoples have been found to digest annoyances, tegument diseases and other allergic symptoms.

In agricultural country, polyacrylamide is used as a stabilizer ( 25-30 % solutions ) in weedkiller glyphosate ( ROUNDUP™ ) preparation. Polyacrylamides are mixed up with assorted organic dissolvers organizing inspissating agents, and so combined with weedkillers to increase the weedkillers wetting agents capablenesss ( Bouse et al. , 1996 ) . Harmonizing to Mansor ( 1996 ) , the glyphosate is the most celebrated weedkiller used to work out the weeds job all over Malaysia. This weedkiller is used for the control of a broad scope of broadleaf weeds and grasses in agricultural estate harvests such as gum elastic, oil thenar and chocolate. It is estimated up to 8 million liters of glyphosate were used in twelvemonth 2000 and from that information, at least 2 million liters of polyacrylamide is dumped into the dirt and the rivers every old ages ( AGRIQUEST, 2000 ) .

By and large, most portion of polyacrylamides is atoxic. However, due to the polymerisation procedure, these polymers can hold a remainder of its monomer, acrylamide ; a peripheral nervus toxin ( McMollister et al. , 1965 ) . The scope of acrylamide that might pollute polyacrylamide is in between 0.05 to 5.0 % of the concluding merchandise ( Croll et al. , 1974 ) . After flocculation with polyacrylamides, acrylamide will remnants in the H2O due to its high H2O solubility and have high inclination non to be absorbed by deposit and sludge, although some of it may be trapped in the deposit ( Brown et al. , 1980 ) .

2.1.3 Production of Acrylamide

For the production of many chemical compounds, normally big sum of energy needed to bring forth the reaction, and this can adversely impact the environment. Even though there are many alternate biotechnological production procedures exist, they are frequently hampered by economic sciences, although it is known to hold potentially good with regard to environmental protection. Nevertheless, progressively terrible environmental restraints will prefer procedures that can be done under milder conditions ( Yamada and Kobayashi, 1996 ) .

Normally biotransformations are used commercially when conventional chemical attacks are excessively expensive. In contrast to the conventional use of all right chemicals, trade good chemicals used in biotransformation are low-cost, have a larger demand, and are produced and sold in high volume. In add-on, trade good chemicals are characterized by the low cost of natural stuffs compared with the cost of production which characterizes all right chemicals. One of the most of import trade good chemicals used in coagulants, dirt conditioners and stock additives for paper intervention and paper size, and for adhesives, pigments and crude oil recovering agents is acrylamide.

Conventional chemical synthesis involves hydration of propenonitrile with the usage of Cu salts as a accelerator. However, this chemical method has assorted jobs: ( I ) the rate of acrylic acid formation is higher than that acrylamide formation, ( two ) the dual bond of both substrate and merchandise causes the formation of by- merchandise such as nitrylotrispropionamide and ethene cyanohydrate and ( three ) polymerisation occurs at the dual bond of both substrate and merchandise. Figure 2 shows the comparative flow sheet for the microbic and conventional procedures.

For that ground, the enzymatic transition from propenonitrile to acrylamide could be done by micro-organisms ‘ catabolyzing propenonitrile. Since it is repressive for nitrile hydratase activity when added to the reaction mixture at a high concentration, propenonitrile, which functions as a substrate, was added in little parts to the mixture. More than 99 % of the substrate ( in this instance, propenonitrile ) was converted to acrylamide without formation of any by merchandises ( Yamada and Kobayashi, 1996 ) .

2.2 Acrylamide as pollutant

The taint of acrylamide monomers in the environment through the usage of polyacrylamide in China clay, paper industry, and H2O industry have occur long ago ( Bachmann et al. , 1992 ) . The open workers will hold symptoms of numbness, limb hurting, skining tegument, and sudating manus. Acrylamide monomers can come in the environment by many ways. In the acrylamide production, closed system is now being used. Therefore, the production processes of acrylamide are improbable to be beginning of environmental taint, except if there is a job such as leaking from the reactor. Acrylamide discharge to H2O and environment besides occur from acrylamide-based cloaca grouting and wastepaper recycling.

