alpha-Rhamnosidase activity in the marine isolate Novosphingobium sp PP1Y and its use in the bioconversion of flavonoids

Crude protein extracts of Novosphingobium sp. PP1Y, a microorganism isolated from polluted marine waters in Pozzuoli (Italy), were analyzed for the presence of glycosidase activities. Particular attention was devoted to a alpha-L-rhamnosidase activity able to hydrolyze several flavonoids of interest for the pharmaceutical and food industries. This activity had an alkaline pH optimum and a moderate tolerance to the presence of organic solvents, appealing features for its possible biotechnological uses. An increase of the a-L-rhamnosidase activity in PPI V crude extracts was induced by adding naringin to the growth medium, suggesting the possibility to use material from Citrus industrial waste to induce the glycosidase activity expressed by strain PPlY and produce simultaneously high-added-value molecules from the hydrolysis of their flavonoids. In order to investigate on the enzymatic mechanism of PPlY a-L-rhamnosidase activity, hydrolysis products of PNP-alpha-L-rhamnopyranoside were analyzed by H-1-NMR experiments. The kinetic behaviour clearly indicated an inverting mechanism of hydrolysis for this novel enzymatic activity. (C) 2014 Elsevier B.V. All rights reserved.