Environmental control system of microbial fermentation process

The fermentation process is more complex, involving the growth and metabolism of microbial cells, and is a dynamic process of time-change, randomization and variability of input and outputBecause some variables (bacterial concentration, matrix concentration, product yield, etc.) are difficult to detect online, can not be directly as the accused variable, so in the fermentation process mainly using quality-related variables, such as temperature, stirring speed, p H, dissolved oxygen, ventilation, foam, etcas the accused variablesIn view of the importance of the various environmental parameters affecting microbial metabolism during fermentation, the key control of temperature pH, dissolved oxygen and foam height is mainly introduced(1) temperature controltemperature control has a optimal growth temperature for specific microorganismsTherefore, the control of the fermentation temperature of the microbial fermentation process is very important to the parameters of the microbial growth environmentPID control algorithm is the most widely used and technically mature basic control algorithm in industrial engineering, considering its simple structure, easy to adjust parameters, high control accuracy, wide applicability, and the function of non-residual differenceSo the temperature control uses this algorithm, and separately constitutes the control loop(2) PH controlpH is another important environmental parameter for microbial growthIn the fermentation process, it must be strictly controlled, otherwise it will seriously affect the metabolism of microorganisms and the synthesis of metabolitesBecause the characteristics of the fermentation process pH adjuster object is more time-change, the addition of pH regulator and the change of the fermentation liquid pH is complex, in some pH near, the pH change is very sensitive to the amount of the added pH regulator, while the sensitivity is significantly reduced near the other pHThe problem can be solved by using the control peristaltic pump's break-in time to adjust the pH in the fermentation fluid(3) dissolved oxygen concentration controlin the process of oxygen-consuming fermentation, oxygen is a necessary raw material for microbial growth, if oxygen supply is insufficient, will inhibit the growth and metabolism of microorganisms, for this reason, in the fermentation process, to maintain a certain concentration of dissolved oxygen DOThe main factors affecting dissolved oxygen concentration DO are the amount of air supplied, the speed of the mixing paddle and the pressure of the fermentation tank At present, the control of dissolved oxygen concentration in domestic fermentation tanks is mainly achieved by regulating the speed of the mixing pad or regulating the amount of air supplied, and is mostly manual operation, the control accuracy is not high The DO concentration variable (main parameter) can be used as the charged variable, with stirring speed (subparameter) as the control means, to form a series control system with the main and sub-two circuits The actual value of the speed is constantly changed with the change of dissolved oxygen in the fermentation tank, and finally the main parameter is controlled at the given value   (4) liquid level and defoaming control in the pre-fermentation period, microbial growth is strong Add the liquid full load, stirring motor full speed start, air flow volume to the maximum, when the fermentation liquid floating very strong, a little careless, may produce the phenomenon of escape liquid At this time, the defoamer must be added in time to reduce the foam, to prevent the fermentation liquid floating Using the resistance bar as the level detection element, when the fermentation liquid surface reaches a certain height, automatically open the valve of the defoamer, when the liquid surface drops back to normal, automatically close the defoamer valve In defoaming control, the process is slow to respond, so a time delay should be added to the control loop to prevent the addition of excessive defoamers.