Because of the high H2O solubility, acrylamide can easy pollute H2O system and non likely to be beginning of air contamination due to its low vapour force per unit area. The use of polyacrylamide flocculants that contain residuary degrees of acrylamide monomer is a major beginning of imbibing H2O contaminate by acrylamide. Public can expose to the acrylamide taint from the polyacrylamide that used as flocculants agent in H2O intervention system ( Brown et al. , 1980, Howard, 1989 ) . In drinkable H2O intervention, polyacrylamide containing in it must non transcend more than 0.05 % ( w/v ) monomer. It may non be removed in most of the technique used in H2O intervention procedure ( Croll et al. , 1974 ) . Igisu et al. , ( 1975 ) has reported the instances of acrylamide toxic condition in Japan as a consequence of acrylamide contaminate the H2O supply. Acrylamide was found to stay in tap H2O at least for two month after flocculation with polyacrylamides as it is H2O soluble and is non readily absorbed by deposit ( Brown et al. , 1980 ) .

The recommended criterion for imbibing H2O in Malaysia was set on the footing of WHO Guidelines of 1976. The maximal allowable degree of acrylamide containing in imbibing H2O of Malaysia is 0.0005 mg/L ( National Technical Committee, 2000 ) . In both tap H2O and river country where polyacrylamide ware used for the intervention of drinkable tap H2O, acrylamide was detected at degrees of less than 5µg/L. In West Virginia ( USA ) , acrylamide was reported to incorporate 0.024 – 0.041 mg/L in the sample collected from public imbibing H2O supply ( Brown and Rhead, 1979 ) .

In Malaysia, study by The Environmental Quality Report ( 1997 ) showed that a sum of 908 H2O quality Stationss along 117 rivers were monitored by six parametric quantities viz. pH, dissolved O, biological O demand, ammoniacal N and suspended solids are taken for consideration to calculate the quality index. Based on the computation by 1997 WQI, merely 24 rivers were categorized as clean, 68 somewhat polluted and 25 rivers polluted. In footings of NH3-N ( Ammoniacal Nitrogen ) contain in the river, a sum of 93 rivers were categorized as polluted. This is mostly due to livestock agriculture and domestic waste ( Malaysia Environmental Quality Report, 1997 ) .

Environmental pollution of acrylamide may caused by the disposal or leaching of residuary monomer from polyacrylamides. Report from the Toxic Chemical Release stock list ( TRI ) shows that estimated 5, 912, 663 pound were released to the environment from 43 installations that manufactured or used acrylamide in United States in 1996 ( TRI96, 1998 ) . In 1999, the figure of installations increased to 90, and the sum of acrylamide released is drastically increased up to 7, 542, 385 pound. 99.6 % of the entire acrylamide released was on the belowground dirt injection. Statistic shows that 24, 874 pound of acrylamide were released to air from 44 installations. Twenty-one installations, each were found to let go of & gt ; 100 pound of acrylamide to air, which represented 98.7 % of the entire emanation ( TRI99, 2001 ) . Other 1999 from the sum released with the sum of 370 pounds were to H2O and another 6, 289 pound to land ( TRI99, 2001 ) .

Acrylamide besides can be exposed to the working environment. Even the little sum of polyacrylamide used in industry can ensue in acrylamide taint in the workplace. Exposure of acrylamide can happen during the production of acrylamide and polyacrylamide, during acrylamide grouting, and besides during chemicals readying in research lab. Peoples who work in industries that use acrylamide and polyacrylamide such as in building, plastics fabrication, cosmetics, paper and mush, excavation, and agricultural industry are potentially exposed to acrylamide poisoning. There is no study sing acrylamide exposure and toxic condition for grouters, but the exposure for these peculiar individual may be greater than workers in other industry ( WHO, 1985 ) .

1950s is the twelvemonth where acrylamide grouts were started to utilize in USA ( Mona et al. , 2001 ) . Acrylamide grouts by and large consist of a 19:1 mixture of acrylamide and a cross-linking agent ( EU Risk Assessment Report, 2002 ) . In the terminal of 1970, the production of acrylamide grout in USA dropped because of the human wellness concern by the operators. However, in 1989 about 43 % of grouts still be used in USA ( Mona et al. , 2001 ) .

In 1997, merchandise Rocha-Gil ( Siprogel ) that contains acrylamide and methylolacrylamide ( N-hydroxymethylacrylamide ) was used in the building site for constructing tunnel in Hallands? sen, Sweden and in Romeriksporten, Norway ( Mona et al. , 2001 ) . In both countries, the H2O released from the building sites causes the high concentration of acrylamide in receiver ‘s Waterss ( Swedish Environmental Protection Agency, 1997 ) ; Sverdrup et al. , 1999 ; Kallqvist et al. , 1997 ) .

In the center of the assorted utilizations of polyacrylamide, it is assorted with assortment of organic dissolvers to organize inspissating agents that are so combined with weedkillers ( i.e. , glyphosate ) to hike its surfactant capablenesss ( Bouse et al. , 1986 ) . For the commercial weedkiller, polyacrylamide is used as linear ( 25 % to 30 % solutions ) to cut down spray impetus and to move as a wetting agent ( Smith et al. , 1996 ) . Glyphosate preparation can be more toxic than glyphosate entirely, for illustration: RoundupTM can be 30 times more toxicant to angle than the glyphosate itself ( Servizi et al. , 1987 ) .

Surveies show that heat ( Burrows et al. , 1981 ) , light ( Reddy et al. , 1994 ) , and environmental status ( Kay-Shoemaker et al. , 1998 ) , promoted the depolymerisation of polyacrylamide to acrylamide. Photodegradation of polyacrylamide is a major factor in environmental debasement.

There are no studies available sing acrylamide concentration contaminate in workss and nutrient merchandises. Suggested that workss and nutrients merchandise may expose to acrylamide via air or contaminated H2O during growing or industry. However, acrylamide may show in nutrients result from the Maillard reaction between the amino acerb asparagine and certain cut downing saccharides when the nutrients is prepare at high temperatures ( Mottram et al. , 2002 ; Stadler et al. , 2002 ) . Acrylamide degree will increase with the clip of heating. Maillard reaction is a reaction that produces the tasty crust and aureate coloring material in fried and adust nutrients ( Friedman, 2003 ) .

In heated protein-rich nutrients, moderate degrees of acrylamide ( 5-50 mg/kg ) were detected and even higher content were detected ( 150-4000 mg/kg ) in carbohydrate-rich nutrients, such as murphy, Beta vulgaris rubra, besides commercially potato merchandises and chip staff of life. Acrylamide can non be detected in unwarmed or boiled nutrients ( & lt ; 5 mg/kg ) .

2.3 Toxicity of Acrylamide

Yang et Al. ( 2005 ) has evaluated the toxicity of acrylamide. The consequence showed the mutagenic authority of acrylamide for Salmonella strains TA98 and TA100. Mice that exposed to acrylamide via intraperitoneal injection at dosage of = 50 mg/kg shows an increasing in the incidence of chromosomal aberrances in its bone marrow cells ( Chiak and Vontorkova 1988 ) . Marlowe et al. , ( 1986 ) survey shows that group of mice received individual of unwritten dosage of 116-121 mg/kg. Acrylamide has been found in epithelial tissue of unwritten pit and gorge, liver and saddle sore vesica. High concentration of acrylamide was present in kidneys, testicle, and pancreas. Besides causes several histopathological lesions in the seminiferous tubules, acrylamide besides shows effects of toxicological on male rat ‘s generative system. Research by Ikeda et al. , ( 1987 ) suggested that continuity of acrylamide or its metabolites in ruddy blood cell following repeatedly exposure of acrylamide in Canis familiariss and hogs.

Acrylamide can damage nervous system, doing numbness and failing in the manus and pess. Acrylamide can impact human wellness through inspiration, soaking up through tegument, doing a roseola or firing experiencing on contact. It can besides do loss of balance, slurred address, and heavy perspiration. Contact may do oculus Burnss and a skin roseola. Approximately 20, 000 workers were potentially exposed to acrylamide in 1976 ( NIOSH, 1984, IARC 1986 ) .

Acrylamide is a toxic three-carbon compound incorporating an amide group and an a, & A ; szlig ; -unsaturated olefin bond ( David et al. , 2005 ) . This compound will respond with nucleophilic compounds via a Michael add-on. It exerts toxic effects by organizing adducts to nucleophilic medieties such as sulfhydryl groups incorporating proteins and aminic acids ( Barber et al. , 2001 ) . Human exposure to acrylamide is chiefly occupational from cuticular contact. Acrylamide or its metabolites bind to RNA, DNA, and protein in a scope of tissues.

