Production and characterization of bioethanol from Solanum lycopersicum stalk hydrolysates by the simultaneous saccharification and fermentation using Zymomonas mobilis and Saccharomyces cerevisae

The limited oil reserves, pollution concerns, global warming has led to an increased financial support for sustainable and environmental friendly sources of energy. In the last decades there is an increasing interest in the development of the bioethanol production from lignocellulosic residues, which do not compete directly with food. However, the low efficient conversion of cellulosic biomass to biofuels hinders its success hence the need to constantly explore new, cheap and readily available raw materials. In this work, the capability of typed strains of Z. mobilis, S. cerevisiae as well as the co culture of Z. mobilis and S. cerevisiae (1:1) to produce ethanol by saccharification and fermentation process from tomato stalk was investigated and compared. The results shows the optimal ethanol yield of 4.00, 6.70 and 10.97% (v/v) was obtained from S. cerevisiae, Z. mobilis and the co culture of S. cerevisiae and Z. mobilis after 6 days of fermentation. The combination of S. cerevisiae and Z. mobilis yielded the highest ethanol when compared with the yields obtained when the organisms were used separately since the combination of the bacteria and yeast undergoes EMP and ED pathways which converts sugar into alcohol. The identity of the produced ethanol was confirmed by its density and IR spectrum. The results of this study suggest that agro waste should no longer be discarded but converted to useful products like bioethanol since it contains fermentable sugars.