Enzymatic processes for the purification of trehalose

A dual-enzyme process aiming at facilitating the purification of trehalose from maltose is reported in this study. Enzymatic conversion of maltose to trehalose usually leads to the presence of significant amount of glucose, by-product of the reaction, and unreacted maltose. To facilitate the separation of trehalose from glucose and unreacted maltose, sequential conversion of maltose to glucose and glucose to gluconic acid under the catalysis of glucoamylase and glucose oxidase, respectively, is studied. This study focuses on the hydrolysis of maltose with immobilized glucoamylase on Eupergit® C and CM Sepharose. CM Sepharose exhibited a higher protein adsorption capacity, 49.35 ± 1.43 mg/g, and was thus selected as carrier for the immobilization of glucoamylase. The optimal reaction temperature and reaction pH of the immobilized glucoamylase for maltose hydrolysis were identified as 40°C and 4.0, respectively. Under such conditions, the unreacted maltose in the product stream of trehalose synthase-catalyzed reaction was completely converted to glucose within 35 min, without detectable trehalose degradation. The conversion of maltose to glucose could be maintained at 0.92 even after 80 cycles in repeated-batch operations. It was also demonstrated that glucose thus generated could be readily oxidized into gluconic acid, which can be easily separated from trehalose. We thus believe the proposed process of maltose hydrolysis with immobilized glucoamylase, in conjunction with trehalose synthase-catalyzed isomerization and glucose oxidase-catalyzed oxidation, is promising for the production and purification of trehalose on industrial scales.