초록
<P><SMALL>l</SMALL>-Ascorbic acid (<SMALL>l</SMALL>-AA) is an essential nutrient that is extremely unstable and cannot be synthesized by the human body. Therefore, attempts have been performed to develop biologically active <SMALL>l</SMALL>-AA derivatives with improved stability. This work presents a facile, scalable, and efficient enzymatic transgalactosylation of lactose to <SMALL>l</SMALL>-AA using β-glucosidase (TN0602) from <I>Thermotoga naphthophila</I> RKU-10. β-Glucosidase TN0602 displays high transgalactosylation activity at pH 5.0, 75 °C, and <SMALL>l</SMALL>-AA/lactose ratio of 2:1 to form a novel <SMALL>l</SMALL>-AA derivative [2-<I>O</I>-β-<SMALL>d</SMALL>-galactopyranosyl-<SMALL>l</SMALL>-ascorbic acid (<SMALL>l</SMALL>-AA-Gal)] with a maximal productivity of 138.88 mmol L<SUP>–1</SUP> in 12 h, which is higher than most reports of enzymatic synthesis of <SMALL>l</SMALL>-AA-α-glucoside. Synthetic <SMALL>l</SMALL>-AA-Gal retains most <SMALL>l</SMALL>-AA antioxidant capability and presents dramatically higher stability than <SMALL>l</SMALL>-AA in an oxidative environment (Cu<SUP>2+</SUP>). In conclusion, this work reports a new way to valorize dairy waste lactose into a novel molecule <SMALL>l</SMALL>-AA-Gal, which could be a promising <SMALL>l</SMALL>-AA derivative to be used in a wide range of applications.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jafcau/2017/jafcau.2017.65.issue-41/acs.jafc.7b03173/production/images/medium/jf-2017-031739_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jf7b03173'>ACS Electronic Supporting Info</A></P>