Expression and display of a novel thermostable esterase from Clostridium thermocellum on the surface of Bacillus...

Esterases expressed in microbial hosts are commercially valuable, but their applications are limited due to high costs of production and harsh industrial processes involved. In this study, the esterase-DSM (from Clostridium thermocellum) was expressed and successfully displayed on the spore surface, and the spore-associated esterase was confirmed by western blot analysis and activity measurements. The optimal temperature and pH of spore surface-displayed DSM was 60 and 8.5 °C, respectively. It also demonstrates a broad temperature and pH optimum in the range of 50-70, 7-9.5 °C. The spore surface-displayed esterase-DSM retained 78, 68 % of its original activity after 5 h incubation at 60 and 70 °C, respectively, which was twofold greater activity than that of the purified DSM. The recombinant spores has high activity and stability in DMSO, which was 49 % higher than the retained activity of the purified DSM in DMSO (20 % v/v), and retained 65.2 % of activity after 7 h of incubation in DMSO (20 % v/v). However, the recombinant spores could retain 77 % activity after 3 rounds of recycling. These results suggest that enzyme displayed on the surface of the Bacillus subtilis spore could serve as an effective approach for enzyme immobilization.