Trehalose production with a new enzymatic system from Sulfolobus solfataricus KM1

An amylolytic activity that converts soluble starch to α,α-trehalose (trehalose) was found in the cell homogenate of the hyperthermophilic, acidophilic archaeum Sulfolobus solfataricus KM1. Two enzymes, a glycosyltransferase and an α-amylase, which are essential for this activity, were purified to homogeneity. A glycosyltransferase catalyzed the conversion of maltooligosaccharides to glycosyltrehaloses and an α-amylase catalyzed the hydrolysis of glycosyltrehaloses to trehalose. The glycosyltransferase transferred an oligomer segment of maltooligosaccharide to the C1–OH position of glucose, located at the reducing end of the maltooligosaccharide, to produce a glycosyltrehalose having an α-1,1 linkage. The α-amylase hydrolyzed only the α-1,4 glucosidic linkage adjacent to the trehalose unit of the glycosyltrehaloses. Their activities were maximal at 70–80°C and 70–85°C, with high thermostability, respectively. The genes encoding for both enzymes were cloned and expressed in Escherichia coli. The regions highly conserved in α-amylase family exist in the amino acid sequences of these enzymes. A new process for trehalose production from starch was developed using the purified enzymes. The yield of trehalose from starch was 81.5% using these two enzymes. This review describes our efforts to reveal in detail the characters of these enzymes involved in practical trehalose production.