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-α-glucanotransferase (TAαGTase). Upon the enzyme treatment, the chain-length distributions of isoamylolytically debranched products became broader [degree of polymerization (DP): 3—40] than those of untreated corn starches. In addition, a variety of cycloamyloses (CAs) with different sizes were formed by the glucanotransfer activity of TAαGTase. CAs with DP 5—40 were detectable in all of the TAaGTase-treated corn starches. From the results of high-performance anion-exchange chromatography and high-performance size-exclusion chromatography analyses, it was suggested that the amount of CAs produced by the enzyme treatment increased as the amylose content of the starches increased. Thus, we concluded that the extent of modification of starch molecules was enhanced in proportion to amylose content by the transfer activity of TAαGTase. This finding could be useful for developing an efficient process of CA production using this enzyme.