Yeast adaptation

In the meanwhile, yeasts adapt themselves to the cold conditions and begin alcoholic fermentation. Fermentation is slow but regular, usually carried out by Saccharomyces cereuisiae and Saccharomyces bayanus. The fermentation has to be kept under constant surveillance as the low temperatures, combined with the high sugar content, may lead to premature and unwanted fermentation cessation, even when selected cultures of yeasts are added. 

Temperature extremes Yeasts have problems growing when the temperature is too low. Therefore, too low temperature at the beginning of the process can lead to a deficient yeast population. On the other hand, if the temperature is too high (more than 30 °C) the fermentation is at considerable risk of stopping. For that reason, thermic control of fermentations is nowadays indispensable. Another aspect to take into account is that sudden changes of temperature may provoke serious problems in fermentation. As previously mentioned, yeasts adapt their membrane composition to maintain the correct fluidity. A drastic temperature decrease can provoke excessive rigidity in the membranes before yeasts can adapt to it. 

The primary organs for copper storage are the liver and spleen, where the metal is found in the cytosol in superoxide dismutase see Copper Proteins with Type Sites) or metallothionein see Metallothiondns) In response to a copper challenge, yeast adaptively synthesizes metallothionein to detoxify the metal. Copper is also bound, transported, and assimilated into tissues by ceruloplasmin. 

Fermentations—The saccharified wort obtained in the manner described is run into fermenting vessels and treated with yeast to start the fermentation special distilling yeast is used, that is, selected culture yeasts adapted to distilling conditions. If pressed yeast is added about 2 lbs, are employed for everj lOO gallons of wort. Usually, however, a preliminary fermentation is made iu a good malt wort, this provides a culture of vigorous yoimg yeast cells, and is added to the main wort in the proportion of 4 to 5 per cent. 

Figure 1.3 Oscillations in the populations of paramecia and yeast. (Adapted from D Ancona, 1954.)...

Figure 6.4. Viability of S. cerevisiae (open circles) and O. oeni (closed squares) with bacteria inoculated on the same day as the yeast. Adapted from Semon et al. (2001) with the kind permission of the Australian Journal of Grape and Wine Research.

Figure 15.2. Representative shapes of ascospores found in yeasts. Adapted from Yarrow (1998) with the kind permission of Elsevier Ltd.

Figure 24.4 Examples of circuit motifs in yeast (adapted from Lee et al, 2002). The rectangles denote promoter regions on a gene (Gl, G2, etc.), and the circles are transcription factors (TFl, TF2, etc.).

Strassbuig, K., Walther, D., Takahashi, H., Kanaya, S., Kopka, J. Dynamic transcriptional and metabolic responses in yeast adapting to temperature stress. OMICS 2010,14,249-259. 

Kahr, H., Helmberger, S., Jager, A.G., 2011. Yeast Adaptation on the Substrate Straw. Bioenergy Technology, World Renewable Energy Congress, 8—13. 

Page 1176 (Figure 28 11) is adapted from crystallographic coordinates deposited with the Protein Data Bank PDB ID 6TNA Sussman J L Holbrook S R Warrant R W Church G M Kim S H Crystal Structure of Yeast Phenylalanine tRNA I Crystallographic Refinement / Mol Biol 1978 126 607 (1978)... 

In the acid hydrolysis process (79—81), wood is treated with concentrated or dilute acid solution to produce a lignin-rich residue and a Hquor containing sugars, organic acids, furfural, and other chemicals. The process is adaptable to all species and all forms of wood waste. The Hquor can be concentrated to a molasses for animal feed (82), used as a substrate for fermentation to ethanol or yeast (82), or dehydrated to furfural and levulinic acid (83—86). Attempts have been made to obtain marketable products from the lignin residue (87) rather than using it as a fuel, but currently only carbohydrate-derived products appear practical. 

