Original Title: Simple Understanding of Bioreactor Bioreactor refers to any suitable environment or engineering device that provides a biochemical reaction. It usually refers to the use of enzymes (driven by one or a group of enzymes) or organisms (such as microorganisms) to make the device have the function of simulating organisms, which can carry out biochemical reactions outside cells, and can carry out both aerobic and anaerobic reactions in the process of simulation. These systems are used in wine, tissue engineering, biochemical engineering, pharmaceutical production, degradation of organic pollutants, etc. And other applications is a very important device. 。 In terms of sources, it can be divided into natural bioreactors (such as human stomach) and engineering bioreactors (such as fermentation tanks, immobilized enzyme or immobilized cell reactors, etc. These bioreactors are usually cylindrical, with volumes ranging from several liters to several cubic meters, often made of stainless steel). It can be divided into Batch reactor, fed batch and Continuous reactor (such as continuous stirred tank reactor and chemostat) according to the way of adding raw materials. Bioreactors are not the same as chemical reactors. Chemical reactors often require pressurization and heating in the process from raw materials to products, which is a high energy-consuming device. Bioreactors, on the other hand, can be chemically synthesized at room temperature and pressure with the participation of enzymes and microorganisms. Therefore, after the advent of bioreactors, the chemical industry sector has paid attention to them. Chemical engineering experts believe that the process of chemical synthesis should be changed to biology as much as possible, so the design of ideal bioreactors has become an important task of modern biotechnology industry. The microorganisms grown in the bioreactor may be immersed in a liquid medium or attached to the surface of a solid medium. The soaked culture material can be divided into suspension and immobilization: Suspended bioreactors do not require special attachment surfaces, so a greater variety of organisms can be used and larger scale culture operations can be performed than with immobilized cultures; however, in continuous operation, the microorganisms are removed from the reactor along with the effluent. Immobilization is a general term describing a variety of cells, particle attachments, or encapsulations. It can be applied to essentially all types of biocatalysis, including enzymes, organelles, animal and plant cells. It is very useful in a continuously operated process because the organisms are not removed with the reactor effluent, but is therefore limited in the scale of operation because the microorganisms are only present on a limited vessel surface. Examples of large-scale immobilized cell bioreactors: Moving media bioreactor (MBBR) Packed bed reactor (packed bed) A fibrous bed bioreactor Biofilm Biofilm reactor Bioreactor design The design of bioreactors is a complex scientific task of biochemical engineering research. The goal of design is to create an optimal environment in which microorganisms or cells can perform their functions and produce products with impurity levels within standards. Variables such as temperature, jacketed glass reactor ,wiped film evaporator, nutrient concentration, pH, and gas solubility (especially with respect to aerobic fermentation of oxygen) in the bioreactor all affect the growth and productivity of the organism. Temperature: The temperature of the fermentation medium can be maintained by the use of cooling jackets, coils alone, or both; in the case of exothermic fermentation reactions, an additional external heat exchanger is required. In a fed-batch system, the nutrients required for the growth of the microorganisms may be continuously added to the fermenter during cultivation, or added to the reactor at the beginning of fermentation. PH value: Use a small amount of acid or alkali to measure and adjust the pH value of the culture medium. The pH value required for different biochemical reactions varies. Gas Solubility: The reaction gas (especially oxygen) is an essential reactant for aerobic (and less anaerobic) fermentation, but due to the low solubility of oxygen for water, which is the basis of almost all fermentation media, its content is relatively scarce (20.95%) for air, so it is necessary to continuously add air (or pure oxygen) to the reaction system. The rising bubbles in the solution serve to thoroughly mix the fermentation medium and also to "get rid" of waste gases, such as carbon dioxide, in the solution. In general, bioreactors are pressurized to increase the amount of dissolved oxygen in the water. Oxygen is usually transported by agitation, which also keeps the nutrients evenly distributed and helps the homogeneous fermentation reaction; gas dispersers (Gas dispersing agitators) are tools used to break up the bubbles and distribute them evenly throughout the vessel. Fouling impairs the overall efficiency of the bioreactor, particularly the exchange of heat in the system. Therefore, to avoid fouling, bioreactors must be designed for easy cleaning. Internal surfaces are usually made of stainless steel to facilitate cleaning and disinfection; typical bioreactors are cleaned batch-to-batch or are designed to reduce the possibility of fouling in continuous operation. The heat transfer capability of a bioreactor is an important part of the design because the overall reaction is indirectly or directly affected by how well the system conducts heat; small conduits can be cooled using cooling jackets, but larger conduits may require coils or external heat exchangers. Expand the full text Sewage treatment Bioreactors are also designed to treat sewage and wastewater. Three wastewater treatment methods are exemplified below: Trickling filter method For the most efficient system, a free-flowing and chemically inert culture medium can be provided to allow the bacteria to decompose the raw sewage. These processes typically pass through a series of separate, sequential large reactors, mechanical separators, or cyclones to accelerate the separation of water and sludge. The Aerators process allows oxygen to be dissolved in the sewage and culture medium to accelerate the decomposition of pollutants. It can treat a large amount of sewage at the same time, so it is often used in urban wastewater treatment. Activated sludge process Submersible mixers provide agitation in anoxic bioreactors to keep solid particles suspended in solution, thereby ensuring that bacteria and organic matter have a chance to "meet" and decompose. The biochemical oxygen demand (Biochemical Oxygen Demand, BOD) of the liquid is reduced enough to be used again. A large amount of solid organic matter, i.e., biosolids, is produced in the process of treating sewage by this method, which can be collected and further treated or dried as fertilizer. Microbial self-purification method A very simple sewage treatment bioreactor refers to setting up a septic tank (leaving the sewage in place) and adding (or not) media to provide a suitable environment for bacteria; In this system, biosludge itself is the main nutrient provider of bacteria (activated sludge) and belongs to a closed system, so it is not affected by floods or saturated ground,wiped film evaporator, but it takes a long time to treat. Therefore, it is suitable for areas with sufficient land and regardless of the efficiency of sewage treatment. Microorganisms are the power engine of biological wastewater treatment, and it is important to closely monitor the quantity and quality of microorganisms in the bioreactor. This can be monitored using an ATP test. 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