Sakaguchi flasks (500 ml) containing 100 ml of the basal medium with glucose were sterilized by autoclaving at 121 ◦C
for 20 min,aseptically inoculated with spores from a fresh agar slant, and then incubated on a reciprocal shaker at 30 ◦C for 24 h (150 oscillations/min; amplitude 70 mm).