The alginate lyase from Isoptericola halotolerans CGMCC 5336 as a new tool for the production of alginate oligosaccharides with guluronic acid as reducing end

Abstract

Alginate oligosaccharides are depolymerization products of alginate by enzymatic degradation or physicochemical treatments. Alginate lyase has received great interests due to its use in oligosaccharide preparation. The substrate specificity of alginate lyase directly determines the type and degree of polymerization of alginate oligosaccharides. In this paper, the degradation products of Alginate lyase from Isoptericola halotolerans CGMCC 5336 were size-fractionated by gel filtration chromatography and the fractions were characterized by TLC, HPLC, MS and 1H NMR spectroscopy. The Mw values for these fractions were 352, 528, 704 Da which represented di-, tri-, and tetrasaccharide fragments, respectively. The 1H NMR revealed that the non-reducing ends of these oligosaccharides were 4-deoxy-L-erythro-hex-4-enepyranosyluronate and the reducing ends of these oligosaccharides were all guluronic acid. Therefore, it is believed that the alginate lyase produced by Isoptericola halotolerans CGMCC 5336 was capable of performing β elimination on guluronic acid residue so that low molecular weight oligosaccharides with guluronic acid on the reducing end could be obtained in this way.