Improved beta-carotene and lycopene production by Blakeslea trispora with ultrasonic treatment in submerged fermentation

Response surface methodology (RSM) based on Box-Behnken design (BBD) was employed to investigate the effect of ultrasonic treatment on b-carotene production by Blakeslea trispora. The optimized strategy involved exposing three-day-old mycelial cultures to ultrasonic treatment at a fixed frequency of 20 kHz, power of 491 W, treatment time of 3 min, working time of 3 s, and rest time of 5:8 s, repeated four times at a 24-h interval. Mycelium growth was not significantly promoted under ultrasonic stimulation; however, the glucose metabolism increased by about 10%, the average size of the aggregates significantly decreased, and the uptake rate of imidazole into cells was increased about 2.5-fold. After a 6-d culture, the technique produced 173 mg=L of b-carotene and 82 mg=L of lycopene, which represented an increase of nearly 40:7% and 52:7%, respectively, over the yields obtained in cultures without ultrasonic treatment