Estimation from yeast

PG secreted by K. mancianus CCT 3172 showed activity from pH 4 to 6, with an optimum at pH 5 typical of PG secreted by yeasts. Unlike some pectinases, the activity of PG from K. marxianus CCT 3172 was not affected by buffers used across the pH range studied. The effect of temperature on the activity of PG from K. mancianus was similar to that reported for PGs from yeasts [eg 2]. The relative molecular masses of the four proteins revealed by gel filtration were in close agreement with previous estimates [16,17]. 

The extent of the dissociation in 8 M urea can, moreover, not be estimated from the electrophoretically observed hybrid formation between wheat germ (isoenzyme II) SOD and respectively yeast and bovine SOD. BESOD did namely not dissociate in 8 M urea at 25 °C for at least 72 h, as indicated by sedimentation equilibrium analysis (Af. 32,000). The reactivity of Cys-6 and of the histidine residues was not increased either in that medium... 

The yeast cell cycle has also been analyzed at this high level of chemical detail [17]. The molecular mechanism of the cycle in the form of a series of chemical equations was described by a set of ten nonlinear ordinary differential kinetic rate equations for the concentrations of the cyclins and associated proteins and the cell mass, derived using the standard principles of biochemical kinetics. Numerical solution of these equations 3uelded the concentrations of molecules such as the cyclin, Cln2, which is required to activate the cell cycle, or the inhibitor, Sid, which helps to retain the cell in the resting Gi phase. The rate constants and concentrations ( 50 parameters) were estimated from published measurements and adjusted so that the solutions of the equations yielded appropriate variations, i.e., similar to those experimentally measured, of the concentrations of the constituents of the system and the cell mass. The model also provides a rationalization of the behavior of cells with mutant forms of various system constituents. 

The viscosity of Newtonian suspensions of yeast and bacteria growing as individual cells in a water-like medium can be estimated from the following empirical equation proposed by Thomas. ... 

The structured model is consistent with features of lytic enzyme action and yeast structure reported in the literature. The sequential removal of the two wall layers, followed by protoplast rupture, accurately describes the early lag in protein and carbohydrate release. The presence of residual solids at long reaction times was accounted for stabilization of protoplasts by substances released from lysed cells. The structured model can be used to estimate the effects of several process alternatives, as shown in a simulation of a process for recovery of site-linked enzymes from yeast. 

Another purified enzyme preparation which produces laminaripentaose from insoluble laminarin and from heat-treated pachyman is produced by a strain of Arthrobacter luteus (100,101,102) when grown on yeast cells or / -(1 —>3)-glucan. The enzyme, which was named Zymolase (also referred to as Zymolyase) appeared to be homogeneous by electrophoresis in a Tiselius apparatus and by ultracentrifugation. The molecular weight of the enzyme was estimated from ultracentrifugation to be ca. 20,500. The optimum pH for lysis of viable yeast cells was 7.5. The optimum temperature was 35°C. The optimum pH for heat-treated pachyman hydrolysis was 6.5, and the optimum temperature was 45°C. A Lineweaver-Burk plot with heat-treated pachyman yielded a Km value of 0.04% when the solubilized carbohydrate was assayed by the phenol-sulfuric acid method. Zymolase lost all its activity after incubation at 60°C for 5 min. 

Harvest yeast at OD x) = 0.6-0.7. Do not exceed ODstx) = 0.8. Pool and stir culture in an ice-water bath while collecting cells in the next step. Because light scattering estimates from spectrophotometric optical density measurements are not very precise, different spectrophotometers will give different estimates of cell density. In our laboratory an ODsoo of 0.6 = 5 x 10 cells/ml. 

Figure 1,2. Reversal of maltose hydrolysis catalysed by an extract of dried yeast. The extract, prepared as described in the text, was mixed with solutions of glucose and maltose as described in Table 1.4. At various times (see dates) the amounts of maltose and glucose were estimated from the reducing power and the optical rotation of the solutions. For each experiment (see Table 1.4) the results are plotted as the percentage of the total carbohydrate present as glucose and maltose. (From Hill, 1898 reproduced with the kind permission of the Royal Society of Chemistry from the original paper, (Fig. 5, p. 652).)...

Filtration with 0.37 g washed yeast suspensions at TMP 0.10 bar and a cross-flow velocity (CFV) of 0.20 m s resulted in a much thicker cake and the evolution of cake thickness had to be estimated from drying and weighing of the cake as the MPM was found to be limited to about 40 pm. Incidentally after 60 min the estimated cake thicknesses from drying and weighing was 165 pm with a corresponding specific cake resistance of 5.48 x 10 mkg, which is in excellent agreement with literature values [34, 35]. 

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