Biochemical characterization of a novel α-L-fucosidase from Pedobacter sp. and its application in synthesis of 3'-fucosyllactose and 2'-fucosyllactose.

Fucosyllactoses have gained much attention owing to their multiple functions, including prebiotic, immune, gut, and cognition benefits. In this study, human milk oligosaccharide (HMO) 2'-fucosyllactose (α-L-Fuc-(1,2)-D-Galβ-1,4-Glu, 2'FL) and its isomer 3'-fucosyllactose (α-L-Fuc-(1,3)-D-Galβ-1,4-Glu, 3'FL) with potential prebiotic effect were synthesized efficiently by a novel recombinant α-L-fucosidase. An α-L-fucosidase gene (PbFuc) from Pedobacter sp. CAU209 was successfully cloned and expressed in Escherichia coli (E. coli). The deduced amino acid sequence shared the highest identity of 36.8% with the amino sequences of other reported α-L-fucosidases. The purified α-L-fucosidase (PbFuc) had a molecular mass of 50 kDa. The enzyme exhibited specific activity (26.3 U/mg) towards 4-nitrophenyl-α-L-fucopyranoside (pNP-FUC), 3'FL (8.9 U/mg), and 2'FL (3.4 U/mg). It showed the highest activity at pH 5.0 and 35 °C, respectively. PbFuc catalyzed the synthesis of 3'FL and 2'FL through a transglycosylation reaction using pNP-FUC as donor and lactose as acceptor, and total conversion ratio was up to 85% at the optimized reaction conditions. The synthesized mixture of 2'FL and 3'FL promoted the growth of Lactobacillus delbrueckii subsp. bulgaricus NRRL B-548, L. casei subsp. casei NRRL B-1922, L. casei subsp. casei AS 1.2435, and Bifidobacterium longum NRRL B-41409. However, the growths of E. coli ATCC 11775, S. enterica AS 1.1552, L. monocytogenes CICC 21635, and S. aureus AS 1.1861 were not stimulated by the mixture of 2'FL and 3'FL. Overall, our findings suggest that PbFuc possesses a great potential for the specific synthesis of fucosylated compounds.Key Points• A novel α-L-fucosidase (PbFuc) from Pedobacter sp. was cloned and expressed.• PbFuc showed the highest hydrolysis activity at pH 5.0 and 35 °C, respectively.• It was used for synthesis of 3'-fucosyllactose (3'FL) and 2'-fucosyllactose (2'FL).• The mixture of 3'FL and 2'FL promoted the growth of some Lactobacillus sp. and Bifidobacteria sp.