A comparative study of the regioselectivity of the β-galactosidases from Kluyveromyces lactis and Bacillus circulans in the enzymatic synthesis of N-Acetyl-lactosamine in aqueous media

• Published in: Biotechnology progress Vol. 27; no. 2; pp. 386 - 394
• Main Authors: Bridiau, Nicolas, Maugard, Thierry
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.03.2011; Wiley
• Subjects: Acetylglucosamine - metabolism; Amino Sugars - biosynthesis; Amino Sugars - metabolism; Bacillus - enzymology; Bacillus circulans; beta-Galactosidase - metabolism; Biochemistry; Biochemistry, Molecular Biology; Bioconversions. Hemisynthesis; Biological and medical sciences; Biotechnology; enzymatic synthesis; Fundamental and applied biological sciences. Psychology; Kluyveromyces - enzymology; Kluyveromyces lactis; Life Sciences; Methods. Procedures. Technologies; N-acetyl-lactosamine; regioselectivity; Substrate Specificity; transgalactosylation; Water; β-galactosidase from Bacillus circulans; β-galactosidase from Kluyveromyces lactis; Ascomycota; Kluyveromyces marxianus var. lactis; Enzymatic synthesis; Yeast; Bacillus circulans; Regioselectivity; Enzyme; Bacillaceae; Fungi; Glycosylases; Bacillales; Aqueous medium; Glycosidases; Bacteria; Hydrolases; Comparative study; β-Galactosidase
• ISSN: 8756-7938; 1520-6033; 1520-6033
• DOI: 10.1002/btpr.542

The enzymatic synthesis of N‐acetyl‐lactosamine (LacNAc) was studied in aqueous media with high substrate concentrations using the transgalactosylation of N‐acetyl‐D‐glucosamine (GlcNAc), starting from lactose as a galactosyl donor. The efficiency and regioselectivity of the β‐galactosidases from Kluyveromyces lactis (KlβGal) and Bacillus circulans (BcβGal) were compared. The reaction was optimized by varying the experimental conditions (pH, catalytic activity concentration, and mass concentration ratio of the substrates), which enhanced the synthesis yields with both enzymes and especially with BcβGal. BcβGal catalyzed the formation of the maximal LacNAc concentration obtained (101 mM or 39 g L−1, corresponding to a yield of 11% on the basis of GlcNAc conversion), after 5 h at pH 6.5 and for a substrate mass concentration ratio of 1. This enzyme also gave an optimal synthesis yield of about 17.5%. No change in regioselectivity was observed when using KlβGal, whereas the regioselectivity of BcβGal proved to be subject to variations, the 1–4 and 1–6 linkages being favored under kinetic and thermodynamic control conditions, respectively. Finally, it was demonstrated that the N‐acetyl‐allolactosamine synthesized during the GlcNAc transgalactosylation catalyzed by BcβGal was a thermodynamic product and did not result from a chemical and/or enzymatic isomerization of LacNAc. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011