Production of 3,6-anhydro-l-galactose from agarose by agarolytic enzymes of Saccharophagus degradans 2-40

Saccharophagus degradans 2-40 is capable of hydrolyzing agarose, a red macroalgae-derived polymer, into d-galactose and 3,6-anhydro-l-galactose (L-AHG). Its agarase system is receiving much attention because it can be used to produce fermentable sugar from agarose. L-AHG is commercially unavailable and is considered a rare sugar with a high value. In this study, cells grown on agarose, agar or red macroalgae biomass were found to have a significantly higher agarase activity and AHG-generating activity than those grown on glucose or galactose. From agar-grown cells, both the volumetric activities of agarases and AHG generation in the cell-free lysate were much higher than in the extracellular fraction. Based on the analyses of the enzyme reaction products, from the reaction with the crude enzymes from cell-free lysate, neoagarobiose with a degree of polymerization (DP) 2 appeared to be the only major product in the initial reaction period, but sugars with DPs 2, 4 and 6 were found to be all predominantly produced by the extracellular enzymes in the initial reaction period. Quantitative analysis of AHG using gas chromatography–mass spectrometry with a derivatization step was also found to be highly reproducible and reliable. These results will be useful for producing L-AHG as a rare sugar to investigate its metabolic fate and commercial utilization.