大肠杆菌K5多糖生物合成条件的优化

采用Plackett-Burman实验、正交试验设计方法对K5多糖的生物合成条件进行优化。然后,在摇瓶及5 L发酵罐中进行K5多糖发酵过程研究。结果表明:最佳培养基组成为麦芽糖20 g/L,蛋白胨15 g/L,MnCl4·4H2O0.1 g/L,MgSO4·7H2O 2.0 g/L,KH2PO42.0 g/L,K2HPO49.7 g/L,脱水枸橼酸钠0.5 g/L;250 mL摇瓶最佳装液量为15 mL。优化后5 L发酵罐中K5多糖的质量浓度为1.8 g/L,较优化前的0.3 g/L提高了5倍。

Prediction of Structure-H Gas Hydrate Formation Conditions for Reservoir Fluids

In this work, a thermodynamic model is developed for prediction of structure H hydrate formation. The model combines the Peng-Robinson equation of state for the vapor, liquid and aqueous phases with the extended Ng-Robinson hydrate model for gas hydrate formation of all three structures. The parameters of 14 structure- H hydrate formers are determined based on the experimental data of structure-H hydrates in the literature. The expression of fugacity of water in the empty hydrate phase is correlated for calculating structure-H hydrate formation conditions in the absence of free water. The model is tested by predicting hydrate formation conditions of a number of structure-H hydrate forming systems which are in good agreement with the experimental data. The proposed model is also applied to the prediction of hydrate formation conditions for various reservoir fluids such as natural gas and gas condensate.