Okara and Brewer's Spent Grain (BSG), the food by-products generated during soybean and beer production, respectively, are two of the many food processing side streams that are suitable for human consumption but often discarded. Okara and BSG offer good amounts of both macro and micronutrients. More importantly, they are an exceptional source of proteins. Solid-state fermentation was used to enhance the bioavailability of their intrinsic nutrients. In this study, eight unique strains of Aspergillus Oryzae were used to ferment both Okara and BSG. Subsequently, various quantitative and qualitative analyses were conducted to determine the Total Polyphenolic Content (TPC) and Total Flavonoids Content (TFC) of the fermented biomasses. TPC and TFC were determined via spectroscopic analysis. The microbial fermentation of Okara by Black Koji resulted in the highest increase of TPC and TFC (5- and 13-fold respectively), compared to the control Okara. Meanwhile for BSG, the microbial fermentation by M-1 resulted in the highest increase of TPC in BSG (7-fold).