Coconut Fiber in Immobilization of α-Amylase 303 Applied Biochemistry and Biotechnology Vol. 102–103, 2002 303 *Author to whom all correspondence and reprint requests should be addressed. Copyright © 2002 by Humana Press Inc. All rights of any nature whatsoever reserved. 0273-2289/02/102–103/0303/$12.75 Immobilization of α-Amylase from Bacillus circulans GRS 313 on Coconut Fiber GARGI DEY, VARIMA NAGPAL, AND RINTU BANERJEE* Microbial Biotechnology & Downstream Processing Laboratory, Agricultural & Food Engineering Department, IIT-Kharagpur, 721302, India, E-mail: rb@agfe.iitkgp.ernet.in Abstract A simple and inexpensive method for immobilizing α-amylase from Bacillus circulans GRS 313 on coconut fiber was developed. The immobiliza- tion conditions for highest efficiency were optimized with respect to immo- bilization pH of 5.5, 30°C, contact time of 4 h, and enzyme to support a ratio of 1:1 containing 0.12 mg/mL of protein. The catalytic properties of the immobilized enzyme were compared with that of the free enzyme. The activ- ity of amylase adsorbed on coconut fiber was 38.7 U/g of fiber at its optimum pH of 5.7 and 48°C, compared with the maximum activity of 40.2 U/mL of free enzyme at the optimum pH of 4.9 and 48°C. The reutilization capacity of the immobilized enzyme was up to three cycles. Index Entries: Coconut fiber; adsorption; response surface methodology; amylase; Bacillus circulans GRS 313. Introduction In previous works, α-amylase has been immobilized onto/into a large variety of supports such as controlled pore glass (1,2), collagen (3) , Sephadex and Sepharose (4), and polyaminostyrene (5) . In recent years, the enzyme has been immobilized on nitrocellulose membrane (6) and zirco- nium dynamic membrane (7). However, reports on utilization of natural fiber such as coconut coir for immobilization of amylase are scarce. Coconut coir is a product of the coconut industry that has numerous industrial applications including automobile upholstery, bedding and mattresses, drainage filters, insulation, packaging, brush and broom manu- facturing, reinforcement of thermoplastics, marine cordage and fishnets, and in horticulture as a growing medium/soil substrate. Coir has a water- holding capacity and a cation-exchange capacity of 39–60 meq/100 g (8).