There is a survey in China on workers who were exposed to acrylamide by inspiration between one month and 11.5 old ages in an acrylamide synthesis room. Blood samples were obtained from 41 workers on that industry ( Bergmark et al. , 1993 ) and haemoglobin ( Hb ) was extracted for analysis of acrylamide and glycinamide adducts. Workers were potentially exposed to acrylamide by inspiration and cuticular exposure. Skin desquamation was observed on the custodies indicate that the cuticular exposure occurred. In study by Donovan and Pearson ( 1987 ) terrible symptom of acrylamide toxicity detected within 3 hours of calculated unwritten consumption of acrylamide. This indicates that rapid and extended soaking up of acrylamide by the unwritten path. Hagmar et al. , ( 2001 ) describe his survey on the effects of really high exposure of acrylamide on workers plants in Chinese mill fabricating acrylamide or utilizing acrylamide or utilizing acrylamide in China. 210 workers were found to expose to grouts incorporating acrylamide for about 2 months, and there was important connexion between hemoglobin adduct degrees and exposure classs.

Many surveies have been conducted to measure neurotoxic effects of acrylamide in occupationally-exposed workers ( Deng et al. , 1993 ) . Peoples who have been exposed to acrylamide toxic condition will see early symptoms like skin skining from custodies ; weaken legs, numbness custodies and pess, and damage of the quiver esthesis in the toes and loss of ankle physiological reactions. In Japan, the contaminated H2O supply with acrylamide cause several instances of acute acrylamide toxic condition. Igisu et Al. ( 1975 ) reported a degree of 400 milligrams acrylamide/L in well-water in Japan that had been contaminated from a grouting operation 2.5 metres off. Through consumption and external usage of the well-water that readily contaminated with acrylamide, reportedly that there were five people that have been exposed and experienced the acrylamide toxicity. Poisoning symptoms included memory perturbations, confusion, hallucinations, freak out and truncal ataxy. But within four months period of clip, all of the open individuals have wholly recovered ( Igisu et al. , 1975 ) .

Beside homo, acrylamide besides believe to do abnormalcies in mitotic and meiotic in both animate beings and workss ( Shairashi, 1978 ; Shanker et al. , 1987 ) . The metabolization of acrylamide to epoxide, glycidamide ( 2,3- epoxypropanamide ) , shown to hold neurotoxic potency ( Barber et al. , 2001 ) . High concentration of acrylamide in imbibing H2O of rats resulted in increased of tumour production at the adventitia vaginalis testicle ( Damjanov and Friedman, 1998 ) , adenomas of follicular cells of the thyroid ( Johnson et al. , 1986, Friedman et al. , 1995 ) , and tumour of the mammary fibroadenomas ( Crump, 1999 ) . The manner of action appears to affect binding of acrylamide to dopamine receptors ( Crump, 1999a ; Crump, 1999b ) .

Many early studies suggested that acrylamide toxicity was mediated by multifocal puffinesss and devolution of long medullated axons in the cardinal and peripheral nervous systems ( Gold and Schaumburg, ( 2000 ) ; LoPachin and Lehning, ( 1994 ) ; Spencer and Schaumburg, ( 1976 ) ; Spencer and Schaumburg, ( 1977 ) ; Tilson, ( 1981 ) . Recent surveies have been conducted in rats and show dissociation between development of distal axonopathy in the peripheral nervous systems and authoritative neurological marks such as ataxy, hindfoot splay and hindlimb musculus failing. These symptoms observed in rats that exposed to acrylamide dose ranging of 20 mg/kg or 50 mg/kg per twenty-four hours. But the development of anoxypathy observed merely when the rats is exposed to a low dose of acrylamide, in long term status ( 21 mg/kg per twenty-four hours ) ( Lehning et al. , ( 1998 ) ; Crofton et al. , ( 1996 ) . This deficiency of correspondence proposed that axon devolution did non play a major function in the development of acrylamide neurotoxicity. Therefore, the hypothesized that axonopathy is a non- specific consequence of acrylamide in fact it is related to continuance of acrylamide exposure ( LoPachin et al. , 2000 ) .

