Comparative Study of Bioethanol Production Ability of Bacillus Subtilis and Saccharomyces Cerevisiae Using Peels of Watermelon and Pineapple

Comparative study of bioethanol production ability of Bacillus subtilis and Saccharomyces cerevisiae using peels of watermelon and pineapple was investigated. The peels of watermelon and pineapple are lignocellulosic wastes which can be utilized as a common and cheap substrate for bioethanol production. The peels were prepared, pretreated and then fermented with Bacillus subtilis and Saccharomyces cerevisiae using the solid state fermentation method for five days. The fermentation process was monitored with the determination of titratable acidity, pH, temperature and microbial load using standard techniques and microbiological methods. Proximate and mineral composition together with the bioethanol composition were determined before and after fermentation using conventional procedures. The pH of the substrates decreased from (9.16-3.30), the titratable acidity also decreased from (0.018g/L-0.002g/L) and the temperature was fairly constant. The proximate compositions of the substrates varied with an increase in the ash, moisture, fat and crude fibre composition and decrease in the protein and carbohydrate composition of the fermented substrates as compared to the raw samples. The maximum ethanol yield was obtained from pineapple peels fermented with Saccharomyces cerevisiae (2.51 %0.43 v/v) while the minimum yield was obtained from the peels of pineapple fermented with Bacillus subtilis (1.21 %0.16 v/v). The ethanol yield from the fermentation process indicated that Saccharomyces cerevisiae was more efficient in bioethanol production with the peels of pineapple and watermelon than Bacillus subtilis.