Scale-Up of Duddingtonia flagrans Chlamydospores Production from Laboratory to Pilot-Scale Using a Solid-State Fermentation System

The fungus Duddingtonia flagrans is a biological control tool to reduce infective larvae of gastrointestinal nematode in pastures. To create a commercially available bioproduct based on a nematophagous fungus, an efficient mass production process should be developed that is able to guarantee a good predatory capacity and satisfactory production rates. In this work, solid-state fermentation (SSF) parameters were investigated to produce D. flagrans at pilot-scale. The results showed that the relative humidity was a critical factor to increase productivity and to reduce fermentation time. The best production conditions using a tray bioreactor were a relative humidity in the room at 90% for 2 days, and inoculation by sprinkling. The fermentation process was composed of 7 days under submerged fermentation to produce the inoculum and 7 more days of SSF in a tray bioreactor. The productivity reached was 4.96 × 10⁶ chlamydospores g^-1 of dry substrate day^-1, which is the highest productivity reported to date. The predatory capacity of the chlamydospores produced using this process was 91%. Also, a statistical control process analysis was applied, finding that the process presents stability in the biological activity, yield, and final moisture content of the substrate between batches. Finally, the operational expenses (OPEX) based on the use of the heating and humidification system were estimated, given a final cost of 0.20 USD g^-1 of the fermented substrate.

Production of conidia of the entomopathogenic fungus Metarhizium anisopliae ICB 425 in a tray bioreactor

The use of Metarhizium anisopliae as a bioinsecticide is steeply increasing worldwide. However, to reduce the production costs, it is necessary to develop sophisticated techniques for conidia production. This work aimed to use a tray bioreactor to produce conidia of M. anisopliae ICB-425 in long rice and find the limiting bed depth in which the production is still viable. Experiments have been carried out to assess the influence of the air temperature and relative humidity on the spore concentration in order to determine the limiting temperature. Two scales of bioreactors in plastic packages have been used, containing 10 and 500 g of rice, and the results were similar. In the tray bioreactor, the bed depths of 2, 4 and 6 cm have been used, corresponding to the dry rice weights of 1, 2 and 3 kg, respectively, and the results were similar to the ones in plastic packages. A one-phase heat transfer model has been used to foresee the maximum temperature within the bed and the results agreed fairly well with the experimental ones. Using the model, a bed depth of 7 cm was found to be the limit for the tray bioreactor. The results obtained are very promising for the mass production of conidia of M. anisopliae at lower costs and with more effective control.