4.1. General Information

All the reagents were commercially available and used as received: isopropyl β-D-1-thiogalactopyranoside (Solarbio, Beijing, China); kanamycin (Solarbio, Beijing, China); p-nitrophenyl octanoate (Sigma-Aldrich, St. Louis, MO, USA); plasmid mini kit I (Omega, Norcross, GA, USA); gel DNA extraction mini kit (Vazyme, Nanjing, China); Bradford protein assay kit (Tiangen, Beijing, China); 15% precast mini polyacrylamide gels (Genscript, Nanjing, China); and BeyoGold™ His-tag Purification Resin (Beyotime, Shanghai, China). All the other chemicals were purchased from China Pharmaceutical Chemical Reagent Co., Ltd. (Shanghai, China).