Phosphates yeast requirements

Yeast requires for its growth certain salts which are present in Witte s peptone. If the latter is not available it may be replaced by 20 cc. of a solution made by dissolving 10 grams each of potassium phosphate, magnesium chloride, and calcium nitrate in 1 liter of water. 

Where the nutritional status of must is known (or thought) to be an issue, supplementation is recommended. Unlike yeasts, which grow well on formulations rich in diammonium phosphate, LAB require preformed amino acids and, thus, this source on nitrogen is not particularly stimulatory. Proprietary formulations are available specific for LAB. 

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. 

Riboflavin was first isolated from whey in 1879 by Blyth, and the structure was determined by Kuhn and coworkers in 1933. For the structure determination, this group isolated 30 mg of pure riboflavin from the whites of about 10,000 eggs. The discovery of the actions of riboflavin in biological systems arose from the work of Otto Warburg in Germany and Hugo Theorell in Sweden, both of whom identified yellow substances bound to a yeast enzyme involved in the oxidation of pyridine nucleotides. Theorell showed that riboflavin 5 -phosphate was the source of the yellow color in this old yellow enzyme. By 1938, Warburg had identified FAD, the second common form of riboflavin, as the coenzyme in D-amino acid oxidase, another yellow protein. Riboflavin deficiencies are not at all common. Humans require only about 2 mg per day, and the vitamin is prevalent in many foods. This vitamin... 

The second method also relies on site-specific chemical modification ofphosphoproteins (Oda et al., 2001). It involves the chemical replacement of phosphates on serine and threonine residues with a biotin affinity tag (Fig. 2.7B). The replacement reaction takes advantage of the fact that the phosphate moiety on phosphoserine and phosphothreonine undergoes -elimination under alkaline conditions to form a group that reacts with nucleophiles such as ethanedithiol. The resulting free sulfydryls can then be coupled to biotin to create the affinity tag (Oda et al., 2001). The biotin tag is used to purify the proteins subsequent to proteolytic digestion. The biotinylated peptides are isolated by an additional affinity purification step and are then analyzed by mass spectrometry (Oda et al., 2001). This method was also tested with phosphorylated (Teasein and shown to efficiently enrich phosphopeptides. In addition, the method was used on a crude protein lysate from yeast and phosphorylated ovalbumin was detected. Thus, as with the method of Zhou et al. (2001), additional fractionation steps will be required to detect low abundance phosphoproteins. 

Requirement for Phosphate in Ethanol Fermentation In 1906 Harden and Young, in a series of classic studies on the fermentation of glucose to ethanol and C02 by extracts of brewer s yeast, made the following observations. (1) Inorganic phosphate was essential to fermentation when the supply of phosphate was exhausted, fermentation ceased before all the glucose was used. (2) During fermentation under these conditions, ethanol, C02, and a hexose bisphosphate... 

---