The biosynthesis, structure and gelatinization properties of starches from wild and cultivated African rice species (Oryza barthii and Oryza glaberrima)

• Published in: Carbohydrate polymers 2015-09, Vol.129, p.92-100
• Main Authors: Wang, Kai, Wambugu, Peterson W., Zhang, Bin, Wu, Alex Chi, Henry, Robert J., Gilbert, Robert G.
• Format: Article
• Language: English
• Subjects: African rice; Agriculture; Amylose - chemistry; Biosynthesis enzymes; Chromatography, Gel; Gelatin - chemistry; Gelatinization; Models, Theoretical; Molecular structure; Molecular Weight; Oryza - chemistry; Starch; Starch - biosynthesis; Starch - chemistry
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2015.04.035

•African and Asian rices have different ancestry.•African varieties have unique traits.•Molecular fine structures of a range of these were determined.•These were significantly different, explaining different traits.•The differences were in branching enzymes. The molecular structure and gelatinization properties of starches from domesticated African rice (Oryza glaberrima) and its wild progenitor (Oryza barthii) are determined and comparison made with Asian domesticated rice (Oryza sativa), the commonest commercial rice. This suggests possible enzymatic processes contributing to the unique traits of the African varieties. These have similar starch structures, including smaller amylose molecules, but larger amounts of amylose chains across the whole amylose chain-length distribution, and higher amylose contents, than O. sativa. They also show a higher proportion of two- and three-lamellae spanning amylopectin branch chains (degree of polymerization 34–100) than O. sativa, which contributes to their higher gelatinization temperatures. Fitting amylopectin chain-length distribution with a biosynthesis-based mathematical model suggests that the reason for this difference might be because O. glaberrima and O. barthii have more active SSIIIa and/or less active SBEIIb enzymes.