Corn cobs were obtained from
local agricultural fields around Iksan, South Korea. Cobs were washed thoroughly
and dried in sunlight, then ground to 2 mm particle size using a sterile blender.
The prepared material was soaked in deionized water at 80°C for 12–48 h to increase
porosity and bulk density. Then the material was pressed to remove the
water and dried in the shade. Five grams of the dry substrate was placed in a
250 mL Erlenmeyer flask and a nutrient salt solution (2 mL) containing (g/L):
KH2PO4, 2; NH4NO3, 5; NaCl, 1; and MgSO4·7H2O, 1 (9, 10) was added by adjusting
different pH (pH 1–8). Initial moisture content was adjusted to 50% (w/w)
with distilled water. Flask contents were mixed thoroughly, autoclaved at 121°C
for 20 min, and cooled to room temperature. The flask was inoculated with the
M. purpureus KACC 42430 spore suspension (6 × 105 spores/mL) and incubated
at 30°C and 50% humidity for 7 d. Unless otherwise indicated, these conditions
were maintained throughout the experiment. All experiments were conducted in
triplicate and means ± standard deviations are reported