Release characteristic and mechanism of bound polyphenols from insoluble dietary fiber of navel orange peel via mixed solid-state fermentation with Trichoderma reesei and Aspergillus niger
Puyou Xue, Wang Liao, Yi Chen, Jianhua Xie, Xinxin Chang, Guanyi Peng, Qing Huang, Yudan Wang, Nian X. Sun, Qiang Yu
Abstract
Dietary fiber (DF) is a carrier of abundant bound polyphenols (BP). The present work was to investigate the release characteristic and mechanism of BP from the insoluble dietary fiber of navel orange peel (NOP-IDF) by mixed solid-state fermentation (SSF) with Trichoderma reesei and Aspergillus niger. The optimized fermentation conditions were set as follows: inoculation ratio of T. reesei to A. niger 3:1, delayed inoculation time 28 h and initial pH 6.5. The compositions of BP were identified and quantified by UPLC-ESI-QTOF-MS/MS and HPLC-ESI-QQQ-MS/MS, then the biotransformation pathways were partially speculated. Moreover, cellulase, xylanase and β-glucosidase activities were strongly correlated with the BP content. The SEM showed the cell wall and the crystalline structure of the NOP-IDF was effectively decomposed. Furthermore, mixed SSF significantly enhanced in vitro antioxidant activities of BP. In summary, our study demonstrated that mixed SSF was a feasible method for the BP release.