Ethylene oxide-propylene oxide copolymers in yeast fermentations

Newsome, Graham (1989). Ethylene oxide-propylene oxide copolymers in yeast fermentations. MPhil thesis The Open University.



Ethylene oxide - propylene oxide copolymers are prepared by addition of ethylene oxide to polypropylene glycol. One of the uses of these compounds is to inhibit foam formation in aqueous media.
The main purpose of this work has been to try to determine how variation of molecular weight and ethylene oxide content of these polymers changes their efficiency of foam inhibition in a particular foaming system, namely an aerobic yeast fermentation. In addition attempts have been made to study the effect of the polymers upon yeast growth and again to relate this to variations in molecular weight and ethylene oxide content.
The results obtained show that polymers with ethylene oxide contents below 15% by weight were most effective with respect to inhibition of foaming. Increasing the molecular weight of these polymers resulted in more effective control of foaming.
The results also show that all of the polymers studied caused a reduction in yeast growth although this effect was less marked with a polymer having a molecular weight of 2271 and an ethylene oxide content of 11% by weight.
Methods have also been developed for purification of the commercially available polymers and characterisation of them using gel permeation chromatography and carbon-13 NMR.

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