| Ultrasound is physics energy. Under the condition of low intensity and proper frequency, cavitation will be come into being, which give birth to surge and whirlpool. And part and temporarily negative suppress will be formed in liquid which produce non-stabilization vacuole and bladder. When those vacuole and bladder is closed, it will produce fierce wave and make pressure aggrandizement to thousands of atmospheric pressure around liquid, which will destroy gravitation adsorption among many substance or molecule. Power of slender cavitation destroying cell is very little and may produce tiny injure in the face of cell, cell wall breaking partly, which have an increase of cell membrane penetrability, and the cell membrane allows substance within to leave and that outside to enter the cell easily. So it strengthens matter transport and accelerates cell metabolism and target outcome biosynthesize. In this thesis, low frequency effecting growth and second metabolize of Ecemothecium ashbyii are researched, aim to cast about for different stimulation manner effect fermentation of E. ashbyii and provide some reference for ultrasound application in fermentation industry.The main research contents and results are as follows:Firstly, ultrasound effecting growth basic rule of E. ashbyii was investigated. Ultrasonic power known and frequency being 18,20,24,28,30 kHz respectively were load during the fermentation of E. ashbyii . All of the media were stimulated once 12 h, and treatment time was 30 min including 30 s working and 30 s resting time in turns. Several key biochemical parameters related to cell growth were measured. The result of the present show the all of the given different frequency of ultrasonic treatment could promote mycelium growth, at the same time also improve output of riboflavin, and the optimum frequency was about 24 kHz. After 24 kHz ultrasonic incontinuous treatments, the fermentation time was shortened by 36 hours and productivity rate of riboflavin was increased by about 2 times compared with the control groups. Secondly, during the different growth phase, ultrasonic of 24 kHz effecting riboflavin biosynthesize was investigated. It was found that at the phase of mycelium growth, because ultrasonic treatments promote mycelium quantity accumulate; the outcome of riboflavin was increased. It was significant difference; at the phase of riboflavin biosynthesize, owing to ultrasonic stimulation promote riboflavin secrete to outside and keep riboflavin from feedback second metabolize, it was great significantdifference.Thirdly, at the phase of riboflavin biosynthesize, ultrasonic treatment at different time effecting riboflavin biosynthesize was investigated. Until the fermentation time was 14 h, ultrasonic stimulation promote evidently riboflavin secrete to outside. The likelihood is that before 104 h, an outcome of riboflavin was not enough to withdrawn riboflavin biosynthesize. Along with fermentation processing, a lot of riboflavin was produced within cell and begin to withdrawn riboflavin biosynthesize. Ultrasonic loaded could promote riboflavin secrete to outside and enhance riboflavin output.Fourthly, after, in the broth, ultrasonic was treated, riboflavin was released into the broth. But following the fermentation time was coming, within cell riboflavin was biosynthesize and content of offspring was increasingly increased, at the same time, offspring in the broth could be adsorbed by cell wall. So riboflavin biosynthesize was restrained again. From 104 h to 112 h, ultrasonic treatment should be loaded every 1.5 h.Lastly, a HPLC method was presented for simultaneous determination of pyruvate during ultrasonic stimulation. It was found that ultrasonic could give birth to pyruvate change, at the same time, concentration of pyruvate change relation to dry weight of mycelium and content of riboflavin. It showed that ultrasonic treatment might effect TCA cycle and influence the whole metabolize course, in the end, result in riboflavin biosynthesize.
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