Hidefumi Yoshii

Large-scale preparation of (S)-ethyl 3-hydroxybutanoate with a high enantiomeric excess through baker's yeast-mediated bioreduction

Abstract Large-scale preparation of ( S )-ethyl 3-hydroxybutanoate (E 3-HB), an important chiral starting material, by bakers yeast-mediated bloreduction of ethyl acetoacetate was investigated. In preliminary studies, we found that the procedure using ethanol as an energy source for the bioreduction, which we developed recently, was better than that using carbohydrate for large-scale preparation, as the cells were inactivated faster with carbohydrate than ethanol. Both the yield and the optical purity of the product were considerably improved by applying the fed-batch operation to the yeast-mediated bioreduction using ethanol as an energy source. In this method, the concentrations of ethyl acetoacetate and ethanol were maintained during the reaction at less than 1 mM and about 200 mM, respectively. Finally, large-scale preparation of ( S )-E 3-HB was effectively performed using a bubble-column reactor with 10 l of medium, and the final reaction medium contained 6% (w/w) ( S )-E 3-HB with > 99% enantiomeric excess. Thus, a new scaled-up method based on the use of ethanol as the energy source was devised for bakers yeast-mediated bioreduction.

Effects of water and alcohol on the formation of inclusion complexes of d-limonene and cyclodextrins

Abstract Systematic studies have been carried out on the role of water and alcohol in the formation of inclusion complexes between d-limonene and α-, β- and γ-cyclodextrin (CD) by a micro-aqueous method. The inclusion complex was barely formed at zero water content for all CDs. Above the specific water content for each CD, formation of the inclusion complex correlated well with an equation which was derived on the autocatalytic assumption for the inclusion phenomenon. The inclusion complex correlated well with an equation which was derived on the autocatalytic assumption for the inclusion phrnomenon. The minimum water content, which was defined as 1% of the maximum concentration of the inclusion complex formed, coincided with the number of water molecules inside the cavity of the CD. In the presence of ethanol, a significant amount of the inclusion complex was formed for β- and γ-CD/limonene systems, particularly at lower moisture content. However, for α-CD the inclusion fraction decreased significantly i...

NAD(P)H regeneration using ethanol as an energy source in baker's yeast-mediated bioreduction

Abstract A scheme for NAD(P)H regeneration from the corresponding oxidized form through the oxidative pathway of ethanol in bakers yeast cells was studied. Bakers yeast-mediated bioreduction of carbonyl compounds coupled with the oxidative pathway of ethanol is efficient and clean compared with the earlier procedure using carbohydrates as the energy source. To study NADH regeneration, the bioreduction of acetol catalyzed by NADH-dependent carbonyl-reducing enzymes was examined by using ethanol or acetate as the energy source under several aeration conditions, including an anaerobic environment. The results suggested that NAD+ formed on the reduction of the carbonyl group was mainly regenerated as NADH through alcoholic oxidation into acetate. NADPH regeneration was then studied in the same manner by examining the bioreduction of ethyl acetoacetate catalyzed by NADPH-dependent carbonyl-reducing enzymes. The results suggested that NADPH was regenerated through acetate oxidation into carbon dioxide. Thus, a total scheme for NAD(P)H regeneration using ethanol as the energy source, coupled with bioreduction, was proposed.

Oxidation stability of eicosapentaenoic and docosahexaenoic acid included in cyclodextrins

We have proposed a novel method for complexing of the ω-3 polyunsaturated fatty acids (PUFA), such as eicosapentaenoic and docosahexaenoic acids, with cyclodextrin as dry powders by a twin-screw kneader. The effect of various oxidation conditions on powdery PUFA were investigated. Further, the powdery PUFA developed was employed in the preparation of fish meal as a functional sea food paste.

Large-scale preparation of (R)-1,2-propanediol through baker's yeast-mediated bioreduction

Abstract A procedure for the preparation of ( R )-1,2-propanediol on a large scale by bakers yeast-mediated bioreduction of acetol using ethanol as an energy source is reported. The bioreduction, catalyzed by NADH-dependent oxidoreductase, was effectively performed using a bubble-column reactor with fed-batch operation. When the reactor with 10 l of medium was bubbled at an aeration rate of 3 l /min, the final reaction medium contained 4 %(w/w) ( R )-1,2-propanediol with >98% enantiomeric excess.

Quantitative Analysis by X-Ray Diffraction of the Inclusion Complex Formed by d-Limonene in a β-Cyclodextrin/Maltodextrin Mixed Powder.

The level of the inclusion complex between β-Cyclodextrin (β-CD) and d-Limonene in a pure β-CD and β-CD/maltodextrin mixed powder was measured by X-ray diffraction. The relative integral intensity at 2θ=5-7° and 11-12° correlated well with the molar fraction of d-Limonene to the total moles of β-CD and the maltodextrin mixture. Solid state (13)C-CP/MAS NMR results correlated well with those by X-ray diffraction.

A Short-Cut Method for Estimating l -Menthol Retention Included in Cyclodextrin During Drying a Single Drop

Good taste and flavor of the spray-dried powder products are the most important quality factors. In the present study, molecular encapsulation in cyclodextrin has been applied to prevent the loss of hydrophobic flavor compounds during drying. We have also proposed a new short-cut method for estimating flavor retention. We have applied this method to calculate the final retention of l-menthol encapsulated in a blend of β-cyclodextrin and maltodextrin during drying of a single droplet.

Improvement of l-Menthol Retention by Cyclodextrin During Drying

Various kinds of liquid foods have been dried in powder form by spray drying. The key technique in drying is to prevent the loss of volatile components in the food liquid. In this study, a molecular encapsulation method using cyclodextrins was used to improve the retention of hydrophobic flavor components during drying of a single droplet. Significant improvement of the 1-menthol retention was observed under various drying conditions. Numerical calculations based on the selective diffusion hypothesis could estimate well the final retention of l-menthol under various concentrations of cyclodextrin and maltodextrin.

Effect of Water and Alcohol on the Formation of Inclusion Complex between Cyclodextrins and d-Limonene by Twin Screw Kneader

To enhance the storage stability of essential oils such as d-limonene, the molecular inclusion complex powder of d-limonene in α- or β-cyclodextrin was made by using a twin screw kneader. The influence of water and alcohol content on the formation of the inclusion complex was studied in comparison with the inclusion complex by the micro-aqueous method. There were many differences in the quantity of the inclusion complex between the two methods, particularly at a low water content. For α-cyclodextrin, the addition of alcohol inhibited the formation of the inclusion complexes.

NAD(P)H Regeneration in Yeast Cells Using Ethanol as Energy Source

Reduced nicotinamide cofactors, NAD(P)H, are regenerated from NAD(P)+ through the pathway for ethanol oxidation in baker’s yeast, Saccharomyces cerevisiae, that is coupled with bioreductions of carbonyl compounds. In this paper, the relationship between the ability using ethanol as energy source for the NAD(P)H regeneration and the culture condition on oxygen absorption rate was examined. The cells grown under the anaerobic condition could hardly use ethanol as energy source and those abilities increased with increasing the rate of oxygen absorption under the culture condition.