AFM studies of water-soluble wheat arabinoxylans - Effects of esterase treatment

The degradation products of water-soluble wheat arabinoxylans treated with Aspergillus niger ferulic acid esterase (FAEA-able to cleave 5,5′- and 8-O-4′-ferulic acid dimers) have been characterised by atomic force microscopy (AFM) and size exclusion chromatography. The AFM images of arabinoxylans confirmed that a small proportion (∼15%) of the population of arabinoxylan molecules contain xylan-based branches attached to the xylan-based backbone. Treatment with FAEA reduced the contour length of the molecules suggesting that certain dimeric ferulic acid linkages may play a previously unconfirmed role in the elongation of arabinoxylans. Overnight treatment with FAEA led to a reduction in the density of branches suggesting that they may also be linked to the backbone through phenolic linkages.