Four fractions having transferase enzyme activity were obtained from the broth of Aspergillus foetidus by ammonium sulphate precipitation and DEAE-cellulose chromatography. The optimum temperature was 60 degrees C and pH stability in the range 4-6 for fractions. The pH optima, heat sensitivity and kinetic parameters for the four fractions were however not the same. All four enzyme fractions could not utilise lactose and cellobiose to synthesise iso-oligosaccharide and showed different transferase activity on maltose and sucrose for synthesis of iso-oligosaccharides. HPLC iso-oligosaccharide product analysis of these transferase enzymes revealed that the four forms of enzymes are distinct, producing oligosaccharides like panose, kestose and nystose or acting as hydrolytic enzymes depending on the conditions. (C) 2000 Elsevier Science Ltd. All rights reserved.