The Fermentation of Beet Sugar Syrup to Produce Bioethanol

Fermentation of sugar or starch-containing substrates by yeast to produce ethanol for use as a liquid fuel has been an accepted technology for many years. Currently, the most popular substrates are sugar cane molasses and starch from maize or wheat. Interest in renewable liquid fuels is growing and other substrates are now being considered, choice of these depends on local conditions. This paper presents findings from work carried out on syrup from sugar beet, an ideal crop for cultivation in the United Kingdom and parts of Europe. Fermentation of this substrate was found to be successful. The process of backsetting was investigated as a way of reducing water usage and effluent disposal. This was found to have no effect on ethanol production provided compensation was made for increases in gravity caused by glycerol levels. Backsetting was also found to be beneficial to yeast growth. As yeast remain in the fermented substrate, the effect of distillation on yeast cells was also investigated. It was found that dead yeast cells are present in backset and thus persist into subsequent fermentations. This can cause difficulties in viability measurement if the methylene blue method is used.