Physicochemical Properties and Biological Activities of DEAE-Derivatized Sphingomonas Gellan

摘要

Physicochemical characteristics and biological activities of Sphingomonas gellan(S-gellan)were investigated.The S-gellan weight fractions of Glc and GlcUA were 0.45 and 0.25,respectively,and the molar ratio of Glc:Rha:GlcUA was approximately 4:2:3.The S-gellan was chemically derivatized with diethylaminoethyl chloride-HCI(DEAE-HCI),and the resulting modified S-gellan contained both positive and negative charges.The elemental and IR analyses were conducted to confirm the successful incorporation of DEAE groups into S-gellan.A large increase in nitrogen fraction was observed from the derivatized S-gellan by elemental analysis.The IR absorption bands induced by C-H,C-N,and C-O-C stretching were noticeable at 2950,1310-1380,and 1000-1150 cm~(-1),respectively,resulting from the DEAE substitution.The characteristic CH_3 and CH_2 peaks originated from the DEAE group were detected in the ~1H NMR spectrum of the derivatized S-gellan as well.The solubility of native S-gellan was improved almost twice from 40% to 75% after DEAE derivatization,while water holding capacity(WHC)drastically decreased from 10026% to 245%.Oil binding capacity(OBC)of S-gellan also significantly dropped from 1528% to 331% after the derivatization.The bile acid binding capacity of S-gellan was indirectly determined by measuring the holding capability of cholic acid inside the dialysis membrane(MWCO 12000-14000 Da).Once S-gellan was DEAE derivatized,there was substantial increase in the cholic acid retardation index(CRI).Up to 9 h of dialysis,the derivatized S-gellan released 29.3% less of cholic acid compared to the control group that did not contain S-gellan.From these results of the improved water solubility and stronger bile acid binding capacity,it would be suggested that the DEAE-derivatized S-gellan has more advantages than gellan itself for functional food applications.