3. Results and discussion
3.1. Sweet sorghum juice: evaluation of fermentability
The kinetic profile of ethanol production from sweet sorghum
juice is shown in Fig. 2. The initial sugar concentrations (sucrose
127 g L1; glucose 23 g L1 and fructose 12 g L1) were completely
converted into ethanol within 11 h of fermentation. The maximum
ethanol concentration was 72 g L1 with a yield of 0.443 g ethanol
per g of sugars consumed. This ethanol yield corresponds to 87% of
the theoretical yield and a volumetric productivity of 6.5 g L1.h1.
The lower yield when compared to cane juice fermentation was
likely a consequence of high cell growth (8e17 g L1) and the nonpretreatments
of sweet sorghum juice, e.g., liming, sulfitation and
juice clarification, employed in sugarcane-based ethanol
production.