Method for obtaining a biologically active botulinum toxin, which comprises the steps of: (a) obtaining a culture medium that is substantially free of animal derived products and comprises 4-8% by weight of a soy derivative, and cultivating a Clostridium botulinum bacteria in the culture medium； (b) provide a fermentation medium that is substantially free of animal derived products and comprises: (i) 4-8% by weight of a soy derivative, (ii) 0-3% by weight of an extract of yeast, and (iii) 1-2% by weight glucose； (c) fermenting the Clostridium botulinum bacteria in the fermentation medium under conditions that allow the production of a botulinum toxin, including: (i) carrying out the fermentation stage at a pH between 5.0 and 5.5 after initial cell growth, (ii) carry out the fermentation stage for between 45 hours and 75 hours, (iii) carry out the fermentation stage at a temperature between 33 ° C and 36 ° C, and (iv) carry out the stage of fermentation in an anaerobic atmosphere； and (d) recovering a biologically active botulinum toxin from the fermentation medium, in which the recovery stage is a purification procedure free of animal products.Método para obtener una toxina botulínica biológicamente activa, que comprende las etapas de: (a) obtener un medio de cultivo que está sustancialmente libre de productos derivados de animales y comprende el 4-8% en peso de un derivado de soja, y cultivar una bacteria Clostridium botulinum en el medio de cultivo； (b) proporcionar un medio de fermentación que está sustancialmente libre de productos derivados de animales y comprende: (i) el 4-8% en peso de un derivado de soja, (ii) el 0-3% en peso de un extracto de levadura, y (iii) el 1-2% en peso de glucosa； (c) fermentar la bacteria Clostridium botulinum en el medio de fermentación en condiciones que permiten la producción de una toxina botulínica, incluyendo: (i) llevar a cabo la etapa de fermentación a un pH de entre 5,0 y 5,5 tras el crecimiento celular inicial, (ii) llevar
