A novel solid substrate fermentation system was used to produce fuel ethanol from sweet sorghum and sweet potato using a thermotolerant Saccharomyces cerevisiae strain (VS3) and a local isolate of amylolytic Bacilllus sps. (VB9). The process was carried out on a laboratory scale using broth cultures. Alcohol produced was estimated by gas chromatography after an incubation time of 72 h at 37 and 42 degrees C. More ethanol was produced in co-culture with a mixed substrate than with the thermotolerant yeast (VS3) alone. The maximum amount of ethanol produced in co-culture with a mixed substrate was 5 g/100 g of substrate at 37 degrees C and 3.5 g/100 g of substrate at 42 degrees C.