Riboflavin processing

S. j-iite /ti-based microbial riboflavin process in the year 2000. 

The enrichment program followed in the United States is (/) the enrichment of flour, bread, and degerminated and white rice using thiamin [59-43-8] C 2H y N O S, riboflavin [83-88-5] C2yH2QN4Na02P, niacin [59-67-6] CgH N02, and iron [7439-89-6]-, (2) the retention or restoration of thiamin, riboflavin, niacin, and iron in processed food cereals (J) the addition of vitamin D [67-97-0] to milk, fluid skimmed milk, and nonfat dry milk (4) the addition of vitamin A [68-26-8], C2qH2qO, to margarine, fluid skimmed milk, and nonfat dry milk (5) the addition of iodine [7553-56-2] to table salt and (6) the addition of fluoride [16984-48-8] to areas in which the water supply has a low fluoride content (74). 

Riboflavin is also made by aerobic culturing of Pichiaguilliermondii on a medium containing n-Q g-Q paraffins in a yield of 280.5 mg/L (53). A process employing Pichia yeasts, such as P. miso, P. miso Mogi, or P. mogii, in a medium containing a hydrocarbon as the carbon source, has been patented... 

Processes employing Toru/opsis yjlinus (55), Hansenu/apoljmorpha (56), Brevibacterium ammoniagenes (57), A.chromobactor butrii (58), Micrococcus lactis (59), Streptomjces testaceus (60), and others have also been patented. These procedures yield, at most, several hundred milligrams of riboflavin per Hter. 

Deazariboflavin. In 5-dea2ariboflavin (24), the N-5 of riboflavin is replaced by CH it serves as cofactor for several flavin-cataly2ed reactions (109). It was first synthesi2ed in 1970 (110) improved synthetic processes were reported later (111). 

Flavins — Riboflavin is first of all essential as a vitamin for humans and animals. FAD and FMN are coenzymes for more than 150 enzymes. Most of them catalyze redox processes involving transfers of one or two electrons. In addition to these well known and documented functions, FAD is a co-factor of photolyases, enzymes that repair UV-induced lesions of DNA, acting as photoreactivating enzymes that use the blue light as an energy source to initiate the reaction. The active form of FAD in photolyases is their two-electron reduced form, and it is essential for binding to DNA and for catalysis. Photolyases contain a second co-factor, either 8-hydroxy-7,8-didemethyl-5-deazariboflavin or methenyltetrahydrofolate. ... 

Stahmann, K.-P, Revuelta, J.L., and Seulberger, H., Three biotechnical processes using Ashbya gossypii, Candida famata and Bacillus subtilis compete with chemical riboflavin production, Appl. Microbiol. Biotechnol., 53, 509, 2000. 

Since many essential nutrients (e.g., monosaccharides, amino acids, and vitamins) are water-soluble, they have low oil/water partition coefficients, which would suggest poor absorption from the GIT. However, to ensure adequate uptake of these materials from food, the intestine has developed specialized absorption mechanisms that depend on membrane participation and require the compound to have a specific chemical structure. Since these processes are discussed in Chapter 4, we will not dwell on them here. This carrier transport mechanism is illustrated in Fig. 9C. Absorption by a specialized carrier mechanism (from the rat intestine) has been shown to exist for several agents used in cancer chemotherapy (5-fluorouracil and 5-bromouracil) [37,38], which may be considered false nutrients in that their chemical structures are very similar to essential nutrients for which the intestine has a specialized transport mechanism. It would be instructive to examine some studies concerned with riboflavin and ascorbic acid absorption in humans, as these illustrate how one may treat urine data to explore the mechanism of absorption. If a compound is... 

Fig. 10 Urinary excretion of riboflavin (A, B) and ascorbic acid (C, D) in humans as a function of oral dose. Graphs A and C illustrate the nonlinear dependence of absorption on dose, which is suggestive of a saturable specialized absorption process. Graphs B and D represent an alternative graph of the same data and illustrate the reduced absorption efficiency as the dose increases. (Graphs A and C based on data in Ref. 39 and graphs B and D based on data in Ref. 40.)...

Since long retention times are often applied in the anaerobic phase of the SBR, it can be concluded that reduction of many azo dyes is a relatively a slow process. Reactor studies indicate that, however, by using redox mediators, which are compounds that accelerate electron transfer from a primary electron donor (co-substrate) to a terminal electron acceptor (azo dye), azo dye reduction can be increased [39,40]. By this way, higher decolorization rates can be achieved in SBRs operated with a low hydraulic retention time [41,42]. Flavin enzyme cofactors, such as flavin adenide dinucleotide, flavin adenide mononucleotide, and riboflavin, as well as several quinone compounds, such as anthraquinone-2,6-disulfonate, anthraquinone-2,6-disulfonate, and lawsone, have been found as redox mediators [43—46]. 

Note that this overall reaction requires three coenzymes that we encountered as metabolites of vitamins in chapter 15 NAD+, derived from lucotiiuc acid or nicotinamide FAD, derived from riboflavin and coenzyme A(CoASH), derived from pantothenic acid. In the overall process, acetyl-SCoA is oxidized to two molecules of carbon dioxide with the release of CoASH. Both NAD+ and FAD are reduced to, respectively, NADH and FADH2. Note that one molecule of guanosine triphosphate, GTP, functionally equivalent to ATP, is generated in the process. 

Riboflavin undergoes a reversible and overall two-electron reduction process, in two overlapping one-electron steps. Both the final product and the one-electron reduction intermediate show acid base equlibria in the pH range 6-7. Thus a number of species take part in the redox process. Experimental investigation aimed at deriving the related equlibrium constants involves generation of the dihydro-... 

In general, vitamins appear to be at least as stable during UHT processing as during conventional pasteurization (Mehta 1980). Levels of the fat-soluble vitamins A, D, and E, as well as those of the water-soluble vitamins, riboflavin, nicotinic acid, pantothenic acid, and biotin in milk, are not decreased by UHT processing. Furthermore, no loss of... 

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