Immobilization of a Novel EST_BAS Esterase from <em>Bacillus altitudinis</em> onto an Epoxy Resin: Characterization and Regioselective Synthesis of Chloramphenicol Palmitate

• Main Authors: Fengying Dong, Xudong Tang, Xiaohui Yang, Lin Lin, Dannong He, Wei Wei, Dongzhi Wei
• Format: Article
• Language: English
• Published: MDPI AG 2019-07-01
• Series: Catalysts
• Subjects: <i>Bacillus altitudinis</i>; esterase; regioselectivity; transesterification; chloramphenicol palmitate
• Online Access: https://www.mdpi.com/2073-4344/9/7/620

Novel gene <i>est_BAS</i> from <i>Bacillus altitudinis</i>, encoding a 216-amino acid esterase (Est_BAS) with a signal peptide (SP), was expressed in <i>Escherichia coli</i>. Est_BASΔSP showed the highest activity toward <i>p</i>-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.