Biocatalytic Production of Hetero-Chitosan Oligosaccharides as Anti-oxidants

  • Swati Jaiswal
  • Pushplata Tripathi
  • Sujata SinhaEmail author
Part of the Sustainable Agriculture Reviews book series (SARV, volume 35)


Abundantly available chitin/chitosan and their derivatives are full of useful bioactivities. They have numerous applications in industries like food, wastewater treatment, pharmaceuticals, agriculture, cosmetics etc. However, their insolubility in water plays spoilsport in way of their use as cost-effective biomolecules for various sectors. Breakage of chitosan to smaller oligosaccharides solves this problem to larger extent preferably using highly specific enzymes. It is well known that that bioactivities of oligosaccharides improve upon hydrolysis to lower molecular weight chitosan i.e. chitooligosaccharides. Availability and production of anti-oxidant chitooligosaccharides by non-chemical approach is desirable for consumer satisfaction. Bioprocessing of chitin/chitosan generated from marine waste to be used as bioactive chitooligosaccharides, can reduce both environmental and human health hazards to a great extent.

Here we review (1) biocatalytic approaches for chitooligosaccharides production, (2) bioprocess strategies for large scale production, (3) functionalization and (4) anti-oxidant activity of chitooligosaccharides. Specific and non-specific biocatalysts are used for chitooligomer preparation either by hydrolysis and transglycosylation approaches. Cellulase enzymes have been found to be most frequently used non-specific enzymes for chitosan hydrolysis but microbial chitosanases show excellent performance for chitooligosaccharides production both in terms of yield and specificity. Transglycosylation also have been found to be promising for chitooligosaccharides production especially at small scale. Combination reactors have been found to be most suitable for upscaling of chitooligomer production. Immobilized packed column with ultrafiltration membrane reactors are used for simultaneous hydrolysis and separation of chitooligomers. Chemically synthesized derivatives of chitooligomers have been reported in many studies by introducing carboxyl, quaternized amino, amino ethyl, sulfate, gallyl and many more groups. Amino ethyl, Gallyl, sulphated, phenolic acid conjugated and carboxylated derivatized chitooligomers have shown anti-oxidant activity. Anti-oxidant activity of chitooligomers and relation with their structure and polymerisation has been well established. Chitooligomers longer than trimer show good activity while best activity has been reported in degree of polymerisation from 10 to 12. Acetylation of chitooligomers leads to improvement in anti-oxidant activity than their deacetylated version.


Anti-oxidant Oligosaccharides Chito-oligosaccharides Chitosanase Chitin Chitosan Radical-scavenging DPPH Bioactivity 



2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid


butylated hydroxyanisole


butylated hydroxytoluene


chloramphenicol acetyltransferase






degree of deacetylation


5,5-dimethyl-1-pyrroline N-oxide


deoxyribonucleic acid


deoxyribonucleic acid




electron spin resonance


ferric reducing power


glutathione peroxidase


kilo Dalton


polyacrylonitrile nanofibrous membrane


quaternised carboxymethyl chitooligosaccharide


reactive oxygen species


superoxide dismutase


thiobarbituric acid reactive substances


tertiary butyl hydroquinone



Corresponding author acknowledges Department of Science & Technology, Government of India for financial support vide reference no (SR/WOS-A/LS-1004/2015) and (SR/WOS-A/LS-129/2009) under Women Scientist Scheme.


