The scale-up of the Knoevenagel-condensation between vanillin and barbituric acid carried out in planetary ball mills is investigated from an engineering perspective. Generally, the reaction proceeded in the solid state without intermediate melting and afforded selectively only one product. The reaction has been used as a model to analyze the influence and relationship of different parameters related to operation in planetary ball mills. From the viewpoint of technological parameters the milling ball diameter, dMB, the filling degree with respect to the milling balls' packing, ΦMB,packing, and the filling degree of the substrates with respect to the void volume of the milling balls' packing, ΦGS, have been investigated at different reaction scales. It was found that milling balls with small dMB lead to higher yields within shorter reaction time, treaction, or lower rotation frequency, rpm. Thus, the lower limit is set considering the technology which is available for the separation of the milling balls from the product after the reaction. Regarding ΦMB,packing, results indicate that the optimal value is roughly 50% of the total milling beakers' volume, VB,total, independent of the reaction scale or reaction conditions. Thus, 30% of VB,total are taken by the milling balls. Increase of the initial batch sizes changes ΦGS significantly. However, within the investigated parameter range no negative influence on the yield was observed. Up to 50% of VB,total can be taken over by the substrates in addition to 30% for the total milling ball volume. Scale-up factors of 15 and 11 were realized considering the amount of substrates and the reactor volume, respectively. Beside technological parameters, variables which influence the process itself, treaction and rpm, were investigated also. Variation of those allowed to fine-tune the reaction conditions in order to maximize the yield and minimize the energy intensity.

The allosteric enzyme ADP-Glc pyrophosphorylase (AGPase) catalyzes the synthesis of ADP-Glc, a rate-limiting step in starch synthesis. Plant AGPases are heterotetramers, most of which are activated by 3-phosphoglyceric acid (3-PGA) and inhibited by phosphate. The objectives of these studies were to test a hypothesis concerning the relative roles of the two subunits and to identify regions in the subunits important in allosteric regulation. We exploited an Escherichia coli expression system and mosaic AGPases composed of potato (Solanum tuberosum) tuber and maize (Zea mays) endosperm subunit fragments to pursue this objective. Whereas potato and maize subunits have long been separated by speciation and evolution, they are sufficiently similar to form active mosaic enzymes. Potato tuber and maize endosperm AGPases exhibit radically different allosteric properties. Hence, comparing the kinetic properties of the mosaics to those of the maize endosperm and potato tuber AGPases has enabled us to identify regions important in regulation. The data herein conclusively show that both subunits are involved in the allosteric regulation of AGPase. Alterations in the small subunit condition drastically different allosteric properties. In addition, extent of 3-PGA activation and extent of 3-PGA affinity were found to be separate entities, mapping to different regions in both subunits.Starch has many applications in industry as well as serving as an energy source in animal and human nutrition. ADP-Glc pyrophosphorylase (AGPase) catalyzes a rate-limiting step in starch synthesis. Modification of the regulatory properties of this enzyme increases starch yields in potato (Solanum tuberosum) tubers, and maize (Zea mays), wheat (Triticum aestivum), and rice (Oryza sativa) seeds (Stark et al., 1992;Giroux et al., 1996;Smidansky et al., 2002Smidansky et al., , 2003. Seed yield and plant biomass increases are conferred by deregulation of endosperm AGPase. Accordingly, AGPase has attracted wide interest for potential crop improvements.Plant AGPases are tissue specific. They are heterotetramers of two small and two large subunits. Though forms of each subunit share significant sequence homology, the small subunit is generally more conserved than is the large subunit (Smith-White and Preiss, 1992). Sequence comparisons of the large subunits divide AGPases into four groups: stem/ tuber, leaf, fruit/root, and endosperm AGPases. Further differences among AGPases are discernable in regulatory properties. While most plant AGPases are activated by 3-phosphoglyceric acid (3-PGA) and inhibited by phosphate (Ghosh and Preiss, 1966;Dickinson and Preiss, 1969;Sowokinos and Preiss, 1982;Kleczkowski et al., 1993aKleczkowski et al., , 1993bSikka et al., 2001), extent of regulation varies from organ to organ. Leaf, potato tuber, and tomato (Lycopersicon esculentum) fruit AGPases are sensitive to 3-PGA and phosphate, while endosperm AGPases, except for that of rice (Sikka et al., 2001), are less sensitive to the regulators. AGPases also differ in subcell...

The influence of the operating frequency, the milling ball and grinding stock filling degree, the material of the milling balls and beakers, the milling ball diameter and the size of the milling beakers on the temperature increase inside the milling beakers in a mixer ball mill was investigated. These parameters influence the temperature progression and the equilibrium temperature of the system. The grinding stock filling degree with regard to the void volume in the milling ball package showed huge influence on the heating rate and the equilibrium temperature. In this context, the behavior of the temperature progression changes if the complete void volume is filled with the grinding stock.