Enzymatic chain elongation of A-, B-, and C-type grain starches by amylosucrase: Universal structure-function rules...

Amylosucrase presents a promising, eco-friendly tool for starch modification, offering precise control over structural properties vital to health and industrial applications. This study investigates its effect on native starches with A-, B-, and C-type crystallinity from six botanical sources under consistent reaction conditions. Through systematic enzymatic chain elongation, we observed significant shifts in molecular architecture, particularly the enrichment of B₂ (polymer chains with 25-36 glucose units) and B₃ (those with more than 37 glucose units) chains, regardless of the starch's origin. These structural reconfigurations prompted partial crystalline transitions (A- and C-type shifting toward B-type), elevated relative crystallinity, and markedly improved thermal properties. Notably, resistant starch (RS) content increased by 23-57 %, while rapidly digestible starch declined, enhancing the nutritional profile. Correlation analysis revealed that RS was positively associated with long-chain structures and higher gelatinization temperatures, underscoring the functional benefits of the enzymatic treatment. Our findings demonstrate the broad applicability of amylosucrase as a one-step strategy to engineer starches with superior resistance to digestion and enhanced structural order. This approach offers a scalable pathway for developing functional food ingredients targeting metabolic health, especially in diabetes and glycemic management.