Steviol is a diterpene isolated from the plant Stevia rebaudiana that has a potential role as an antihyperglycemic agent by stimulating insulin secretion from pancreatic beta cells and also has significant potential to diminish the renal clearance of anionic drugs and their metabolites. In this study, the lacS gene, which encodes a thermostable β-glycosidase (SSbgly) enzyme from the extremely thermoacidophillic archaeon Sulfolobus solfataricus, was cloned and expressed in E. coli Rossetta BL21(DE3)pLyS using lactose as an inducer. Through fermentation, SSbgly was expressed as a 61 kDa protein with activity of 24.3 U/mg and the OD600 of 23 was reached after 18 h induction with 10 mM lactose. Purified protein was obtained by Ni-Sepharose chromatography with a yield of 92.3%. SSbgly hydrolyzed steviol glycosides to produce steviol with a yield of 99.2%. The optimum conditions for steviol production were 50 U/ml SSbgly and 90 mg/ml Ste at 75 °C as determined by the response surface method.
Bibliographical noteFunding Information:
This work was partially supported by Agriculture, Food and Rural Affairs Research Center Support Program, Ministry of Agriculture, Food and Rural Affairs, Republic of Korea (D. Kim) and by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF- 2015R1D1A1A01056929 ; D. Kim, and 2015R1D1A4A01020522 ; T.T. Hanh Nguyen) and by OTTOGI Corporation through Research and Publication Projects.
All Science Journal Classification (ASJC) codes
- Applied Microbiology and Biotechnology