Characterization of a novel arabinose-tolerant -l-arabinofuranosidase with high ginsenoside Rc to ginsenoside Rd bioconversion productivity

Aims(i) To investigate the enzymatic characterization of -l-arabinofuranosidase from Thermotoga thermarum DSM5069. (ii) To evaluate the performance of its excellent properties on converting ginsenoside Rc to ginsenoside Rd. Methods and ResultsThe thermostable -l-arabinofuranosidase (Tt-Afs) gene from T.thermarum DSM5069 was cloned and overexpressed. Recombinant Tt-Afs was purified, and its molecular weight was approx. 55kDa. Its optimal activity was at pH 50 and 95 degrees C. It has high selectivity for cleaving the outer arabinofuranosyl moieties at the C-20 carbon of ginsenoside Rc and its sugar-tolerance makes Tt-Afs a promising candidate for the production of ginsenoside Rd. In a reaction at 85 degrees C and pH 50, 25gl(-1) of ginsenoside Rc was transformed into 218gl(-1) of Rd within 60min, with a corresponding molar conversion of 994% and a high ginsenoside Rd productivity of 21800mgl(-1)h(-1). ConclusionsWe have successfully cloned and overexpressed the novel -l-arabinofuranosidase from T.thermarum DSM5069. The high ginsenoside Rd productivity and detailed characterization of recombinant Tt-Afs was provided. Significance and Impact of the StudyThe result shows a high productivity on the bioconversion from high concentration ginsenoside Rc to ginsenoside Rd, which also give rise to a potential commercial enzyme application.