Characterisation and immunomodulatory activities of alkaline extracted and enzymatic modified arabinoxylans from corn bran

The relationship between the molecular structures of corn bran arabinoxylans (AXs) and their immune-modulating activities (the structure-activity relationship) was investigated. This study extracted AXs from corn bran using alkaline and developed AXs modification process using three types of endoxylanases from Thermomyces lanuginosus, Neocallimastix patriciarum and Penicillium funiculosum. Furthermore, the non-modified and modified AXs with different molecular structures were investigated with respect to their ability to modulate nitric oxide (NO) production in vitro as an indication of their immunomodulatory potential. From the corn bran, using alkaline treatment, the recovery rate of AX was up to 80% (dry matter basis) of total corn bran AX and the Mw distribution of extracted AXs was in the high Mw range (100KDa to 794KDa). Following enzymatic modification, more than 30% of AXs extracted were reduced to the lower Mw range (0.1KDa to 10KDa). In vitro studies showed that the extracted and modified AXs significantly elevated the level of NO synthesis by human U937 cells (p<0.05). The results also indicated there was an obvious dose-response effect for each of AX samples but the effective range over which they work is different. Modified AXs with higher portion of low Mw showed a significant lower optimum dose range than extracted AXs with higher portion of high Mw (p<0.05). The study suggested that the Mw distribution of AX is a determinant for their optimum dose on NO production by macrophage, thereby affects its immune-modulatory activity.