Yeast treatment

In addition to 9—12, several useful chiral carbonyl compounds have been obtained from the diols obtained by yeast treatment of the corresponding a-hydroxyketones. As a part of a study (2) on the substrate specificity of the multienzymic conversion shown in Eq. 2, a serie of racemic a-hydroxyketones has been prepared and submitted to the yeast treatment. The reduction process is stereospecific, but depending upon... 

Furthermore, yeast treatment of the a-acetoxy ketone 53, bearing two oxygen substituents ( ) at a and affords the carbinol 54 in 20 % yield, somewhat less than 10 % of the (2R) diastereoisomer, and 70 % of recovered starting material. From the carbinol 54, crystalline 55 is obtained, which may be converted through suitable manipulation of the protecting groups and ozonolysis, into A-deoxy-D-talo-hexose 56. The minor diastereoisomer similarly affords A-deoxy-D-xylo-hexose 57. Thus, in the yeast treatment of 53, as the results of the enzymic kinetic resolution, the (2S, 4S, 5R) diol 55, a carbohydrate-like chiral synthon, is accessible out of eight possible isomers. 

Similar carbohydrate-like chiral synthons are obtained by yeast reduction of the -acetoxyketones 58 and 59 ( ), bearing in 1,6 and 1,5 relationship, respectively, two masked carbonyl functions accessible chemoselectively with different reagents. The mode of reduction of 58 and 59 is, however, opposite. Whereas yeast treatment of 58 affords... 

The bioreduction of carbonyl compounds with reductases has been exploited for many years, especially in the case of ketones, with baker s yeast Saccharomyces cerevisiae) being the most popular biocatalyst [45]. For instance, yeast treatment of 3-chloropropiophenone affords the expected (lS)-3-chloro-l-phenylpropan-l-ol, which was treated with trifluorocresol in tertrahydrofuran in the presence of tri-phenylphosphine and diethyl azodicarboxylate at room temperature to give (3R)-l-chloro-3-phenyl-3-[4-(trifluoromethyl)phenoxy]propane and the later reaction with methylamine leads to (R)-fluoxetine that is an important serotonin uptake inhibitor (Scheme 10.19) [46]. 

If the smear shows the oval buds or pseudohyphae of yeast, treatment is initiated with amphotericin B 0.15% with or without flucytosine. If the ulcer foils to respond to this treatment, the most common alternative is fluconazole 1% applied topically in conjunction with 200 mg taken orally. 

Humanserumalbumin 582 amino acids with 17 disulphide bridges Albutein (Alpha Therapeutic Corporation) Yeast Treatment of hypovolemic shock Adjunct in haemodialysis... 

Uses in hair bleaches as an oxidizer and bleacher decolorizing and deodorizing oils, in electroplating, in making soluble starch reducer and retarder in photography in yeast treatment in analytical chemistry. ABCD. UCU A... 

With a special (usually oxidized or heated) odor, the result of treatment or aging ( d) Without film yeast involvement... 

Regulations specify a considerable Hst of additives and treatments which may be permitted under controlled limits and conditions. It is important to note that no wine receives mote than a few of these treatments, and many have none. For example, most grape musts ferment readily without additions, but some extra nitrogen source for the yeasts is occasionally beneficial. If some is requited, ammonium phosphate is the most commonly used. 

Other bacterial strains identified as biodegrading poly(vinyl alcohol) iaclude Flavobacterium (95) 2in.dFicinetobacter (96) and many others, as well as fungi, molds, and yeasts (97). Industrial evaluations at Du Pont (98) and Air Products (99) iadicate that over 90% of poly(vinyl alcohol) entering wastewater treatment plants is removed, and hence no environmental pollution is likely. 

Bakery Products. Sorbates are used in and/or on yeast-raised and chemically leavened bakery products. The internal use of sorbates in yeast-raised products at one-fourth the amount of calcium—sodium propionate that is normally added provides a shelf life equal to that of propionate without adversely affecting the yeast fermentation. Sorbates added at one-tenth the propionate level reduce the mix time by 30% (126). This internal treatment combined with an external spray of potassium sorbate can provide the same or an increased shelf life of pan breads, hamburger and hot-dog buns, English muffins, brown-and-serve roUs, and tortillas. The total sorbate useful in or on these baked goods ranges from 0.03 wt % for pan breads to 0.5 wt % for tortillas 0.2—0.3 wt % sorbic acid protects chemically leavened yellow and chocolate cakes (127). Emit-pie fillings and icings can be protected with 0.03—0.1 wt % sorbates. 

Mutation. For industrial appHcations, mutations are induced by x-rays, uv irradiation or chemicals (iiitrosoguanidine, EMS, MMS, etc). Mutant selections based on amino acid or nucleotide base analogue resistance or treatment with Nystatin or 2-deoxyglucose to select auxotrophs or temperature-sensitive mutations are easily carried out. Examples of useful mutants are strains of Candida membranefaciens, which produce L-threonine Hansenu/a anomala, which produces tryptophan or strains of Candida lipolytica that produce citric acid. An auxotrophic mutant of S. cerevisiae that requires leucine for growth has been produced for use in wine fermentations (see also Wine). This yeast produces only minimal quantities of isoamyl alcohol, a fusel oil fraction derived from leucine by the Ehrlich reaction (10,11). A mutant strain of bakers yeast with cold-sensitive metaboHsm shows increased stabiUty and has been marketed in Japan for use in doughs stored in the refrigerator (12). 

The quality of flour used ia the production of yeast-raised products depends on several factors, including the quality and characteristics of the wheat variety, the environmental conditions under which the wheat was grown, the skill of the miller in separating the endosperm of the wheat kernel from the germ and bran, and the proper treatment of the flour in the mill. 

The yeast pyruvate decarboxylase is rather specific with respect to the acyl moiety that is added to the aldehyde. Only a few 2-oxo acids can be used as acyl donors besides pyruvic-acid39. For example, treatment of benzaldehyde with 2-oxobutanoic acid and 2-oxopentanoic acid, respectively, and prewashed Saccharomyces cerevisiae gave the corresponding (/ )-acyloin derivatives in 15 25% yield with an enantiomeric excess >95%. 

Dynamic kinetic resolution of a-alkyl-P-keto ester was conducted successfully using biocatalysts. For example, baker s yeast gave selectively syn(2R, 3S)-product [29a] and the selectivity was enhanced by using selective inhibitor [29b] or heat treatment of the yeast [29c]. Organic solvent was used for stereochemical control of G. candidum [29d]. Plant cell cultures were used for reduction of 2-methyl-3-oxobu-tanoate and afforded antialcohol with Marchantia [29e,f] and syn-isomer with Glycine max [29f]. 

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