Solid-State Fermentation of Agro-Industrial By-Products

The solid-state fermentation (SSF) of agro-industrial by-products such as okara, pomegranate peel, and cranberry pomace presents a sustainable approach to enhance the release of bioactive compounds. This study investigated the effects of different microbial cultures—<i>Rhizopus oligosporus<...

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Bibliographic Details
Main Authors: Yannick Erismann, Wolfram Manuel Brück, Wilfried Andlauer
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Nutraceuticals
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Online Access:https://www.mdpi.com/1661-3821/5/2/11
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Summary:The solid-state fermentation (SSF) of agro-industrial by-products such as okara, pomegranate peel, and cranberry pomace presents a sustainable approach to enhance the release of bioactive compounds. This study investigated the effects of different microbial cultures—<i>Rhizopus oligosporus</i>, <i>Aspergillus oryzae</i>, <i>Streptococcus thermophilus</i>, and a co-culture of <i>R. oligosporus</i> and <i>S. thermophilus</i>—on the bioconversion of bioactive compounds in 100% okara, okara with 2% pomegranate peel, and okara with 1% cranberry pomace. The objective was to assess whether co-culture fermentation with molds and <i>S. thermophilus</i> augments the release of bioactive compounds in okara-based fermentations through synergistic enzymatic activity. Over a period of 72 h, isoflavone transformation (daidzin, daidzein, genistin, and genistein), pH evolution, and water activity were assessed. The co-culture system exhibited improved bioconversion, leading to significant (<i>p</i> < 0.01) increases in daidzein and genistein in pure okara compared to the starting material. The highest polyphenol content (0.908 mg/g) and antioxidant capacity (24.9 mg Trolox eq/g) were recorded in 100% okara. However, pomegranate peel inhibited β-glucosidase activity, delaying the release of isoflavone aglycones. These findings confirm that co-culture fermentation is an effective strategy for enhancing the bioactive properties of okara-based fermentations. This facilitates the release of bioactive aglycones and supports the upcycling of agro-industrial by-products into functional food ingredients. Future research should focus on optimizing fermentation parameters to further enhance the release of bioactive compounds.
ISSN:1661-3821