Optimization of the medium composition of a biphasic production system for mycelial growth and spore production of Aschersonia placenta using response surface methodology

The culture media for mycelial growth and sporulation of the entomopathogenic fungus Aschersonia placenta were optimized using the response surface method (RSM). Interactions of medium components and the optimization of a biphasic production system were studied using Box-Behnken design (BBD) with three levels of three variables. Experimentation confirmed that the model developed based on RSM and BBD successfully predicted mycelia production (R2 = 0.9336) and conidia production (R2 = 0.9532). In the first phase, mycelial dry weight was highest (2.14 ± 0.17 g per 100 ml of culture, mean ± SE) when the concentrations (g/l) of glucose, vitamin B6, and MgSO4·7H2O were 31.4, 11.5, and 0.64, respectively. In the second phase, conidia production was highest (9.31 ± 0.48 × 107 spores per cm2) after 18 d of cultivation in the medium containing 33.8 g/l of millet, 1.11 g/l of KH2PO4, and 0.37 g/l of MgSO4. Mycelial and conidial yields were 3.6- and 10-fold greater, respectively, with the optimized media than with the non-optimized basal media. The results indicate that RSM and BBD methods are effective for increasing the production of A. placenta mycelia and conidia.

Graphical abstractDownload full-size imageHighlights► A biphasic system was used to increase conidial production by Aschersonia placenta. ► Media compositions were optimized using response surface methodology. ► Conidial production was substantially greater with optimized vs. nonoptimized media.