Figure 9.12 Schematic diagram of the structure of the heterodimeric yeast transcription factor Mat a2-Mat al bound to DNA. Both Mat o2 and Mat al are homeodomains containing the helix-turn-helix motif. The first helix in this motif is colored blue and the second, the recognition helix, is red. (a) The assumed structure of the Mat al homeodomain in the absence of DNA, based on Its sequence similarity to other homeodomains of known structure, (b) The structure of the Mat o2 homeodomain. The C-terminal tail (dotted) is flexible in the monomer and has no defined structure, (c) The structure of the Mat a 1-Mat a2-DNA complex. The C-terminal domain of Mat a2 (yellow) folds into an a helix (4) in the complex and interacts with the first two helices of Mat a2, to form a heterodimer that binds to DNA. (Adapted from B.J. Andrews and M.S. Donoviel, Science 270 251-253, 1995.)...

ENZYMATIC ANALYSIS WITH CARBOXYPEPTIDASES. Carboxypeptidases are enzymes that cleave amino acid residues from the C-termini of polypeptides in a successive fashion. Four carboxypeptidases are in general use A, B, C, and Y. Carboxypeptidase A (from bovine pancreas) works well in hydrolyzing the C-terminal peptide bond of all residues except proline, arginine, and lysine. The analogous enzyme from hog pancreas, carboxypeptidase B, is effective only when Arg or Lys are the C-terminal residues. Thus, a mixture of carboxypeptidases A and B liberates any C-terminal amino acid except proline. Carboxypeptidase C from citrus leaves and carboxypeptidase Y from yeast act on any C-terminal residue. Because the nature of the amino acid residue at the end often determines the rate at which it is cleaved and because these enzymes remove residues successively, care must be taken in interpreting results. Carboxypeptidase Y cleavage has been adapted to an automated protocol analogous to that used in Edman sequenators. 

The notion that the segment containing C3 and T3 is important for conformational adaptability of the protein is supported by mutations in yeast. Mutations of the genes of the H-ATPase of Saccharomyces cerevisiae resulted in a thermo-sensitive... 

Figure 5.3. Systematic mating ofyeast two-hybrid bait and prey pools. Each yeast ORF was cloned individually into both as a DNA binding domain fusion (bait) and activation domain fusion (prey). The bait fusions were introduced into a MATa strain and the prey fusions were introduced into a MATa strain. The bait and prey fusions were pooled in sets of 96 clones to generate a total of 62 pools of each. The pools were systematically mated (62 x 62) in a total of 3844 crosses. Interacting clones were selected and the bait and prey inserts were PCR amplified and sequenced to determine their identify. Figure adapted from Ito et al. (2001).

Figure 5.4. Example of a small region of a hypothetical protein interaction network. Each letter represents a different yeast protein. The white boxes and gray boxes represent genes that are involved in the same function while the hatched boxes indicate proteins of unknown function. The A protein is likely to be involved in the same process as the white box protein and the J protein is likely to be involved in the same process as the gray box proteins because of the multiple interactions within the network. The connection between the E and I proteins indicates communication between the cellular processes. Figure adapted from Hazbun and Fields (2001).

Piper, P., Calderon, C.O., Hatzixanthis, K. and Mollapour, M. (2001) Weak acid adaptation the stress response that confers yeasts with resistance to organic acid food preservatives . 

Each of the steps involved in RDM has been used separately in many organisms and for the study of various mRNAs. Thus, although the protocol presented herein is for the analysis of yeast cells grown at optimal conditions, it could be adapted easily to other experimental systems. It might also be applied for in vitro systems or extracts (e.g., reticulocytes lysate), yet we have not performed such experiments. 

With the exception of gel filtration, all modes of biochromatography are, in principle, adaptable to EBA. Separations based on ion exchange [27], Protein A affinity [28] and IMAC [29] have been published. The list of feed includes bacterial fermentation broth [30], cell homogenate [31] and renatured inclusion bodies [32], yeast fermentation broth [29] and cell homogenate [27] as well as mammalian or hybridoma cell culture broth [33]. EBA is also an accepted method in the production of medicinal products. Although, considering the problems in initial processing discussed earlier... 

Fig. 6. Ure2p filaments are infectious. (A, B) Negatively stained micrographs of Ure2p filaments (A) before and (B) after sonication, which was found to be necessary for effective transformation of filaments. (C) Color spectrum of [URE3] variants in randomly chosen colonies after transformation of yeast cells with Ure2p filaments. (D) Conversion efficiency to [URE3] status is dependent on Ure2p filament concentration. All panels adapted from Figure 2 of Brachmann et al (2005).

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