Enzymatic Process for the Carrageenolytic Bioconversion of Sulfated Polygalactans into beta-Neocarrabiose and 3,6-Anhydro-D-galactose

초록

Oligosaccharides and anhydro-sugars derived from carrageenan have great potential as functional foods and drugs showing various bioactivities, including antioxidant, anti-inflammatory, antiviral, antitumor, and cytotoxic activities. Although preparation of sulfated carrageenan oligosaccharides by chemical and enzymatic processes has been widely reported, preparation of nonsulfated beta-neocarrabiose (beta-NC2) and the rare sugar 3,6-anhydro-D-galactose (D-AHG) was not reported in the literature. Based on the carrageenan catabolic pathway in marine heterotrophic bacteria, an enzymatic process was designed and constructed with recombinant kappa-carrageenase, GH127/GH129 alpha-1,3 anhydrogalactosidase, and cell-free extract from marine carrageenolytic bacteria Colwellia echini A3T. The process consisted of three successive steps, namely, (i) depolymerization, (ii) desulfation, and (iii) monomerization, by which carrageenan oligosaccharides, beta-NC2, and D-AHG were obtained from kappa-carrageenan. Unlike the chemical process, enzymatic hydrolysis yields oligosaccharides with the desired degree of polymerization facilitates specific removal of sulfated groups, free of toxic byproducts, and avoids chemical modifications. The final optimized enzymatic process produced 0.52 g of beta-NC2 and 0.24 g of D-AHG from 1 g of kappa-carrageenan. The carrageenolytic process designed for the enzymatic hydrolysis of kappa- carrageenan can be scaled up for the mass production of bioactive carrageeno-oligosaccharides.

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