Microorganism Types and Fermentation Media Affect the Antioxidant Activity and Total Phenolic Content of Soybean Hulls — 63p — ¹Shishir Roka, ^1,2Anye Catharine Nora Drum, ¹Santosh Thapa, ¹Ruchita Bhattarai, ¹Bishnu Karki

¹Department of Biology and Microbiology, South Dakota State University, Brookings, SD, 57007, USA

²Federal Technological University of Parana, Dois Vizinhos, Brasil

Soybean hulls (SBH), an agro-industry byproduct, are produced in significant quantities but have limited applications. SBH is a rich source of antioxidants and polyphenols, which offer significant health advantages including lowering the incidence of cancer, diabetic symptoms, and cardiovascular illnesses, despite being predominantly employed as dietary filler in ruminant animal diets and fire logs. Growing interest is in developing methods to extract polyphenolic compounds with high antioxidant activities from naturally occurring substrates using green and sustainable mechanisms. Many studies have highlighted the phenolic and biological activity of different soybean products. Fermentation has emerged as a tool to boost the antioxidant activities of diverse substrates. Nevertheless, studies on the polyphenolic content and antioxidant activities of SBH extracts are scarce. In this study, finely ground SBH were mixed with water at 10% substrate-to-liquid ratio and inoculated separately with three different fungal strains (Aureobasidium pullulans, Trichoderma reesei, and Aspergillus niger) in submerged conditions. The fermentation was performed for five days at 30 °C and 150 rpm. Additionally, experiments were conducted by replacing water with cheese whey (a liquid byproduct of the dairy industry) to determine if the combination of cheese whey and SBH could enhance the total phenolic content and antioxidant activities. Samples were either separated into solids and liquid via centrifugation or collected directly without separation. The total phenolic content and antioxidant activities were determined in both cases. Results indicated that SBH with water exhibited significantly higher antioxidant activity than those fermented with cheese whey. Overall, fermentation elevated SBH antioxidant activity with A. niger yielding the highest level of antioxidant activities among the three micro-organisms. This study demonstrates the potential of SBH as a beneficial source of antioxidants when processed via fermentation, contributing to the development of sustainable and health-promoting applications for this plentiful byproduct.

South Dakota State University
Dr. Bishnu Karki