Teaching games for fermentation

One of the first computer games for biotechnology taught some characteristics of the older batch fermentation system that had all its ingredients at the start (Bungay, 1971). That game FERMT.BAS portrays a typical pilot plant assignment with sequential runs in small fermenters where the recipe for the medium and the conditions must be specified. The simulation of a non-growth-related fermentation considers exhaustion of most of the sugar before product formation commences. Modern practice is to feed sugar to maintain a low level that supports product synthesis rather than growth. FERMT.BAS was translated to a JavaScript version that is now obsolete in view of a newer version using a Java applet.

Go directly to the game

Improvements to FERMT:

The old game asked for amount of inoculum. There is no reason to discard inoculum. The new version uses all from the seed fermenter.

The new game asks for sterilization time, an important parameter.

Inorganics such as Na₂SO₄, phosphates, CaCO₃, and the like are usually not critical but deserve consideration and are in the new version.

Tips:

Duplicate specification seldom yield identical results. This is realistic.

You will learn some names of common nutrients and begin to appreciate the complexities of interactions in recipes.

The objective of this game is to optimize profit. You manipulate variables but have only eight small vessels (fermenters) with which to experiment. Expected yield and profit are computed for a full-scale production batch using your recipes. You formulate different recipes and get back some data and profit figures. The problem is to use the information from one run to plan the next set of recipes. In our course, students are graded on the logic of their approaches plus a bonus if profit is superior to the class average.

Each of the variables may be harmful in excess. Product formation starts when growth is complete. Several of the variables interact in producing effects.

Variables: (Usually per cent by weight.)

Sugar. More sugar results in more growth but prolongs the growth phase. Since product formation commences only after the growth phase is over, there must be a compromise between getting abundant growth and having sufficient time for the organisms to make product. Scheduling restraints for the plant fix the total time for a run.

Oil. Excess oil is harmful both to growth and to product formation. Oil also serves as an antifoam agent. High air flows promote foaming and greatly increase oil consumption.Oil can causes losses because of emulsions during solvent extraction. The game adds to purification cost when there is too much oil.

Soymeal. This relatively inexpensive complex nitrogenous material from soybeans contains some vitamins, other undefined essential ingredients, and toxic ingredients. Some soymeal is beneficial; too much is detrimental. Any ingredient containing solids makes sterilization more difficult because lumps resist heat penetration.

Corn steep. This complex nitrogenous material, a byproduct of corn processing, contains some of the same factors as soymeal. The same comments apply.

Air. Oxygen is essential for both the growth and production phases. Although air is cheap, high aeration is harmful because oil consumption for antifoam becomes excessive. Units are volumes of air per minute per volume of batch (VVM). More than about 2 VVM would probably be impossible for a real process, and antifoam oil usage can become unreasonable.

Trace ingredients, e.g., vitamins. All the vitamins and trace elements are lumped into a category called vitamins. Small amounts are found in soymeal and distillers solubles, but some supplementation may be desirable. Excess trace elements reduce the rate of product formation. The game assusmes that these delicate materials are sterilized by membrane filtration and added after sterilization of the big batch.

Minerals. Inoganic compounds

Profit is calculated by subtracting the cost of the ingredients, operating costs and purification costs from the value of the product. Common sense is of some help, e.g., vitamins are used in much smaller amounts than is sugar.

HINTS:

1. Use more sugar than nitrogenous compounds.
2. Too much of anything is bad.

FERMT inspired a more elaborate game called JERMFERM (Mateles, 1978) in which the player specifies concentrations of glucose, soybean meal, phosphate, and salts, the agitation and aeration rates, fermenter operating volume, inoculum size, and the duration of the fermentation. Whereas FERMT is based on running parallel experiments in the pilot plant, individual fermentations are studied with JERMFERM. It has no time restraints and lets the player examine the results from each fermenter before specifying the next run. A sequential search technique has been reported for optimizing JERMFERM (Saguy, 1982).

Quite a few games have been developed at different institutions, and we have evaluated all that we could find. In most cases, the authors had quite specific teaching objectives that require more explanation than usually accompanies the programs.

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References:

Bungay, HR, "FERMT, a fermentation game based on process development", Process Biochemistry 6: 38-39 (1971)
Mateles, RI, "JERMFERM, a process development game" Biotechnol. Bioengr. 20: 2011-2014 (1978)
Saguy, I, "Utilization of the 'complex method' to optomize a fermentation process", Biotechnol. Bioengr. 24: 1519-1525 (1982)