  1. Aam BB, Heggset EB, Norberg AL, Sørlie M, Vårum KM, Eijsink VGH (2010) Production of chitooligosaccharides and their potential applications in medicine. Mar Drugs 8:1482–1517. CrossRefPubMedPubMedCentralGoogle Scholar
  2. Abdel-Aziz SM, Kahil T, Keera AA (2014) Kinetic behavior of free and in situ immobilized chitosanases produced by the fungus Mucor rouxii. World Appl Sci J 30:1–09. CrossRefGoogle Scholar
  3. Aiba S (1994) Preparation of N-acetylchitooligosaccharides by hydrolysis of chitosan with chitinase followed by N-acetylation. Carbohydr Res 265:323–328. CrossRefPubMedGoogle Scholar
  4. Akiyama K, Kawazu K, Kobayashi A (1995) A novel method for chemo-enzymatic synthesis of elicitor-active chitosan oligomers and partially N-deacetylated chitin oligomers using N-acylated chitotrioses as substrates in a lysozyme-catalyzed transglycosylation reaction system. Carbohydr Res 279:151–160. CrossRefPubMedGoogle Scholar
  5. Ando T, Kataoka S (1980) Acylations of chitin with acid anhydrides in trichloroacetic acid systems. Kobunshi Ronbunshu 37:1–7. CrossRefGoogle Scholar
  6. Anraku M, Gebicki JM, Iohara D, Hisao T, Kaneto U, Toru M, Hirayamaa F, Otagiri M (2018) Antioxidant activities of chitosans and its derivatives in in vitro and in vivo studies. Carbohydr Polym 199:141–149. CrossRefGoogle Scholar
  7. Cabrera JC, Messiaen J, Cambier P, Van Cutsem P (2006) Size, acetylation and concentration of chitooligosaccharide elicitors determine the switch from defence involving PAL activation to cell death and water peroxide production in Arabidopsis cell suspensions. Physiol Plant 127:44–56. CrossRefGoogle Scholar
  8. Chang SH, Wu CH, Tsai GJ (2018) Effects of chitosan molecular weight on its antioxidant and antimutagenic properties. Carbohydr Polym 181:1026–1032. CrossRefGoogle Scholar
  9. Chatelain PG, Pintado ME, Vasconcelos MW (eds) (2014) Evaluation of chitooligosaccharide application on mineral accumulation and plant growth in Phaseolus vulgaris. Plant Sci 215:134–140. CrossRefGoogle Scholar
  10. Chen AS, Taguchi T, Sakai K, Kikuchi K, Wang MW, Miwa I (2003) Antioxidant activities of chitobiose and chitotriose. Biol Pharm Bull 26:1326–1330. CrossRefPubMedGoogle Scholar
  11. Cho SY, Lee JH, Song MJ, Park PJ, Shin ES, Sohn JH (2010) Effects of chitooligosaccharide lactate salt on sleep deprivation-induced fatigue in mice. Biol Pharm Bull 33:1128–1132. CrossRefPubMedGoogle Scholar
  12. Choi WS, Ahn KJ, Lee DW, Byun MW, Park HJ (2002) Preparation of chitosan oligomers by irradiation. Polym Degrad Stab 78:533–538. CrossRefGoogle Scholar
  13. de Assis CF, Araújo NK, Pagnoncelli MGB, da Silva Pedrini MR, de Macedo GR, dos Santos ES (2010) Chitooligosaccharides enzymatic production by Metarhizium anisopliae. Bioprocess Biosyst Eng 33:893–899. CrossRefPubMedGoogle Scholar
  14. de Assis CF, Costa LS, Melo-Silveira RF, Oliveira RM, Pagnoncelli MGB, Rocha HAO, Macedo GR, Santos ES (2012) Chitooligosaccharides antagonize the cytotoxic effect of glucosamine. World J Microbiol Biotechnol 28:1097–1105. CrossRefPubMedGoogle Scholar
  15. Dou J, Tan C, Du Y, Bai X, Wang K, Ma X (2007) Effects of chitooligosaccharides on rabbit neutrophils in vitro. Carbohydr Polym 69:209–213. CrossRefGoogle Scholar
  16. El-Sayed ST, Omar NI, El Sayed ESM, Shousha WG (2017) Evaluation antioxidant and cytotoxic activities of novel chitooligosaccharides prepared from chitosan via enzymatic hydrolysis and ultrafiltration. J Appl Pharm Sci 7:50–55. CrossRefGoogle Scholar
  17. Eom TK, Senevirathne M, Kim SK (2012) Synthesis of phenolic acid conjugated chitooligosaccharides and evaluation of their antioxidant activity. Environ Toxicol Pharmacol 34:519–527. CrossRefPubMedGoogle Scholar
