Suchergebnisse

Last years, the concept of resistant starch (RS) has evoked a new interest in researchersin the context of bioavailability of starch and its use as a source of dietary fiber. Based on clinicaland animal research, RS has been proposed to be the most potentially beneficial starch fraction forhuman health. In this study, the effects of amylose starch as a fraction of RS on development andlifespan of fruit fly Drosophila melanogaster were investigated. In both Canton S and w1118 strains, thediet with 20% amylose RS delayed fly development, increased triacylglyceride level in the body ofadult insects and reduced their lifespan compared to the diet with 4% amylose starch. Thus, ourdata clearly demonstrate that amylose starch at high concentrations may negatively affect fruit fly

Near-infrared reflectance spectroscopy (NIRS) was used to determine the total starch and amylose contents in various kinds of cereals namely wheat, waxy rice, non-waxy rice, millet, sorghum, waxy maize, buckwheat, barley, and hulless oat. The partial least-squares (PLS) analysis and principal component regression (PCR) were used to establish the calibration models. PLS model achieved a better effect than PCR at 1100 - 2500 nm, and the coefficient of determination (R2) of the calibration and prediction sets were both higher than 0.9 after the best pre-treatment method, first derivative plus Savitzky-Golay. Additionally, the root mean square error (RMSE) was lower than 2.50, and the root mean square error of cross-validation (RMSECV) was less than 3.50 for starch. By comparing PLS models at different waveband regions, the optimal determination results for starch and amylose were obtained at 1923 - 1961 and 1724 - 1818 nm, respectively. NIRS was found to be a successful method to determine of the starch and amylose contents in various cereals.

Tacca (Tacca leontopetaloides) tubers have a high amylose content which can be modified to increase the resistant starch content. The present work therefore aimed to study the influence of acid hydrolysis, enzymes, and autoclaving cooling treatments on resistant starch content formation from Tacca starch. To this end, the amylose and resistant starch contents, and the microstructure of the samples were determined. Results showed that Tacca starch treated by a combination of acid, enzyme, and autoclaving cooling treatments had the highest resistant starch content which increased from 4.09 to 61.96%, with amylose content increasing from 31.62 to 77.87%. This showed a strong correlation between the increased amylose and resistant starch contents. The microstructure of the starch granules changed from a globular shape into a crystalline structure through SEM observation.

Starch properties can be modified by mutating genes responsible for the synthesis of amylose and amylopectin in the endosperm. However, little is known about the effects of such targeted modifications on the overall starch biosynthesis pathway and broader metabolism. Here we investigated the effects of mutating the OsSBEIIb gene encoding starch branching enzyme IIb, which is required for amylopectin synthesis in the endosperm. As anticipated, homozygous mutant plants, in which OsSBEIIb was completely inactivated by abolishing the catalytic center and C-terminal regulatory domain, produced opaque seeds with depleted starch reserves. Amylose content in the mutant increased from 19.6 to 27.4% and resistant starch (RS) content increased from 0.2 to 17.2%. Many genes encoding isoforms of AGPase, soluble starch synthase, and other starch branching enzymes were up-regulated, either in their native tissues or in an ectopic manner, whereas genes encoding granule-bound starch synthase, debranching enzymes, pullulanase, and starch phosphorylases were largely down-regulated. There was a general increase in the accumulation of sugars, fatty acids, amino acids, and phytosterols in the mutant endosperm, suggesting that intermediates in the starch biosynthesis pathway increased flux through spillover pathways causing a profound impact on the accumulation of multiple primary and secondary metabolites. Our results provide insights into the broader implications of perturbing starch metabolism in rice endosperm and its impact on the whole plant, which will make it easier to predict the effect of metabolic engineering in cereals for nutritional improvement or the production of valuable metabolites. ; We would like to acknowledge funding from Ministry of Economy and Competitiveness, Spain (RTI2018-097613-BI00 to C.Z., PGC2018-097655-B-I00 to P.C., and AGL2017-85377-R to T.C.); Generalitat de Catalunya Grant 2017 SGR 828 to the Agricultural Biotechnology and Bioeconomy Unit; and the European Union Framework Program DISCO (from discovery to final products: a next-generation pipeline for the sustainable generation of high-value plant products; Project 613513) to P.D.F.