Tower fermentation of sugar cane juice

Summary

Sugar cane juice, of feed fermentables concentration of 100–180g/l, was simply and rapidly fermented to ethanol in a tower fermenter, using a naturally flocculant yeast. Stable cell densities of 65–80g dry wt/l were obtained. Conversion and ethanol productivity data are given as a function of throughput and initial feed concentration. The limitation to fermenter performance with this yeast was imposed by carryover of non-fermented sugars, principally fructose, rather than washout of the yeast flocs under high hydraulic loadings (residence times of less than 1.5 hours). Further improvement of the fermenter performance may be achieved by strain selection.