Characterization of two novel thermostable esterases from Thermoanaerobacterium thermosaccharolyticum

This paper first describes characterization of two thermostable esterases (ThLip1 and ThLip2) from the thermophilic bacterium Thermoanaerobacterium thermosaccharolyticum DSM 571. The recombinant esterase ThLip1 was active at 80 °C, pH 6.5 and maintained approx. 85% of original activity after 2 h incubation at 75 °C. Kinetic parameters, K_m, V_max and k_cat/K_m for 4-Nitrophenyl caprylate (pNPC) were 3.52 ± 0.47 mM, 191.18 ± 1.82 μmol min^-1 mg^-1 and 20.80 ± 0.07 mM^-1 s^-1, respectively. The purified recombinant esterase ThLip2 was optimally active at pH 6.5 and 75 °C and it was stable against a pH range of 6.0-8.0 possessing 2 h half-life at 80 °C. Kinetic experiments at 75 °C with pNPC as a substrate gave a K_m of 3.37 mM, V_max of 578.14 μmol min^-1 mg^-1and k_cat of 231.2 s^-1. The hydrolysis of linalyl acetate were carried out using ThLip1 and ThLip2 as catalyst, affording linalool yields over 140 mg/l in 10 h.