*Article* **Characterization of a Biofilm Bioreactor Designed for the Single-Step Production of Aerial Conidia and Oosporein by** *Beauveria bassiana* **PQ2**

**Héctor Raziel Lara-Juache 1, José Guadalupe Ávila-Hernández 2, Luis Víctor Rodríguez-Durán 3,\* , Mariela Ramona Michel 1, Jorge Enrique Wong-Paz 1, Diana Beatriz Muñiz-Márquez 1, Fabiola Veana 1, Mayra Aguilar-Zárate <sup>4</sup> , Juan Alberto Ascacio-Valdés <sup>5</sup> and Pedro Aguilar-Zárate 1,\***


**Abstract:** *Beauveria bassiana* is an entomopathogenic fungus that is used for the biological control of different agricultural pest insects. *B. bassiana* is traditionally cultivated in submerged fermentation and solid-state fermentation systems to obtain secondary metabolites with antifungal activity and infective spores. This work presents the design and characterization of a new laboratory-scale biofilm bioreactor for the simultaneous production of oosporein and aerial conidia by *B. bassiana* PQ2. The reactor was built with materials available in a conventional laboratory. *KLa* was determined at different air flows (1.5–2.5 L/min) by two different methods in the liquid phase and in the exhaust gases. The obtained values showed that an air flow of 2.5 L/min is sufficient to ensure adequate aeration to produce aerial conidia and secondary metabolites by *B. bassiana*. Under the conditions studied, a concentration of 183 mg oosporein per liter and 1.24 <sup>×</sup> <sup>10</sup><sup>9</sup> spores per gram of support was obtained at 168 h of culture. These results indicate that the biofilm bioreactor represents a viable alternative for the production of products for biological control from *B. bassiana*.

**Keywords:** *Beauveria bassiana*; biological control; oosporein; spore production
