(723c) Bioethanol Production Using Simultaneous Saccharification and Fermentation (SSF) Technique with Dioscorea Rotundata (Yam) As Raw Material

The low water requirements of tubers as cassava and Dioscorea (yam) and their high starch mass concentration are an opportunity to use them on a market that can enhance the agro-industry of the on development countries. The scope of the research includes a decrease in the energetic requirements and the possibility to explore new crops as raw materials for producing bioethanol.

This research evaluates the productivity and yield of bioethanol production, using Simultaneous Saccharification-Fermentation (SSF) technique with Dioscorea Rotundata (yam) as raw material. The pretreatment began with a starch gelatinization for 30 minutes at 68°C; then starch was hydrolized with amylase for 60 minutes over 90°C and glucoamylase for 30 minutes at the same conditions. After the hydrolysis beginning, the system was cool to 30°C and inoculated with yeast (SafCider-Fermentis). The samples rested on controlled warming for 26 hours, taking samples from them. Simultaneously, the technique applied to measure the reducing sugars concentration was DNS and ethanol concentration was calculated by HPLC.

The yam concentration used on each sample were 10 w/w%, 12.5 w/w%, 15w/w% and 18w/w%. However, the results show that the 10 w/w% sample achieved the best result, in contrast to the suggested concentration of 12.5% w/w% (J. Murgas & M. Vasquez, 2012), who last 50 hours on fermentation with Separated Hydrolysis-Fermentation (SHF). In addition, the fermentation occurs faster than the references that have employed SSF method in other types of crops, with approximately 22 hours of fermentation and at least 33% of the reduction in fermentation time. Furthermore, the process achieved a 90% of enzymatic hydrolysis yield, getting the 67 w/w% of total yam mass added as reducing sugars. On the other hand, the best ethanol yield obtained was 46.67 l/ton and 0.188 g/l h as productivity. Nevertheless, fermentation yield was 12.9%, a low value if it is compared with the typical fermentation yield that is between 49.5% and 52%. This deviation was related to a low ethanol selectivity of the yeast used on the samples.