초록
<P>The synthesis of galactooligosaccharides (GOS) catalyzed by β-galactosidase from <I>Aspergillus oryzae</I> (Enzeco) was studied. Using 400 g/L of lactose and 15 U/mL, maximum GOS yield, measured by HPAEC-PAD, was 26.8% w/w of total carbohydrates, obtained at approximately 70% lactose conversion. No less than 17 carbohydrates were identified; the major transgalactosylation product was 6′<I>-O</I>-β-galactosyl-lactose, representing nearly one-third (in weight) of total GOS. In contrast with previous reports, the presence of at least five disaccharides was detected, which accounted for 40% of the total GOS at the point of maximum GOS concentration (allolactose and 6-galactobiose were the major products). <I>A. oryzae</I> β-galactosidase showed a preference to form β(1→6) bonds, followed by β(1→3) and β(1→4) linkages. Results were compared with those obtained with β-galactosidases from <I>Kluyveromyces lactis</I> and <I>Bacillus circulans.</I> The highest GOS yield and specific productivity were achieved with <I>B. circulans</I> β-galactosidase. The specificity of the linkages formed and distribution of di-, tri-, and higher GOS varied significantly among the three β-galactosidases.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jafcau/2013/jafcau.2013.61.issue-5/jf304354u/production/images/medium/jf-2012-04354u_0006.gif'></P>