Improved octyl glucoside synthesis using immobilized b-glucosidase on PA-M with reduced glucose surplus inhibition

A b-glucosidase extracted from bitter almond (Prunus dulcis var. amara) was immobilized on polyamine microspheres (PA-M) for catalytic octyl glucoside (OG) synthesis from glucose and octanol through reversed hydrolysis. The immobilization increased the activity of enzyme at pH 6.0–7.0, and the optimal reaction temperature for immobilized enzyme was identical to the free enzyme. The thermal stability and solvent tolerance of enzyme were increased by its immobilization. In the co-solvent system using 10% t-butyl alcohol and 10% (v/v) water, the yield of OG was increased by 1.7-fold compared to the yield from the system without co-solvent. Based on dynamic and Dixon plot analyses, the initial reaction velocity (V0) increased approximately threefold on immobilization and the OG synthesis was inhibited by surplus glucose. The inhibition dissociation constants for free and immobilized enzyme were 219mM and 116mM, respectively. A fed-batch mode was applied in the OG synthesis to minimize substrate inhibition. After 336 h of reaction, the OG yield and the conversion rate of glucose reached 134mM and 59.6%, respectively. Compared to the batch operation, the fed-bath operation increased the OG yield and the conversion rate of glucose by 340% and 381%, respectively. ARTICLE HISTORY Received 8 January 2017 Revised 21 March 2017 Accepted 9 June 2017