Molecular identification of Staphylococcus xylosus MAK2, a new α-l-rhamnosidase producer

Naringinase Biosynthesis by Aspergillus niger on an Optimized Medium Containing Red Grapefruit Albedo

This study aimed to develop a method of naringinase biosynthesis by Aspergillus niger KMS on an optimized culture medium. The concentration of the six medium components in shake flasks was optimized by the Box and Wilson factor gradient method. Naringinase's substrate, naringin, powdered albedo, flavedo, and red grapefruit segment membranes were used to stimulate naringinase biosynthesis. Rhamnose was chosen as the carbon source, while the nitrogen source was yeast extract and sodium nitrate. Naringinase biosynthesis was most favorable in the culture medium with the following composition (g 100 mL): 3.332-NaNO₃; 3.427-yeast extract; 0.184-KH₂PO₄; 0.855-red grapefruit albedo; 0.168-naringin; 2.789-rhamnose. The obtained Aspergillus niger KMS culture fluid was concentrated, thereby precipitating the protein. As a result, a naringinase preparation with high activity, equal to 816 µmol × min^-1 × g^-1, was obtained.

Purification and characterization of a naringinase from Aspergillus aculeatus JMUdb058

A naringinase from Aspergillus aculeatus JMUdb058 was purified, identified, and characterized. This naringinase had a molecular mass (MW) of 348 kDa and contained four subunits with MWs of 100, 95, 84, and 69 kDa. Mass spectrometric analysis revealed that the three larger subunits were β-D-glucosidases and that the smallest subunit was an α-L-rhamnosidase. The naringinase and its α-L-rhamnosidase and β-D-glucosidase subunits all had optimal activities at approximately pH 4 and 50 °C, and they were stable between pH 3 and 6 and below 50 °C. This naringinase was able to hydrolyze naringin, aesculin, and some other glycosides. The enzyme complex had a K(m) value of 0.11 mM and a k(cat)/K(m) ratio of 14,034 s(-1) mM(-1) for total naringinase. Its α-L-rhamnosidase and β-D-glucosidase subunits had K(m) values of 0.23 and 0.53 mM, respectively, and k(cat)/K(m) ratios of 14,146 and 7733 s(-1) mM(-1), respectively. These results provide in-depth insight into the structure of the naringinase complex and the hydrolyses of naringin and other glycosides.

Updates on naringinase: structural and biotechnological aspects

Naringinases has attracted a great deal of attention in recent years due to its hydrolytic activities which include the production of rhamnose, and prunin and debittering of citrus fruit juices. While this enzyme is widely distributed in fungi, its production from bacterial sources is less commonly known. Fungal naringinase are very important as they are used industrially in large amounts and have been extensively studied during the past decade. In this article, production of bacterial naringinase and potential biotechnological applications are discussed. Bacterial rhamnosidases are exotype enzymes that hydrolyse terminal non-reducing α-L-rhamnosyl groups from α-L-rhamnose containing polysaccharides and glycosides. Structurally, they are classified into family 78 of glycoside hydrolases and characterized by the presence of Asp567 and Glu841 in their active site. Optimization of fermentation conditions and enzyme engineering will allow the development of improved rhamnosidases for advancing suggested industrial applications.