Yeast lysis

The experimental result was expressed in terms of the regression equation shown in equation 4. The linear effect of individual glucanases on yeast lysis is expressed by b, b, and b, whereas coefficients b 2 ... 

Microbial interactions that occur in wine may be beneficial or detrimental to wine quality depending on the species involved. Examples of detrimental interactions are the inhibition of S. cerevisiae by Lactobacillus species and the inhibition of O. oeni by S. cerevisiae when MLF is desired. However, the inhibition of O. oeni may also be beneficial to wine quality if MLF is undesirable. Additional beneficial interactions include the stimulation of LAB growth due to yeast lysis and the inhibition of Pediococcus species by O. oeni. A better understanding of the complex interactions between LAB and S. cerevisiae will lead to the selection of compatible yeast and bacterial strains for the induction of alcoholic and malolactic fermentations. 

The two models of yeast lysis presented here have been developed to serve two different purposes. The simple model is a lumped, two-step model which follows the major features of the data and may prove useful for design of lysis reactors. The structured model, which can account for the source of protein within the cell, was developed to gain a mechanistic basis for predicting the effects of untested process conditions, and to aid insight into the physical processes at work during lysis. 

Figure 3 Simple model simulation of yeast lysis...

The simple and structured model simulations for yeast mass and soluble protein, peptides and carbohydrates are compared in Figure 6 for the yeast and enzyme concentration shown in Figures 3 and 4, and in Figure 7 for a concentrated yeast cell slurry. The simple model fits the data fairly well at both yeast concentrations, in every variable except the peptides. The fit for all variables at longer reaction times is directly related to use of the extent-of-reaction term Y , in the yeast lysis equation. 

Flash-pasteurization (heating between 72 and 76°C for 20 seconds) seems to be effective. It improves the fermentability of wines with stuck fermentation (Dubemet, 1994). This operation is valid for red, rose and dry white wines and should be carried out before inoculating. Its heating effect can be likened to the effect observed during thermo-vinification (Section 12.8.3). In spite of the destruction of yeasts, the heated musts ferment especially well. The effects of this process merit further study but several explanations can be proposed fermentation by a sole strain avoiding microbial antagonisms addition of nntri-tive elements due to yeast lysis elimination of toxic substances and modification of the colloidal structure. 

The subcellular location of PG was studied in cells disrupted by osmotic lysis through formation and disruption of sphaeroplasts from self-induced anaerobically-grown cells. A discontinuous sucrose-density gradient produced four bands labelled I, II, III and IV. Band I included many vesicles and a peak of alkaline phosphatase activity (a vacuolar marker in yeasts), NADPH cytochrome c oxidoreductase activity, an endoplasmic reticulum marker, and... 

Three bacterial species (E. coli, P. putida, and S. rubidae) were separated on isoelectric focusing in methylcellulose coated capillaries, and three bacterial species (P. fluorescens, E. aerogenes, and M. luteus) and the yeast S. cerevisae, were separated by capillary electrophoresis in the presence of polyethylene oxide.101 The polymers served to minimize adsorption to the walls without causing cellular lysis. 

Suspend cell pellet with minimal volume of lysis buffer and pack into the back of a plastic syringe. Dispense yeast through syringe into LN25 to make frozen yeast beads or noodles (Schultz, 1999). Frozen yeast can be stored at —80° or processed immediately. 

After 2 h incubation of the prepared antibody beads with UV-crosslinked extract in a cold room, the beads are washed 4 x with 100 /A RIPA buffer (50 mMTris-HCl pH 7.5, 150 rnMNaCl, 1% NP-40, 0.5% sodium deoxycholate, and 0.1% SDS) and lx with genomic DNA lysis buffer (50 mM Tris, pH 7.4, 10 mM EDTA, 500 mM NaCl, 2.5 mM DTT, 0.5 mM spermidine, 1% Triton X-100). Approximately 300 /(I of PK solution (1 mg/ml proteinase K in genomic DNA lysis buffer and 0.2 U//A RNase inhibitor) is added to the total lysate previously kept on ice and the beads are then incubated at 37° for 30 min. Gently flick the tubes to resuspend the beads every 10 min during the incubation. After removal of the proteinase K solution, 300 /A of RNA extraction solution (4 M guanidine thiocyanate, 0.5% sarkosyl, and 25 mM sodium citrate, pH7) is added to the beads, incubated for 10 min and the supernatant is mixed with 30 fig yeast tRNA (as a carrier) and 30 fil of 3 M sodium acetate. The RNA solution is phenol-chloroform extracted, ethanol-precipitated, and the pellet washed once with 70% ethanol. The dry pellet is used for 1st strand cDNA synthesis, followed by PCR analysis. The removal of proteins... 

The experiment based on the two-level factorial design as described by Box and Wilson (19) was carried out in order to check the influence of the individual glucanases (g ) of Streptomyces sp. 1228 lytic enzymes system on the degree of yeast cell lysis (y). 

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