Continuous computer controlled production of formate dehydrogenase (FDH) and isolation on a pilot scale

A continuous production process has been developed up to pilot scale (300 l) for FDH production with the methylotrophic yeast Candida boidinii. A high cell mass specific FDH activity (50 U/g) is achieved by process computer controlled supply of pure methanol to operate the reactor at an optimum methanol concentration of 10 g/l. The maximum FDH spacetime yield achievable with this process control involves a residence time of 7 h. The FDH space-time yield (STY) and FDH concentration are a function of the oxygen transfer rate (OTR) of the fermenter (maximum STY = 255 U/(l h) at k_La = 870 l/h). For a reasonable compromise between high FDH space-time yield and high FDH concentration, an optimum residence time is adjustable by regulating the supply of nutrient salt solution in relation to the OTR of the fermenter. On a pilot scale (200 l continuously stirred tank reactor) roughly 4 million U of FDH were produced within 10 days at a residence time of 14.3 h. Isolation of intracellular FDH enzyme was performed using extraction with an aqueous two-phase system (PEG/K₂HPO₄). A technical product quality of 1.2 U/mg FDH was achieved without any chromatographic purification step.     

Accuracy improvement technique for measuring stress intensity factors in photoelastic experiment

Fracture coefficients, together with the exact origin of the crack, were extracted from data sets produced an overdeterministic system solved by an iterative least squares method. Power series type williams equations were used in the analyses. The accuracy evaluation indicated that the first four terms of williams equations are sufficient to describe the stress field in the vicinity of the crack tip for both mode I and mixed mode cases. Experimental study showed that the first two terms of williams equations, which are the same as the modified westergaard equations, cannot be used to extract mixed mode fracture parameters accurately within the data collection region of 0.07 <r/a <0.30, where r and a are radial coordinate and crack length for an edge crack, respectively.     

Preparation of percycloalkylphosphines by catalytic hydrogenation using a Rh/Pt catalyst of the adams type

By smooth catalytic hydrogenation phenylated phosphine oxides are reduced to the corresponding cyclohexyl derivatives using a Rh/Pt catalyst. In chiral phosphines the optical activity is restored.     

Sur les proprietes magnetiques des bronzes fluores de vanadium MxVF3α (M = K,Rb, Cs)

The magnetic properties of the α-M_xVF₃ fluorides have been investigated from 4.2 to 550 K. An antiferromagnetic behavior has been observed, the Néel temperature being in each case close to 18 K for x = 0.25. Below the ordering point a weak ferromagnetic component appears, which decreases sharply from potassium to cesium. This behavior is compared with that of the VF₃ fluoride and of the homologous α-M_xFeF₃ phases (M = K, Rb, Cs).     

Incidence of heterogeneity due to polymer incompatibility on the reaction between telechelic prepolymers and on the mechanical properties of the multiblock copolymers formed

The polycondensation reaction between telechelic poly(dimethylsiloxanes) and α,ω-difunctional polystyrenes (or substituted polystyrenes) in toluene solution is very fast, in spite of the heterogeneous nature of the reaction medium. In the first part of the article is reported a qualitative approach of the condensation reaction in relation to the microscopic structure of the reaction medium. The second part is devoted to an investigation of the mechanical and thermomechanical behaviour of the multiblock copolymers which results from intramolecular phase separation.