In fermenters and ancillary equipment (air purification system, temperature, pressure and flow control systems, etc. and the corresponding pipeline valves) in which a part of the problem may cause fermentation failure. Therefore, enterprises should first establish the "prevention" concept, starting from the device to prevent possible contamination caused by the fermentation of various risks.
■ ensure tightness fermenter
Fermenter fermentation production of major equipment. Prior to use, the need to carefully examine the fermenter, mixing system such as checking their rotation without exception, mechanical seals are tight, the screws are loose tank, the tank clogging pipes, laminated or tank coil leaks and tank valves are tight connections and so on.
Currently, mechanical seals get in fermentor widely used, it replaces the previous stirring shaft packing form, but if the installation or use of high precision mechanical seal system is inappropriate, seal leaks still occur, causing contamination. Therefore, when the installation should pay attention to the agitator shaft. It is understood that the use of a fermentation plant Xinjiang intermediate bearing rod fixed adjustable by adjusting the position of the intermediate bearing to reduce rocking agitator shaft, and the use of multi-spring balanced mechanical seal, the use of different directions of the spring force of the stirring shaft offset portion offset effectively achieved the seal.
■ endoscopic removal flush pipes
In order to facilitate the fermentation tank fermentation conditions observed in a large fermenter generally set flush endoscopic steam pipes. However, once the steam is condensed in the pipe, the condensed water can not be fully guaranteed sterile, and therefore should be removed steam pipe flushing endoscope, reducing contamination risks. If you can not see because of the large tank mist, you can use a higher brightness light endoscopy.
■ PVDF membrane purification effect reliable
Traditional air purification system using activated carbon, cotton, fine glass fiber paper as a filter, whose filter effect is poor, and complicated to operate. At present, the domestic membrane filtration technology is more mature, as with polyvinylidene fluoride (PVDF) microporous membrane filter made of folded filter not only high precision, and high traffic. Note the use of technical personnel as long as the former dehumidify air filter off the oil, according to specifications of the filter sterilization, sterile air can be guaranteed. Further, problems due to PVDF membrane air moisture insensitive, hydrophobic membrane itself is strong, and therefore solve the past, when the air humidity is too large cotton filter or the like can not be used. A fermentation plant in Xinjiang for 10 tons fermenter using PVDF filter purification effect were investigated. Technical staff in the filter hung a test vial, the vial with the measured air LB medium after sterilization is not common bacterial inoculation, continuous access filtered to monitor filter effect (as long as the common bacterial culture LB keep clear, it shows the filter run properly). The results showed that the plant 10 tons fermenter filter after three months of continuous use, measuring vial of sterile examination showed bacterial culture LB, therefore microporous membrane (PVDF) purifying effect is reliable.
■ Periodic inspection and monitoring system
Fermentation medium for a thorough sterilization process is the use of high temperature steam so oversaturated variety of bacteria, fungi, protein coagulation and death. In the pharmaceutical industry sterilization of warm-up time, the opening of the steam valve, sterilization temperature, pressure and foam control, sterilization, there are stringent requirements, any link problems are prone to contamination. General industrial sterilization temperature at 110 ℃, sterilization pressure of 0.5 MPa or more, and to ensure the accuracy of the sterilization temperature and pressure depend on various temperature probes, pressure sensors and other monitoring systems. Therefore, on a regular basis such probes, sensors and other detection is very important. Further, as the fermenter volume increases, corresponding to the same tank pressure pot temperature decreased, so that when the correlation was found to change the temperature and pressure, the temperature shall prevail.
■ valve should adopt a soft seal
Valve is the most used in the fermentation equipment ancillary equipment, most of them using a cut-off valve. Valve for sealing medium can be divided into four, namely nominal level, low leakage level, steam level and atomic level. Nominal level and low level leakage sealing closure requirements applicable to non-tight valve, such as a valve to control the flow. Steam-tight seal seat, stem and body connection portion of the valve for steam and most other industries. Atomic seal sealing medium suitable for high demanding applications, such as spacecraft and nuclear power equipment. Because the fermentation industry using high-temperature steam sterilization of fermentation equipment, so the valve sealing requirements of the medium is steam-tight.
Because the valve is opened during the fermentation process frequently, often subject to corrosion, erosion and cavitation damage, so the valve vice structure that seat and close contact with each other to shut down parts of selected portions of the more critical. Vice-sealing valve structure is divided into two kinds of soft seal and hard seal. Hard vice structure is hermetically sealed against the seat and closed the tiny pieces of elastic-plastic deformation and squeeze each other to form a closed circular sealing contact line occur. Although this type of valve in the initial application of good sealing effect, but the fermentation valve opens more frequently, easy to wear the contact wire previously formed, or leaving dirty due to pipeline sealing surface indentation damage. Sealing and hard seal structure elastic deformation is small, the formation of new sealing contact line is very difficult, so long-term use may cause the valve to leak, the fermentation failure. Soft sealing valve closure member generally use soft pads, the use of elastic-plastic deformation of the gasket to form a larger annular sealing contact with a wide belt to add plug uneven sealing surface, forming a seal to eliminate the gap. Its precision is generally less demanding, any special requirements, body material can be stainless steel, soft seal off pieces with replaceable PTFE gasket, so can be changed frequently to ensure that the valve PTFE gasket tightness.
■ attention to the valve seal inspection
If the quality of the stem and the valve body machining hole shut-off valve is not good, or because of long-term use leads to wear leaving with the gap filler stem the increase will lead to media leaks from the valve stem at a phenomenon known as Valve "seal leak." However, in the fermentation, the valve seal checks are often overlooked. In 2003, the valve seal leakage had to make a continuous fermentation plant in Xinjiang Cordyceps contamination pouring a month, a large enterprise economic losses. Therefore, the fermentation of the valve seal leakage should not only pay attention to the structure of vice, but also to pay attention to the seal leakage.
In fermentation, the fermentation process due to the requirement, some of the fluid flow by the valve is not installed, as in some of the fermenter, the sampling valve is a first valve near the fermentor, prior to sampling in order to sterilize the valve, Installation and broth-flow valve is reversed, so as to install a valve at the bottom of a small sampling of additional steam flow valve. Sealing requirements on the sampling valve seal structure is very high, otherwise the fermentation broth may penetrate the seal structure of the sampling valve from leaking even in the sealing structure, resulting in contamination of fermentation.
Currently, the domestic cut-off valve, mostly multi-packing structure and packing structure is also attached rigid spacers, or the upper seal ring with a disc spring, thereby enhancing the ability of self-adjusting sealing force, improved sealing performance. Sealing leaks, rather alter the structure of domestic valve seal is difficult, can be solved by changing the type of filler leakage problems. For example, the current expansion of new alternative to conventional PTFE packing asbestos and expanded graphite packing, its wear resistance, corrosion resistance, good sealing effect. The main thing is dead air system and tank, followed by seeds, operating systems and devices. If it is then more likely spores dead, more than a large area of the air system. You can track the sterility test, to see the time and bacteria contamination shaped relationship, it is best to prepare sterile seed to fermentation tanks are tracking.
Seeds can not have bacteria.
Air filters should durability.
Note that not too much foam.
Ensure sterility air system;
Tank tightness, especially in some corners should pay special attention;
If you want to move species, but also to ensure sterility pipeline and dead;
To ensure proper seed, no contamination, no variation;
If the mid-feeding, feeding system must guarantee sterility.