VITAMINS

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This monograph outlines several microbial processes, which were recently developed in our laboratory, for large-scale production of vitamin-related compounds. A new optical resolution process of racemic pantolactone to obtain the D-enantiomer, a chiral bilding block for the commercial production of D-pantothenic acid, was developed. ln this optical resolution, a novel fungal enzyme, lactonase, which was found in Fusarium oxysporum, is used. The enzyme catalyzes D-enantiomer-speific hydrolysis of pantolactone. Thus, DL-pantolactone is easily separated to D-pantoic acid and L-pantolactone. A novel bioreduction system, in which Escherichia coli transformant cells co-expressing genes of an NAD(P)H-dependent carbonyl reductase and glucose dehydrogenase as a cofactor regenerator are used as a catalyst, was developed for asymmetric reduction of prochiral carbonyl compounds to chiral alcohols. The system, in which an NADPH-dependent carbonyl reductase from Candida magnoliae or Sporobolomyces salmonicolor is used, has been successfully used for large-scale production of ethyl 4-chloro-3-hydroxybutanoate stereoisomers. This bioreduction system has been shown to be applicable to the production of many other useful chiral alcohols, by replacing the carbonyl reductase gene with other appropriate reductase genes. Mycelia of a filamentous fungus Mortierella alpina 1S-4 are potential source of triacylglycerols rich in arachidonic acid. Under the optimal culture conditions for large-scale production, the oil accumulated in the fungal mycelia reaches 500〜600 mg/g dry mycelia (13.5〜20 g/I). The oil contains 30〜70% arachidonic acid in the total fatty acids. Mutant strains derived from M. alpina 1S-4 and defective in desaturases or elongases of arachidonic acid biosynthesis are useful for the production of oils containing unique polyunsaturated fatty acids of n-3, n-9 or other families. Washed cells of several lactic acid bacteria well transform linoleic acid to the corresponding conjugated acids (CLAs)such as c9,t11-and t9,t11-CLAs. Hydration of linoleic acid to form the corresponding 10-hydroxyoctadecenoic acids and dehydration of the hydroxy acids to CLAs were suggested to be involved in this transformation.

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Some nutritional aspects on vitamin B_6 and its related compounds, which were obtained in our laboratory, were reviewed. With the combinations of analytical methods, which were novelly developed by ourselves and feeding exneriment using rats, bioavailability of some vitamin B_6 derivatives was evaluated by means of some criteria well-established already. ln order to search the metabolic reaction critically affected upon vitamin B_6 deficiency, biosynthesis of the poly-unsaturated fatty acids and methionine metabolism were scrutinized by measuring enzyme activities and monitoring the concentrational changes in some intermediates. lt was suggested that S-adenosylmethionine and S-adenosylhomocysteine, which are intermediates of methionine metabolism, were very important metabolites impaired under vitamin B_6 deficient conditions.

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