Cultures, propagation

Addition of up to 200 ppm sulfur dioxide to grape musts is customary. Strains of S. cerevisiae and S. bayanus grown in the presence of sulfite, become tolerant of fairly high concentrations of SO2. Cultures propagated in the winery are added in Hquid suspension, usually at 1—2% of the must volume. Many strains are available in pure culture. Factors such as flocculence, lack of foaming, fast fermentation, lack of H2S and SO2 formation, resistance to sulfur dioxide and other inhibitors, and flavor production will affect strain choice. No strain possesses all the desired properties. 

Vaccines There are two IND (investigative new drug) human unlicensed VEE vaccines available. The first, named TC-83, developed in the 1960s is a live, attenuated cell-culture-propagated vaccine produced by the Salk Institute, and is not effective against all the serotypes in the VEE complex. It is used in a single subcutaneous dose of 0.5 mL. 

Submerged fermentation procedures are used almost exclusively today. A few surface fermentation processes (on liquids or solids) are still used. Cost comparisons of labor, air compression, infection, etc., can be made, but modem batch fed, highly instrumented and computerized submerged methods predominate. Submerged methods are also the predominant culture propagation technique. The general principle is to have the fewest possible... 

C. Prophylaxis/Vaccine. Investigational vaccines are currently being tested. An experimental vaccine, designated TC-83 is a live, attenuated cell-culture-propagated vaccine. A second investigational product that has been tested in humans is the C-84 vaccine, prepared by formalin-inactivation of the TC-83 strain. 

After the cropping period ends, the spent straw is used as fodder for farm animals or is saved for future inoculations. The strain is kept kept alive by continous transfer onto fresh substrates. (See Chapter VI on natural culture). Propagating spawn in this way, however, is less assured than sterile methods. 

It is known that if the medium includes several substrates metabolized by a particular strain of microorganisms, the substrate providing the maximum culture propagation rate is consumed first. As this substrate is going to exhaust, bacteria subsequently consume other substrates, which provide lower rates of cell multiplication. 

Agar, which is low in metabolizable or inhibitory substances, debris, and thermoduric spores, is ideal for the propagation and pure culture of yeasts, molds, and bacteria. Agar also meets the other requirements of ready solubiUty, good gel firmness and clarity, and a gelation temperature of 35—40°C and a gel melting temperature of 75—85°C. A clarified and purified form of the bacterial polysaccharide, geUan gum, is the only known satisfactory substitute. 

Specific procedures exist for storing (16,17) and propagating microorganisms to obtain reproducible fermentations. The stock culture is stored frozen (<—80°C) or freeze-dried. To prepare the inoculum (seed) mixture, an aUquot is taken and grown in consecutive soHd or Hquid cultures of increasing volume. The volume of the last step, the seed fermentor, is typically 4—12% of the main fermentor volume. 

Incubation The introduction of microorganisms into a culture medium with a view to growing a large number of identical cells all by propagation. 

Overview. In the cultures of luminous bacteria, the bacterial cells are not luminous in their early stages of propagation. The formation of bioluminescence system is controlled by a substance called autoinducer that is produced by the cells of luminous bacteria. 

The autoinducer is a low molecular weight compound that is easily leached from the cells into the culture medium. By the propagation of bacterial cells, the concentration of the autoinducer in the medium increases. When the concentration reaches a certain threshold, the biosynthesis of bioluminescence system begins, and the bacteria become luminescent. The process is also called quorum sensing (Fuqua et al., 1994). 

A batch process is customary for producing antibiotics. Submerged culture is used to propagate fungus with suitable carbohydrate resources. This assumption is based on simplicity in calculations and the normal use of penicillin in die pharmaceutical industry. Assume we... 

At present, cell culture work is done mostly by hand by horticulturists in large greenhouses (Plate 3). Chemical engineers could greatly increase the usefulness of this method of plant propagation by developing efficient automated processes for producing plants from cloned cells. 

The testing of disinfectants for virucidal activity is not an easy matter. As pointed out earlier (Chapter 3), viruses are unable to grow in artificial culture media and thus some other system, usually employing living cells, must be considered. One such example is tissue culture, but not all virus types can propagate under such circumstances and so an alternative approach has to be adopted in specific instances. The principles of such methods are given below. 

---