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The effects of continuous propagation on the growth of microorganisms Butterworth, Earl McKenzie

Abstract

The method of continuous propagation has been employed successfully to culture four organisms; Lactobacillus plantarum Pseudomonas aeruginosa. Azotobacter vinelandi and Torula cremoris. The varied cultural requirements of these organisms made it necessary to adapt a basic apparatus to meet these individual requirements before satisfactory growth or fermentation could be attained. An apparatus satisfactory for the continuous growth of the aerobic organism Ps. aeruginosa was constructed. It was found that there was a correlation within certain limits between the rate of flow of sterile broth and the population level of the organism. The continuous propagation apparatus used with Ps. aeruginosa was modified to permit a satisfactory fermentation by an anaerobic organism L. plantarum. It was shown that a constant maximum yield of lactic acid could be obtained from a lactose medium when the rate of flow of the medium through the apparatus was properly adjusted. Azotobacter vinelandi was cultured continuously on a whey medium. It was shown that the lactic acid in whey could be used by the organism as the energy source for the nitrogen fixing process. It was also shown that the protein and protein breakdown products in whey did not inhibit nitrogen fixation by the organism. Maximum yields (31.4 mgms./1OO ml) of fixed nitrogen were obtained with Azotobacter grown continuously on a nitrogen free medium. An apparatus which seperated growth and fermentation was constructed for the fermentation of whey by Torula cremoris. The amounts of ethyl alcohol obtained with this apparatus were greater than those reported for the batch method. An attempt was made to increase the vitamin content of whey by growing the yeast Torula cremoris in it under conditions of controlled fermentation. However, no increase in nutritive value of the whey was observed. In some cases the B vitamin content was decreased slightly.

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