Characterization of 4,6-α-glucanotransferase enzymes and their functional role in Lactobacillus reuteri

Starch, in rice, potato or corn, has been and is the main dietary carbohydrate of human beings. However, the abundant and quick release of high calorie glucose from starch after food intake by human beings is currently considered to be unhealthy and may cause chronic diseases, such as obesitas, diabetes or cardiovascular disease. Therefore, a reduction of the digestibility of starch via various modifications is highly demanded. In view of cost, sustainability and substrate availability, physical treatment of starch to produce resistant or slowly digestible starch, is most practical. However, the physically processed starch suffers losses upon boiling, baking or other food processing, which limits its application in many food products. Thus, structural modification through enzymatic treatment of starch has received increasing attention. For this purpose, the 4,6-α-glucanotransferase enzymes are explored and deeply studied in the Microbial Physiology group, headed by Prof. Lubbert Dijkhuizen, in the University of Groningen. These enzymes are capable of converting (α1→4) linkages of a starch substrate into (α1→6) linkages, forming a modified type of starch which is shown to be a soluble dietary fiber. It shows the potential of the 4,6-α-glucanotransferases to be of commercial value. However, industrial application is still a challenge because these enzymes are only available in relatively minor amounts. There is also a general lack of reliable enzyme activity assays needed to study such enzymes. These topics are addressed in this PhD thesis, also focusing on elucidation of the 4,6-α-glucanotransferase reaction mechanism by 3D structural protein analysis and mutagenesis

Compression for quantum population coding

We study the compression of n quantum systems, each prepared in the same state belonging to a given parametric family of quantum states. For a family of states with f independent parameters, we devise an asymptotically faithful protocol that requires a hybrid memory of size (f/2)log(n), including both quantum and classical bits. Our construction uses a quantum version of local asymptotic normality and, as an intermediate step, solves the problem of compressing displaced thermal states of n identically prepared modes. In both cases, we show that (f/2)log(n) is the minimum amount of memory needed to achieve asymptotic faithfulness. In addition, we analyze how much of the memory needs to be quantum. We find that the ratio between quantum and classical bits can be made arbitrarily small, but cannot reach zero: unless all the quantum states in the family commute, no protocol using only classical bits can be faithful, even if it uses an arbitrarily large number of classical bits.Comment: 14 Pages, 4 Figures + Appendi

Characterization of 4,6-α-glucanotransferase enzymes and their functional role in Lactobacillus reuteri

Starch, in rice, potato or corn, has been and is the main dietary carbohydrate of human beings. However, the abundant and quick release of high calorie glucose from starch after food intake by human beings is currently considered to be unhealthy and may cause chronic diseases, such as obesitas, diabetes or cardiovascular disease. Therefore, a reduction of the digestibility of starch via various modifications is highly demanded. In view of cost, sustainability and substrate availability, physical treatment of starch to produce resistant or slowly digestible starch, is most practical. However, the physically processed starch suffers losses upon boiling, baking or other food processing, which limits its application in many food products. Thus, structural modification through enzymatic treatment of starch has received increasing attention. For this purpose, the 4,6-α-glucanotransferase enzymes are explored and deeply studied in the Microbial Physiology group, headed by Prof. Lubbert Dijkhuizen, in the University of Groningen. These enzymes are capable of converting (α1→4) linkages of a starch substrate into (α1→6) linkages, forming a modified type of starch which is shown to be a soluble dietary fiber. It shows the potential of the 4,6-α-glucanotransferases to be of commercial value. However, industrial application is still a challenge because these enzymes are only available in relatively minor amounts. There is also a general lack of reliable enzyme activity assays needed to study such enzymes. These topics are addressed in this PhD thesis, also focusing on elucidation of the 4,6-α-glucanotransferase reaction mechanism by 3D structural protein analysis and mutagenesis