Kinetic characterization of galacto‐oligosaccharide (GOS) synthesis by three commercially important β‐galactosidases

Abstract

Many β-galactosidases show large differences in galacto-oligosaccharide (GOS) production and lactose hydrolysis. In this study, a kinetic model is developed in which the effect of lactose, glucose, galactose, and oligosaccharides on the oNPG converting activity of various β-galactosidases is quantified. The use of oNPG as a competing substrate to lactose yields more information than can be obtained by examining only the conversion of lactose itself. The reaction rate with lactose or oligosaccharides as substrate relative to that with water as acceptor is much higher for the β-galactosidase of Bacillus circulans than the bgalactosidases of Aspergillus oryzae and Kluyveromyces lactis. In addition, the β-galactosidase of B.circulans has a high reaction rate with galactose as acceptor, in contrast to those of A. oryzae and K. lactis. The latter two are strongly inhibited by galactose. These differences explain why β-galactosidase of B. circulans gives higher yields in GOS production than other β-galactosidases. Many of the reaction rate constants for the β-galactosidase isoforms of B. circulans increase with increasing molecular weight of the isoform. This indicates that the largest isoform β-gal-A is most active in GOS production. However, its hydrolysis rate is also much higher than that of the other isoforms, which results in a faster hydrolysis of oligosaccharides as well.

Structural Dissection of the Active Site of Thermotoga maritima β-Galactosidase Identifies Key Residues for Transglycosylating Activity

“…Production of commercial GOS is carried out with enzymes from Bifidobacterium bifidum for β(1,3)-GOS, Cryptococcus laurentii or Bacillus circulans for β(1,4)-GOS and a mixture of Aspegillus oryzae and Streptococcus thermophilus for β(1,6)-GOS [33][34][35][36][37][38][39] . Production of GOS in high yield and with a broad chemical repertoire, are two major biotechnological challenges.…”

Continuous Production of Galacto-Oligosaccharides by an Enzyme Membrane Reactor Utilizing Free Enzymes

“…Industrial GOS production is carried out by GRAS- or QPS-certified enzymes that are usually of Aspergillus oryzae , Kluyveromyces lactis , or Bacillus circulans origin. The ß-galactosidase from Bacillus circulans has been favored by producers due to their thermostability and higher GOS yields compared to other commercial enzymes [ 9 , 10 , 11 ].…”

Reaction kinetics and galactooligosaccharide product profiles of the β-galactosidases from Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae

“…b-Galactosidases from the bacterium B. circulans, the yeast K. lactis and the fungus A. oryzae are used in the dairy industry because of their high transgalactosylation activity and different ranges of products (Cataldi, Campa, & De Benedetto, 2000;Neri et al, 2009;Warmerdam, Zisopoulos, Boom, & Janssen, 2014;Zhou & Chen, 2001). Other formulations are produced using two enzymes, e.g.…”