Fermentation process kinetics. Reprinted from Journal of Biochemical Microbiological Technology and Engineering VOl. 1, No. 4 Pages 413-29 (1959)

Information on fermentation process kinetics is potentially valuable for the improvement of batch process performance; it is essential for continuous process design. An empirical examination of rate patterns in various fermentations discloses three basic types: (1) 'growth associated' products arising directly from the energy metabolism of carbohydrates supplied, (2) indirect products of carbohydrate metabolism and (3) products apparently unrelated to carbohydrate oxidation. Effects of operating variables on the primary kinetic processes, growth, sugar utilization and antibiotic formation, in the penicillin process, illustrate the special nature of this type.     

Application of mass and energy balance regularities in fermentation. Reprinted from Biotechnology and Bioengineering, Vol. XX, No. 10, Pages 1595-1621 (1978)

Material and energy balances for fermentation processes are developed based on the facts that the heat of reaction per electron transferred to oxygen for a wide variety of organic molecules, the number of available electrons per carbon atom in biomass, and the weight fraction carbon in biomass are relatively constant. Mass-energy balance equations are developed which relate the biomass energetic yield coefficient to sets of variables which may be determined experimentally. Organic substrate consumption, biomass production, oxygen consumption, carbon dioxide production, heat evolution, and nitrogen consumption are considered as measured variables. Application of the balances using direct and indirect methods of yield coefficient estimation is illustrated using experimental results from the literature. Product formation is included in the balance equations and the effect of product formation on biomass yield estimates is examined. Application of mass-energy balances in the optimal operation of continuous single-cell protein production facilities is examined, and the variation of optimal operating conditions with changes in yield are illustrated for methanol as organic substrate.     

The cultivation of animal cells at controlled dissolved oxygen partial pressure. Reprinted from Biotechnology and Bioengineering Vol. X, Issue 6, Pages 801-814 (1968)

A 3-liter culture vessel has been developed for the growth of animal cells in suspension at controlled pH and dissolved oxygen partial pressure (pO(2)). The culture technique allows metabolically produced CO(2) to be measured; provision can be made to control the dissolved CO(2) partial pressure. In cultures containing a low serum concentration, gas sparging to control pO(2) was found to cause cell damage. This could be prevented by increasing the serum concentration to 10%, or by adding 0.02% of the surface-active polymer Pluronic F68. The growth of mouse LS cells in batch culture without pO(2) control was found to be limited by the availability of oxygen. Maximum viable cell populations were obtained when dissolved pO(2) was controlled at values within the range 40-100 mm Hg.     

Technological problems in cultivation of plant cells at high density. Reprinted from Biotechnology and Bioengineering, Vol. XXII, No. 6, Pages 1203-1218 (1981)

Using Cudrania tricuspidata cells as model plant cells which have high sensitivity to hydrodynamic stress, technological problems in the cultivation of the plant cells at high density were investigated. Using "shake" flasks on a reciprocal shaker and Erlenmeyer flasks on a rotary shaker and with a high supply of oxygen in order to obtain high cell densities in shaken cultures, particle breakdown and damage to the largest cell aggregate group (above 1981 microm in diameter) occurred and normal cell growth became impeded. The mass-transfer coefficient (K) for a model solid-liquid system (beta-naphthol particles and water) in place of a system of plant cells and a liquid medium was proposed as an intensity index of hydrodynamic stress effects on plant cells in suspension cultures under various conditions in the bioreactor systems. Normal cell growth was obtained under culture conditions for K values less than about 4.4 x 10(-3) cm/sec. The characteristics of various bioreactors used until now were investigated by considering the three main technological factors (capacity of oxygen supply, intensity of hydrodynamic stress effects on plant cells, and intensity of culture broth mixing and air-bubble dispersion). The most suitable bioreactor for culturing plant cells at high density was a jar fermentor with a modified paddle-type impeller (J-M). The yield of cell mass in the 10-liter J-M (working volume 5 liter) was about 30 g dry weight per liter of medium.