  18. Feng T, Du Y, Li J, Wei Y, Yao P (2007) Antioxidant activity of half N-acetylated water-soluble chitosan in vitro. Eur Food Res Technol 225:133–138. CrossRefGoogle Scholar
  19. Fernandes JC, Eaton P, Nascimento H, Gião MS, Ramos ÓS, Belo L (2010) Antioxidant activity of chitooligosaccharides upon two biological systems: erythrocytes and bacteriophages. Carbohydr Polym 79:1101–1106. CrossRefGoogle Scholar
  20. Hamed I, Özogul F, Regenstein JM (2016) Review: regenstein industrial applications of crustacean by-products (chitin, chitosan, and chitooligosaccharides). Trends Food Sci Technol 48:40–50. CrossRefGoogle Scholar
  21. Huang R, Rajapakse N, Kim SK (2006) Structural factors affecting radical scavenging activity of chitooligosaccharides (COS) and its derivatives. Carbohydr Polym 63:122–129. CrossRefGoogle Scholar
  22. Huang HC, Hong L, Chang P, Zhang J, Lu SY, Zheng BW, Jiang ZF (2015) Chitooligosaccharides attenuate Cu2+-induced cellular oxidative damage and cell apoptosis involving Nrf2 activation. Neurotox Res 27:411–420. CrossRefPubMedGoogle Scholar
  23. Il’ina AV, Varlamov VP (2004) Hydrolysis of chitosan in lactic acid. Appl Biochem Microbiol 40:300–303. CrossRefGoogle Scholar
  24. Il’ina AV, Varlamov VP (2015) In vitro antitumor activity of heterochitooligosaccharides (a review). Prikl Biokhim Mikrobiol 51:5–14. CrossRefPubMedGoogle Scholar
  25. Je JY, Park PJ, Kim SK (2004) Free radical scavenging properties of hetero chitooligosaccharides using an ESR spectroscopy. Food Chem Toxicol 42:381–387. CrossRefPubMedGoogle Scholar
  26. Jeon YJ, Kim SK (2000) Continuous production of chitooligosaccharides using a dual reactor system. Process Biochem 35:623–632. CrossRefGoogle Scholar
  27. Jing H, Li H (2015) Chitooligosaccharide prolongs vase life of cut roses by decreasing reactive oxygen species. Kor J Hort Sci Technol 33:383–389. CrossRefGoogle Scholar
  28. Karadeniz F, Artan M, Kong CS, Kim SK (2010) Chitooligosaccharides protect pancreatic β-cells from hydrogen peroxide-induced deterioration. Carbohydr Polym 82:143–147. CrossRefGoogle Scholar
  29. Kaur S, Dhillon GS (2015) Review: recent trends in biological extraction of chitin from marine shell wastes. Crit Rev Biotechnol:44–61. CrossRefGoogle Scholar
  30. Khairullin RM, Yarullina LG, Troshina NB, Akhmetova IE (2001) Chitooligosaccharide-induced activation of o-phenylenediamine oxidation by wheat seedlings in the presence of oxalic acid. Biochemist 66:286–289. CrossRefGoogle Scholar
  31. Kim S K (ed) (2011) Chitin, chitosan, oligosaccharides and their derivatives: biological activities and applications. CRC Press, Boca Raton, 225p.
  32. Kim SK, Rajapakse N (2005) Review: enzymatic production and biological activities of chitosan oligosaccharides (COS). Carbohydr Polym 62:357–368. CrossRefGoogle Scholar
  33. Kim KW, Thomas RL (2006) Antioxidative activity of chitosans with varying molecular weights. Food Chem 101:308–313. CrossRefGoogle Scholar
  34. Koryagin AS, Erofeeva EA, Yakimovich NO, Aleksandrova EA, Smirnova LA, Mal’kov AV (2006) Analysis of antioxidant properties of chitosan and its oligomers. Bull Exp Biol Med 142:461–463. CrossRefPubMedGoogle Scholar
  35. Laokuldilok T, Potivas T, Kanha N, Surawang S, Seesuriyachan P, Wangtueai S (2017) Physicochemical, antioxidant, and antimicrobial properties of chitooligosaccharides produced using three different enzyme treatment. Food Biosci 18:28–33. CrossRefGoogle Scholar
