Obtaining a Functional Food Ingredient Based on Oat Bran Fermented by Lacticaseibacillus casei

Using agro-industrial by-products as substrates for the growth of probiotic strains is an alternative for increasing their added value. This study aimed to design and optimize the production of a functional ingredient (FI) with L. casei immobilized in oat bran (OB). A Box–Behnken experimental design was applied to study the effects of hydration level (HL), milk whey supplementation, and initial inoculum concentration (IC) on probiotic growth. According to the design, systems containing 1 g of OB, supplemented with 0 to 0.4 g of whey/g OB and HL from 5 to 20 mL of water/g OB, were sterilized and inoculated with an IC in the range of 5.61 to 7.61 log (CFU/g OB). After incubation at 37 °C for 24 h with orbital shaking, the systems were washed, centrifuged, and vacuum-dried. Independent variables were optimized to maximize cell count and growth and minimize cell count after drying. The optimal conditions found were for HL: 15 mL of water/g OB; for whey: 0.3 g/g OB; and for the IC: 5.79 log (CFU/g OB), which were recorded within the studied range. This result demonstrates the feasibility of optimizing the production of a dried FI based on OB as a substrate for L. casei.