This study aimed to select lactic acid bacteria (LAB) strains based on their antagonistic activity and mycotoxin mitigation capacity, develop a biocompatible multistrain consortium, and evaluate its application for the fermentation of extruded wheat bran. The selected strains were assessed for biocompatibility, and a four-strain consortium comprising Lacticaseibacillus casei, Levilactobacillus brevis, Pediococcus acidilactici, and Latilactobacillus curvatus was established. The consortium was propagated in supplemented sour whey and subsequently applied to wheat bran fermentation. Compared with the two-strain formulations, the four-strain consortium reduced the total bacterial count by 1.6-fold and the yeast and mold count by 1.75-fold after 36 h of fermentation. The consortium also produced the most pronounced acidification of the substrate, reducing the pH from 5.65 to 3.82 and increasing titratable acidity from 0.20 to 4.40 °N (22.0-fold). In contrast, fermentation with the two-strain formulations reduced the pH to 4.02 ± 0.01, while titratable acidity increased by 20.5–20.6-fold. After 36 h of fermentation, the viable LAB count in the substrate fermented with the four-strain consortium reached 7.23 ± 0.11 log₁₀ CFU/g, compared with 6.23 ± 0.02 and 6.42 ± 0.01 log₁₀ CFU/g in the substrates fermented with the two-strain formulations. These findings indicate that the developed four-strain consortium represents a promising starter culture for wheat bran fermentation and highlight its potential for the valorization of cereal by-products into value-added feed material through LAB fermentation. All experiments were conducted in vitro, and the effectiveness of the proposed approach under animal feeding conditions requires further experimental validation.