Ultra-high specific surface cellulose fibers with an average diameter of 500 nm were generated from electrospinning and alkaline hydrolysis of cellulose acetate and used as porous supports for enzyme immobilization. The cellulose fiber surfaces were reacted with polyethylene glycol (PEG) diacylchloride to simultaneously add amphiphilic spacers and reactive end groups for coupling with a lipase enzyme. The quantity of reactive carboxylic acid on the fiber surfaces could be readily controlled by COCl/OH molar ratios and PEG lengths. The highest free acid (COOH) content of 1.0 mmol per gram of cellulose was obtained at 10 COCl/OH ratio with the 600-Da PEG diacylchloride. Enzyme coupling on such PEG-attached cellulose was optimal in the presence of a water-soluble carbodiimide [1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)] at a very low EDC/COOH molar ratio of 0.2 under acidic condition and at ambient temperature. Whereas the free lipase retained only 25% of its original activity, the fiber-bound lipase possessed much superior retention of catalytic activity after exposure to cyclohexane (81%) and toluene (62%) and hexane (34%). The fiber-bound lipase also exhibited significantly higher catalytic activity at elevated temperatures than the free form, that is, 10 times at 70 degreesC. The ultra-fine, fibrous, and porous structures were retained throughout alkaline hydrolysis, activation, coupling, and activity assays. (C) 2004 Wiley Periodicals, Inc.