  36. Li X, Liu BO, Wang X, Han Y, Su H, Zeng X (2012) Synthesis, characterization and antioxidant activity of quaternized carboxymethyl chitosan oligosaccharides. J Macromol Sci A 49:861–868. CrossRefGoogle Scholar
  37. Li K, Xing R, Liu S, Li P (2016) Advances in preparation, analysis and biological activities of single chitooligosaccharides. Carbohydr Polym 139:178–190. CrossRefPubMedGoogle Scholar
  38. Liaqat F, Rengin E (2018) Review: chitooligosaccharides and their biological activities. Carbohydr Polym 184:243–259. CrossRefPubMedGoogle Scholar
  39. Liu HT, Li WM, Xu G, Li XY, Bai XF, Wei P (2009) Chitosan oligosaccharides attenuate hydrogen peroxide-induced stress injury in human umbilical vein endothelial cells. Pharmacol Res 59:167–175. CrossRefPubMedGoogle Scholar
  40. Lodhi G, Yon SK, Hwang JW, Kim SK, Jeon YJ, Je JY (2014) Chitooligosaccharide and its derivatives: preparation and biological applications. Biomed Res Int:1–13. Google Scholar
  41. Lu X, Guo H, Zhang Y (2012) Protective effects of sulfated chitooligosaccharides against hydrogen peroxide-induced damage in MIN6 cells. Int J Biol Macromol 50:50–58. CrossRefPubMedGoogle Scholar
  42. Lu C, Park MK, Lu C, Lee YH, Chai KY (2015) A mussel-inspired chitooligosaccharide based multidentate ligand for highly stabilized nanoparticles. J Mater Chem B 3:3730–3737. CrossRefGoogle Scholar
  43. Luo Z, Dong X, Ke Q, Duan Q, Shen L (2014) Chitooligosaccharides inhibit ethanol-induced oxidative stress via activation of Nrf2 and reduction of MAPK phosphorylation. Oncol Rep 32:2215–2222. CrossRefPubMedGoogle Scholar
  44. Mendis E, Kim MM, Rajapakse N, Kim SK (2007) An in vitro cellular analysis of the radical scavenging efficacy of chitooligosaccharides. Life Sci 80:2118–2127. CrossRefPubMedGoogle Scholar
  45. Montilla A, Ruiz-Matute AI, Corzo N, Giacomini C, Irazoqui G (2013) Enzymatic generation of chitooligosaccharides from chitosan using soluble and immobilized glycosyltransferase (Branchzyme). J Agric Food Chem 60:10360–10367. CrossRefGoogle Scholar
  46. Mourya VK, Inamdar NN (2009) Trimethyl chitosan and its applications in drug delivery. J Mater Sci Mater Med 20:1057–1079. CrossRefPubMedGoogle Scholar
  47. Mourya VK, Inamdar NN, Choudhari YM (2011) Chitooligosaccharides: synthesis, characterization and applications. Polym Sci Ser A 53:583–612. CrossRefGoogle Scholar
  48. Ngo DN, Lee SH, Kim MM, Kim SK (2009) Production of chitin oligosaccharides with different molecular weights and their antioxidant effect in RAW 264.7 cells. J Funct Foods 1:60–198. CrossRefGoogle Scholar
  49. Ngo DH, Qian ZJ, Ngo DN, Vo TS, Wijesekara I, Kim SK (2011) Gallyl chitooligosaccharides inhibit intracellular free radical-mediated oxidation. Food Chem 128:974–981. CrossRefGoogle Scholar
  50. Ngo D, Ngo D, Vo T, Ryu B, Van TQ, Kim S (2012) Protective effects of aminoethyl-chitooligosaccharides against oxidative stress and inflammation in murine microglial BV-2 cells. Carbohydr Polym 88:743–747. CrossRefGoogle Scholar
  51. Nidheesh T, Pal GK, Suresh PV (2015) Chitooligomers preparation by chitosanase produced under solid state fermentation using shrimp by-products as substrate. Carbohydr Polym 121:1–9. CrossRefPubMedGoogle Scholar
  52. Oh SH, Ryu BM, Ngo DH, Kim WS, Kim DG, Kim SK (2017) 4-hydroxybenzaldehyde-chitooligomers suppresses H2O2-induced oxidative damage in microglia BV-2 cells. Carbohydr Res 440–441:32–37. CrossRefPubMedGoogle Scholar
  53. Park PJ, Je JY, Kim SK (2003) Free radical scavenging activity of chitooligosaccharides by electron spin resonance spectrometry. J Agric Food Chem 51:4624–4627. CrossRefPubMedGoogle Scholar
