Preparation of bioactive neoagaroligosaccharides through hydrolysis of Gracilaria lemaneiformis agar: A comparative study

Hydrolysis of Gracilaria lemaneiformis agar by beta-agarase was compared with HCl hydrolysis. The results showed that optimum catalysis conditions for the beta-agarase were pH 7.0 at 45 degrees C. Mass spectroscopy, thin-layer chromatography and GPC results showed that the polymerization degrees of the hydrolysis products by the beta-agarase were mainly four, six and eight( more specific than the hydrolysate by HCl). The enzymatic degradation products of agar were distinctly different from those of HCl hydrolysis in the ratios among galactose and 3,6-anhydro-galactose and sulfate group contents. The NMR spectrometry proved that the products of beta-agarase were neoagaroligosaccharides, which was not found in the agarolytic products by HCl. The neoagarotetraose inhibited tyrosinase activity competitively with the K-I value of 16.0 mg/ml. Hydroxyl radical-scavenging ability of neoagaroligosaccharides was much greater than that of agar HCl hydrolysate. This work suggests that neoagaroligosaccharide products produced by our beta-agarase could be more effective in function than products from acid hydrolysis. (C) 2017 Elsevier Ltd. All rights reserved.