RESUMEN
In its September 2020 issue, Wirtschaftsdienst published an article entitled "Bremst die Doppik öffentliche Investitionen? Ergebnisse aus drei aktuellen Evaluationsstudien" by Désirée Christofzik, Florian Dorn, Stefanie Gäbler, Christian Raffer and Felix Rösel. Stephan Stüber takes a different view in a reply, and Christofzik et al. explain their point of view in a response.
RESUMEN
Phytases are enzymes involved in organic phosphorus cycling in nature and widely used as feed additives in animal diets. Thermal tolerance is a desired property of phytases. The objectives of this study were to screen and characterize bacterial phytases from Chilean hydrothermal environments. In this study, 60% (30 of 63) of screened thermophilic (60 °C) isolates showed phytase activity in crude protein extracts. The characterization of phytase from two selected isolates (9B and 15C) revealed that both isolates produce phytases with a pH optimum at 5.0. The temperature optimum for phytate dephosphorylation was determined to be 60 and 50 °C for the phytases from the isolates 9B and 15C, respectively. Interestingly, the phytase from the isolate 15C showed a residual activity of 46% after incubation at 90 °C for 20 min. The stepwise dephosphorylation of phytate by protein extracts of the isolates 9B and 15C was verified by HLPC analysis. Finally, the isolates 9B and 15C were identified by partial sequencing of the 16S rRNA gene as members of the genera Bacillus and Geobacillus, respectively.
Asunto(s)
6-Fitasa/química , 6-Fitasa/metabolismo , Bacterias/enzimología , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Respiraderos Hidrotermales/microbiología , 6-Fitasa/genética , Bacterias/clasificación , Bacterias/genética , Bacterias/aislamiento & purificación , Proteínas Bacterianas/genética , Estabilidad de Enzimas , Concentración de Iones de Hidrógeno , Cinética , TemperaturaRESUMEN
The aim of this study was to compare the biochemical properties of seven commercially available phytase products as well as their catalytic performance in an in vitro simulation of the digestive tract of poultry. Their enzymatic properties relevant with respect to phytate dephosphorylation in the digestive tract of birds were determined under identical assay conditions. All phytase products included in the study showed an acid pH optimum of activity and were capable of releasing the organically bound phosphate from phytate during the in vitro simulation. However, their overall biochemical properties and relative catalytic performances were remarkably different. The in vitro degradation system was considered as a simple and useful tool to evaluate the suitability of a phytase to be used as a feed supplement. Although relevant factors such as dietary P levels, intestinal phytase, and P absorption are not implemented in the system, this approach might help to reduce the number of feeding trials necessary in the search for a better suited phytase for animal feeding application.