Optimal beta-galactosidases for producing high-titer 3,6-anhydro-L-galactose from red-algal agarobiose

초록

3,6-Anhydro-L-galactose (L-AHG) is a monomeric sugar in agarose derived from red macroalgae. Owing to its various physiological activities such as anti-inflammation, moisturizing, skin whitening, anti-colon cancer, and anti-cariogenicity, L-AHG is a potential functional ingredient. In our previous study, a simple and efficient two-step L-AHG production process was designed for high-titer L-AHG production, where a single enzyme was used after the liquefaction of agarose by acid prehydrolysis. However, the enzyme used did not completely hydrolyze agarobiose (AB). Therefore, in this study, for the efficient hydrolysis of AB and the high-titer production of L-AHG, various beta-galactosidases belonging to glycoside hydrolase families 1, 2, 35, and 42 were compared by testing their substrate specificities and kinetic parameters. Among the five beta-galactosidases, Bga42A, originating from Bifidobacterium longum ssp. infantis ATCC 15,697, showed the highest substrate specificity. Consequently, the two-step process utilizing Bga42A as a single enzyme resulted in a high-titer production of L-AHG at 85.9 g/L, demonstrating the feasibility of producing L-AHG from agarose.

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