Immobilization of a Novel ESTBAS Esterase from Bacillus altitudinis onto an Epoxy Resin: Characterization and Regioselective Synthesis of Chloramphenicol Palmitate

Novel gene estBAS from Bacillus altitudinis, encoding a 216-amino acid esterase (Est BAS) with a signal peptide (SP), was expressed in Escherichia coli. Est BASΔSP showed the highest activity toward p-nitrophenyl hexanoate at 50 °C and pH 8.0 and had a half-life (T 1/2) of 6 h at 50 °C. Est BASΔSP was immobilized onto a novel epoxy resin (Lx-105s) with a high loading of 96 mg/g. Fourier transform infrared (FTIR) spectroscopy showed that Est BASΔSP was successfully immobilized onto Lx-105s. In addition, immobilization improved its enzymatic performance by widening the tolerable ranges of pH and temperature. The optimum temperature of immobilized Est BASΔSP (Lx-Est BASΔSP) was higher, 60 °C, and overall thermostability improved. T 1/2 of Lx-Est BASΔSP and free Est BASΔSP at 60 °C was 105 and 28 min, respectively. Lx-Est BASΔSP was used as a biocatalyst to synthesize chloramphenicol palmitate by regioselective modification at the primary hydroxyl group. Conversion efficiency reached 94.7% at 0.15 M substrate concentration after 24 h. Lx-Est BASΔSP was stable and could be reused for seven cycles, after which it retained over 80% of the original activity. View Full-Tex