A multistep enzyme catalysis was successfully implemented to produce long-chain α,ω-dicarboxylic and ω-hydroxycarboxylic acids from renewable fatty acids and plant oils. Sebacic acid as well as ω-hydroxynonanoic acid and ω-hydroxytridec-11-enoic acid were produced from oleic and ricinoleic acid.

Ginsenosides are the principal components responsible for the pharmaceutical activities of ginseng. The minor ginsenosides, which are also pharmaceutically active, can be produced via the hydrolysis of the sugar moieties in the major ginsenosides using acid hydrolytic, heating, microbial, and enzymatic transformation techniques. The enzymatic method has a profound potential for ginsenoside transformation, owing to its high specificity, yield, and productivity, and this method is increasingly being recognized as a useful tool in structural modification and metabolism studies. In this article, the transformation methods of ginsenosides, the characterization of microbial glycosidases with ginsenoside hydrolyzing activities, and the enzymatic production of minor ginsenosides are reviewed. Moreover, the conversions of ginsenosides using cell extracts from food microorganisms and recombinant thermostable beta-D-glycosidases are proposed as feasible methods for use in industrial processes.

No abstract

D-Tagatose has attracted a great deal of attention in recent years due to its health benefits and similar properties to sucrose. D-Tagatose can be used as a low-calorie sweetener, as an intermediate for synthesis of other optically active compounds, and as an additive in detergent, cosmetic, and pharmaceutical formulation. Biotransformation of D-tagatose has been produced using several biocatalyst sources. Among the biocatalysts, L-arabinose isomerase has been mostly applied for D-tagatose production because of the industrial feasibility for the use of D-galactose as a substrate. In this article, the characterization of many L-arabinose isomerases and their D-tagatose production is compared. Protein engineering and immobilization of the enzyme for increasing the conversion rate of D-galactose to D-tagatose are also reviewed.

No abstract

The noncharacterized gene previously proposed as the D-tagatose 3-epimerase gene from Agrobacterium tumefaciens was cloned and expressed in Escherichia coli. The expressed enzyme was purified by three-step chromatography with a final specific activity of 8.89 U/mg. The molecular mass of the purified protein was estimated to be 132 kDa of four identical subunits. Mn 2؉ significantly increased the epimerization rate from D-fructose to D-psicose. The enzyme exhibited maximal activity at 50°C and pH 8.0 with Mn 2؉ . The turnover number (k cat ) and catalytic efficiency (k cat /K m ) of the enzyme for D-psicose were markedly higher than those for D-tagatose, suggesting that the enzyme is not D-tagatose 3-epimerase but D-psicose 3-epimerase. The equilibrium ratio between D-psicose and D-fructose was 32:68 at 30°C. D-Psicose was produced at 230 g/liter from 700-g/liter D-fructose at 50°C after 100 min, corresponding to a conversion yield of 32.9%.The International Society of Rare Sugars defines rare sugars as monosaccharides and their derivatives that rarely exist in nature. According to this definition, D-psicose is a rare sugar. Rare sugars have recently attracted much attention due to their many uses, including uses as low-calorie sweeteners and bulking agents (11,12,14,17,18), as immunosuppressants in allogeneic orthotopic liver transplantation in rats (6), as potential inhibitors of various glycosidases (20), in ischemiareperfusion injury of the rat liver (5), and in segmented neutrophil production without other detrimental clinical effects (21). The rare sugars can be made by microbial and enzymatic reactions with ketose epimerase, aldose isomerase, aldose reductase, and oxidoreductase. Bioproduction strategies for all rare sugars have been illustrated with ring form structures (4).D-Psicose, a carbon-3 epimer of D-fructose, is present in small quantities in commercial carbohydrate or agricultural products. This rare sugar is absorbed poorly in the digestive tract (19), has zero energy for growth, is a useful sweetener used as an aid for weight reduction (18), represses hepatic lipogenic enzyme activity (16), and is nontoxic (17). Even though few studies have investigated the ability of D-tagatose 3-epimerase to convert D-fructose into D-psicose (7-9, 22), only one enzyme source, D-tagatose 3-epimerase from Pseudomonas cichorii, has been used for D-psicose production (8). The enzyme was purified and characterized (8), and the D-tagatose 3-epimerase gene was then cloned on the basis of the Nterminal amino acid sequence of the purified D-tagatose 3-epimerase. The gene was expressed in Escherichia coli and then characterized (7).In this study, the noncharacterized gene previously proposed as the D-tagatose 3-epimerase gene from Agrobacterium tumefaciens was cloned and expressed in E. coli. Biochemical properties such as metal ions, pH, temperature, epimerization reactions, and kinetic parameters were investigated. Determination of the equilibrium ratio and bioconversion between D-fructose and D-psicose by the D-psic...

No abstract

No abstract