Enzymatic Preparation Of Gracilaria Agaro-olgosaccharides And The Prebioticeffects On Lactobacillus

Agar was consisted of agarose and agaropectin,and it was used for the biochemical,clinical,pharmaceutical,food and other fields.Agaro-oligosaccharides,derived from agarose,had plenty of important biological activities,such as antioxidant activity,slowing down starch hydrolysis and easily absorption by human body,etc.In this study,different polymerization degrees of a gar oligosaccharides were hydrolyzed from Gracilaria agar by agarase and the antioxidant and hypolipidemic activity of Gracilaria agaro-oligosaccharides were measured.Then,after agaro-oligosaccharides was added to lactic acid bacteria,the experiments were conducted to investigate the growth promotion effects and the storage improvement effects at low temperature.Moreover,the gastrointestinal tolerance of lactic acid bacteria was also studied.At last,studies was carried out on the spray drying of probiotics and investigated whether the addition of agar oligosaccharide played a role in the viability of lactic acid bacteria during spray-drying.First of all,the agaro-oligosaccharide with different polymerization degrees was abtained by hydrolysis of gracilaria polysaccharide using agarase.Then,a further observation on antioxidant activity and cholesterol-lowering activity of the agaro-oligosaccharides in different polymerization degrees was implemented.The results showed that gracilaria agaro-oligosaccharides in polymerization?DP?3 degree possessed good free radical scavenging effect and cholesterol-lowering effect.DPPH clearance rate is 11.8%;the ABTS⁺clearance rate is 48.7%;the·OH clearance rate is 87.8%;the value of inhibition rate IC₅₀0 of pancreatic lipase is2.44 mg/mL;the value of inhibition rate IC₅₀0 of alpha amylase is 2.86 mg/mL.Secondly,the article made a observation on the effect which gracilaria agaro-oligosaccharides in different polymerization degrees acted on the lactic acid bacteria.The results showed that the right amount of gracilaria agaro-oligosaccharides can effectively promote the growth of lactic acid bacteria,including that the best amount of agaro-oligosaccharides for the growth of Bulgaria lactobacillus is 5 g/L DP3 and the best for Streptococcus thermophilus is3 g/L DP3.Furthermore,which agaro-oligosaccharides acted on the keep-alive effect of lactic acid bacteria under 4?storage was observed.The living bacterium number was 9.40 x 10⁸/mL in a storage of 21 days through added 5 g/L DP3 oligosaccharide into Bulgaria lactobacillus.Compared with matched group without added oligosaccharide,the living bacterium number increased by 36 times,while added 5 g/L DP3 oligosaccharide into Streptococcus thermophilus,the living bacterium number was 3.74×10⁹/mL in a storage of 21 days,the viable count was 2.6times higher than the control group.Experimental results of simulated gastric juice and inte stinal juice in vitro showed that agaro-oligosaccharide could significantly increase the tolerance of lactic acid bacteria in digestive tract,and the best amount of agaro-oligosaccharide in Bulgaria lactobacillus simulated gastric juice and intestinal juice respectively are 3 g/L,the degree of polymerization?DP?3 and 5 g/L,the degree of polymerization?DP?3,respectively;the best amount of agaro-oligosaccharide in Streptococcus thermophilus simulated gastric juice and intestinal juice respectively are 5 g/L,the degree of polymerization?DP?5 and 3 g/L,the degree of polymerization?DP?5,respectively.Finally,the added amount of gracilaria agaro-oligosaccharide in powder state was optimized in the preparation of lactic acid bacteria using the single factor method.In the preparation of Bulgaria lactobacillus,its survival rate reached 87.5%in the condition of 5 g/L of the agaro-oligosaccharide with polymerization?DP?3.Compared with the match group,its survival rate increased by 16.1%,while in the preparation of streptococcus thermophilus,its survival rate reached 79.8%in the condition of 5 g/L of the agaro-oligosaccharide with polymerization?DP?5.Compared with the match group,its survival rate increased by 15.4%.Then the spray and drying preparation process of the lactic acid bacteria in a dry powder state is optimized.Under the condition of optimum process,the Bulgaria lactobacillus and Streptococcus thermophilus was prepared to a dry powder state and their survival rates were 89.2%and 80.4%,respectively.