Comparison of releasing bound phenolic acids from wheat bran by fermentation of three Aspergillus species

Wheat bran was fermented at 28 degrees C for 7days under 70% humidity by Aspergillus niger, Aspergillus oryzae and Aspergillus awamori. Total phenolic content (TPC) of the unfermented sample was 1531.5gg(-1) wheat bran. After the fermentation of Aspergillus awamori, Aspergillus oryzae and Aspergillus niger, TPC reached 5362.1, 7462.6 and 10707.5gg(-1), respectively. The antioxidant activity in the extractions of fermented wheat bran also increased significantly compared with the unfermented sample (P<0.05). Aspergillus niger showed the greatest capacity to release bound ferulic acid (416.6gg(-1)). Aspergillus oryzae and Aspergillus awamori had the advantages of releasing more chlorogenic acid (84.0gg(-1)) and syringic acid (142.3gg(-1)), respectively. The destructive effect of Aspergillus niger on wheat bran structure was the strongest, followed by that of Aspergillus oryzae. This effect of Aspergillus niger may be due to its higher cellulase, xylanase, arabinofuranosidase and -xylosidase activities. Besides, Aspergillus oryzae possessed higher -glucosidase activity, and Aspergillus awamori had higher -amylase and feruloyl esterase activities. Aspergillus niger may be the best to release bound phenolic acids in the three Aspergillus species. These will provide the helpful information for understanding mechanism of the fermentation by Aspergillus species releasing bound phenolic in wheat bran.