Immobilisation of Fenugreek b-amylase on chitosan/PVP blend and chitosan coated PVC beads: A comparative study Garima Srivastava, Sonam Roy, Arvind M. Kayastha ⇑ School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi 221005, India article info Article history: Received 10 May 2014 Received in revised form 19 August 2014 Accepted 25 September 2014 Available online 6 October 2014 Keywords: b-Amylase Trigonella foenum-graecum Immobilisation Response Surface Methodology abstract A Box–Behnken design of Response Surface Methodology (RSM) was utilised for optimisation of param- eters affecting immobilisation of Fenugreek b-amylase on chitosan coated PVC (polyvinyl chloride) beads and beads made from chitosan/PVP (polyvinylpyrrolidone) blend, which resulted in 85.2% and 81% immo- bilisation efficiency, respectively. Immobilisation resulted in shift of pH optima while the optimum tem- perature remained unaffected. Enhancement in thermal stability of the enzyme was observed on conjugation with both the matrices. The immobilised enzyme appeared suitable for industrial applica- tions due to the non-toxic nature of chosen matrices, ease of immobilisation procedure, enhanced stabil- ity and reusability with retention of 72% and 60% residual activity after 10 uses for the enzyme immobilised on chitosan coated PVC beads and on the beads of chitosan/PVP blend, respectively. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction b-Amylase, a-1,4-glucanmaltohydrolase (E.C. 3.2.1.2) catalyses the release of b-maltose from the non-reducing ends of a-1,4-glu- cans and is known to play central role in complete degradation of starch to metabolisable or fermentable sugars during the germina- tion or malting of cereal grains. The saccharifying activity and malt- ose production by the enzyme finds a great commercial value in food, beverage and pharmaceutical industries, where it is exploited in bread making, production of malt, maltose rich syrups (for phar- maceutical dispensing), and maltitol (non-digestible sweetner). It is utilised as the exclusive source of carbon in the production of Dip- theria Pertusis Tetanus vaccine. b-Amylase has also been found use- ful in structural studies of starch and glycogen (Ziegler, 1999). The ease of production, substrate specificity and green chemis- try make biocatalysts favourable and widely accepted in diverse sectors. However, the unstable nature of most of the enzymes, high costs of isolation and technical difficulties in the recovery of enzyme leads to their limited application. Enhancement in enzyme productivity and the development of novel techniques for increas- ing their shelf-life are the current demands of world’s biotechno- logical industries. Immobilisation has been suggested as a powerful tool for improvisation of enzyme properties. The performance of the immobilised enzyme system is regulated by the composition, mor- phology and surface characteristics of the matrix. Characteristics of an ideal matrix include inertness, physical strength, stability, rege- nerability, ability to increase enzyme specificity or activity along with reduction in product inhibition, non-specific adsorption and microbial contamination. Moreover, the ideal immobilisation procedure should be simple and limit the use of toxic or highly unstable reagents (Mateo, Palomo, Fernandez-Lorente, Guisan, & Fernandez-Lafuente, 2007). A great deal of attention in the recent years has been given to polymer blends as it is a simple and effective method to develop new materials showing unique properties which are unachievable by the individual polymer (Suknuntha, Tantishaiyakul, Vao- soongnern, Espidel, & Cosgrove, 2008). Another important means of tailoring the physical and chemical properties of materials is modification of the surfaces. Deposition or spraying of a polymeric coating from a solution on the microspheres leads to modification of the surface by providing comparatively crude control of the structural and surface properties of the material. Chitosan is a natural polymer having amino and hydroxyl groups present on its backbone, which can serve as proton donor/proton acceptor in formation of hydrogen bond interaction with other polymers (Suknuntha et al., 2008). The solubility of PVP (polyvinylpyrrolidone) makes it an interesting material for several different polymer-assisted synthesis applications. It has been used in mucoadhesion formulation. Blending with other poly- mers enhances the mucoadhesion capability of PVP. Both chitosan and PVP are biocompatible and non-toxic. The blend of chitosan http://dx.doi.org/10.1016/j.foodchem.2014.09.145 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +91 542 2368331; fax: +91 542 2368693. E-mail addresses: garimasri99@gmail.com (G. Srivastava), sonam.insatiable@ gmail.com (S. Roy), kayasthabhu@gmail.com (A.M. Kayastha). Food Chemistry 172 (2015) 844–851 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem