Forced aeration promotes high production and productivity of infective conidia from Metarhizium robertsii in solid-state fermentation

Metarhizium genus is an important biological control agent. Most industrial conidia production processes are based on the use of plastic bags or containers containing similar to 1 kg of substrate. Static bioreactors, such as packed columns, trays, and plastic bags, are used for different scale conidia production. However, the effect of aeration mechanism on conidia production and quality has not been evaluated. Therefore, the productivity and quality of conidia produced in three types of bioreactors were evaluated. M. robertsii strain Xoch 8.1 was used to determine the effect of temperature and airflow rate on conidia production and quality. The productivity of viable conidia in the packed column bioreactor was up to 1.8 and 1.5 times higher than that obtained with tray and bag bioreactors, respectively. Conidial infectivity was similar for the three types of bioreactors. Forced convection aeration in the packed columns resulted in higher levels of conidia production and productivity without affecting their quality. This study shows that forced aeration in tubular bioreactor allows the highest conidia production and productivity; additionally, the forced aeration allows the on-line monitoring of the production of CO2 during the fermentation process, as a tool to associate this measurement to conidiation patterns.