Plant design, fermentation

Although the first two possibilities can lead to severe problems in the fermentation of amino acids, these problems can be prevented by using proper plant design maintenance of hygienic conditions throughout the operation reservation of large batches of raw material with uniform qualities. Much more severe (and much more difficult to control) are the last two possibilities which will now be discussed in more detail. 

Many aspects of the design of biochemical reactors are like those of ordinary chemical reactors. The information needed for design are the kinetic data and the dependence of enzyme activity on time and temperature. Many such data are available in the literature, but usually a plant design is based on laboratory data obtained with small fermenters. Standard sizes of such units range from 50 to 1000 L capacity. 

FIGURE 6.25 Configuration of a batch system membrane plant designed for microfiltration of fermentation broth. 

Aseptic systems are used to transfer the inoculum to the vessel, to allow the removal of routine samples during fermentation, for early harvesting of aliquots when the vessel becomes full as a consequence of the media additions and to transfer the final contents to the extraction plant when fermentation is complete. Asepsis is assured by engineering design and by steam, which must reach all parts of the vessels and associated pipework. Any pockets of air or rough surfaces that steam does not penetrate could act as reservoirs for foreign growth. 

The text is written from a practical and operating viewpoint, and all of the contributing authors have been chosen because of their industrial background and orientation. Several of the chapters which were in the first edition have been either deleted or replaced by other chapters which are more germane to current fermentation practice. Those chapters which were retained have been updated or have been rewritten to reflect current practice. Several new chapters were introduced to reflect current emphasis on cell cultures, nutritional requirements, statistical methods for fermentation optimization, cross-flow filtration, environmental concerns, and plant design... 

Dnring the period since World War II, collaborations between biochemists, applied microbiologists, and chemical engineers have evolved in several complementary directions, as their joint efforts have led to the successful development of innovative processes based on biochemical transformations that take place in creatively designed fermenters and bioreactors. This equipment has been tailormade to satisfy not only the safety, sanitation, and microbiological constraints imposed by the FDA and its counterparts in other nations, but also the labile and shear-sensitive nature of animal and plant cells. The equipment used in traditional facilities for manufacturing biopharmaceutical products consists of stainless steel bioreactors/fermenters, tanks, piping, valves, and so on, that are quasi permanent installations. 

Figure 2 An illustration of the various research activities underway to develop the next generation bioethanol plant. The 3 key areas of R D are in pretreatments, enzyme hydrolysis andfermentations. Significant efforts focus on process engineering cmd plant designs with the following at the core SHF -separate hydrolysis and fermentation, SSF - a simultaneous saccharification-fermentation, or SSCF - a simultaneous saccharification-cofermentation.

It is my belief that the availability of on-line computer control has enabled the food process plant designer to achieve this end. Countless plants dealing with the blending of wine or fruit juices, the fermentation and maturation of beer, the continuous production of ice cream and the aseptic processing of a wide range of food products, now rely upon process logic as written in computer programs. 

The therapeutically active dmg can be extracted from plant or animal tissue, or be a product of fermentation (qv), as in the case of antibiotics. Frequentiy, it is synthesized and designed to correlate stmcture with therapeutic activity. Pharmacologic activity is first tested on laboratory animals. When the results ate encouraging, physical and chemical properties are determined in the so-called preformulation stage, and analytical procedures are developed for quahty control (see Qualityassurance/qualitycontrol). 

A suitable means of scale-up for aerobic processes is to measure the dissolved oxygen level that is adequate in small equipment and to adjust conditions in the plant until this level of dissolved oxygen is reached. However, some antibiotic fermentations and the production of fodder yeast from hydrocarbon substrates have very severe requirements, and designers are hard-pressed to supply enough oxygen. 

To make MFCS a commercial reality, two separate bioprocesses had to be developed, sealed up, and brought on line in a manufacturing plant. The first bioprocess was a fermentation to manufaoture the neoessary enzyme. The second process used the enzyme to convert dextrose to FIFCS. The early involvement of chemical engineers in the design of these processes, and their fruitful interaction with biologists, was a key to the success of these two endeavors. 

Extraction of PHA from plants is likely to be a major factor affecting the production cost of PHA from crops and, therefore, the economic viability of this approach. In contrast to production of PHA from bacterial fermentation, where the production system is designed to produce only PHA, an agricultural production of PHA is likely to be most viable only through the recovery of not only PHA but also all other useful components of the harvested crop, i.e., oil, proteins, and carbohydrates. This fact, combined with the lower level of PHA accumulation in plants in comparison to micro-organism, is likely to make PHA recovery from plants a challenging task. 

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