Enhancing the stability of a carboxylesterase by entrapment in chitosan coated alginate beads

Abstract

A carboxylesterase isolated from Aeromonas caviae MTCC 7725 was immobilized by entrapping it in chitosan coated calciumalginate beads. This was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fouriertransform infrared spectroscopy (FTIR). The activity of the native and immobilized enzyme was measured at various temperatures, pHlevels, and organic solvents. The optimum temperature for activity of the native enzyme was found to be 40 °C and this increased to 50°C on immobilization. The immobilized enzyme showed enhanced stability and high residual activity in various organic solvents ascompared to the free enzyme. An environmentally benign approach was used for the synthesis of ethyl salicylate using the immobilizedenzyme. The product obtained was confirmed by GC-MS. The kinetic parameters, such as $K_m$ and $V_{max}$, were also determined forthe native and immobilized enzyme. The immobilized enzyme retained 50% of its activity after five cycles. The immobilized enzymeretained 80% and 40% of its activity at 4 °C and at 37 °C, respectively, at the end of 40 days. The results obtained from our study showthat the immobilized enzyme can serve as a robust catalyst for industrial applications.