Biocatalytic production of ethyl butyrate from butyric acid with immobilized Candida rugosa lipase on cotton cloth

A novel method involving polyethylenimine (PEI) coating and glutaraldehyde cross-linking processes was developed to immobilize Candida rugosa lipase onto cotton cloth. After the systematic investigation, the optimal lipase immobilization was achieved when 0.1 g lipase was loaded on 1.5 g support, which was pretreated with 10 ml of 1.0 mg/ml PEI solution at pH 8.0. Subsequent catalytic analysis of immobilized lipase for ethyl butyrate synthesis was also carried out in the Erlenmeyer flasks. The results indicated that when optimal 0.25 M ethanol and 0.6 M butyric acid were catalyzed by the immobilized lipase at 25 °C, the highest conversion yield of 91.2% and 1.27 mmol h−1 g−1 productivity of ethyl butyrate were obtained. Furthermore, a kinetic model of Ping Pong Bi-Bi mode with inhibition of both substrates was proposed and validated by experimental data. To explore the practical potential of immobilized lipase, its operational stability was evaluated and the residual activity was remained about 50% after 12 repeated recycles, with a half-life time of about 300 h for the immobilized lipase. Finally, a recycle batch reactor using immobilized lipase was developed for ethyl butyrate production. The achieved result of 0.85 M final ethyl butyrate concentration, with the conversion of 70.6% and the productivity of 1.45 mmol h−1 g−1, had revealed the promising potential of this immobilized lipase in practical applications.