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Aflatoxins can be produced on a synthetic medium in submerged culture. Glucose, sucrose, or fructose are the preferred carbon sources, and Casamino Acids are the preferred nitrogen source. Ammonia is almost as good a nitrogen source. Zinc is required at levels of at least 0.4 mg per liter. Concentrations of aflatoxin of 60 to 80 mg per liter (as determined by optical-density measurements of a chloroform extract of the unfiltered broth) can readily be obtained in indented shake flasks; somewhat lower yields were obtained in 5-liter fermentors.

Several bacteria utilizing C1-compounds as sole carbon sources were grown on these substrates in continuous culture. The molar yield values (g of cell dry wt/mol of substrate utilized) of bacteria which utilize C1-compounds via the ribulose monophosphate pathway were between 15.7 to 17.3 when grown on methanol; while the molar yield values of bacteria which use the serine pathway for the assimilation of C1-compounds varied between 9.8 and 13.1. The molar yield values of different bacteria which use the serine pathway decreased as the oxidation levels of the C1-growth substrates increased. On formaldehyde the values were between 7.2 to 9.6, whereas on formate the values varied from 3.3 to 6.9. It appears that bacteria utilize C1-compounds more efficiently via the ribulose monophosphate pathway than via the serine pathway. The oxidation step from methanol to formaldehyde (and from methylamine to formaldehyde) in the bacteria studied may be energy yielding. A comparison has been made between the experimental yield values obtained and theoretical values.

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SummaryA procedure for measuring the rate of heat production from a fermentation has been developed. The method is based on measuring the rate of temperature rise of the fermentation broth resulting from metabolism, when the temperature controller is turned off. The heat accumulation measured in this manner is then corrected for heat losses and gains. A sensitive thermistor is used to follow the temperature rise with time. This procedure is shown to be as accurate as previous methods but much simpler in execution. Using this technique, the rate of heat production during metabolism was found to correlate with the rate of oxygen consumption. Experiments were performed using bacteria (E. coli and B. subtilis), a yeast (C. intermedia), and a mold ( A . niger). The substrates investigated included glucose, molasses, and soy bean meal. The proportionality constant, for the correlation is independent of the growth rate, slightly dependent on the substrate, and possibly dependent on the type of organism growth. This correlation has considerable potential for predicting heat evolution from the metabolism of microorganisms on simple or complex substrates and providing quantitative parameters necessary for heat removal calculations.