Study of sugarcane pieces as yeast supports for ethanol production from sugarcane juice and molasses

Due to the environmental concerns and the increasing price of oil, bioethanol was already produced in large amount in Brazil and China from sugarcane juice and molasses. In order to make this process competitive, we have investigated the suitability of immobilized Saccharomyces cerevisiae strain AS2.1190 on sugarcane pieces for production of ethanol. Electron microscopy clearly showed that cell immobilization resulted in firm adsorption of the yeast cells within subsurface cavities, capillary flow through the vessels of the vascular bundle structure, and attachment of the yeast to the surface of the sugarcane pieces. Repeated batch fermentations using sugarcane supported-biocatalyst were successfully carried out for at least ten times without any significant loss in ethanol production from sugarcane juice and molasses. The number of cells attached to the support increased during the fermentation process, and fewer yeast cells leaked into fermentation broth. Ethanol concentrations (about 89.73-77.13 g/l in average value), and ethanol productivities (about 59.53-62.79 g/l d in average value) were high and stable, and residual sugar concentrations were low in all fermentations (0.34-3.60 g/l) with conversions ranging from 97.67-99.80%, showing efficiency (90.11-94.28%) and operational stability of the biocatalyst for ethanol fermentation. The results of this study concerning the use of sugarcane as yeast supports could be promising for industrial fermentations.