Fungal-mediated biotransformation of soybean supplemented with different cereal grains into a functional compound with antioxidant, anti-inflammatory and antitumoral activities

Abstract

The aim of this study was to select fungal strains and alternative substrates to increase the production of bioactive compounds by solid-state bioprocessing using soybeans. Initially, from a total of 17 fungi strains, R. oligosporus NRRL 3267, R. oligosporus NRRL 2710, and R. arrhizus NRRL 2582 were pre-selected for presenting the greatest antioxidant activities during soybean fermentation. The three Rhizopus strains were cultured in soybeans supplemented with different cereal grains (brown rice, wheat, corn, and oat) aiming to achieve a higher antioxidant activity. Soybean supplementation with brown rice increased the concentration of phenolic compounds (0.697 to 6.447 mg GAE g-1) significantly compared with the only use of soybean (1.792 to 3.10 mg GAE g-1), using R. oligosporus NRRL 2710. The improved fungal-mediated biotransformation process (R. oligosporus NRRL 2710 with soybeans and brown rice) generated an isoflavone aglycone-rich product, containing different antioxidant compounds, such as trans-cinnamic acid, gallic acid, myricetin, quercetin, and kaempferol. The fermented substrate also showed great potential to inhibit hyaluronidase enzyme (anti-inflammatory activity) and against CaCo-2 tumor cells growth (antitumor activity). The resulting compound could serve as a value-added food and/or feed ingredient and a rich source of bioactive compounds.