Fermentation industry media

Despite the advantages of continuous cultures, the technique has found little application in the fermentation industry. A multi-stage system is the most common continuous fermentation and has been used in the fermentation of glutamic add. The start-up of a multi-stage continuous system proceeds as follows. Initially, batch fermentation is commenced in each vessel. Fresh medium is introduced in the first vessel, and the outflow from this proceeds into the next vessel. The overall flow rate is then adjusted so that the substrate is completely consumed in the last vessel, and the intended product accumulated. The concentration of cells, products and substrate will then reach a steady state. The optimum number of vessels and rate of medium input can be calculated from simple batch experiments. 

Filter aids are widely used in die fermentation industry to improve the efficiency of filtration. It is a pre-coated filter medium to prevent blockage or blinding of the filter by solids, which would otherwise wedge diemselves into the pores of the cloth. Filter aid can be added to the fermentation broth to increase the porosity of the cake as it formed. This is only recommended when fermentation product is extracellular. Filter aid adds to the cost of filtration. The minimum quantity needed to achieve the desired result must be established experimentally. Fermentation broths can be pretreated to improve filtration characteristics. Heating to denature proteins enhances the filterability of mycelial broths such as in penicillin production. Alternatively, electrolytes may be added to promote coagulation of colloids into larger, denser particles, which are easier to filter. The filtration process is affected by the viscosity and composition of the broth, and the cell cake.5... 

The chemical reactions involved in biological processes are often very sensitive to the hydrogen-ion concentration of the medium. In industries such as the fermentation industry the control of the pH of the materials being processed is very important. It is not surprising that the symbol pH was introduced by a Danish biochemist, S. P. L. Sprensen, while he was working on problems connected with the brewing of beer. 

Wheat bran, which contains cellulose, protein and other nutrients, is an excellent medium for solid-state fermentation [25,47]. Wheat bran is also widely used in other fermentation industries but is still too expensive for economic cellulase production. Agricultural residue is cheaper. For example [30,48], after pretreatment by 4 % NaOH at 121 °C for 0.5 -1.0 h, wheat straw was used as raw material. After mixing with nutrient salts, adding water to a water content of 80%, then adjusting the pH to 5.8, the medium was used for solid-state fermentation. The final cellulase activity was reported to be as high as 200-430 FPIU per gram of cellulose. Deschamps et al. [49] used a mixture of wheat straw and bran (80 20) as raw materials for solid-state fermentation the... 

The diversity of fluid characteristics is so great from one microorganism to another that little generalization is possible. Moreover the products and kinds of fermentation processes are likely to expand, particularly the use of hydrocarbons and natural gas for biosynthesis. Therefore, much more work is needed to determine the influence of fermentation fluid characteristics on the fermentation process and product recovery. It needs not only studies of superior and more quantitative measurements of the physical properties of cells, such as cell density, cell size, the electrostatic property of the cell surface, specific heat and heat conductivity of cells, but also on the properties of cell suspensions, such as morphology, viscosity and surface tension, to obtain the fundamental data for practical equipment design and to control unit operations in the fermentation industry, such as mechanical separation and disintegration of cells for product recovery, medium sterilization, air sterilization, control of dispersion, as well as the actual fermentation process. 

Ji XJ, Huang H, Du J, Zhu JG, Ren LJ, Li S, Nie ZK. (2009b). Development of an industrial medium for economical 2,3-butanediol prodnction through co-fermentation of glucose and xylose by Klebsiella oxytoca. Bioresour Technol, 100,5214—5218. 

In submersion processes, the microorganisms grow in a liquid medium. Except in traditional beer and wine fermentation, the medium is held in Fermentors (see) and stirred to obtain a homogeneous distribution of cells and medium. Most processes are aerobic, and for these the medium must be vigorously aerated. Most important industrial processes (production of biomass and protein, antibiotics and enzymes and some forms of sewage treatment) are carried out by submersion processes. 

Figure 11 Typical time course of A. mediiemmci fermentation in an industrial medium.

The industrial strains of lactic acid bacteria can completely ferment a medium of 12-15 % sugar in 2-4 days with greater than a 90 % yield of lactic acid. All of these bacteria are considered homofermentative in that they utilize a homolactic fermentation pathway, producing two molecules of lactic acid for each molecule of hexose. As diagrammed in O Fig. 1.10, the Embden-Meyerhof pathway is used in the homolactic fermentation. 

At present, most media in the fermentation industry are sterilized by batch methods. Overexposure of the medium to heat is inherent in batch sterilization processes. But continuous sterilization, when properly operated, can minimize damage to the medium. 

For the industrial production of riboflavin as pharmaceuticals, the traditional methodology comprising the dkect condensation of (13) with (14) in an acidic medium with continuous optimisation of the reaction conditions is stiU used (28). A great part of riboflavin manufactured by fermentative methods is used for feeds in the form of concentrates. The present world demand of riboflavin may be about 2500 t per year. Of this amount, 60%, 25%, and 15% are used for feeds, pharmaceuticals, and foodstuffs, respectively. The main producers are Hoffmann-La Roche, BASF, Merck Co., and others. 

A typical fermentation medium for penicillin production contains lactose, com steep Hquot, and calcium carbonate (3,153,154). In most industrial processes the carbohydrate source, glucose, beet molasses, or lactose, is continuously added to the fermentation. The rate of glucose addition must be carefully monitored, by pH or rate of oxygen depletion, because the synthesis of penicillin is markedly reduced in the presence of excess glucose. 

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