Fungal morphology and metabolite production in submerged mycelial processes.

A modular simulation package for fed-batch fermentation: penicillin production

A rapid and internally consistent technique has been developed to measure the volumetric oxygen transfer coefficient, k L a, in fermentation systems. The method consists of tracing the dissolved O 2 concentration of the fermentation broth during a short interruption of the aeration. The O 2 concentration trace thus obtained can be analyzed to determine the values of k L a. Additional experiments on prolonged O 2 starvation, carried out to find the limitation of the technique, suggest that O 2 uptake rate will vary if a prolonged (2-10 min.) O 2 starvation occurs.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/bit.22566

Dynamic measurement of the volumetric oxygen transfer coefficient in fermentation systems.

Filamentous fungi are important organisms industrially and continue to attract research interest as microbiologists attempt to overcome the problems associated with their behavior in submerged culture. This review critically examines the literature describing these problems and where available suggests possible solutions to them. The influence of the chemical and physical environment on culture morphology, the process engineering challenges presented by different fungal morphologies, and the relationship between fungal morphology and metabolite production are all discussed.

Growth of filamentous fungi in submerged culture: problems and possible solutions

Measuring Growth Rates in Microalgal Cultures

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.

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Fermentation process kinetics

Growth and lactic acid production by L. delbrueckii was studied in a dialysis culture system and the inhibitory effect of lactate confirmed by removing lactate from the culture medium by dialysis. It has been shown that lactate inhibits growth after the log phase and that the maintenance of low lactate concentrations after this point permits higher specific growth rates and higher maximum cell concentrations. Acid production is also significantly higher in a dialysis culture system. Finally, a modification of the Luedeking‐Piret model, incorporating the lactate inhibition effect, is proposed.

Growth and acid production by Lactobacillus (L.) delbrueckii in a dialysis culture system

The success of fermentation processes often depends upon the maintenance of an environment sufficient in oxygen concentration so as not to limit or impair normal respiratory activity. Maintenance of such an environment is, in turn, largely dependent on the adequacy of oxygen transfer from air to the liquid medium. Of the possible pathways for oxygen transport, absorption into the medium and subsequent diffusion to the cells is undoubtedly the main one in submerged fermentation. Bartholomew et al. (1950b), Hixson and Gaden (1950), and Wise (1951) were the first to consider the mechanisms of oxygen transfer in fermentation systems, and they developed essentially identical methods for the quantitative expression of absorption rates. The absorption of oxygen into aqueous solutions, especially fermentation media, is generally considered as a liquid-film controlled mass-transfer operation. As such it should be expected that the mass-transfer rate, specifically the \"oxygen absorption\" rate for this case, is a function of those physical properties of the broth which affect interfacial area, turbulence, and boundary (film) conditions. Two such properties which undergo considerable change during many fermentations are surface tension and viscosity. For an excellent treatise on the subject of oxygen transfer in fermentations, the reader is referred to the recent review by Finn (1954). Apparently, no reports have been published of the changes in the rate of oxygen transfer which are due to physical property alterations of the broth as the fermentation progresses. Many fungal fermentations produce thick non-Newtonian3 broths as the mycelium

Effects of liquid physical properties on oxygen transfer in penicillin fermentation.

Two kinds of mathematical models have been developed for batch penicillin fermentations: (1) general models, based on averaged, nondimensionalized cell and penicillin synthesis curves from plant, scale fermentors and (2) particular models developed from specific sets of experimental data from two sources. Parameter-temperature functions used with the general models were assumed to have general shapes which could apply to many fermentations, i.e., they were based on the familiar temperature response of enzyme-catalyzed reactions. Parameter-temperature functions for the particular models were determined from experimental data for batch runs at various temperatures.

Optimization of batch fermentation processes. I. Development of mathematical models for batch penicillin fermentations.

Optimization methods based on the continuous maximum principle and the calculus of variations were used to calculate optimum temperature profiles for batch penicillin fermentations. These methods were first applied to several general models to develop effective techniques for the numerical solution of the equations. Subsequently, these methods were applied to two particular models, derived from experimental data, and the optimum temperature profiles were determined. The results indicated that an improvement, in penicillin yield of about 15% was possible if the optimum temperature profiles were followed.

Elmer L. Gaden

Papers

Fermentation process kinetics

Growth and acid production by Lactobacillus (L.) delbrueckii in a dialysis culture system

Effects of liquid physical properties on oxygen transfer in penicillin fermentation.

Optimization of batch fermentation processes. I. Development of mathematical models for batch penicillin fermentations.

Optimization of batch fermentation processes. II. Optimum temperature profiles for batch penicillin fermentations