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CSIRO-INRA linkages : starch hydrolysis by α-amylases

Starch is a versatile product. In addition to being a major source of carbohydrates in people’s diets it has well over 700 non-food derived applications, such as in bulking agents, paper and adhesive.

Many biological and industrial processes, such as mammal digestion, plant metabolism and biofuel production, rely on the hydrolysis of native starch by amylolytic enzymes. These enzymes, represented mostly by α-amylases, break down the starch macromolecules to small carbohydrates and finally simple glucose molecules.

The Cereal Quality Group of CSIRO Agriculture and Food, based in Canberra, together with INRA Unité de Recherches Biopolymères, Interactions et Assemblages in Nantes, have developed a strong common interest in studying the impact of α-amylase in cereal quality and food production.

One such research interest is the beneficial effects α-amylase on bread quality and malting. It is thought that the addition of α-amylase results in the production of fermentable sugar, via starch hydrolysis, thereby fuelling fermentation. In baking, it contributes to shorter fermentation and increases loaf volume.

At the laboratory scale, it has been shown that starch digestion is governed by (1) the type of enzyme digesting the starch. (Each enzyme has a proper mode of action depending on the specific substrate) and (2) the structure and morphology of the starch granule. However, the influence of starch structure on amylolysis in industrial processes remains unclear.

In collaboration with Synchrotron SOLEIL (Paris), researchers have used the unique high-resolution UV imaging setup of the DISCO beamline to localize at high resolution, α-amylase action on starch without staining or use of a fluorescent probe. Like a precise amylase GPS, this has enabled researchers to follow, live and in 3D, the mode of action of a-amylase and the associated morphological changes of starch granules at different stages of their hydrolysis.

As part of the CSIRO/INRA linkage, researchers are now developing a model using a large wheat populations that will predict the degradability of wheat starches by industry grade baking improver α-amylases. This model would make possible to predict starch degradability by commercial α-amylases based on genetic information or structural analysis. It would also provide valuable information on new ways to tailor starch for industrial purposes, for both baking and malting as well as green chemistry and biofuel production.

 

Kamal KANSOU, Materials Processing and Behavior team, Bioplymeres Interactions Assemblages

Dr Jean-Philippe Ral, Cereal Quality, Crop improvement for novel products


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