Fermentation Engineering

The author hopes that this chapter will enable the fermentation engineer to decide when crystallization may be useful in his process and what basic information he will have to provide the crystallizer designer. 

However, several significant problems must be resolved. The fermentation sample contains various constituents such as proteins, lipids, and sugars. These compounds easily attach on the surface of a probe and a cuvette and cause the problem of shift of the optical density. It becomes a problem when the cell density increases to a hundred times with development of the fermentation. The increase causes the shift of the baseline of the NIR spectrum. Furthermore, the attachment of the bubbles generated by the fermentation on the surface of a probe and a cuvette also causes shift of the optical value measured. These problems should be studied as soon as possible to make sure the bright future of NIR in fermentation engineering. 

B. Atkinson and F. Mavituna, Biochemical Engineering andBiotechnology Handbook, 2nd ed., Macmillan Pubhshers Ltd., Basingstoke, UK, 1991. An exceptional collection of information on all aspects of fermentation with an exhaustive and up to date bibhography. 

J. E. Bailey and D. F. Ohis, Biochemical Engineering Fundamentals, 2nd ed. McGraw-HiU Book Co., Inc., New York, 1986. A very good treatise describing the apphcation of basic engineering principles to fermentation technology. 

H. C. Vogel, Fermentation and Biochemical Engineering Handbook, Noyes Publishing, Inc., Park Ridge, N.J., 1983. 

Progress in fermentation technology has made it possible to raise the accumulation and the yield of L-glutamic acid above 100 g/L and 60% based on the total amount of sugar. AppHcation of genetic engineering techniques for further improvement is also in progress. 

A Chinese pubHcation (47) with 17 references reviews the use of genetically engineered microorganisms for the production of L-ascorbic acid and its precursor, 2-KGA (49). For example, a 2-keto-L-gulonic acid fermentation process from sorbose has been pubUshed with reported yields over 80% (50). 

The fermentation in these big vessels (max 3—5 brews) is normally performed pressureless, but several investigations have been made on fermentation under pressure and using somewhat higher temperatures in order to reduce the time needed still further. Some brewers agree with the statement that no yeast yet known can tolerate this extra stress and at the same time ferment a beet of equivalent excellent quaUty, but new selected yeast strains (genetic engineering) in the future may be better suited to these conditions. 

Lime-Sulfuric. Recovery of citric acid by calcium salt precipitation is shown in Figure 3. Although the chemistry is straightforward, the engineering principles, separation techniques, and unit operations employed result in a complex commercial process. The fermentation broth, which has been separated from the insoluble biomass, is treated with a calcium hydroxide (lime) slurry to precipitate calcium citrate. After sufficient reaction time, the calcium citrate slurry is filtered and the filter cake washed free of soluble impurities. The clean calcium citrate cake is reslurried and acidified with sulfuric acid, converting the calcium citrate to soluble citric acid and insoluble calcium sulfate. Both the calcium citrate and calcium sulfate reactions are generally performed in agitated reaction vessels made of 316 stainless steel and filtered on commercially available filtration equipment. 

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