High-yield cycloamylose production from sweet potato starch using Pseudomonas isoamylase and Thermus aquaticus 4-α-glucanotransferase

An optimal reaction condition for producing cycloamylose (CA) from sweet potato starch was investigated using a combination of isoamylase (from Pseudomonas sp.) and 4-alpha-glucanotransferase (from Thermus aquaticus, TA alpha GT). Starch was debranched by isoamylase for 8 h and subsequently reacted with TA alpha GT for 12 h. The yield and purity of CA products were determined using HPSEC and MALDI-TOFMS, respectively. Consequently, the maximum yield was 48.56%, exhibiting the highest CA production efficiency ever reported from starch. The CA products showed a wide range of the degree of polymerization (DP) with the minimum DP of 5. CA was also produced by simultaneous treatment of isoamylase and TA alpha GT. The yield was 3.31%, and the final products were contaminated by multiple branched and linear molecules. This result suggests that a former reaction condition (the sequential addition of isoamylase and TA alpha GT) is preferable for producing CA from sweet potato starch.