  54. Park PJ, Lee HK, Kim SK (2004) Preparation of hetero-chitooligosaccharides and their antimicrobial activity on Vibrio parahaemolyticus. J Microbiol Biotechnol 14:41–47. Retrieved from: Google Scholar
  55. Pham-Huy LA, He H, Pham-Huy C (2008) Free radicals, antioxidants in disease and health. Int J Biomed Sci 4:89–96. CrossRefPubMedPubMedCentralGoogle Scholar
  56. Popa-Nita S, Lucas JM, Ladavière C, David L, Domard A (2009) Mechanisms involved during the ultrasonically induced depolymerization of chitosan: characterization and control. Biomacromolecules 10:1203–1211. CrossRefPubMedGoogle Scholar
  57. Qu D, Han J (2016) Investigation of the antioxidant activity of chitooligosaccharides on mice with high-fat diet. Rev Bras Zootec 45:661–666. CrossRefGoogle Scholar
  58. Rao MS, Chander R, Sharma A (2006) Radiation processed chitosan a potent antioxidant. Food Technol 27:188–194.
  59. Salgaonkar N, Prakash D, Nawani NN, Kapadnis BP (2015) Comparative studies on ability of N-acetylated chitooligosaccharides to scavenge reactive oxygen species and protect DNA from oxidative damage. Indian J Biotechnol 14:186–192. Google Scholar
  60. Santos-Moriano P, Woodley JM, Plou FJ (2016) Continuous production of chitooligosaccharides by an immobilized enzyme in a dual-reactor system. J Mol Catal B Enzym 133:211–217. CrossRefGoogle Scholar
  61. Sindhi V, Gupta V, Sharma K, Bhatnagar S, Kumari R, Dhaka N (2013) Review: potential applications of antioxidants. J Pharm Res 7:828–835. CrossRefGoogle Scholar
  62. Singh P (2016) Review: effect of chitosans and chitooligosaccharides on the processing and storage quality of foods of animal and aquatic origin. Nutr Food Sci 46:51–81. CrossRefGoogle Scholar
  63. Sinha S, Tripathi P, Chand S (2012a) A new bifunctional chitosanase enzyme from Streptomyces sp. and its application in production of antioxidant chitooligosaccharides. Appl Biochem Biotechnol 167:1029–1039. CrossRefPubMedGoogle Scholar
  64. Sinha S, Dhakate SR, Kumar P, Mathur RB, Tripathi P, Chand S (2012b) Electrospun polyacrylonitrile nanofibrous membranes for chitosanase immobilization and its application in selective production of chitooligosaccharides. Bioresour Technol 115:152–157. CrossRefPubMedGoogle Scholar
  65. Sinha S, Chand S, Tripathi P (2014) Microbial degradation of chitin waste for production of chitosanase and food related bioactive compounds. Appl Biochem Microbiol 50(2):125–133. CrossRefGoogle Scholar
  66. Sinha S, Chand S, Tripathi P (2016a) Enzymatic production of glucosamine and chitooligosaccharides using newly isolated exo-β-d-glucosaminidase having transglycosylation activity. 3 Biotech 6(1):1–9. CrossRefGoogle Scholar
  67. Sinha S, Chand S, Tripathi P (2016b) Recent progress in chitosanase production of monomer-free chitooligosaccharides: bioprocess strategies and future applications. Appl Biochem Biotechnol 180:883–899. CrossRefPubMedGoogle Scholar
  68. Sun T, Yun Z, Jing X, Xuhong Y (2011) Antioxidant activity of N-acyl chitosan oligosaccharide with same substituting degree. Bioorg Med Chem Lett 21:798–800. CrossRefPubMedGoogle Scholar
  69. Usui T, Hidenori M, Kiyoshi I (1990) Enzymic synthesis of useful Chito-oligosaccharides utilizing transglycosylation by chitinolytic enzymes in a buffer containing ammonium sulfate. Carbohydr Res 203:65–77. CrossRefPubMedGoogle Scholar
  70. Valko M, Leibfritz D, Moncol J, Cronin MTD, Mazur M, Telser J (2007) Free radicals and antioxidants in normal physiological functions and human disease. Int J Biochem Cell Biol 39:44–84. CrossRefPubMedGoogle Scholar
