Algal-oligosaccharide-lysates prepared by two bacterial agarases stepwise hydrolyzed and their anti-oxidative properties

Abstract

Twenty algal-oligosaccharide-lysates (AOLs), derived from six agars and four algal polysaccharide extracts (APEs), were treated first with agarases with 250 or 500 agarase activity units (AU), which were produced from the agar-liquefying bacterial strain Pseudomonas vesicularis MA103, named MA103-agarases. The AOLs were then treated with agarases (250 or 500 AU) derived from the agar-softening bacterial strain Aeromonas salmonicida MAEF 108, named MAEF 108-agarases. Anti-oxidative properties of the AOLs were evaluated by five in vitro methods. The AOL obtained from the APE of Porphyra dentate, digested by 250 AU of MA 103-agarases, and by 250 AU of MAEF 108-agarases, designated as A250-Por, showed better results than the 19 other AOLs. This result is in accordance with the level of soluble total polyphenols (STP) of A250-Por, which was also higher than the remainder of the AOLs tested. The AOL derived from the APE of P. dentate, digested by 500 AU of MA103-agarases and then 500 AU of MAEF108-agarases, and designated as B500-Por, displayed the second highest data in four potential evaluation methods, except in H2O2 scavenging capacity. In this study, certain agars or APEs digested by specific agarases can present an increasing antioxidative capacity. These agars include Bitek agar, Agar powder, Bacteriological, Agar Bacteriological, and Guanghui agar, plus APEs of Gracilaria sp. and Monostroma nitidum decomposed stepwise by two agarases. The fraction of polyphenols (<1 kDa) that were derived from A250-Por showed anti-oxidative activities on α, α-diphenyl-β-picrylhydrazyl (DPPH) assay and reducing power determination, while the remaining four agar-lytic fractions obtained from A250-Por did not exhibit anti-oxidative activity. This phenomenon may suggest that anti-oxidative properties of AOLs originate in polyphenols. Algal-oligosaccharide-lysates may have potential use as a health food.