Cellobiose phosphorylase (EC 2.4.1.20, CBPase) is an enzyme that catalyzes the reversible phosphorolysis of cellobiose into α-D-glucose 1-phosphate (G-1-P) and D-glucose. As the acceptor specificity of the reverse reaction is broad, CBPase can synthesize hetero β-disaccharides from G-1-P and monosaccharides as acceptors. Here, in order to develop an efficient system for producing a rare β-disaccharide like 4-
O-β-D-glucopyranosyl-D-xylopyranose (GX) using CBPase, two attempts were examined. Firstly, the CBPase gene from
Cellvibrio gilvus was heterologously expressed as an intracellular enzyme using
Aspergillus oryzae. The recombinant CBPase was enclosed in the mycelia of the host cell by cold acetone treatment and prepared as a mycelial dry powder. Secondly, to facilitate the synthesis of GX by removing glucose from the reaction mixture, a commercial dry yeast was added to the reaction mixture. The powdered CBPase-yeast combined system produced an approximately 3.5 times higher yield of GX from cellobiose than the reaction without yeast.
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