Dermatophytes are keratinophilic and keratinolytic fungi capable of invading, colonizing and causing lesions in keratin-rich tissues, such as the epidermis, hair and nails. This fungal infection, called dermatophytosis, is one of the most prevalent zoonoses in the world with a high economic burden. Treatment with oral and topical antifungals, such as terbinafine and azoles, is essential to prevent transmission. However, fungal resistance to conventional treatment highlights the need to develop new therapeutic strategies for the management of this dermatopathy. In this context, delta-endotoxins produced by Bacillus thuringiensis have a mechanism of action that provides fungal control, representing a safe and effective alternative for the management of this infection. Therefore, the present study aimed to optimize the production and encapsulate delta-endotoxins with antifungal activity against pathogenic fungi associated with animal dermatophytosis. The concentration of reducing sugars in a culture medium based on forage cactus required for the development of Bacillus thuringiensis var. israelensis was evaluated. Based on the results obtained, a factorial design was performed to supplement the culture medium with minerals, aiming to optimize the production of delta-endotoxins with greater toxicity against Microsporum canis, Microsporum gypseum and Trichophyton mentagrophytes. The toxins produced in the optimized culture medium, based on forage cactus supplemented with MnSO₄ and K₂HPO₄, and in the Luria Bertani (LB) culture medium were evaluated for antifungal activity. For this purpose, the CLSI 38-A2 protocol was used to determine the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC). The delta-endotoxins produced in the palm-based culture medium showed greater toxicity compared to those produced in the LB medium, resulting in MICs of 0.06 to 0.13 µg-mL and 0.98 to 1.96 µg-mL, respectively. For the MFC, the values obtained were 0.06 to 0.26 µg-mL in the palm medium and 1.96 to 3.92 µg-mL in the LB medium. Thus, it is concluded that the use of alternative culture medium promotes the production of delta-endotoxins with greater antifungal activity, showing efficacy against the etiological agents M. canis, M. gypseum and Trichophyton mentagropytes.