Journal of Scientific & Industrial Research Vol. 63, June 2004, pp 540-547 An economical, simple and high yield procedure for the immobilization/ stabilization of peroxidases from turnip roots Syed Musthapa M 2 , Suhail Akhtar 1 , Amjad Ali Khan 1 and Qayyum Husain 1 * 1 Department of Biochemistry, Faculty of Life Science, Aligarh Muslim University, Aligarh 202 002 Received: 16 October 2003; accepted: 10 March 2004 Ammonium sulphate fractionated peroxidases from turnip roots (Brassica rapa) were entrapped in calcium alginate gels for high yield immobilization of enzymes. Enzymes were cross-linked with 0.5 per cent glutaraldehyde to increase the molecular dimension of the enzyme; this resulted in the loss of 8 per cent of enzyme activity. Alginate entrapped soluble and cross-linked peroxidases exhibited high stability against temperature, pH, urea and storage than the soluble preparation and were markedly more stable as compared to directly entrapped soluble enzyme preparation. Entrapped cross-linked peroxi- dase preparation showed retention of very high enzyme activity after six repeated uses. Alginate entrapped soluble peroxi- dase preparation rapidly lost its activity after each use. The results suggested that such preparations have great potential in the construction of bioreactors to be used for the removal of aromatic compounds from polluted wastewaters/industrial ef- fluents. Keywords: Cross-linking, Entrapment, Glutaraldehyde, Immobilization, Peroxidase, Stabilization, Turnip roots IPC Code: Int. Cl. 7 : C 12 N 11/16 Introduction Peroxidases (1.11.1.7) are ubiquitous proteins having applications in wide range of fields such as medicine, chemical synthesis, and in the analysis of food, chemical, clinical and environmental samples 1,2 . More recently, peroxidases have been employed for several novel applications such as detoxification and removal of various organic pollutants like phenols, aromatic amines, and dyes from polluted waste- water 3-6 . They have also been used as catalyst in phenolic resin synthesis, fuel and chemical production from wood pulp, production of dimeric alkaloids, bio-bleaching processes, and oxidation/biotransformation of or- ganic compounds 7-9 . This great diversity of applications is due to wide substrate specificity of peroxidase ca- talysis 10 . Soluble enzymes have certain inherent limitations and cannot be employed at the large-scale while immobilized enzymes, on the other hand, offer several advantages. However the high cost and low yield of im- mobilized enzyme preparation are two important limitations in their applications 11,12 . Among the techniques used for immobilization, entrapment in natural biopolymers is favored due to various reasons, e.g., non-toxicity of the matrix, variation in the bead size of the gel, and high yield of immobilization 13,14 . Horseradish roots rep- resent the traditional source for the commercial production of peroxidases but they are not available in northern India. Turnip can be considered as an alternative source of peroxidases due to its easier availability. Several ear- lier reports indicate that the biochemical and kinetic properties of turnip peroxidases are quite comparable to the commercially available horseradish peroxidases 15,16 . Here for the first time an effort has been made to immobilize turnip peroxidases in calcium alginate beads. The purpose of this study was to reduce the cost of commercially available enzyme for its immobilization and utilization on large-scale. Alginate entrapped peroxidase preparations exhibited very high yield of immobiliza- tion and stability against various forms of denaturants and storage. This preparation showed significantly high reusability after six repeated uses. Materials and Methods