Ethanol fermentation from sugarcane at different maturities

Experiments were done employing cane particles obtained from sugarcane at different growth stages until maturation in order to estimate the sugarcane growth stage where production of ethanol and carbohydrate consumption were optimized. The non-flowering cane variety NA56 was cultivated and samples taken at different time intervals for two consecutive years. Two Saccharomyces cerevisae strains were selected from four strains initially compared. Sucrose was poorly consumed in young cane which was an unexpected result. Fructose on the other hand was the hexose that remained in the medium at the end of fermentations especially when using mature sugarcane. There was an increasing trend in ethanol production as a function of DAP (days after planting) as expected, however a plateau was reached after 225 DAP and the maximum value obtained was between 300 and 325 DAP. The NA56 cane variety is usually harvested around 350 DAP for commercial sugar production. Hence a difference of approximately 25 days less in the field might be needed for maximum ethanol production. On the other hand, it was clear from the data that cane harvesting for ethanol production should not be done after the recommended DAP for commercial sugar production. If this is done, the excess fructose present will not be completely utilized by yeast. Finally it was found that yeasts showing more affinity to sugarcane fibers showed better ethanol yields in all the DAP interval.