Yeast monolayer

Figures 4A and 4B are scanning electron micrographs of a an ultrafilitration polysulfone membrane with a 30,000-Dalton mol wt cutoff at low and high magnification, respectively. The image was taken during the protein-filtration portion of cycle 10 ( 3100 s), for an SMY experiment with 5.0 g/L of cellulase in the primary feed, 5.36 of g/L yeast in the secondary feed, and Py=Ph = 15 psi. The majority of the membrane is covered by an SMY, but in a few places the SMY is absent or has been eroded. Note that the SMY is mostly monolayered, compared with the multilayered SMY seen during microfilitration. This difference is apparently due to the lower flux in ultrafiltration.

Water activity has a profound effect on the rate of many chemical reactions in foods and on the rate of microbial growth (Labuza 1980). This information is summarized in Table 1-9. Enzyme activity is virtually nonexistent in the monolayer water (aw between 0 and 0.2). Not surprisingly, growth of microorganisms at this level of aw is also virtually zero. Molds and yeasts start to grow at aw between 0.7 and 0.8, the upper limit of capillary water. Bacterial growth takes place when aw reaches 0.8, the limit of loosely... 

U., Utesch, T., Mroginski, M.A., Hildebrandt, P., and Weidinger, I.M. (2008) Gated electron transfer of yeast iso-1 cytochrome c on self-assembled monolayer-coated electrodes. Journal of Physical Chemistry ,112,15202-15211. 

Eukaryotic as well as most prokaryotic membranes are bllayers of phospholipid and protein. Each monolayer, which is about 2.1 nm thick (19,20), is believed to contain the sterol in a nonhomogeneous distribution, and at least in some cases sterol can move between the monolayers. This process is called "flip-flop". Sterol has been found both in the mitochondria (21) and the plasma membrane of cerevlslae (13.18), and the ability to support the growth of anaerobic yeast presumably Is associated with Its membranous function. 

Brown TA, Smith DG (1976) The effects of silver nitrate on the growth and ultrastructure of the yeast Cryptococcus albidus. Microbios Lett 3 155-162 Burd A, Kwok CH, Hung SC, Chan HS, Gu H, Lam WK, Huang L (2007) A comparative study of the cytotoxicity of silver-based dressings in monolayer cell, tissue explant, and animal models. Wound Repair Regen 15 94—104... 

Figure 2.8 shows a series of photomicrographs of yeast deposition on the AN membrane. The deposition occurs uniformly and reaches a complete monolayer within 2-3 min. After 5 min of filtration, the cake has at least two layers of yeast cells, as evident from the black image. 

The DVO micrographs for removal of a yeast cake from cellulose acetate (CA) membranes by backpulses provide a different picture. Figure 2.19 shotvs the fouled membrane and then the cleaned membrane after a series of individual backpulses. The cells are removed nonuniformly in patches and there is no monolayer remaining on the membrane surface. Indeed, after four individual backpulses with a cumulative duration tj, = 1 s, the membrane is 94% dean. Mores and Davis [21] also found that almost complete flux recovery was obtained by backpulses of 1 s or more. 

In recent years, various methods of synthesis of nano-size particle systems have been established. They have used aqueous [22] and non-aqueous [23] solutions, reversed micelles [24], vesicles [24], BLMs [24], surface monolayers [25], clays [26], zeolites [27], Langmuir-Blodgett films [28], peptides [29] aM yeast cells [30], The main idea of the dted variety of synthesis methods is to control the partide size either by spatial conditions (e.g. the size of pores 29], oititi in media [24,27]) or kinetics of synthesis reaction [22]. Another >arameter, which in many cases decreases the partide size, is temperature [2, 1. ... 

Staining Applications Biomolecules brain spinal cord chromosomes DNA embryos fungi lymph vessels mitochondria neurons nucleic acids sperms tissue culture monolayers yeast cell hairs "... 

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