Why would Aspergillus Oryzae produce lactase when no lactose is present?
"Although beta-galactosidase is mainly produced for utilization in the hydrolysis of lactose in milk or whey, in natural systems this enzyme is also involved in the breakdown of galactan-based hemicelluloses. Wheat bran contains almost 30% hemicellulose, including considerable amounts of galactose residues (Salo and Kotilainen, 1970). Similar residues are presumably also present in spent grain (wheat). "


From the paper linked in the question.