Effect of amylose content in corn starch modification by Thermus aquatiqus 4-alpha-glucanotransferase.

Corn starches with different amylose contents were enzymatically modified using Thermus aquaticus 4-alpha-glucanotransferase (TAalphaGTase). On treating, chain length distribution of the product became broader (degree of polymerization; DP 3-40) after isoamylolysis when compared to the untreated corn starch. In addition, a variety of different size cycloamyloses were formed by glucanotransferring activity of TAalphaGTase. Cycloamyloses (CAs) with DP 5-40 were detectable in all of the TAalphaGTase-treated corn starches. The amount of CAs produced by the enzyme treatment seems to increase as amylose content of starch increased when judged by high-performance anion exchange chromatography (HPAEC) and high-performance size exclusion chromatography (HPSEC) analyses. Thus, it was suggested that the extent of modification on starch molecules was enhanced in proportion to amylose content of starch by transferring activity of TAalphaGTase. In turn, it could be useful for developing an efficient process of CA production using this enzyme.