4-Nitrophenyl-α-L-fucopyranoside

2′-Fucosyllactose (2′-FL) is one of the nutrient ingredients in human milk, which has various beneficial health effects. α-l-fucosidase is a biotechnological tool for 2′-FL preparation. Here, a novel and efficient α-l-fucosidase OUC-Jdch16 from the fucoidan-digesting strain Flavobacterium algicola 12076 was heterologously expressed and applied to produce 2′-FL in vitro. OUC-Jdch16 belongs to glycoside hydrolases (GH) family 29 and exhibits the highest 4-nitrophenyl-α-l-fucopyranoside-hydrolyzing activity at 25°C and pH 6.0. OUC-Jdch16 could catalyze the synthesis of 2′-FL via transferring the fucosyl residue from pNP-α-fucose to lactose. Under the optimal transfucosylation conditions, the yield of the transfucosylation product reached 84.82% and 92.15% (mol/mol) from pNP-α-fucose within 48 h and 120 h, respectively. Moreover, OUC-Jdch16 was capable of transferring the fucosyl residue to other glycosyl receptors with the generation of novel fucosylated compounds. This study demonstrated that OUC-Jdch16 could be a promising tool to prepare 2′-FL and other novel glycosides.

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.