A metabolomics approach to evaluate post-fermentation enhancement of daidzein and genistein in a green okara extract

• Main Authors: Gupta, Sulagna, Chen, Wei Ning
• Other Authors: School of Chemical and Biomedical Engineering
• Format: Article
• Language: English
• Published: 2022
• Subjects: Engineering::Chemical engineering; Okara; Fermentation
• Online Access: https://hdl.handle.net/10356/159566
• Institution: Nanyang Technological University

BACKGROUND: Okara is a major agri-industrial by-product of the tofu and soymilk industries. Employing food-wastes as substrates for the green production of natural functional compounds is a recent trend that addresses the dual concepts of sustainable production and a zero-waste ecosystem. RESULTS: Extracts of unfermented okara and okara fermented with Rhizopus oligosporuswere obtained using ethanol as extraction solvent, coupled with ultrasound sonication for enhanced extraction. Fermented extracts yielded significantly better results for total phenolic content (TPC) and total flavonoid content (TFC) than unfermented extracts. A qualitative liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) analysis revealed a shift from glucoside forms to respective aglycone forms of the detected isoflavones, post-fermentation. Since the aglycone forms have been associated with numerous health benefits, a quantitative high-performance liquid chromatography (HPLC) analysis was performed. Fermented okara extracts had daidzein and genistein concentrations of 11.782±0.325 μgmL–1 and 10.125±1.028 μgmL–1, as opposed to that of 6.7±2.42 μgmL–1 and 4.55±0.316 μgmL–1 in raw okara extracts, respectively. Lastly, the detected isoflavones were mapped to their metabolic pathways, to understand the biochemical reactions triggered during the fermentation process. CONCLUSION: Fermented okara may be implemented as a sustainable solution for production of natural bioactive isoflavonoids genistein and daidzein.