Enzymatical Preparation Of Biologically Active Oligogalacturonides From Pericarp

Biologically active oligogalacturonides(OGAs)were the first plant oligosaccharides to be discovered,and biologically active.As a new type of biologically active oligosaccharides,they have a brilliant and wide potentials in biotechnology.This research aims to the preparation of different degree of polymerization and saturation oligogalacturonides(OGAs)from citrous fruit peels hydrolyzed by pectinase and pectin lyase.Fermentation conditions of Aspergillus niger wz003 were investigated to improve the yield of highly active pectin lyase in this paper.The factors affecting polygalacturonase activity was also examined.The optimized fermentation medium was summarized below(g/L):wheat bran 60,cornmeal 40,yeast extract 20,carrot 12,CaCO₃ 10.After the inoculation with 8%(v/w,10⁶ cells/mL)A.niger wz003,the medium was cultivated at 30℃for 2 days (the original pH 7.0).The pectin lyase activity could reach 375.3 U / mL, 6.2 times higher than that under basic conditions,while the activity of polygalacturonase was reduced efficiently to 29.4 U / mL.Pectin from citrous fruit peels was extracted and then the optimum conditions for preparation of saturation and unsaturation oligogalacturonides were investigated by single factor and orthogonal tests. The monosaccharides after hydrolyzafion were fermented using yeast. Ethanol was added to precipitate polysaccharides.Finally,the pectinhydrolyzed liquid was separated using ultra-filtration to get oligogalacturonides with different degree of polymerization.The anti-bacterial activity of the pectic oligosaccharides was investigated.The results showed that the pectic oligosaccharides had more significant anti-bacterial effects towards the tested microbes than the native pectin in acid conditions.The oligosaccharides with the degree of polymerization 5-15 had the best anti-bacterial activity.Its minimum inhibition concentration(MIC)was 0.4--0.7%to Staphylococcus aureus, Escherichia coli and Bacillus subtilis.The effect of antibacterial activity was boosted up when the pectic oligosaccharides were combined with antiseptic chemicals.