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• Content of poorly soluble naringin substrate was increased by resin adsorption. • Resin adsorption improve naringin biotransformation efficiency. • Liter-scale hydrolysis of naringin at high concentration was performed. • The enzymatic product naringenin could be purified from the resin. Naringenin, a natural plant flavonoid found in citrus fruits, has been reported to exhibit a wide range of pharmacological functions, including anticancer, antioxidant, antiatherogenic, antithrombotic, and vasodilator activities. Naringenin can be produced from the naringinase (NGase)-catalyzed enzymatic hydrolysis of naringin. However, the poor solubility of naringin in aqueous systems considerably limits the efficiency of naringenin biocatalysis. In this work, a novel substrate adsorption system was proposed for naringin adsorption to increase the efficiency of naringin hydrolysis and naringenin production. Three Amberlite macroporous resins, namely, XAD-4, XAD-7HP and XAD-16, were investigated for their naringin adsorption capacities and effects on NGase hydrolysis. Results indicated that the physical properties of the resins played a critical role in naringin adsorption and naringenin enzymatic synthesis. Naringin hydrolysis was carried out using free and adsorbed substrates. The substrate adsorption strategy could increase the catalytic efficiency at a high naringin concentration. In addition, the reaction conditions for enzymatic naringenin synthesis were optimized, and naringenin was prepared at a liter scale with a high substrate concentration. These results suggested that substrate adsorption is a promising strategy to increase the enzymatic hydrolysis efficiency of naringenin in aqueous systems. [ABSTRACT FROM AUTHOR]

Naringinase plays a rather important role in reducing the bitterness of juice by hydrolyzing naringin. A novel extracellular naringinase was purified from Aspergillus oryzae 11250 cultured in the presence of orange peel. A 26.78-fold purification rate was achieved by salt-induced precipitation, followed by anion-exchange and gel filtration chromatography with 32% recovery and specific activity of 2194.62 units per mg protein (U/mg). The optimum pH and temperature for naringinase activity were 5.0 and 45 °C, respectively. This enzyme was stable at 30 °C for 5 h. The K m and V max of naringinase toward naringin determined by Lineweaver-Burk method were 1.60 ± 0.13 mM and 126.21 ± 5.52 μmol/(min mg), respectively. The enzyme activity was inhibited completely by Ag + at 10 mM. Naringinase is capable of hydrolyzing naringin, neohesperidin, and some other glycosides. A supplement of 6 U/mL of this naringinase in citrus juice sufficiently removed naringin to relieve the bitterness of citrus juice. These properties make the enzyme an ideal candidate for commercial application in the debitterization of orange juice. [ABSTRACT FROM AUTHOR]

Abstract: New rhamnolipids were obtained via the development of a synthesis procedure consisting of two biocatalyzed steps. In the first step, naringinase was used to introduce a primary alcohol function onto rhamnose by glycosylation of 1,3-propanediol. In the second step, immobilized lipase B from Candida antarctica catalyzed the esterification of the primary hydroxyl group with mono- and di-carboxylic fatty acids of increasing chain length (from C8 to C14). For the monoic acids, the initial rate and 24h yield decreased with increasing chain length. For the dioic acid, the number of carbon atoms of the acid did not influence these parameters. The new rhamnolipid obtained with tetradecanoic acid showed very good surface properties. At pH 5, it had a very low critical aggregation concentration of 1.70μM and it diminished water''s surface tension to 27.6mN/m. It was also able to form stable insoluble monolayers. On the other hand, the rhamnolipid formed with tetradecanedioic acid showed far less interesting surface properties. [Copyright &y& Elsevier]

Abstract: In this work, a biocatalytic system was chosen to enable the deglycosylation of natural glycosides in order to improve their biological activity. Naringinase, which has both alpha-l-rhamnosidase and beta-d-glucosidase activities, was the enzyme used. Naringin, the glycoside substrate used in this bioconversion, and its aglycone product naringenin are compounds with interesting pharmacological activities such as anti-oxidant and anti-inflammatory; naringenin also acts as an anti-carcinogenic and neuroprotective agent, demonstrating a high potential for use by the pharmaceutical industry. Sol–gel, an innovative technique performed in aqueous media, was developed for naringinase immobilization in lens-shaped particles. Different sol–gel precursors, including tetramethoxysilane (TMOS), methyltrimethoxysilane (MTS), 3-aminopropyltrimethoxysilane (APS) and diglycerylsilane (DGS) with different aging times were tested in five consecutive trials. The best results were obtained with TMOS and TMOS/DGS after 4h aging time and TMOS/glycerol and DGS at 14h aging time. The characterization of these matrices was performed with respect to their diameter, volume, naringin and naringenin partition coefficients, and the optimum temperature and pH for naringinase activity. The operational stability of the bioencapsulated naringinase in the selected sol–gel matrices was studied through successive reutilizations. The naringinase sol–gel matrix (TMOS, DGS and TMOS/DGS) deactivation studies followed the Sadana model. The matrix TMOS/glycerol showed a constant 100% residual activity after 50 consecutive runs. [Copyright &y& Elsevier]

Aspergillus niger MTCC 1344 was used to produce extracellular naringinase in a complex (molasses, yeast extract and salts) medium. An initial medium pH 4.5 and cultivation temperature 30 °C were optimal for enzyme production. Among various carbon and organic nitrogen sources used, molasses and peptone were the most effective for enzyme yield. The rate of enzyme production was enhanced when metal ions were added to the medium. Fermentation conditions are described which produced a higher rate of enzyme synthesis. An increase in initial sugar concentration from 6 to 10 g l-1 in the fermentation medium produced decreased naringinase synthesis while cell mass growth increased with the increase of sugar concentration. At a higher sugar level (10 g l-1) the production of cell mass decreased. [Copyright &y& Elsevier]