Yeasts practical applications

SCX column on H PLC), the eluates were directly transferred onto a reversed-phase HPLC column, and subsequently the eluates from the second column were validated by tandem MS. Of 78 existing proteins, 75 were correctly identified. The analysis of an enriched yeast ribosomal fraction identified over 80% of the subunits in the complex (Lui, 2002). According to the described method of validation and optimization, the potential of this method lies within practical application due to automation and up-scaling. 

Recently it has been shown that Cu(I), as well as its analog Ag(I), can activate metallothionein gene transcription in yeast by binding directly the ACEI trans-activator protein [8 Our experiments with the Ag(I) ion show that it does not appear to mimic the effect of Cu on the accumulation of qrt c-552 mRNA. This could indicate either that the active metalloregulator of the cyt c-552 gene is Cu(II) rather than Cu(I) or that the sensory molecule that responds to Cu is exquisitely specific for Cu (ys. other metals) as the regulator. This level of specificity combined with the extreme sensitivity of the response, < 100 nM total (chelated + free) Cu, suggest that the ( t c-552/Cu-response system could find practical application as a metal ion biosensor. 

The isolation of the pure crystalline TPP from brewer s yeast extract, as carried out by Lohmann and Schuster, involved various precipitations as barium, picric acid, and phosphotungstic acid salts, fractional precipitation with solvents, and an adsorption with fuller s earth. The method has no practical application. 

Enzyme reductions of carbonyl groups have important applications in the synthesis of chiral compounds (as described in Chapter 10). Dehydrogenases are enzymes that catalyse, for example, the reduction of carbonyl groups they require co-factors as their co-substrates. Dehydrogenase-catalysed transformations on a practical scale can be performed with purified enzymes or with whole cells, which avoid the use of added expensive co-factors. Bakers yeast is the whole cell system most often used for the reduction of aldehydes and ketones. Biocatalytic activity can also be used to reduce carbon carbon double bonds. Since the enzymes for this reduction are not commercially available, the majority of these experiments were performed with bakers yeast1 41. 

Ideally microbial cells should be consumable directly as food or food ingredients. However, because of their nucleic acid content the presence of undesirable physiologically active components the deleterious effects of cell wall material on protein bioavailability and the lack of requisite and discrete functional properties, rupture of cells and extraction of the protein is a necessary step. Importantly, for many food uses (particularly as a functional protein ingredient) an undenatured protein is required. For these reasons and for many potential applications of yeast protein(s) it is very desirable to separate cell wall material and RNA from the protein(s) for food applications. Much research is needed to develop a practical method for isolation of intact, undenatured yeast proteins from the yeast cell wall material to ensure the requisite nutritional and functional properties. 

Elemental S (crystalline or colloidal form) can accumulate as a residue in must as the result of its use as a vineyard agrochemical, where it is used to control grape vine powdery mildew Erysiphe necator and various pests. Direct reduction of S to H2S is induced by the highly reductive conditions that exist at the yeast cell surface during fermentation. This mechanism is of little practical importance except when the application of elemental S is not used according to manufacturers recommendations, such as application within the recommended with-holding period before grape harvest (Rankine 1963 Rauhut and Kiirbel 1994 Thomas et al. 1993). 

Elaboration of the fermentation technology also falls in this period, development accelerated, however, only after World War II. Outstanding results have been attained in the research and application of several other biotransformation procedures as well (e.g., in the transformation of antibiotics). Vitamin B12 production on an industrial scale was first introduced to the world in Hungary. Improvement of yeast strains and their application in the alcohol-, yeast- and wine industries became general practice in the 1960s, together with operation with up-to-date microbial methods for dairy products. Based on results attained abroad, several modern bioprocess plants started operation in the 1970s. 

More recently, this challenge has been addressed through the evolution of modified tRNA synthetases that attach the unnatural amino acid to the tRNA molecules directly [54-57]. This allows bacteria or yeast to generate their own tRNA molecules, thus expanding the approach to large-scale applications. In one instance, bacterial hosts capable of biosynthesizing even the new amino acid have also been developed [58]. As this method continues to improve with respect to practicality and accessibility, it is certain to provide many new avenues for selective protein modification. 

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