Fermentation processes design

Although there are a multitude of possible different fermentation process designs, most... 

These materials would primarily be used in large scale fermentations. The economic implications of a fermentation medium on the profitability of a process have to be considered before fermentation process design can be started. 

Generally, for most fermentation processes to yield a good quality product at a competitive price, at least six key criteria must be met. (/) Fermentation is a capital intensive business and investment must be minimised. (2) The raw materials should be as cheap as possible. (J) Only the highest yielding strains should be used. (4) Recovery and purification should be as rapid and as simple as possible. (5) Automation should be employed to minimise labor usage. (6) The process must be designed to minimise waste production and efftciendy use all utilities (26,27). 

The actual fermentation process is known as the incubation phase and is just part of the batch cycle. A complete fermentation cycle can typically include the following steps, most likely depending on bioreactor design ... 

Biosensors are analytical devices that incorporate a biological component and a transducer. These must be in close proximity with one another and preferably in intimate contact, i.e. the biological component immobilized on to the transducer. Such devices are available in disposable forms, e.g. for measurement of blood glucose in diabetic patients, evaluation of the freshness of uncooked meat. Other designs are suitable for continuous use, e.g. on-line monitoring of fermentation processes, the detection of toxic substances. 

Figure 8 is a schematic flow diagram for the hydrolysis of waste newsprint. Most of the process design criteria and the economic evaluations of the saccharification process have been based on newsprint as substrate. Notable analyses are those of Wilke and co-workers (21) and Humphrey (22). In the hydrolysis, the substrate is first pretreated (milling), to make it more accessible to the enzyme. Saccharification takes place in a reaction vessel, where the substrate is contacted with the enzyme solution from the fermentation vessel. Glucose solution is separated from unreacted substrate at the outlet of the vessel and the solution passes on to a concentration stage before the sugar is used in the yeast fermentation to produce alcohol. 

The initial emulsification studies employed a 1 L reactor vessel with baffles originally designed for fermentation processes. Subsequent studies were successively scaled up from 1 L to 3, 10, and 100 L. Variations due to differences in reactor configuration were minimized by utilizing geometrically similar reactors with approximately the same D/Tratio (i.e., 0.36-0.40). Maa and Hsu contended that separate experiments on the effect of the baffle area... 

As in the case of enzymes, whole cells can be immobilized for several advantages over traditional cultivation techniques. By immobilizing the cells, process design can be simplified since cells attached to large particles or on surfaces are easily separated from product stream. This ensures continuous fermenter operation without the danger of cell washout. Immobilization can also provide conditions conducive to cell differentiation and cell-to-cell communication, thereby encouraging production of high yields of secondary metabolites. Immobilization can protect cells and thereby decrease problems related to shear forces. 

Many alternative fermenters have been proposed and tested. These fermenters were designed to improve either the disadvantages of the stirred tank fermenter-high power consumption and shear damage, or to meet a specific requirement of a certain fermentation process, such as better aeration, effective heat removal, cell separation or retention, immobilization of cells, the reduction of equipment and operating costs for inexpensive bulk products, and unusually large designs. 

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