Acrylamide grouts that used in the edifice of tunnels in Hallandsasen, Sweden, and in Romeriksporten, Norway in 1997. Large-scale of Rhoca-Gil used to construct the 8.6km tunnel in Hallandsasen ( Mona et al. , 2001 ) . After a few hebdomad of injection, the symptoms of acrylamide toxic condition were observed in fish and cattle downstream the site of the undertaking. Not merely that, the symptoms of acrylamide toxic condition besides were observed in people who works in the tunnel ( Swedish Environmental Protection Agency, 1997 ) . Undertaking in Romeriksporten is to construct a 14km long railway tunnel. The building site is located in the center of Olso City, chief airdrome Gardermoen. The big H2O escape makes the company decided to utilize Rhoca-Gil 110/25 as grouting agent to halt escape of the H2O ( Mona et al. , 2001 ) . 73 workers were examined by the Norse Occupational Health Services. From that figure, 4 workers detected to hold skin effects due to acrylamide exposure. Another 7 workers were found to hold somewhat decrease of nervus ( Kjuus et al. , 1998 ) . Based on the incident that occurred, Norse authorities semen to a determination to censor the usage of acrylamide- and methylolacrylamide used as grouting agent for the building site in the late 1997 ( Norse State Pollution Authorities, 1997 ) .

2.4 Bioremediation

Manufacturing, processing, and managing large-scale and big measures of chemicals have led to serious surface, subsurface of dirt and H2O taint with assortment of unsafe and risky toxic compounds. There was a big addition in the diverseness of organic compounds that are industrially produced and which were heedlessly release into the environment. Chemicals which have been synthesized in big measures differ well in chemical construction from natural organic compounds. The chemicals are designated as xenobiotic because of their comparative refractoriness to biodegradation ( Singh and Ward, 2004 ) . The accretion of many chemical compounds in the environment, peculiarly in dirt and H2O are important concern because of their toxicity, every bit good as their carcinogenicity belongingss and besides because of the high potency of the compounds to roll up in populating systems.

Biodegradation is an of import remotion mechanism for the big measures of chemical that released in our environment. The consequence of biodegradation is a lessening in the measure of chemicals present in the environment and is a critical technique in forestalling the accretion and continuity of the chemicals ( Shimp et al. , 1990 ) . Biodegradation of organic chemicals is one of the critical procedures that determine the destiny and behavior of xenobiotics in the environment.

The ability of bugs to degrade pollutants into harmless components has been explored as a mean to biologically handle contaminated environments, and today it is the topics of many research probes and real-world applications ( Jim et al. , 2005 ) . Now, it is besides the being the footing for the emergent field of bioremediation.

Bioremediation can be defined as any procedure that uses micro-organisms or their enzymes to return the environment altered by contaminations to its original status. Mueller et al. , ( 1992 ) defined the bioremediation is the usage of micro-organisms, workss or biologically active agents in order to degrade sequester and conjugate environmental pollutants.

Attention in bioremediation for the contaminated dirt and H2O has increased in the last two decennaries chiefly because of the ability of the micro-organisms to degrade the toxic compounds which were known to be immune to the natural biological procedures in the environment. It is known that the micro-organisms in the environment oxidize many natural merchandises and semisynthetic compounds to carbon dioxide ( CO2 ) and this constitutes an of import portion of the C rhythm on the Earth ( Dagley, 1975 ) . These bugs possess assorted enzymes capable of change overing the toxic environmental pollutants into non-toxic compounds, which may function as C and N substrates ( Ingvorsen et al. , 1991 ) .

The utilizations of micro-organism for bioremediation procedure determine by the status of the taint site whether it can be used autochthonal or exigenous. Generally, many of the degrading-microorganisms used for this procedure are of course happening and members of stable microbic communities ( Lindstrom et al. , ( 1991 ) ; Stevens et al. , ( 1991 ) . Nowadays, in order to heighten the debasement capablenesss of the micro-organism, recent research has developed the usage of familial technology and choice techniques for the isolation of the mark micro-organism.

2.5 Degradation of polyacrylamide to acrylamide

As discuss earlier in this portion, acrylamide polymer, polyacrylamide is one of the major compound in industrial application. Polyacrylamide is used as flocculants agent in H2O intervention procedure to increase the procedure of sludge thickener and dewatering. It is besides used as cement binder ( Dos Santos et al. , 2003 ) , in sugar refinement ( Bologna et al. , 1999 ) , every bit good as preparation with pesticides to increase the surfactant capablenesss.

