Yeast numbers, measurement

FIGURE 7.1 NIR spectra from different fermentations of rye with yeast. The seven spectra have been measured in reflection mode in opaque mashes. Wavelength interval is 1100-2300 nm the number of data points is 241. The samples differ in the ethanol contents (62.2-84.1 g/L). 

Wodicka et al. (1997) created such an array for measuring yeasf gene expression based upon 25-mer oligonucleotides covering 6200 ORFs. Each ORF was represented by 20 PM and 20 MM probes. Why so many probes Simply put, not all probes hybridize in a predictable manner. Averaging across a number of probes improves the outcome. Thus, the yeast expression chip comprised over 65,000 probe features and required a set of four chip subarrays. 

Flow cytometry [141, 142] is a technique that allows the measurement of multiple parameters on individual cells. Cells are introduced in a fluid stream to the measuring point in the apparatus. Here, the cell stream intersects a beam of light (usually from a laser). Light scattered from the beam and/or cell-associated fluorescence are collected for each cell that is analysed. Unlike the majority of spectroscopic or bulk biochemical methods it thus allows quantification of the heterogeneity of the cell sample being studied. This approach offers tremendous advantages for the study of cells in industrial processes, since it not only enables the visualisation of the distribution of a property within the population, but also can be used to determine the relationship between properties. As an example, flow cytometry has been used to determine the size, DNA content, and number of bud scars of individual cells in batch and continuous cultures of yeast [143,144]. This approach can thus provide information on the effect of the cell cycle on observed differences between cells that cannot be readily obtained by any other technique. 

Experimental data and graphs of function (25) (inverted coordinates) describing growth of yeast in the presence of chromium and nickel salts are presented in Figure 2 [14]. In the limits of measurements accuracy the calculated curves are in good agreement with experimental data under change of number approximately by six orders. 

Fig. 10.6. Sensitivity of Rcelp to chloromethyl ketones and peptidyl (acyloxy)methyl ketones. Reporters based orr Ras (A) arrd a-factor (B) arrd were used to measure the impact of TPCK, TLCK, Phe-Lys AOMK (FKBK), and Phe-Ala AOMK (FABK) on the activity of yeast Rcelp as measured through fluorescence output (A) or a biological readout assay (B) DMSO is the solvent control. A schematic for each assay is shown on the left of the panel, and a graphical representation of data collected with the assay is shown on the right. Numbers on top of each bar in the graph reflect the percent activity observed relative to the DMSO-treated control. ABZ is aminobenzoic acid DNP is dinitrophenol. Data is reproduced in part with permission from Ref. [74].

We also have used the microanalytical system (Figure 2) for examining the metal content of a number of eukaryotic RNA polymerases (26, 27,28). The results for RNA polymerase I from yeast are shown, in Figure 4 (26). As shown previously for the reverse transcriptases, the droplet fractions were measured for protein and zinc content and for enzyme activity. The results show one major peak of protein/enzyme... 

As isolated from yeast or after expression in E. coli. All constants were determined from steady-state kinetic measurements at 25°C, 10 mM Tris-HCl, pH 7.5, / = 0.10 M NaCl. Ferricy-anide (1 mM) was used as electron acceptor. Values of kcM correspond to the number of moles of l-lactate oxidized per mole of enzyme per second (these values can be doubled to express them in mole electron equivalents). 

Under appropriate conditions the rate of reproduction of yeasts and bacteria is extremely rapid, with doubling rates measured in minutes, so that there is little delay in building up the number of cells to maximize the conversion rate of raw material (Table 16.1). 

Horitsu [100] immobilises yeast cells on the surface of a ceramic carrier by the different charge of carrier and cells. Using this set-up, soy sauce, beer and sake are produced with fermentation times much shorter, up to 10 times, than in conventional processing. Kawase et al. [101] study this immobilisation behaviour by measuring zeta-potentials and find a neat correlation of this potential with the number of adsorbed cells. 

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