Sterilization yeast

Fig. S.—Emil Fischer s fermentations on a semi-micro scale using an apparatus of the size shown, (a) —70 mg sugar, 0.35 ml water, 0.35 ml sterilized yeast extract, and 13 mg yeast species (b) S-trap for evolved C02 (c) aqueous barium hydroxide.

Fermentation broths are suspensions of microbial cells in a culture media. Although we need not consider the enhancement factor E for respiration reactions (as noted above), the physical presence per se of microbial cells in the broth will affect the k a values in bubbling-type fermentors. The rates of oxygen absorption into aqueous suspensions of sterilized yeast cells were measured in (i) an unaerated stirred tank with a known free gas-liquid interfacial area (ii) a bubble column and (iii) an aerated stirred tank [6]. Data acquired with scheme (i) showed that the A l values were only minimally affected by the presence of cells, whereas for schemes (ii) and (iii), the gas holdup and k a values were decreased somewhat with increasing cell concentrations, because of smaller a due to increased bubble sizes. 

After sterilization, yeast is added to initiate fermentation. McConnell and Schramm (1995) recommend inoculation with no less than 10% by volume. Moreover, as the pH of honey is naturally low and because it is poorly buffered, the pH of must may drop during fermentation to a point limiting yeast efficiency. pH reduction can result from the synthesis of acetic and succinic acids by the yeast cells (Sroka and Tuszynski, 2007). While a rapid decline in pH inhibits undesirable microbial activity (Sroka and Tuszynski, 2007), it also reduces the dissociation of fatty acids in the wort, potentially slowing yeast metabolic action. For this, addition of a buffer is important to maintain the pH within a range of 3.7-4.0 throughout fermentation (McConnell and Schramm, 1995). Calcium carbonate, potassium carbonate, potassium bicarbonate, and tartaric acid are potential candidates. However, as some of these salts can add a bitter-salty... 

Sterilized yeast medium is stored in 90-mL volumes without a carbon source (glucose) or amino acid supplements. 

S. cerevisiae is produced by fed-batch processes in which molasses supplemented with sources of nitrogen and phosphoms, such as ammonia, ammonium sulfate, ammonium phosphate, and phosphoric acid, are fed incrementally to meet nutritional requirements of the yeast during growth. Large (150 to 300 m ) total volume aerated fermentors provided with internal coils for cooling water are employed in these processes (5). Substrates and nutrients ate sterilized in a heat exchanger and then fed to a cleaned—sanitized fermentor to minimize contamination problems. 

Filtering. Conditioning or 1 agering gives the beer its desired organoleptic properties, but it stiU contains yeast, protein-tannin complexes, etc, ie, it has a hazy appearance. A high quaHty beer must be clear and totaUy sterile, have coUoidal stabiHty, and yeast must be removed to aUow the beer to have biological stabiHty. The protein-tannin complexes must also be removed so as not to upset the coUoidal stabiHty. 

Dauer-haftigkeit, /, durability, permanence, -haltbarkeit, /. Mech.) fatigue endurance, -hefe, /. permanent yeast, zymin. -leistung, /. continuous output, -magnet, m. permanent magnet, -milch,/, sterilized milk condensed milk dried milk. 

Two 300 ml Erlenmeyer flasks are prepared, each of them containing 60 ml of the following vegetative medium in tap water 0.6% peptone, 0.3% dry yeast and 0.05% calcium nitrate. The pH after sterilization by heating in an autoclave to 120°C for 20 minutes is 7.2. 

For this purpose a fermenter made of stainless steel having a 50 liter capacity is charged with 30 liters of a nutrient solution of 0.1% yeast extract, 0.5% cornsteep and 0.2% glucose, heated for one-half hour at 120°C for sterilization purposes, and after cooling, inoculated with a bacterial suspension of Bacillus lentus MS 2B4. 

Fe" (2 ppm), casein hydrolyzate (0.2 g/dl), yeast extract (0.2 g/dl), corn steep liquor (0.2 ml/dl), polypeptone (0.1 g/dl), meat extract (0.1 g/dl) and sodium ribonucleate (10 mg/dl) were poured into respective test tubes and each tube was sterilized at 115°C for 10 minutes. Thereafter separately sterilized calcium carbonate was added in the amount of 2 g/dl and then cells of Bacillus subtUis S26910 were Inoculated into the above media and cultured with shaking at 30°C for 20 hours. 

As described in U.S. Patent 2,929,763, methandrostenolone may be made by a fermentation route. 2 g of sodium nitrate, 1 g of primary potassium orthophosphate, 0.5 g of magnesium sulfate heptahydrate, 0.5 g of potassium chloride, 50 g of glucose and 1 g of Difco yeast extract are dissolved in one liter of tap water, brought to pH 5 by addition of a sodium hydroxide solution and sterilized. The resulting nutrient solution is inoculated with 50 cc of a 4-day-old shaking culture of Didyniel/a lycopersici and shaken for 48 hours at 27 C, whereby the culture becomes well developed. 

A small fermentation tank (5,000 parts by volume capacity) was charged with 3,000 parts by volume of a culture medium (pH 6.0) comprising 3% glucose, 1 % polypepton, 0.5% yeast extract and 0.5% malt extract. The medium was sterilized by heating in a conventional manner and cooled. This medium was inoculated with 150 parts by volume of a pre[Pg.1565]

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