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Updated: Jun 4, 2026

Analysis and Specification of Starch Granule Size Distributions
Published on: March 4, 2021
Mechanisms underlying the modification of corn starch granules by raw starch-degrading amylase with
Lingli Zhong1, Wenming Chang1, Kai Yang1
1Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
Abstract:
In our previous study, CBM20 domain truncation in raw starch-degrading amylase AmyM shifted its substrate preference from amylose to amylopectin double-helical regions, markedly enhancing hydrolysis of corn starch granules. Here, normal corn starch was progressively hydrolyzed by AmyM and its CBM20-truncated variant AmyM-TR2 to matched degrees of hydrolysis (DH 15%, 25%, and 45%). AmyM caused apparent amylose content to decrease from 39.8% to 35.8% in M-15 and then increase to 41.1%, whereas AmyM-TR2 induced the opposite trend, reaching a maximum of 44.0% in T-25. AmyM broadly hydrolyzed amylopectin B1 chains and reduced rapidly digestible starch from 56.4% to 45.1-46.8%, facilitating chain rearrangement and partial recovery of ordered structure. In contrast, AmyM-TR2 preferentially cleaved long A and short B1 chains associated with double helices, decreasing slowly digestible starch to 19.3% in T-25 and causing sustained structural disruption. These distinct action modes led to divergent gelatinization and retrogradation behaviors. Nevertheless, corn starch granule modification by both enzymes followed a two-stage progressive modification pattern, in which the dominant regulation shifted from early surface compositional remodeling to later co-regulation by molecular composition and internal structural order, providing insight into the coupled evolution of composition, structure, and functionality in enzyme-modified granular starch.
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