Surveies by Marcus et al. , ( 2002 ) showed that temperature, visible radiation, biological, chemical, every bit good as mechanical promoted the debasement of polyacrylamide to acrylamide. Consequence from survey by Eldon, ( 1997 ) indicate that photolytic effects or energy cause polyacrylamide debasement to acrylamide. The light energy can interrupt chemical bonds, therefore, degrading polymers ( Decker, 1989 ; Rabek, 1987 ; Grassie and Scott, 1985 ) . It is in line with study by Crosby, ( 1976 ) suggested that polyacrylamide is compose of C-C, C-H, and C-N bonds. Those bond strengths are about 340, 420, and 414 kj/mol, severally, and these bonds can be broken down by wavelength of 325, 288, and 288nm, severally.

The debasement of polyacrylamide by micro-organisms as beginning of N for the micro-organism ‘s growing has been examined by Kay-Shoemake et al. , ( 1998 ) . Result obtained indicates that there were present of enzymes capable of biological hydrolysis of the amide to organize NH3 and an acid. However, the survey of polyacrylamide debasement for C beginning of the micro-organism growing showed negative consequence. This can reason that the bacteria studied non incorporating required enzymes to degrade the C anchor of polyacrylamide to fulfill their C demand.

2.6 Degradation of acrylamide

Polyacrylamides for the most portion are non-toxic. However, after polymerisation, these polymers can hold a residue of acrylamide, a known peripheral nervus toxin ( Eldon et al. , 1997 ) . On release to the environment, acrylamide may undergo a figure of debasement depending upon the topographic point into which the release occurs. Due to its high H2O solubility, most likely acrylamide will be eliminated from the ambiance by rain out ( European Commission, 2002 ) .

The debasement of acrylamide in river was studied by Brown et al. , ( 1980 ) . Two parametric quantities were used in this survey, which were sterilized river H2O and non-sterilized river H2O. Tested river H2O was added with acrylamide monomer at concentration of 0.5 and 5 mg/L. Then, the samples were stored under anaerobiotic conditions. No debasement was observed in any samples after 41 yearss incubation. For non-sterilized river H2O, debasement was observed. The absence of acrylamide debasement in sterilized river H2O proposes that the debasement occurs through a biotic procedure, with abiotic procedure such as hydrolysis and photolysis being negligible.

There is a study sing the considerable acclimatization period required for the remotion of acrylamide in H2O ( Croll et al. , 1974 ; Brown et al. , 1980 ) compared to dirty where acrylamide monomer was quickly hydrolyzed ( Abdelmagid and Tabatabai, 1982 ) . Acclimated microorganisms wholly degrade acrylamide in 2 yearss, comparison to non-acclimated micro-organisms where 12 yearss needed to wholly degrade the same concentration of acrylamide at 10-20 ppm in river H2O ( U.S EPA, 1985 ) .

Many species of micro-organism has ability in degrading acrylamide as their C or/and N beginning for growing. These bantam beings can degrade acrylamide under visible radiation or dark, every bit good as in anaerobic or aerophilic conditions ( Brown et. al. , 1980 ) . Wang and Lee ( 2007 ) have reported sing the ability and public presentation of bacteriums on degrading acrylamide utilizing Ralstonia Eutropha. The consequence indicated that the bacteriums could take acrylamide at concentration below 1446 mg/L. There is besides a study sing acrylamide debasement by bacteriums under aerophilic and anaerobiotic status. Under aerophilic status, Pseudomonas stutzeri could use acrylamide at maximal concentration of 440 mg/L ( Wang and Lee ( 2001 ) . The acrylic acid and ammonia byproducts were used as C and N beginning, severally.

2.7 Effectss of Heavy metals

Heavy metals taint has been one of the environmental jobs presents. The spread of heavy metals in the environment can be caused by the waste merchandises disposal ( Lasat, 2002 ) . Beside that, it is besides due to such industries that involve in metal processing, burning of wood, coal and mineral oil, and from the usage for works protection ( Schinner and Klauser, 2005 ) . The widespread of heavy metals in environment non merely affected dirt, H2O resources and endanger human wellness ( Shi et. al. , 2001 ) , but besides consequences in the decrease of microbic diverseness and activities in dirt ( Lasat, 2002 ; Akmal et. al. , 2005 ) . Soil microorganisms play an of import portion in recycling the mineral and in the decomposition of organic affair ( Wardle and Ghani, 1995 ) . It is besides of import in the debasement of others toxic compound in the dirt. The used of micro-organisms for the environmental bioremediation intents can be disrupted by the nowadays of heavy metals in the bioremediation site. So, this is one of major restriction facet in bioremediation.

