Conditions to optimize mass production of Metarhizium anisopliae (Metschn.) Sorokin 1883 in different substrates

Lorena Barra-Bucarei1, Pedro Vergara2, and Amparo Cortes3
One of the best alternatives to reduce the amount of chemical insecticides released into the environment is biological agents. Metarhizium anisopliae (Metschn.) Sorokin 1883 (Hypocreales: Clavicipitaceae) is an entomopathogenic fungus with great potential as a biological pesticide to biologically control pests. However, the relatively high cost of the substrate needed for its mass production system increases product price and discourages its use. The objective of this study was to optimize the mass production conditions of M. anisopliae for use as a biological control agent using two solid substrates, new parboiled rice (NPR) and recycled parboiled rice (RPR). Conidial production was optimized by the response surface methodology (RSM). The effects of the temperature, time, and molasses variables and the interactions between them (conidia g-1) were determined. For the NPR substrate, it was determined that the significant variables were time and temperature, and the interactions were temperature ´ molasses and temperature ´ time. For the RPR substrate, the significant variables were temperature and time, and the interactions were time ´ molasses and temperature ´ time. Both substrates obtained the highest industrial yields at 25 °C for a period of 20 d. Given that the percentage of molasses was not critical for yields, it is recommended that it be set at 5% to reduce costs. Finally, it was possible to use the RPR substrate from the M. anisopliae production itself as an alternative to solid substrate; mean industrial performance (conidia g-1) was higher than values obtained with NPR and at a lower cost.
Keywords: Biological control, entomopathogenic fungi, mass production, optimization, response surface methodology.
1Instituto de Investigaciones Agropecuarias, INIA Quilamapu, Av. Vicente Méndez 515, Chillán, Chile.
2Universidad Tecnológica Metropolitana, Facultad de Ingeniería, Dieciocho 161, Santiago, Chile.
3Universitat de Barcelona, Facultat de Farmàcia, Joan XXIII 27, 08028, Barcelona, España.