Enzymatic Preparation,Biological Activity And Applications Of Carrageenan Oligosaccharides

Carrageenans are sulfated galactans consisting of D-galactose residues linked by alternating?-1,4 and?-1,3 linkages which is a commercially important group in the cell walls of red seaweeds.The three most industrially exploited carrageenans,namely,?-,?-and?-carrageenan,are distinguished by different sulfate content.Carrageenan oligosaccharides,derived from carrageenan,have been reported to show potential antioxidant,anti-tumor,anti-viral,anti-clotting and inhibition of angiogenesis activities.A?-carrageenase-producing bacterium from Pseudoalteromonas sp.ASY5 was isolate by our laboratory in the previous work.The optimization of the enzymolysis technology of carrageenan was conducted and the enzyme liquid was obtained by the fermentation of the strain ASY5.Then the carrageen oligosaccharides of different average degree were obtained and the biology activity of them was studied.The main research results were listed as follows:First of all,the carrageenan oligosaccharides were obtained by enzymatic preparation,and used total sugar and reducing sugar content as an evaluation index to optimize hydrolysis conditions and the enzymatic hydrolysis products were analyzed using the method of thin-layer chromatography?TLC?and electrospray ionization-mass spectrometry?ESI-MS?.The results showed the optimal enzymatic hydrolysis conditions were that the substrate concentration,pH,reaction temperature,and shaking speed were 12 g/L,7.0,40°C,and 100rpm,respectively.The amount of reducing sugars yield increased from the beginning of 0.91mg/mL to 1.61 mg/mL,77%yield improved.The Km and Vmax values of the enzyme for?-carrageenan were 171.96 mg/mL and 0.925 mg·mL-1·min-1,respectively.In addition,the result of optimal process validation test could consistent with 20 L enlarge experiment,the enzymatic hydrolysate optimization was identified by thin-layer chromatography and mass spectrography,and it was shown that the main product was disaccharide.Furthermore,in vitro antioxidant activity and antimicrobial activities about 6 different average degree of polymerization of carrageenan oligosaccharides,which were degraded by Eucheuma poiysaccharide and refined carrageenan,were investigated.All of the six kinds of oligosaccharides were shown antioxidant capacity in a certain range of concentrations.ABTS radical scavenging ability and Fe²⁺chelating ability have shown good linear relationship with carrageenan oligosaccharides concentrations.For DPPH radical,OH radical and ABTS radical scavenging ability,the lower average degree of polymerization have shown the better scavenging effect.But the average degree of polymerization of 8 presents better Fe²⁺chelating ability.Overall,Eucheuma oligosaccharides and carrageenan oligosaccharides can be achieved with similar antioxidant activity.Unfortunately,six kinds of oligosaccharides did not exhibit inhibitory effect on five tested bacterias.Finally,tilapia fish were soaking in six kinds of oligosaccharides,firstly.And then the sensory evaluation,thiobarbituric acid value?TBA value?,meat pH were applied to as evaluation indexs.The optimal treatment group is about the average degree of polymerization of 6 carrageenan oligosaccharide?PD-6?.And the lower degrees of polymerization of oligosaccharides show a better preservation effect.The next step,tilapia fish were soaking in PD-6 solution about 0-10 mg/mL concentration with six kinds of indexs,sensory evaluation,pH,acid value,TBA value,TVB-N value and the total number of colonies,were evaluated.Finally to find that the concentration of 3 mg/mL about PD-6 solution has the best effect on tilapia preservation and could extend refrigerated shelf life to 1 or 2 days.