The presence of heavy metals in environment decreased the activity and diverseness of micro-organisms in the environment, and upseting the balance of population interactions within the community ( Wang et. al. , 2010 ) . Most of the old surveies has been conducted affecting dirt micro-organisms, stated that toxicity of heavy metals has been related to their entire concentration in dirt ( Huang and Shindob, 2000 ) . The higher the heavy metals concentration, the greater their consequence on microbic community. In add-on, study by Zarnovsky et. al. , ( 1994 ) shows that activated sludge micro-organisms and procedure efficiency were inhibited by Cd, Cr, and nickel at concentrations above 10 mg/L. Heavy metal exert their toxic consequence by interaction with enzymes, therefore cause suppression of many metabolic procedures within the micro-organisms ( Gassic and Korban, 2006 ) .

2.8 Cell immobilisation

Immobilization of microbic cells is a new attack in biotechnology particularly in the bioremediation country to take the environmental taint. Immobilization of microbic cells is a procedure which involve the entrapment of populating micro-organism ‘s cell by utilizing a semi-permeable polymeric gel construction ( Moslemy et. al. , 2002 ) . The engineering of cell immobilisation has been reported to hold been successfully used in bioremediation intent ( Cassidy et. al. , 1996 ) .

Surveies by old research workers reported that there are many advantages of utilizing immobilized cells for the remotion of environmental pollutants over free-cells preparation. The used of gel matrix in cell immobilisation technique can protect the microbic cells from biotic emphasis ( Smith et. al. , 1996 ) , and besides from abiotic emphasis such as the toxic compounds repressive consequence ( Cassidy et. al. , 1997 ) . Beside that, it besides enhanced the microbic endurance every bit good as improves the physiological activity ( Weir et. al. , 1995 ) . Cell immobilisation besides has high productiveness, as the cells are confined and the cell densenesss are high ( Lee et. al. , 1994 ) .

There are many methods proposed to immobilise microbic cells. These methods include cross-linking, cell entrapment, and encapsulation. In cell immobilisation technique, one of import standard is to utilize immobilisation matrices with high unity to guarantee that it can forestall the microbic cells from leaking out into the environment ( Premkumar et. al. , 2002 ) . Ideal matrix for immobilisation method should hold the ability to forestall cell flow within the matrix, functional at utmost temperatures, can be used in inconsiderate H2O conditions for illustration contaminated H2O, and let the flow of O and other foods through the matrix. Normally used immobilisation matrices include alginate beads, polyacrylamide gel, activated C, agarose, k-carrageenan, and gellan gum beads ( Chung et. al. , 2003 ; Somerville et. al. , 1977 ; Bandyopadhyay et. al. , 1999 ; Knaebel et. al. , 1996 ; Audet and Lacroix, 1989 ; Moslemy et. al. , 2003 ) .

Several type of barm and bacteriums strain such as Pseudomonas aeruginosa ( Prabu and Thatheyus, 2007 ) , Acinetobacter sp. and Sphingomonas sp. ( Liu et. al. , 2009 ) , every bit good as barm, Candida tropicals ( Wang and Gong, 2007 ) , are reported to hold been successfully immobilized and used for the debasement of acrylamide, phenol, and pyrene severally. The consequences show that the immobilized cells have better debasement ability compared to free-cells of the micro-organisms.

The used of gellan gum for encapsulation of microbic cells has been proposed from old survey by Moslemy et. al. , ( 2002 ) as it has many advantages than the usage of k-carrageenan and alginate. Gellan gum is produce by the micro-organism, Sphingomonas alodea ( ATCC 31461 ) . Sphingomonas Elodea was once known as Pseudomonas Elodea ( Donner and Douds, 1995 ) . Gellan gum is a additive tetrasaccharide. It has high molecular weight, dwelling about 50,000 residues and usually, it is de-esterified by alkali intervention before used in nutrient processing industry. General chemical construction of gellan gum is presented in figure 3. Gellan gum can organize gels when there is positive charged ion ( cations ) available or added. Therefore, the texture and the thickness of gellan gum can be controlled depends on the add-on of Ca, Mg, K, and Na salts. Gellan gum-encapsulated cell affect the production of microbeads by emulsification-internal gelation.

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