Targeted Fermentation of Agro-Industrial By-Products

The fermentation of agro-industrial by-products such as okara, pomegranate peel, and cranberry pomace using solid-state fermentation (SSF) offers a sustainable approach to enhancing bioactive compound release. This study examined the effects of different microbial cultures—Rhizopus oligosporus, Aspergillus oryzae, Streptococcus thermophilus, and a co-culture of R. oligosporus and S. thermophilus—on the bioconversion of bioactive compounds in 100% okara, okara with 2% pomegranate peel, and okara with 1% cranberry pomace. Over 72 h, isoflavone transformation (daidzin, daidzein, genistin, and genistein), pH evolution, and water activity were assessed. The co-culture system demonstrated superior bioconversion, leading to increases of 752% and 1050% in daidzein and genistein, respectively, in pure okara. The highest polyphenol content (0.908 mg/g) and antioxidant capacity (24.9 mg Trolox eq/g) were observed in 100% okara. Pomegranate peel inhibited β-glucosidase activity, slowing liberation of isoflavone aglycons. These findings highlight co-culture fermentation as an effective strategy for enhancing the bioactive potential of okara-based formulations, , by releasing highly bioactive aglycones and promoting the upcycling of agro-industrial by-products into functional food ingredients. Future research should focus on optimizing fermentation parameters to further enhance bioactive compound release.