Effect of filamentous fungi fermentation on the extractability and physicochemical properties of β-glucan in oat bran.

Oat bran was fermented by filamentous fungi to improve the extractability of β-glucan. Box-Behnken experimental design and response surface methodology were used to obtain the maximum extractability of β-glucan. Inoculum volume, fermentation temperature, and time were evaluated as three variables. Under optimal fermentation conditions, the extractability of β-glucan in oat bran increased to 45.57 ± 1.82% and 51.10 ± 2.32% by Aspergillus niger and Rhizopus oryzae, respectively. The extractability was about 3-fold of that before fermentation (16.86 ± 0.76%). Fermentation of oat bran by Aspergillus niger and Rhizopus oryzae reduced the molecular weight of the extracted β-glucan from 6.74 × 105 to 2.84 × 105 and 2.20 × 105  Da, respectively. Correspondingly, the apparent viscosity of the extracted β-glucan decreased after fermentation. But the increased extractability compensated for the reduced molecular weight in the formation of viscous solution. The molecular structure and cellotriosyl/cellotetraosyl ratio were not affected by filamentous fungi fermentation.