  71. Vårum KM, Holme HK, Izume M, Stokke BT, Smidsrød O (1996) Determination of enzymatic hydrolysis specificity of partially N-acetylated chitosans. Biochim Biophys Acta, Gen Subj 1291(1):5–15. CrossRefGoogle Scholar
  72. Vasconcelos MW (2012) Chitosan and chitooligosaccharide utilization in phytoremediation and biofortification programs: current knowledge and future perspectives. Front Plant Sci 5:1–4. CrossRefGoogle Scholar
  73. Vidanarachchi J, Kurukulasuriya M, Kim SK (2010) Chitin, chitosan, and their oligosaccharides in food industry. In: Chitin, chitosan, oligosaccharides and their derivatives. CRC Press, Boca Raton, pp 543–560. CrossRefGoogle Scholar
  74. Vo TS, Ngo DH, Bach LG, Ngo DN, Kim SK (2017) The free radical scavenging and anti inflammatory activities of gallate-chitooligosaccharides in human lung epithelial A549 cells. Process Biochem 54:188–194. CrossRefGoogle Scholar
  75. Wu GJ, Tsai GJ (2004) Cellulase degradation of shrimp chitosan for the preparation of a water-soluble hydrolysate with immunoactivity. Fish Sci 70:1113–1120. CrossRefGoogle Scholar
  76. Xia W, Liu P, Liu J (2008) Advance in chitosan hydrolysis by non-specific cellulases. Bioresour Technol:6751–6762. CrossRefGoogle Scholar
  77. Xie C, Xin W, Cimin L, Qinhua W, Zhiyong F, Li S (2016) Chitosan oligosaccharide affects antioxidant defense capacity and placental amino acids transport of sows. BMC Vet Res 12(1):1–8. CrossRefGoogle Scholar
  78. Xu Y, Wang L, Li YK, Wang CQ (2016) Reduction and pH dual-responsive nanoparticles based chitooligosaccharide-based graft copolymer for doxorubicin delivery. Colloids Surf A Physicochem Eng Asp 497:8–15. CrossRefGoogle Scholar
  79. Yamaguchi R, Arai Y, Itoh T (1982) A microfibril formation from depolymerized chitosan by n-acetylation. Agric Biol Chem 46:2379–2381. CrossRefGoogle Scholar
  80. Yang Y, Biao Y (2014) Recent advances in the synthesis of chitooligosaccharides and congeners. Tetrahedron 70:1023–1046. CrossRefGoogle Scholar
  81. Yang Y, Shu R, Shao J, Xu G, Gu X (2006) Radical scavenging activity of chitooligosaccharide with different molecular weights. Eur Food Res Technol 222:36–40. CrossRefGoogle Scholar
  82. Yu BP (ed) (1994) Cellular defenses against damage from reactive oxygen species. Physiol Rev 74(1):139–162. CrossRefGoogle Scholar
  83. Yuan W (2009) Antioxidant activity of chito-oligosaccharides on pancreatic islet cells in streptozotocin-induced diabetes in rats. World J Gastroenterol 15(11):1339. CrossRefPubMedPubMedCentralGoogle Scholar
  84. Zhang H, Zhao X, Yang J, Yin H, Wang W, Lu H, Du Y (2011) Nitric oxide production and its functional link with OIPK in tobacco defense response elicited by chitooligosaccharide. Plant Cell Rep 30:1153–1162. CrossRefPubMedGoogle Scholar
  85. Zhang Y, Zhou X, Lusha J, Du X, Sang Q, Chen F (2017) Enzymatic single-step preparation and antioxidant activity of hetero-chitooligosaccharides using non-pretreated housefly larvae powder. Carbohydr Polym 172:113–119. CrossRefPubMedGoogle Scholar
  86. Zhou TX, Chen YJ, Yoo JS, Huang Y, Lee JH, Jang HD (2009) Effects of chitooligosaccharide supplementation on performance, blood characteristics, relative organ weight, and meat quality in broiler chickens. Poult Sci 88:593–600. CrossRefPubMedGoogle Scholar

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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Swati Jaiswal
    • 1
  • Pushplata Tripathi
    • 2
  • Sujata Sinha
    • 1
    Email author
  1. 1.Department of Biochemical Engineering & BiotechnologyIIT DelhiNew DelhiIndia
  2. 2.School of SciencesIndira Gandhi National Open UniversityNew DelhiIndia

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