Structure function relationships of transgenic starches with engineered phosphate substitution and starch branching.
Potato tuber starch was genetically engineered in the plant by the simultaneous antisense suppression of the starch branching enzyme (SBE) I and II isoforms. Starch prepared from 12 independent lines and three control lines were characterised with respect to structural and physical properties. The lengths of the amylopectin unit chains, the concentrations of amylose and monoesterified phosphate were significantly increased in the transgenically engineered starches. Size exclusion chromatography with refractive index detection (SEC-RI) indicated a minor decrease in apparent molecular size of the amylose and the less branched amylopectin fractions. Differential scanning calorimetry (DSC) revealed significantly higher peak temperatures for gelatinisation and retrogradation of the genetically engineered starches whereas the enthalpies of gelatinisation were lower. Aqueous gels prepared from the transgenic starches showed increased gel elasticity and viscosity. Principle component analysis (PCA) of the data set discriminated the control lines from the transgenic lines and revealed a high correlation between phosphate concentration and amylopectin unit chain length. The PCA also indicated that the rheological characteristics were primarily influenced by the amylose concentration. The phosphate and the amylopectin unit chain lengths had influenced primarily the pasting and rheological properties of the starch gels.
Blennow
Andreas
A
Plant Biochemistry Laboratory, Department Plant Biology, Center for Plant Molecular Physiology (PlaCe), Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark. abl@kvl.dk
Wischmann
Bente
B
Houborg
Karen
K
Ahmt
Tina
T
Jørgensen
Kirsten
K
Engelsen
Søren Balling
SB
Bandsholm
Ole
O
Poulsen
Peter
P
D000687:Amylopectin / Q000737:chemistry; D000688:Amylose / Q000737:chemistry; D001704:Biopolymers / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002845:Chromatography; D004548:Elasticity; D005780:Gelatin / Q000737:chemistry; D005818:Genetic Engineering; D006358:Hot Temperature; D007700:Kinetics; D046911:Macromolecular Substances / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D015999:Multivariate Analysis; D010710:Phosphates / Q000737:chemistry*; D030821:Plants, Genetically Modified; D025341:Principal Component Analysis; D020033:Protein Isoforms; D012212:Rheology; D011198:Solanum tuberosum / Q000737:chemistry; D013213:Starch / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013696:Temperature; D013816:Thermodynamics; D019076:Transgenes; D014783:Viscosity
D001704:Biopolymers; D046911:Macromolecular Substances; D010710:Phosphates; D020033:Protein Isoforms; D005780:Gelatin; D013213:Starch; D000688:Amylose; D000687:Amylopectin