AbstractWheat bran (WB) was subjected to processing with Aureobasidium pullulans (A. pullulans) under selected conditions to partially break down the xylan into soluble products (mainly feruloyl oligosaccharides, FOs). The objective of this study was to investigate the technology for one-step fermentation of WB by A. pullulans without melanin secretion to produce FOs as well as to determine their structural features and antioxidant activity. Initial pH, inoculation quantity, and fermentation temperature were found to be efficient for releasing FOs according to the Plackett-Burman design (PBD). Based on the D-Optimal design, a yield of 904 nmol of FOs / L of fermentation broth was obtained under optimal conditions of initial pH 6.0, inoculation quantity 4.50%, and fermentation temperature 29 oC. Purification of FOs was performed with alcohol precipitation and Amberlite XAD-2. GC, IR, and ESI-MS demonstrated that FOs consist of feruloyl arabinosyl xylopentose (FAX5, Mw986), feruloyl arabinosyl xylotetraose (FAX4, Mw854), feruloyl arabinosyl xylotriose (FAX3, Mw722), and feruloyl arabinosyl xylobiose (FAX2, Mw590). Increasing the FO dose led to increased activity of SOD and GSH-Px in serum of S180 tumor-bearing mice, while the level of MDA was reduced, thus improving its in vivo antioxidant activity.