Ethanol Production From Tobacco Waste Using The Yeast Saccharomyces Cerevisiae

Bioethanol is an ideal fuel to substitute for gasoline(petrol), and the production of ethanol by fermentationhas received special attention because the world energy crisis has enhanced the interest in renewable energy sources. Bioethanol is made from a variety of products such as grain, sucrose-containing feedstocks and lignocellulosic biomass. There is a growing interest to find alternate bioresources apart from sugar cane/beet molassesand starchy crops like sweet sorghum, cassava and sweet potato for production of ethanol. In recent years, bioethanol production from bio-residues has been a hot issue in national and international study. In this study, the potential of tobacco waste for ethanol production has been studied using free and immobilized cells of S. cerevisiae.At first, the concentrated sulfuric acid hydrolysis was studied. The effects of acid loading (20%-60%,w/w), solid / liquid ratio (5%-20%, w/v), hydrolyzing tempetatur(20℃-60℃) and time (20min-180min) on reducing sugar yield were studied using single factor tests and orthogonal experiment. Best results were achieved at 50% (w/w) acid loading, 10% (w/v) solid concentration, 50℃and 100min. At the optimal hydrolysis condition, the maximal ethanol concentration and ethanol yield, with Saccharomyces cerevisiae, were 1.09 g/L and 54.5g/Kg from filtered hydrolysate(diluting 5 times), respectively. However, the maximal ethanol concentration and ethanol yield, with Saccharomyces cerevisiae, were 1.23g/L and 61.5g/kg from unfiltered hydrolysate(adding 70 U/100mL cellulose and diluting 5 times).The influence factors of SSF process using the tobacco waste was investigated through single factor tests. The best fermentation conditions were as follows: temperature was 30℃, fermentation pH was 3.5, the inoculation amount was 10% , the rotational speed was 150 rmp/min. A three-factor, three-level Box-Behnken experimental design was employed , with the amount of cellulase (X₁) , the fermentation time (X₂) , the solid / liquid ratio (X₃) as the independent variables. The response variable was ethanol yield . The optimization formulation was as follows : X₁ , X₂ and X₃ levels of 30U/g , 68h and 5% , respectively.Through the study of batch fermentation of free cells with multi-Saccharomyces cerevisiae, The experimental results suggested the ethanol yield with thress kinds of Saccharomyces cerevisiae has the best result.The influence factors of fermentation process by the immobilized multi-Saccharomyces cerevisiae were investigated.The factors were showed by an order of magnitude: pH, the stuffing rate of immobilized beads, temperature and time. And the best fermentation conditions were as follows: fermentation pH was 3.5, temperature was 35℃, fermentation time was 72h, the stuffing rate of immobilized beads was 15%.