Structure, Physical, and Digestive Properties of Starch from wx ae Double-Mutant Rice

Abstract

Amylopectin is the principal component of starch. The amylose extender (ae) gene encodes the starch-branching enzyme IIb, which is critical in determining the fine structure of endosperm starch. To determine the relationship between the fine structure of amylopectin and its physical properties, rice mutant lines defective in the ae function with altered fine structure of amylopectin and in combination with the waxy (wx) background were selected for comparative studies with primary wild-type and ae starches. The ae mutant endosperms accumulated a high amylose content starch with long amylopectin chains. The ae and wx ae starches showed no significant difference in the unit chain-length distribution of amylopectin and starch granule morphology. The wx ae starch displayed a higher pasting temperature and higher peak viscosity. The gelatinization peak temperatures of the wx, ae, and wx ae starches were 2.2, 13.1, and 17.1 degrees C higher, respectively, than that of the wild-type starch, and the wx ae starch showed a retrogradation peak with a shorter cooling period than that of ae starch. The raw ae and wx ae starches were almost indigestible by alpha-amylase in vitro. Rats fed the wx ae starch showed slowly increasing blood glucose at a lower level than the rats fed the wx or wild-type starch. These results indicate that the primary structure of the rice wx ae amylopectin with enriched long chains changes the granular structure of the starch, including its crystal structure, and results in resistance to in vitro or in vivo degradation.

Characterization of Normal and Waxy Corn Starch for Bioethanol Production

“…Nonetheless, the ae wx corn starch displayed similar hydrolysis kinetics to that of the ae corn starch. The results were in agreement with the previous reports that ae-containing mutant starch was less susceptible to enzymatic hydrolysis than the wild-type counterparts (Gerard et al 2001, Kubo et al 2010). …”

Starch

“…Resistant starch was present in starch that contained an abundance of long chains of amylopectin (Kubo et al 2010a), as well as high amylose . However, some starch goes through the small intestine and remains in its high molecular weight form in the large intestine.…”

Surface structure and water adsorption behavior of waxy/amylose extender (wx/ae) double‐mutant rice starch

“…This was derived from a cross between the wx mutant line EM21 and the ae mutant line EM16 . We also used EM21, which is genetically defective in GBSSI , and the parental cv. Kinmaze , which is a wild‐type (WT) japonica rice.…”