Bioprocess Valorization of Brazilian Agro-Industrial Wastes for Enzyme Synthesis in Protease Production

Proteases are key biocatalysts widely applied in the food, pharmaceutical, detergent, and environmental industries. One of the most costly steps in large-scale enzyme production is the preparation of the culture medium, making agro-industrial wastes attractive as low-cost nutrient sources and potential inducers. The non-conventional yeast Yarrowia lipolytica stands out in bioprocess engineering due to its high secretion capacity, GRAS status, and ability to metabolize diverse industrial residues. In this study, Brazilian agro-industrial by-products, namely Corn steep liquor (CSL), brewer’s yeast residue (BYR), and okara, were evaluated as alternative nitrogen sources for protease production by Y. lipolytica IMUFRJ 50678. Enzyme activity was quantified by the azocasein method at optimized conditions (40 °C, 40 min, pH 5 and 8). After an initial exploratory screening (n = 1), brewer’s yeast residue (BYR) and okara were identified as promising candidates for protease production. These preliminary findings guided subsequent experiments performed in biological triplicate (n = 3), which confirmed the reproducibility and comparative performance of these substrates, showing higher acid protease (AXP) activity in the BYR medium ((5.4 ± 0.3) U/mL), whereas alkaline protease (AEP) activities were comparable between the BYR ((8.4 ± 0.6) U/mL) and okara ((7.5 ± 0.9) U/mL) media. CSL was associated with higher lipase activity ((11.7 ± 0.9) × 103 U/L), while esterase activity was higher in the BYR medium. These findings indicate that agro-industrial residues, particularly BYR and okara, can serve as effective nitrogen sources for protease production by Y. lipolytica IMUFRJ 50678, supporting their use in waste valorization and sustainable bioprocesses.