Agro-industrial residues correspond to all the materials generated from activities that involve the transformation of both crops and livestock to obtain processed or semi-finished products. In Costa Rica, the primary sector of economy generates more than 6.3 trillion tons of organic residues per year. The daily generation of this residues pose environmental and economic problems. In recent years, biotechnological-based alternatives have emerged with the purpose of taking advantage of the high nutritional content of these residues to cultivate microorganisms capable of producing compounds with high demand at a commercial level. The present study evaluates six agro-industrial residues produced in Costa Rica, in order to growth Bacillus subtilis 168.  An optimization of the culture medium was carried out under a complete factorial design 23, where the variables evaluated were carbon, nitrogen and phosphorus sources. Molasses at 10% m/v, wheat bran at 0.5% m/v, and K2HPO4 at 0.01%, as a carbon, nitrogen, and phosphorus sources, respectively, were identified as optimal for the growth of Bacillus subtilis 168.